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J H Temmink

Publications and source records attributed to J H Temmink.

30 records · Page 2Linked to original sources
PubMed1980

Different cytoskeletal domains in murine fibroblasts.

The morphology of the cytoskeleton of normal 3T3 fibroblasts was studied in the electron microscope on embedded and sectioned cells as well as on critical-point-dried whole mounts. Four ultrastructurally different cytoplasmic domains could be distinguished within every 3T3 cell, namely: Cytocortex, ruffle area, endoplasm, and stress fibre. However, many transitions between the different domains were also found. In addition, 2 other domains were occasionally encountered in the same cells. Based on the knowledge that actin is present in relatively high concentration throughout non-muscle cells and that it can, under different physiological conditions, assume different morphological appearances, an attempt has been made to formulate a hypothesis that links the ultrastructural domains to different cellular functions. Many experimental approaches are available to test the hypothesis and at the same time increase our knowledge of the cytoskeleton of 3T3 cells.

Actins↗
PubMed1979

Capping of surface immunoglobulin on 'hairy cells' is independent of energy production.

Capping, independent of metabolic energy, of surface immunoglobulin (S-Ig) on 'Hairy cells' from patients with Hairy cell leukaemia (HCL) is described. As controls leukaemic cells from a patient with a prolymphocytic leukaemia (PLL) and blood lymphocytes from healthy individuals were used. The specificity of the energy-independent capping of the HCL-cells as compared to the controls was tested by incubation of the cells at 4 degrees C in the presence of 0.1 M sodium azide with different FITC-labelled ligands. In order to find an explanation for this phenomenon, the influence of cytochalasin B, colchicine and the combination of both drugs on capping of S-Ig and concanavalin (Con-A)-receptors at 37 degrees C was investigated. Furthermore the effect of Con A on S-Ig capping and vice versa was studied. The results show that only S-Ig on HCL cells could form caps at 4 degrees C in the presence of sodium-azide. Cytochalasin B alone induced a strong inhibition of Con A capping on all 3 cell types, whereas S-Ig capping was unaffected. Colchicine alone had practically no effect. Anti-Ig inhibited subsequent patch and cap formation with Con A on both HCL cells and PLL cells, whereas Con A caps and patches were redistributed by anti-Ig on PLL cells, but not on HCL cells. Conversely, Con A could link S-Ig to other receptors, leading to inhibition of S-Ig capping at 4 degrees C on HCL cells and to co-capping of S-Ig at 37 degrees C on both cell types. In addition Con A induced redistribution of S-Ig caps. The combination of co-capping of S-Ig by Con A, followed by redistribution of the caps by FITC-anti-Ig simulated inhibition of S-Ig capping by Con A on PLL cells. The major conclusions are: in some cases inhibition of capping may actually be caused by redistribution of caps; the energy-independent capping cannot be explained by free diffusion of S-Ig in the membrane through lack of any connexion with receptor-mobility regulating systems. It is proposed that the energy requirement of capping is needed to inactivate a specific mechanism,w which restrains receptor mobility and which is non-operative in HCL cells.

Adult↗
PubMed1978

Preservation of cytoskeletal elements for electron microscopy.

Attached murine fibroblasts were subjected to different fixation and dehydration procedures in order to study the preservation of cytoskeletal elements. The organization of the microtubular and microfilamentous system was identical whether or not post-fixed with osmic acid after glutaraldehyde fixation. Critical point drying did not preserve structures absent in conventionally dehydrated and embedded cells.

Animals↗
PubMed1977

Cell surface microvilli and cell agglutinability.

Detached cells of some transformed mouse fibroblast lines have a villous surface whereas similarly treated cells of other lines are relatively smooth. These differences in surface morphology of detached cells are not reflected in their agglutinability with ConA and they cannot unambigously be explained from their morphology in situ. Treatments of normal and transformed Swiss mouse fibroblasts that induce marked changes in agglutinability with ConA do not cause equivalent changes in surface morphology. It is, therefore, unlikely that agglutinability of mouse fibroblasts by ConA is determined by the number of microvilli on the cell surface.

Agglutination↗
PubMed1976

Surface morphology and agglutinability with concanavalin A in normal and transformed murine fibroblasts.

