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R van Wijk

Publications and source records attributed to R van Wijk.

At least 55 records · Page 3Linked to original sources
PubMed1986

Increase of thermoresistance after growth stimulation of resting Reuber H35 hepatoma cells. Alteration of nuclear characteristics, non-histone chromosomal protein phosphorylation and basal heat shock protein synthesis.

In this paper we demonstrate an increase in thermoresistance of resting Reuber H35 cells upon growth stimulation by serum-containing medium: late G1/early S-phase cells were thermoresistant as compared with G0 phase cells. Increase of thermoresistance during early cell cycle runs parallel with increased tolerance of structural and molecular properties of the cell nucleus. Nuclear shape and chromatin structuring became thermotolerant as determined by geometric and densitometric analysis of Feulgen-stained nuclei. Moreover, increased tolerance was demonstrated by means of the capability for endogenous phosphorylation of isolated non-histone chromosomal proteins (NHCPs). We discuss the molecular basis for this increased thermoresistance after growth stimulation and make a comparison with induction of 'acquired thermotolerance' such as has been observed in studies on fractionated hyperthermia. Both after growth stimulation and after heat shock, an increase of endogenous phosphorylation capacity of isolated NHCPs was observed, while a main enhancement of phosphorylation was found for a NHCP of Mr 95,000. Moreover, the basal synthesis of proteins inducible by heat shock (heat shock proteins) and indicated as HSP65, HSP68 and HSP84 was enhanced in thermoresistant late G1/early S phase cells as compared with thermo-sensitive G0 phase cells. A role for chromatin structuring, NHCP phosphorylation and HSPs in the regulation of thermosensitivity and cell cycling is discussed.

Animals↗
PubMed1986

Effect of serum on heat response of synchronized mouse neuroblastoma cells: protection of cell cycle progression, protein synthesis and survival.

The effect of serum and temperature elevation on proliferation has been studied in synchronized mouse neuroblastoma (Neuro-2A) cells. The effects of serum were studied on the induction of (a) mitotic delay due to a non-lethal heat treatment (30 min at 42.7 degrees C) and (b) the loss of colony-forming capacity after a more extensive heat treatment (45 min at 44 degrees C or a continuous 42.7 degrees C heat treatment). The following results were obtained. Under conditions of serum depletion, cell cycle extension of heated G1 phase cells was more than that of heated G2 phase cells. Serum protected against heat-induced alterations of cell cycle progression in G1- but not in G2 phase cells. This effect of serum could be mimicked by a supplement to the medium of human transferrin, bovine pancreas insulin and selenium, and was correlated with protection of protein synthesis. Serum also affected heat-induced cell killing. Under conditions of serum depletion, G1 phase cells were more resistant to heat compared to G2 cells. The presence of serum during heat treatment further increased the thermoresistance of G1 phase cells, but did not affect sensitivity of G2 phase cells. This effect of serum could not be mimicked by a supplement of transferrin, insulin and selenium. These results indicate that serum protects G1 phase cells for heat-induced changes of cell cycle progression as well as on cell survival, but the mechanisms involved in both phenomena seem to be different.

Animals↗
PubMed1985

Cell cycle-dependent inhibition of human vascular smooth muscle cell proliferation by prostaglandin E1.

We examined the influence of prostaglandins on the initiation of proliferation of growth-arrested human adult aortic and fetal smooth muscle cells. Prostaglandins of the E series (25 nM) exerted a significant (p less than or equal to 0.05) inhibitory effect on DNA synthesis. Inhibition was observed when PGE1 was added in the G1 phase of the cell cycle. PGE1 had no effect when added once DNA synthesis had started. Thus prostaglandins of the E series may inhibit the responsiveness of smooth muscle cells to the mitogenic action of critical growth factors, such as PGDF. This inhibitory response is cell-cycle dependent. Once smooth muscle cells have entered S phase, PGE1 is no longer effective. Our data also suggest that cAMP is involved in the PGE1-induced growth inhibition, since concomitant with PGE1 addition, cAMP levels rose rapidly; addition of the cAMP analogue db-cAMP resulted in a cell-cycle-dependent inhibition pattern comparable to that observed with PGE1.

Alprostadil↗
PubMed1985

Stimulation by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine of rat hepatic polyamine biosynthesis in vivo.

