J.M. van Aken | Utrecht University (original) (raw)

Papers by J.M. van Aken

International Journal of Hyperthermia, 1992

Thermosensitization induced by pretreatment at supra- and subnormal temperatures, rate of protein... more Thermosensitization induced by pretreatment at supra- and subnormal temperatures, rate of protein synthesis and expression of the major heat shock proteins under such conditions was investigated in relation to intrinsic heat sensitivity of rat hepatoma cells, i.e. Reuber H35 and HTC. The high degree of heat susceptibility of H35 cells was reflected by a high degree of thermosensitization after pretreatment by heat (step-down heating) at temperatures of 42-44 degrees C for 30 min or cold for 16 h at temperatures ranging from 0 to 25 degrees C. Sensitization under step-down heating conditions was found to be paralleled by a delayed recovery of protein synthesis. Despite an increased relative rate, enhancement of the absolute rate of synthesis of the major heat shock proteins, HSP28, HSP60, HSP68, HSP70, HSP84 and HSP100, was less pronounced during step-down exposure. Comparable results were obtained during recovery of sensitized H35 cells at 37 degrees C after exposure to heat following pretreatment at 0 degrees C. Furthermore, clear differences in the regulation of the specific HSP synthesis, depending on the particular treatment protocol, were observed.

International Journal of Hyperthermia, 1993

Of two rat hepatoma cell lines, Reuber H35 and HTC, with a different degree of differentiation an... more Of two rat hepatoma cell lines, Reuber H35 and HTC, with a different degree of differentiation and heat sensitivity, treated at 41-44 degrees C for various periods of time, the expression of thermotolerance, recovery of protein synthesis and rate of hsp synthesis were studied in relation to heat-induced cell killing. The temperature dependency of the induction of thermotolerance, either chronic or acute, was different between the cell lines; tolerance of H35 cells being induced at lower temperature than that of HTC cells. Induction of thermotolerance was related to survival decrement and the correlation was similar for both cell lines. Protein syntheses of H35 and HTC cells are equally sensitive for incubation at increased temperature, but recovery of protein synthesis after heat treatment was slightly different between the cell lines; H35 being more delayed than HTC. A strong but different correlation between total amount of protein synthesized after heat treatment and cell survival was found for the two cell lines. The increased heat sensitivity of H35 cells parallels the increased capacity of selective hsp synthesis as compared with that of HTC cells.

Biochemical and Biophysical Research Communications, 1996

Extracellular superoxide production in the Chinese hamster CCL39 fibroblast cell line was detecte... more Extracellular superoxide production in the Chinese hamster CCL39 fibroblast cell line was detected by direct counting of luminol-enhanced chemiluminescence in the presence of horseradish peroxidase (HRP). This superoxide production, which is directly related to cell density, can be inhibited by diphenylene iodonium, a specific inhibitor of NADPH-oxidase. The O 0 2 generation is transiently inhibited following exposure of the cells to elevated temperatures. To study the possible relationship between HSP27 and its modulation of NADPH-oxidase activity we measured the generation of O 0 2 activity in CCL39 cells containing either the gene coding for human HSP27 or a mutant form of this gene leading to HSP27 unable to be phosphorylated. Cells with the enhanced expression of normal human HSP27 as well as the non-phosphorylatable protein exhibited a 20-fold higher superoxide production than control CCL39 cells. Furthermore, we demonstrate that accumulation of normal HSP27 appears to play a role in prevention of NADPHoxidase inhibition by heat.

Cell Biophysics, 1991

We have investigated spontaneous and light-induced photon emission of suspensions of rat hepatocy... more We have investigated spontaneous and light-induced photon emission of suspensions of rat hepatocytes and of HTC hepatoma cells. Rat hepatocytes exhibit spontaneous biophoton emission, but from hepatoma cells this was not detectable. In contrast, after irradiation with white light, the reemission intensity was found to be lower for hepatocytes than for the tumor cell line. Induced photon emission was neither influenced by anaerobiosis nor by the intactness of the cells. Cell-fractionation studies demonstrate that the induced photon emission was caused by the nuclear fraction and by isolated chromatin. Phenol-extracted DNA, however, has lost this capacity. Our data suggest that differences in the chromatin structure may explain the cell-specific induced photon emission.

Journal of Photochemistry and Photobiology B: Biology, 1993

Science in China Series C: Life …

Photon emission (PE) and light-induced photon emission(LPE) of intact brains isolated from chick ... more Photon emission (PE) and light-induced photon emission(LPE) of intact brains isolated from chick embryos have been measured by using the single photon counting device. Experimental results showed that the intensi- ty level of photon emission was detected to be higher from ...