The surface morphology of attached and suspended normal and transformed fibroblasts has been studied with the scanning electron microscope. Normal murine fibroblasts (3T3) grow in vitro with widely extended leading lamellae. During most parts of the cell cycle the surfaces of these cells are practically free of microvilli. When the cells round up for mitosis, their cell surfaces become adorned with many microvilli. In contrast, simian virus 40-transformed fibroblasts (SV3T3) grow more compact, and their cell surfaces remain smooth throughout the life cycle. When confluent 3T3 and SV3T3 cells are suspended with ethylenediaminetetraacetic acid (EDTA) for agglutination assays, similar differences in surface morphology are found: 3T3 cells always bear many microvilli, whereas most SV3T3 cells are essentially free of microvilli. The addition of concanavalin A (Con A) does not influence the surface morphology of the suspended cells. The morphological differences described here may be important for the agglutination process of the normal and transformed 3T3 cells, because they affect the real cell surface area and thus the density of Con A-binding sites.

Agglutination Tests↗
PubMed1976

Surface morphology and agglutination of lectin-treated human lymphocytes and lymphoblasts.

Two human lymphoblasts (Raji and EB3) and normal human peripheral lymphocytes were exposed to different concentrations of Concanavalin A and wheat germ agglutinin. The lectin-induced agglutination was determined and correlated with lectin-induced changes in the surface morphology of these cells as studied in a scanning electron microscope. Whenever the lectin induced high agglutinability in a cell type, it also invariably had a smoothing effect on the cell surface. In contrast, when cells did not agglutinate well with a certain lectin, their cell surface remained essentially rough (villous) after addition of the lectin. The correlation found between increased agglutinability and altered cell surface morphology upon treatment with certain lectins suggests that both phenomena result from one and the same process. Additional evidence for this postulate is presented.

Agglutination↗
PubMed1975

Cell cycle dependent agglutinability, distribution of concanavalin A binding sites and surface morphology of normal and transformed fibroblasts.

In studies on phenotypic reversion of transformed cells to normal growth patterns, we investigated the effect of dibutyryl cyclic AMP (dbc-AMP) and a protease inhibitor (TLCK) on growth of SV40-transformed mouse fibroblasts (3T3). The results did not support the hypothesis that transformed cells grown with dbc-AMP or TLCK are induced to contact-mediated growth control. The growth rate of SV-3T3 cells grown with the drugs was strongly reduced, due to accumulation of the cells in the G2 phase of the cell cycle. In addition, decreased agglutinability with concanavalin A (Con A) of those SV-3T3 cells was not caused by a direct effect of the drugs on the cell surface, but by partial synchronization of the cells in the G2 phase of the cycle. In synchronized cultures agglutinability of transformed cells reached a minimum in G2 and was maximal in mitosis and G1. Normal cells agglutinated only in mitosis. This suggested that agglutinability of cells is somehow cell cycle dependent. Cytochemical investigations on normal and transformed 3T3 cells had shown that Con A-induced redistribution of binding sites on the surface of these cells is not correlated with agglutinability. The present work on replicas confirmed this, but indicated also that normal 3T3 cells have more extended lamellipodia with less Con A binding sites than SV-3T3 cells. Preliminary scanning electron microscope data showed cell cycle dependent changes in 3T3 cells and also showed that confluent 3T3 and SV-3T3 cells suspended for agglutination tests had a different surface morphology. These results may represent additional factors important for differences in cell agglutinability by Con A.

Agglutination↗
PubMed1975

Differences in density of Concanavalin A-binding sites due to differences in surface morphology of suspended normal and transformed 3T3 fibroblasts.

Calculations of the density of Concanavalin A (Con A)-binding sites on normal and transformed fibroblasts have, as yet, been based on the unproven assumption that suspended cells are smooth spheres. We studied the surface morphology of suspended normal and transformed fibroblasts with scanning and transmission electron microscopes, and found a large difference in surface morphology between suspended normal and transformed 3T3 cells. When this difference in surface morphology was taken into account, the estimated cell surface area of normal 3T3 cells was approximately seven times larger than that of transformed 3T3 cells. Since equal numbers of 3H-Con A molecules are bound on normal and transformed cells, the density of Con A-binding sites is approximately seven times greater on transformed than on normal 3T3 cells. The difference in density of Con A-binding sites between normal and transformed fibroblasts might be sufficient to explain the difference in agglutination response, as originally suggested by Burger, and may also be the cause of the different degrees of clustering of Con A-binding sites on the plasma membrane of these cells.

Binding Sites↗