Intraperitoneal injection of the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX), resulted in a rapid and transient induction of rat hepatic ornithine decarboxylase (ODC) activity. Maximal activity was found about 5 hr after application. The levels of putrescine and spermidine increased accordingly, reaching a maximum at 7 and 12 hr following injection, respectively, while the concentration of spermine remained almost constant. The implications of these findings are discussed in relation to the mechanism of induction of ornithine decarboxylase and concomitant polyamine biosynthesis.

1-Methyl-3-isobutylxanthine↗
PubMed1985

Effect of hypothermia on cell kinetics and response to hyperthermia and X rays.

Hyperthermia is a potent radio enhancer. Studies using hypothermia in combination with irradiation have given confusing results due to lack of uniformity in experimental design. This report shows that hypothermia might have potential significance in the treatment of malignant cells with both thermo- and radiotherapy. Reuber H35 hepatoma cells, clone KRC-7 were used to study the effect of hypothermia on cell kinetics and subsequent response to hyperthermia and/or X rays. Cells were incubated at 8.5 degrees C or between 25 and 37 degrees C for 24 hr prior to hyperthermia or irradiation. Hypothermia caused sensitization to both hyperthermia and X rays. Maximum sensitization was observed between 25 and 30 degrees C and no sensitization was found at 8.5 degrees C. At 25 degrees C maximum sensitization was achieved in approximately 24 hr, cell proliferation was almost completely blocked, and cells gradually accumulated in the G2 phase of the cell cycle. In contrast to the effect of hypothermia on either hyperthermia or X rays alone, thermal radiosensitization was decreased in hypothermically pretreated cells (24 hr at 25 degrees C) compared to control cells (37 degrees C). The expression of thermotolerance and the rate of development at 37 degrees C after an initial heating at 42.5 degrees C were not influenced after preincubation at 25 degrees C for 24 hr. The expression of thermotolerance for heat or heat plus X rays during incubation at 41 degrees C occurred in a significantly smaller number of cells after 24 hr preincubation at 25 degrees C. The enhanced thermo- and radiosensitivity in hypothermically treated cells disappeared in approximately 6 hr after return to 37 degrees C.

Acclimatization↗
PubMed1985

Cell killing and sensitization to heat shock by hypothermic incubation of asynchronous and synchronized mouse neuroblastoma cells.

The effect of hypothermia on cell survival and on subsequent response to hyperthermia was studied in asynchronous and synchronized Neuro-2A cells. Cell cycle progression was blocked at temperatures below 27 degrees C. Immediately after shift to hypothermic temperatures, cells became more sensitive to hyperthermia. Development of thermosensitization was time and temperature dependent. Thermosensitization of cells by hypothermia was high at 0 degrees C and 15 degrees-30 degrees C and less at 5 degrees-10 degrees C. Sensitization started to occur before hypothermic cell death became manifest and developed gradually. Hypothermic cell death was observed when the cells were incubated for more than 1 day at temperatures of 0 degrees-24 degrees C with a minimal cell death during incubation at 6 degrees C. Thermosensitization of cells by hypothermia depended on the position of the cell in the cell cycle at the time of shift to hypothermic temperatures. Cells in late G1 and early S phase became more thermosensitive than did cells in G1 or late S-G2 phase. Furthermore G1-S cells were more sensitive to prolonged hypothermia alone than were G1 or late S-G2 cells. In contrast, late S-G2 cells were most sensitive to hyperthermia alone. It is concluded that the temperature- and cell cycle-dependent way of hypothermic induced cell death was similar to the thermosensitization of cells by hypothermia. But thermosensitization became manifest prior to the actual cell death, following hypothermic treatment.

Animals↗
PubMed1984

Effect of serum and growth factors on heat sensitivity in Swiss mouse 3T3 cells.

