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W T Daems

Publications and source records attributed to W T Daems.

At least 37 records · Page 2Linked to original sources
PubMed1986

Measurement of single-cell DNA synthesis by pokeweed mitogen-stimulated mononuclear cells with combined light and scanning electron microscopy.

The response of peripheral blood mononuclear cells to pokeweed mitogen (PWM) stimulation was investigated with combined light (LM) and scanning electron microscopy (SEM). The DNA content of the nucleus of a cell (measured by fluorescence) was compared directly with the diameter and morphological features (by SEM). It was found that upon PWM stimulation lymphocytes transform into blast cells without measurable increase of diploid DNA content (4C) were not seen. The results of DNA fluorescence measurements were comparable with [3H]thymidine uptake profiles, both having peak values on Days 4 and 5 after the start of stimulation. Lymphocyte-enriched populations stimulated by PWM showed a small but distinct population of cells with a diameter of approximately 4-5 micrometers and having a tetraploid DNA content on Days 3, 4 and 5 after the start of stimulation. This reflects the cells' ability to divide in response to mitogen stimulation. SEM showed no characteristic cell-surface morphology for blast cells with increasing DNA content.

DNA↗
PubMed1985

Conjugates of colloidal gold with native and acetylated low density lipoproteins for ultrastructural investigations on receptor-mediated endocytosis by cultured human monocyte-derived macrophages.

The morphological aspects of the binding and internalization of low density lipoproteins (LDL) and acetylated low density lipoproteins (AcLDL) by cultured human monocyte-derived macrophages were investigated. For this purpose, LDL and AcLDL were conjugated to 20 nm colloidal gold particles. After incubation of the cells with the conjugated lipoproteins at 4 degrees C some LDL- or AcLDL-gold complexes were found to be attached to the cell surface, but without characteristic localization. However, after incubation of the cells at 8 degrees C with either LDL-gold or AcLDL-gold, lipoprotein-gold complexes were present in clusters on the plasma membrane, often in coated pits. Cells incubated at 37 degrees C for various time periods showed internalization of both LDL- and AcLDL-gold complexes via small coated and non-coated vesicles and processing of the complexes in smooth-walled endosomes. When the cells were pulse-chased with LDL- or AcLDL-gold for 30 min at 37 degrees C, the gold conjugates occurred in dense bodies, probably lysosomes. The results suggest that although native and modified LDL are reported to be metabolized differently by macrophages, the morphological aspects of the endocytosis of LDL and AcLDL by cultured human monocyte-derived macrophages are similar.

Cell Membrane↗
PubMed1985

Bioreactions at the tissue/hydroxyapatite interface.

The events at the hydroxyapatite implant material/tissue interface in the rat middle ear were studied by light microscopy, autoradiography, morphometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray microanalysis. Deposition of calcium, partially in the form of calcium phosphate, was found at the interface. Resorption of the implant material occurred as the result of mono- and multinuclear phagocyte activity. Resorption decreased 6 mnth after the operation, possibly due to the decreasing number of phagocytes at the interface and the increasing amount of bone in the macropores.

Animals↗
PubMed1985

Visualization of binding and receptor-mediated uptake of low density lipoproteins by human endothelial cells.

Low density lipoproteins (LDL) were conjugated to colloidal gold for investigation of the ultrastructural aspects of binding and receptor-mediated internalization of LDL by cultured endothelial cells from the human umbilical artery and vein. The number of LDL receptors was increased by preincubation in lipoprotein-depleted serum. When the cells were incubated with LDL-gold particles for 2 h at 4 degrees C, the complexes were found in coated pits as well as in clusters attached to the plasma membrane. Small vesicles containing a few LDL-gold complexes appeared in the cytoplasm close to the plasma membrane when the cells were incubated with the conjugate for 5 min at 37 degrees C. After 15 min at 37 degrees C, larger vesicles with a pale matrix and membrane-orientated LDL-gold complexes were seen. After incubation for 30 min at 37 degrees C, colloidal gold particles were present in dense bodies. Quantification of the binding of LDL-gold complexes to the plasma membrane at 4 degrees C showed no differences between arterial and venous endothelial cells.