Journal of Paleolimnology

Lake Uddelermeer (The Netherlands) is characterized by turbid conditions and annual blooms of tox... more Lake Uddelermeer (The Netherlands) is characterized by turbid conditions and annual blooms of toxic cyanobacteria, which are supposed to be the result of increased agricultural activity in the 20 th century AD. We applied a combination of classic palaeoecological proxies and novel geochemical proxies to the Holocene sediment record of Lake Uddelermeer (The Netherlands) in order to reconstruct the natural variability of the lake ecosystem and to identify the drivers of the change to the turbid conditions that currently characterize this lake. We show that the lake ecosystem was characterized by a mix of aquatic macrophytes and abundant phytoplankton between 11,500 and 6000 cal yr BP. A transition to a lake ecosystem with clear-water conditions and relatively high abundances of 'isoetids' coincides with the first signs of human impact on the landscape around Lake Uddelermeer during the Early Neolithic (ca. 6000 cal yr BP). An abrupt and dramatic ecosystem shift can be seen at ca. 1030 cal yr BP when increases in the abundance of algal microfossils and concentrations of sedimentary pigments indicate a transition to a turbid phytoplankton-dominated state. Finally, a strong increase in concentrations of plant and faecal biomarkers is observed around 1950 AD. Canonical Correspondence Analysis (CCA) suggests that reconstructed lake ecosystem changes are best explained by environmental drivers that show long-term gradual changes (sediment age, water depth). These combined results document the long-term anthropogenic impact on the ecosystem of Lake Uddelermeer and provide evidence for pre-Industrial Era signs of eutrophication.

Optical Biopsies, 1995

Photon emission from mammalian cells has been the subject of study for many years. Throughout the... more Photon emission from mammalian cells has been the subject of study for many years. Throughout the history of this field of research the question of a functional biological role of the low intensity emission has been repeatedly raised. The discussion concerns the possible participation of biophotons in intra- and intercellular communication. In this paper we consider the significance of the studies on light-induced photon emission of isolated mammalian cells. Furthermore we report on the source of this light-induced photon emission.

Annals of botany, 2009

Plant species from various taxa 'escape' from low oxygen conditions associated with subme... more Plant species from various taxa 'escape' from low oxygen conditions associated with submergence by a suite of traits collectively called the low oxygen escape syndrome (LOES). The expression of these traits is associated with costs and benefits. Thus far, remarkably few studies have dealt with the expected benefits of the LOES. Young plants were fully submerged at initial depths of 450 mm (deep) or 150-240 mm (shallow). Rumex palustris leaf tips emerged from the shallow flooding within a few days, whereas a slight lowering of shallow flooding was required to expose R. acetosa leaf tips to the atmosphere. Shoot biomass and petiole porosity were measured for all species, and treatments and data from the deep and shallow submergence treatments were compared with non-flooded controls. R. palustris is characterized by submergence-induced enhanced petiole elongation. R. acetosa lacked this growth response. Upon leaf tip emergence, R. palustris increased its biomass, whereas R. ace...

Environmental Management and Health, 1994

Abstract: In the past many scientists have published papers on hormesis, on molecular stress resp... more Abstract: In the past many scientists have published papers on hormesis, on molecular stress responses, and on the similia principle in homoeopathy. Very few, however, have stressed a common base of interdependence of these fields. Reviews the most important ...

Experimental Cell Research, 1971

In Hepatoma Tissue Culture (HTC) cells induction of tyrosine aminotransferase (TAT) by dibutyryl ... more In Hepatoma Tissue Culture (HTC) cells induction of tyrosine aminotransferase (TAT) by dibutyryl cAMP*(DBcAMP) is regulated at some posttranscriptional step. In synchronized HTC cells TAT can be induced by DBcAMP in late G1 and in the S phase of the cell cycle only.

Experientia, 1992

Photon emission from mammalian cells has been subject of study for many years. Growing research a... more Photon emission from mammalian cells has been subject of study for many years. Growing research activity is directed on the photon emission within the field of tumor biology. These studies, applying high-sensitivity photon counting methods, have paid attention to several aspects, including photon emission from serum of tumor-bearing animals, photon emission of tumors and of isolated tumor cells. In addition, research activity is increased with respect to the photon emission induced by white light from cultured tumor cells. In this review we report on the different aspects of spontaneous and induced photon emission of tumor cells as compared to normal cells. Throughout these studies the question of a functional biological role of this spontaneous and light-induced photon emission has been raised and some different points of view will be discussed.

Cellular and Molecular Life Sciences CMLS, 1999

A mild increase in temperature that does not in the presence of cycloheximide, an inhibitor of pr... more A mild increase in temperature that does not in the presence of cycloheximide, an inhibitor of protein exert an effect on tolerance development or synthesis of synthesis. The results showed that reactivation of Luc heat shock proteins (Hsps) in control cells can stimulate was inhibited when heat-treated cells were post-treated these processes when applied to cells that have previ-under mild hyperthermic conditions. The observed inously been heat shocked. To study the underlying mech-crease in Hsp synthesis under mild hyperthermic postanism of this effect, H9c2 cells were stably transfected heat shock conditions therefore appears to be the result with the gene encoding firefly luciferase (Luc). Heat-of an increase in the period during which denatured shock-induced inactivation of Luc and its subsequent proteins are present. In addition, we studied Luc reactivation in the absence of protein synthesis inhibitors. reactivation is frequently used as a model for cellular protein denaturation and renaturation. Luc reactivation This condition led to much higher Luc activity. By estimating half-life times of Luc, the contribution of was determined following a damaging heat shock (43 or new Luc synthesis in this recovery could be determined, 44°C for 30 min) in cells that were subsequently exposed to either control temperatures (37°C) or various and only partially explained the observed increase in Luc reactivation after heat shock. Thus the synthesis of mild hyperthermic conditions (from 38.5 to 41.5°C for 1 h). To prevent changes in Luc activity consequent to other proteins must be important for the renaturation new synthesis of Luc, Luc reactivation was monitored of heat-damaged proteins.