Quiescent Swiss mouse 3T3 cells react to a heat treatment at 46 degrees C for 20 min by changing their flat, well-extended morphology to a round appearance with retracted cytoplasmic processes during the subsequent 2 h at 37 degrees C. The percentage of morphologically changed cells was used to quantify changes in heat sensitivity, or resistance, in response to mitogenic stimulation. Stimulating quiescent cells with serum or with the specific growth factors epidermal growth factor (EGF) and prostaglandin F2 alpha (PGF2 alpha) markedly increased the heat resistance to a 46 degrees C treatment, but only when the heat treatment, but only when the heat treatment was applied within 2-3 h after the addition. When insulin (which is not mitogenic, but synergistic with EGF and PGF2 alpha in these cells) was added alone or in combination with either EGF or PGF2 alpha, it has no effect on the development of heat resistance. Neither did cycloheximide nor tunicamycin inhibit heat resistance induced by EGF, and cycloheximide even enhanced it after 2-4 h. However, adding colcemid before or at the beginning of the heat treatment abolished the increased heat resistance. The results indicate that the resistance to a single heat treatment at 46 degrees C may be related to changes in the metabolic state after mitogenic stimulation, even though these changes need not be reflected in the rate of entry into S phase. Furthermore, the cytoskeletal organization appears to be a crucial component in heat resistance of Swiss 3T3 cells.

Animals↗
PubMed1984

Effect of 1,8-dihydroxy-9-anthrone (anthralin) on rat hepatic ornithine decarboxylase activity in vivo.

Intraperitoneal injection of the non-phorbol tumor promoter anthralin (1,8-dihydroxy-9-anthrone) in male rats resulted in an increase of hepatic ornithine decarboxylase (ODC) activity. Maximal activity was observed 8 h after promoter administration reaching levels about 30 times over control. The kinetics of anthralin dependent ODC induction differed markedly from that by either 12-O-tetradecanoylphorbol-13-acetate (TPA) or phenobarbital (PB) (Bisschop et al., Carcinogenesis 2 (1981) 1282). With anthralin a slow decrease of ODC back to control level is observed approximately within 22 h. In contrast, ODC induction mediated by other tumor promoters like TPA and PB decreased to control levels within 4-6 hours. Administration of a second dose of anthralin 8 h after the first dose prevented the activity decrease as normally observed after a single dose of a tumor promoter. This effect lasted at least 10 h. ODC activity induction occurred in a dose-dependent manner being linear from 10-2000 micrograms anthralin/kg body wt. Pretreatment of the animals either with actinomycin D or with cycloheximide completely blocked anthralin mediated ODC induction suggesting that de novo ODC-mRNA synthesis and subsequent translation is involved in this process.

Animals↗
PubMed1984

Analysis of X-ray-induced cell-cycle perturbations in mouse osteosarcoma cells: a two-signal cell-cycle model.

The effects of X-irradiation on mouse osteosarcoma cells have been studied by time-lapse cinematography and the resulting pedigrees have been analysed statistically. It is shown that the irradiation treatment causes three types of cell kinetic lesions: cell death (disintegration), cell sterilization (failure to divide) and proliferation delay. The first two lesions are the most important with regard to survival of the irradiated cell in a clonal assay. Of these two lesions, sterilization appears to be highly correlated for sister cells, while this is not true for cell disintegration. This indicates that cell survival in a clonal assay may be a function of the ratio of the incidences of these two types of lesions. The X-ray-induced proliferation delay was studied in terms of intermitotic time distributions, mother-daughter correlation and sibling correlation in relation to the current cell-cycle phase at the time of treatment. This analysis shows that the effects of irradiation on these cell-cycle characteristics is highly cell-cycle-dependent. A qualitative model to account for the observations is presented.

Animals↗
PubMed1984

Induction of ornithine decarboxylase and augmentation of tyrosine aminotransferase activity by N-hydroxy-2-acetylaminofluorene and 2-acetylaminofluorene in rat liver. Influence of sex, retinylacetate, indomethacin, and pentachlorophenol.