Blood Vessels↗
PubMed1985

On the origin of peritoneal resident macrophages. I. DNA synthesis in mouse peritoneal resident macrophages.

Mouse resident macrophages were isolated from the unstimulated peritoneal cavity at various intervals after one intravenous injection of tritiated thymidine. EM autoradiography showed that 15 min after the injection, peritoneal resident macrophages, with the characteristic localization of the peroxidatic activity in the rough endoplasmic reticulum and the nuclear envelope, had already incorporated tritiated thymidine. In the peripheral blood, monocytes with silver grains over the nuclei were seen from 12 h onwards with a maximum at 48 h. In the peritoneal cavity labelled monocytes appeared at 24 h. The peak for labelled blood monocytes was not followed by a peak for labelled peritoneal resident macrophages. The conclusion is drawn that resident macrophages from the unstimulated peritoneal cavity are able to proliferate locally.

Animals↗
PubMed1985

On the origin of peritoneal resident macrophages. II. Recovery of the resident macrophage population in the peritoneal cavity and in the milky spots after peritoneal cell depletion.

A kinetic study of the resident macrophage population in the peritoneal cavity and in the milky spots was done in mice depleted of peritoneal cells by repeated peritoneal washing. According to the distribution of the peroxidatic activity, four types of peritoneal macrophages could be distinguished. The size of each of these subpopulations depends on the length of the interval after peritoneal-cell depletion. Tritiated thymidine experiments revealed in the peritoneal cavity and in the milky spots local DNA synthesis by resident and PO-negative macrophages but not by monocytes or exudate macrophages and exudate/resident macrophages. The relationships between the various types of macrophages are discussed. No evidence was found for a relationship between resident macrophages and monocytes or macrophages with PO-positive granules. The PO-negative macrophage population was suggested to be heterogeneous, part of it being derived from monocytes and part having a relationship with the resident macrophages.

Animals↗
PubMed1985

On the origin of peritoneal resident macrophages. III. EM-immunocytochemical studies on the origin of mouse peritoneal resident macrophages.

The origin of resident macrophages was studied in chimera mice, F1(B10M X DBA2)----B10M, by means of EM-immunocytochemical detection of H-2 antigens on the cell surface of donor cells, F1(B10M X DBA2) (H-2d/H-2f haplotype), in the B10M (H-2f haplotype) host. The methodology used was an acceleration of the replacement of host peritoneal resident macrophages, reached by complete peritoneal cell depletion. In mice with successful engraftment of the bone marrow, the recovered peritoneal resident macrophage population showed the H-2d antigenic characteristics of the bone marrow donor. It was concluded that under the experimental conditions of this study peritoneal resident macrophages derive at least partly from precursor cells in the bone marrow.

Animals↗
PubMed1985

Visualization of the interaction of native and modified low density lipoproteins with isolated rat liver cells.

Morphological characteristics of the interaction of low density lipoproteins (LDL) and acetylated low density lipoproteins (AcLDL) with rat liver cells are described. These liver cell types are mainly responsible for the catabolism of these lipoproteins in vivo. Isolated rat liver Kupffer, endothelial, and parenchymal cells were incubated with LDL or AcLDL conjugated to 20 nm colloidal gold. LDL was mainly internalized by Kupffer cells, whereas AcLDL was predominantly found in endothelial cells. Kupffer and endothelial cells displayed different morphological characteristics in the processing of these lipoproteins. Kupffer cells bound LDL at uncoated regions of the plasma membrane often at the base of pseudopodia, and internalized the particles via small smooth vesicles. These uptake characteristics differ from the classical LDL uptake pathway, as described for other cell types, and may be related to the unique recognition properties of the receptor of Kupffer cells as observed in biochemical studies. Liver endothelial cells bound AcLDL in coated pits, followed by rapid uptake. Uptake proceeded through small coated vesicles, and after 5 min of incubation large (600-1200 nm) electron-lucent vacuoles (endosomes) with AcLDL-gold particles arranged along the membrane region were present. The endosomes were often associated closely with the cell membrane which might enable direct recycling of AcLDL receptors. These observations might explain the high efficiency of these cells in the processing of modified LDL in vivo.