IP injection in rats of 2-acetylaminofluorene (AAF) or N-hydroxy-2-acetylaminofluorene (N-OH-AAF) resulted in a transient increase of hepatic ornithine decarboxylase (ODC) and tyrosine aminotransferase (TAT) activity. Maximal activity of ODC was observed 4 hr and of TAT 3 hr after administration of either AAF or N-OH-AAF. A lag-time of 2 hr preceded the increase of ODC and TAT activity. N-OH-AAF dependent ODC induction displayed an almost linear dose-response in the dose range up to 94.1 mumol/kg bw (body weight) when the ODC activity was measured at its maximum 4 hr after administration. Elevation of the dose N-OH-AAF to 126 mol/kg bw resulted in a lower ODC induction. Administration of doses AAF to 31.4 mumol did not change ODC activity. At doses up to 126 mumol/kg bw ODC induction increased linear. TAT induction increased linear in the dose range 15.7-94.1 mumol N-OH-AAF and 31.4-94.1 mumol AAF/kg. Lowering the dose of AAF did not result in a lower ODC or TAT activity. Judged by the effects of actinomycin D or cycloheximide administered 1 hr prior to AAF or N-OH-AAF, the in vivo induction of rat liver ODC activity by AAF and N-OH-AAF appeared to be under transcriptional control, whereas augmentation of TAT activity under influence of AAF or N-OH-AAF appeared the result of (post) translational events. Induction of ODC by AAF or N-OH-AAF was not significantly changed by indomethacin, was slightly increased by pentachlorophenol (PCP) and was synergistically enhanced by retinylacetate (RA). The increase of TAT activity was stimulated by PCP and RA. The effect of PCP indicates that N-sulfonoxy-2-acetylaminofluorene is most probably not involved in the induction of ODC. AAF appeared more effective hepatic ODC inducer in females than males and moreover more effective than N-OH-AAF in females. N-OH-AAF had stronger ODC inducing capacity in males than females. Similar observations were made with respect to TAT activity. When induction of ODC is indicative for a tumor promoting property then the data presented here suggest that tumor promotion of the complete carcinogens AAF and N-OH-AAF is not mediated by N-O-sulfation; this might be due to other metabolic conversions.

2-Acetylaminofluorene↗
PubMed1984

Analysis of K+ and Na+ transport and intracellular contents during and after heat shock and their role in protein synthesis in rat hepatoma cells.

Heat shock at 42 degrees caused a rapid inhibition of protein synthesis in Reuber H35 hepatoma cells. Inhibition was maximal within 5 min after the temperature was increased. After heat shock at 42 degrees for 30 min, protein synthesis was restored in 4 to 5 hr. Heat shock did not inhibit amino acid transport or cause a decrease of cellular amino acid pools, excluding a direct effect of these parameters on the inhibition of protein synthesis. The same heat shock caused a stimulation of Na+-K+ pump activity, as monitored by ouabain-sensitive Rb+ influx, but the activity returned rapidly to pretreated levels after heat shock. Similar effects were observed in the passive K+ efflux. Furthermore, heating did not affect the intracellular K+ and Na+ contents. A clear difference in the effect of temperature on protein synthesis and active K+ and Na+ influx was observed. In an Arrhenius plot, a sharp break for protein synthesis was observed at 40 degrees (D. H. J. Schamhart et al., Radiat. Res., in press, 1984), while no discontinuity was observed in the Arrhenius plot for active K+ and Na+ influxes. The results demonstrate that, during and after heat shock and at various temperatures, the K+ and Na+ balances are in a continuous steady state. Experimental modification of the intracellular K+ and Na+ contents by using ouabain or the Na+ ionophore monensin revealed that, within large limits of intracellular cation contents, protein synthesis is unimpaired. These results exclude any direct involvement of K+ and Na+ in the effects of heat shock on protein synthesis in Reuber H35 hepatoma cells.

Animals↗
PubMed1984

Comparative studies of heat sensitivity of several rat hepatoma cell lines and hepatocytes in primary culture.

Cell survival, cell morphology, rate of protein synthesis, and recovery of protein synthesis have been investigated in two continuously growing rat hepatoma cell lines, namely, Reuber H35 and HTC, and rat hepatocytes in primary culture after exposure at temperatures between 37 and 44 degrees. H35 and HTC cells heated under identical culture conditions and at similar cell densities showed a remarkable difference in thermal sensitivity. For the continuously growing cell lines, the thermosensitivity of survival is reflected by thermally induced morphological alterations and the rate of recovery of protein synthesis but not by the thermally induced initial changes in protein synthesis. With the use of time-lapse cinematography, application of morphological criteria, and determination of the recovery of protein synthesis, the relative heat sensitivity of hepatocytes was evaluated as less than that of H35 cells but comparable to that of HTC cells. Therefore, it appears that hepatoma cell lines originating from the same tissue possess different heat sensitivities.

Animals↗
PubMed1984

Comparative studies of the heat production of different rat hepatoma cells in culture.