Acetylation↗
PubMed1984

Wheat-germ agglutinin binding in four types of mouse peritoneal macrophage. A quantitative EM-cytochemical study.

After stimulation of the mouse peritoneal cavity with newborn calf serum (NBCS), four types of monocyte and macrophage were distinguished on the basis of peroxidase (PO) patterns. These cell types showed heterogeneity in their binding of the lectin wheat-germ agglutinin (WGA). At 16 h after stimulation, monocytes and monocyte-derived macrophages (with PO activity in granules) had a high level of WGA binding; PO-negative macrophages showed moderate WGA binding, and resident macrophages (with PO activity in the RER and nuclear envelope) had low WGA binding. At later time-points after stimulation, each of these cell types lost WGA binding sites. This decrease was related to a process of differentiation and to a modulation, affected by environmental factors. The present results also indicated that PO-negative macrophages can give rise to resident macrophages. Whether these PO-negative cells are monocyte derived or originate otherwise needs further investigation. The fourth type of macrophage, the exudate-resident cell (with PO activity both in granules and in the RER and nuclear envelope), with a WGA binding pattern similar to that of monocytes and monocyte-derived macrophages, was considered not to be a resident precursor cell.

Animals↗
PubMed1984

A centrifugation method for standardized sedimentation of mononuclear human blood cells on glass for scanning electron microscopy.

A centrifugation method for depositing cells on cover-glasses for scanning electron microscopy (SEM) is described. This centrifugation procedure provides a defined and standardized morphology of mononuclear cells from human blood. The method circumvents the highly variable flattening of some blood cells such as monocytes, observed with some methods. The SEM images show fine morphological surface details indicating a well-preserved cell morphology. The cell recovery of the method is sufficiently high and the lymphocyte-monocyte ratio in centrifugation preparations was found identical to the ratio in control smear preparations.

Centrifugation↗
PubMed1983

A comparative study of primary and secondary granules in monocytopoiesis and myelopoiesis of mouse bone marrow.

The differentiation and maturation of monocytes and neutrophil granulocytes were studied in bone marrow of normal mice by electron microscopy and cytochemical assessment of peroxidatic activity. The granule populations of the mature cells of bone marrow were identified and investigated to obtain a basis for the analysis of the earlier stages of maturation. Mature monocytes and neutrophils showed primary and secondary granules, and mature neutrophils had more of both kinds. The size, shape, and number of primary granules proved to offer the most reliable criteria for distinguishing promonocytes and promyelocytes. The primary granules of monocytes were smaller than those of mature neutrophils and were either spherical (smallest diameter 50-200 nm) or elongate (100 X 400 nm). Both granules had a homogeneous matrix. The granules of the granulocytes were either spherical (smallest diameter 200-300 nm) or elongate (150-200 X 300-500 nm), and some of them had a crystalline inclusion.

Animals↗
PubMed1983

Autoradiographical demonstration of C3b receptor activity on resident peritoneal macrophages.

The present study was performed to evaluate the usefulness of 125I-labelled C3b bound to constituents of sheep erythrocyte membranes (125I-C3b-OR) for the demonstration of C3b receptor activity of resident peritoneal macrophages at the electron-microscopical level. The binding of 125I-C3b-OR to the cells was studied in biochemical and autoradiographical experiments. The amount of cell-associated radioactivity was dependent on the presence of unlabelled aggregated C3b (AC3b) in a dose-response manner, and diminished strongly after functional inactivation of the receptor by trypsin treatment. In addition, it was found that at 4 degrees C most of the label was associated with the cell surface. However, when the incubation temperature was raised from 4 degrees C to 37 degrees C, internalization of the label was observed. These results indicate that 125I-C3b-OR is a suitable agent for further characterization of the C3b receptor-function of resident peritoneal macrophages at the electron-microscopical level.