Heat production of H35, HTC, and RLC rat hepatoma cells were measured under identical conditions by differential thermal analysis. Production of thermal energy was determined after sedimentation at various cell densities. Heat production was dependent on cell density and was compared with heat production measurements in suspension cultures by using an isoperibol calorimeter. Thermal energy production of the well-differentiated H35 cell line was approximately three times lower than that of the poorly differentiated HTC and RLC cell lines. A relationship with carbohydrate metabolism is discussed.

Animals↗
PubMed1984

Effect of thermotolerance on thermal radiosensitization in hepatoma cells.

The interaction between hyperthermia and X irradiation was determined in cultured Reuber H35 hepatoma cells with different states of thermosensitivity. Incubation at 41 degrees C followed by 4-Gy X rays resulted after 2 hr in a stabilization of cell survival for heat or plus X rays, with a maximum synergism factor of 1.6. Thermotolerance did not develop during incubation at 41.7 or 42.5 degrees C. When heat treatment of cells was followed by irradiation, the synergism factor for thermal radiosensitization increased with both the amount of thermal cell killing and the amount of X-ray cell killing; the influence of thermal exposure on the synergism factor was greater than that of the X-ray dose. Cells were made thermotolerant either by incubation at 42.5 degrees C for 30 or 60 min followed by an interval at 37 degrees C, or by continuous incubation at 41 degrees C. In both cases thermotolerance was measured by incubation at 42.5 degrees C. No difference was observed between the maximum thermotolerance achieved with both methods. When cells were irradiated in addition to the second heat treatment, thermal radiosensitization was strongly reduced concomitant with the decreased sensitivity to killing by heat.

Acclimatization↗
PubMed1984

Thermotolerance in cultured hepatoma cells: cell viability, cell morphology, protein synthesis, and heat-shock proteins.

Heat treatment at 42 degrees C of cultured Reuber H35 rat hepatoma cells induced both a rapid decrease of the rate of protein synthesis and the rounding up of the cells. Reincubation at 37 degrees C resulted in a gradual flattening of the cells, resumption of protein synthesis, and the synthesis of heat-shock proteins. During the recovery period cells developed a resistance toward a treatment which otherwise should lead to heat-induced cell death. Thermotolerance measured in terms of cell survival was paralleled by thermal resistance of protein synthesis and the cellular ability to refrain from rounding up under heat stress.

Acclimatization↗
PubMed1984

Morphological response and survival of hepatoma cells during fractionated hyperthermia: effect of glycerol.

Reuber H35 rat hepatoma cells rounded and became spherical during hyperthermia at 42.5 degrees C. When returned to 37 degrees C, the cells recovered and spread out again. As soon as the cells had recovered from the morphologically expressed stress, they expressed tolerance to a second hyperthermia treatment as measured by the same end point. Fractionated hyperthermia made the cells thermotolerant as judged by both the morphological and the cell survival response. Glycerol protected the cells against heat damage as measured by less morphological alteration and decreased cell lethality. Protection depended on the glycerol concentration and maximal protection was observed at 6-8%. After heating in the presence of 7% glycerol, cells expressed thermotolerance at an earlier time than in the absence of glycerol, although the rates of development were approximately similar. Cell survival data and morphological responses showed good correlation.

Animals↗
PubMed1983

Effects of exogenous cyclic AMP on growth characteristics and radiation response of Reuber H35 hepatoma cells.

Reuber H35 rat hepatoma cells, clone KRC, were used to study the effect of cyclic AMP on radiation-induced cell death. Treatment of logarithmically growing cultures with 0.5 mM cAMP for 17 hr prior to irradiation resulted in a decreased cell survival. Similar results were obtained with cultures irradiated after treatment with Bt2cAMP. Treatment of H35 cells with cAMP or Bt2cAMP caused inhibition of their proliferation and resulted in an accumulation of cells in early S phase and a depletion of G2-phase cells. In synchronized cultures cells were relatively radioresistant during their S phase. In addition to single-dose treatment with X rays, the effect of Bt2cAMP on radiation-induced cell death was studied during fractionated irradiation with 2.5 Gy per day. This fractionated irradiation resulted in a dose-reduction factor of 1.6 at the 10% survival level and a 10-fold decrease in the surviving cell population due to the cooperative effects of Bt2cAMP on growth rate and radiation survival. The effect of cAMP on radiation-induced mitotic delay was also studied. It appeared that whereas cAMP had no effect on the progression of G2 cells into mitosis, it prevented cells from recovery from the X-ray mitotic delay in G2.

Animals↗