Animals↗
PubMed1983

Heterogeneity in 5'-nucleotidase activity of mouse peritoneal macrophages. An EM-cytochemical and biochemical study.

After stimulation of the mouse peritoneal cavity with newborn calf serum (NBCS), four types of monocyte and macrophage were distinguished on the basis of peroxidase (PO) patterns. Cytochemically, these cells showed strong heterogeneity in 5'-nucleotidase (5'N) activity. Monocytes and monocyte-derived macrophages with PO activity in granules lacked 5'N activity. Resident macrophages (with PO activity in RER and nuclear envelope) generally had significant 5'N activity on the plasma membrane, the pattern showing close correlation with the biochemical findings. The group of PO-negative macrophages comprised both 5'N-negative and 5'N-positive cells. These findings suggest two possibilities, i.e., that monocytes (5'N-)transform via PO-negative cells (5'N -/+) into resident macrophages (5'N +), or that the monocytes and monocyte-derived macrophages and the resident macrophages represent separate lineages. The fourth type of macrophage, the exudate-resident cell (with PO activity both in granules and in the RER and nuclear envelope), occurred only in low numbers and very late after NBCS stimulation, and is therefore considered not to be a transitional cell between monocytes and resident macrophages.

5'-Nucleotidase↗
PubMed1982

Endocytosis in absorptive cells of cultured human small-intestinal tissue: effect of cytochalasin B and D.

The effect of cytochalasin B (CB) and cytochalasin D (CD) on the endocytotic uptake of horseradish peroxidase (HRP) by intestinal absorptive cells was investigated by morphometric methods. The results showed that CD inhibited endocytosis considerably, and without any detrimental side-effects. CB had hardly any effect on the endocytosis of HRP, but caused a significant decrease in the number of apical vesicles and tubules involved in the transport of cell-coat glycoproteins from the Golgi apparatus to the brush border. Electron-microscopic autoradiographic analysis of the effect of CD showed that although endocytosis is inhibited significantly by the drug, the amount of radiolabelled cell-coat material entering the lysosome-like bodies was unaltered compared with control cultures. These observations support our hypothesis that the cell-coat glycoproteins of the absorptive cells enter the lysosome-like bodies by a crinophagic rather than by an exocytotic-endocytotic mechanism.

Cells, Cultured↗
PubMed1982

Heterogeneity of concanavalin A binding by mouse peritoneal macrophages.

The binding of the lectin concanavalin A (Con A) to the cell surface of monocytes and macrophages collected from the stimulated peritoneal cavity of mice was investigated electron microscopically with horseradish peroxidase-gold as an indirect marker. Individual cells were identified by the cytochemical localization of peroxidatic (PO) activity. In monocytes and monocyte-derived macrophages with PO activity in cytoplasmic granules, the degree of Con A binding was lower than in resident macrophages with PO activity in the rough endoplasmic reticulum and nuclear envelope. An even higher degree of Con A labelling was found on the surface of cells devoid of PO activity. Since the above-mentioned cell populations show a different degree of lectin binding, it is suggested that lectin labelling methods might offer a new tool for quantitative investigation of the differentiation of monocytes and resident macrophages.

Animals↗
PubMed1982

Do resident macrophages proliferate?

Immunocytochemical studies on both the light-microscopic and electron-microscopic levels proved that peritoneal resident macrophages derive from a precursor cell in the bone marrow. Evidence that this precursor cell differs from that of the monocyte is described. Progenitor cells of peritoneal resident macrophages were found in the peritoneal milky spots. Peritoneal resident macrophages show local proliferation, as determined by 3H-thymidine labelling and electron-microscopic autoradiography. On the basis of these findings it is postulated that peritoneal resident macrophages derive from locally proliferating progenitor cells which themselves arise from specific stem cells in the bone marrow, differing from the stem cells of the monocyte/granulocyte series.

Animals↗