This study focuses on factors increasing the effectiveness of collaborative learning. Results show that challenging, open, and complex group tasks that required the students to create something new and original evoked effective collaboration.

Extracts of plant adaptogens such as Eleutherococcus senticosus (or Acanthopanax senticosus) and Rhodiola rosea can increase stress resistance in several model systems. We now show that both extracts also increase the mean lifespan of the nematode C. elegans in a dose-dependent way. In at least four independent experiments, 250 microg/ml Eleutherococcus (SHE-3) and 10-25 microg/ml Rhodiola (SHR-5) significantly increased life span between 10 and 20% (P < 0.001), increased the maximum lifespan with 2-3 days and postponed the moment when the first individuals in a population die, suggesting a modulation of the ageing process. With higher concentrations, less effect was observed, whereas at the highest concentrations tested (2500 microg/ml Eleutherococcus and 250 microg/ml Rhodiola) a lifespan shortening effect was observed of 15-25% (P < 0.001). Both adaptogen extracts were also able to increase stress resistance in C. elegans: against a relatively short heat shock (35 degrees C during 3 h) as well as chronic heat treatment at 26 degrees C. An increase against chronic oxidative stress conditions was observed in mev-1 mutants, and during exposure of the wild type nematode to paraquat (10 mM) or UV stress, be it less efficiently. Concerning the mode of action: both adaptogens induce translocation of the DAF-16 transcription factor from the cytoplasm into the nucleus, suggesting a reprogramming of transcriptional activities favoring the synthesis of proteins involved in stress resistance (such as the chaperone HSP-16) and longevity. Based on these observations, it is suggested that adaptogens are experienced as mild stressors at the lifespan-enhancing concentrations and thereby induce increased stress resistance and a longer lifespan.

Postexposure conditioning, as a part of hormesis, involves the application of a low dose of stress following exposure to a severe stress condition. Depending on whether the low-dose stress is of the same type of stress or is different from the initial high-dose stress causing the diseased state, postconditioning can be classified as homologous or heterologous, respectively. In clinical homeopathy, the same distinction is found between isopathic and homeopathic application of low-dose substances. Homeopathy is unique for its Similia principle, which implies that substances causing symptoms in healthy biological systems can be used to treat similar symptoms in diseased biological systems. The evaluation of the Similia principle in an experimental set-up requires the analysis of a complex sequence of ‘damage-disease-treatment-effect’ events. The process of recovery from an insult is then monitored and a possible beneficial effect on this recovery process, upon application of a range of substances in low dose, can subsequently be analyzed using molecular and functional parameters. It is then possible to compare the effect of treatment with the degree of similarity between the diseased state and the effects caused by homologous and/or different heterologous substances. Beneficial effects of postconditioning mild stress conditions have been described in terms of an increase of the synthesis of stress proteins. In this commentary paper, we present additional information on this aspect. The experimental data suggest that the beneficial effect of the low-dose stress condition used as heterologous postconditioning is related to similarity in molecular stress response.

Abstract. The structural interaction of the epidermal growth factor (EGF) receptor and the cytoskeleton of A431 cells has been studied using a monoclonal anti-EGF receptor antibody. This has been done with immunogold labeling using a variety of electron microscopical preparation procedures and EGF binding studies. By providing an image of the membraneassociated cytoskeleton, the dry cleavage method reveals a preferential localization of EGF receptors superimposed upon cytoskeletal filaments. The colocalization of gold particles with cytoskeletal filaments is not affected when pre-labeled cells are extracted with the non-ionic detergent Triton X-100, as visualized by dry cleavage. Using surface replication, this treatment results in visualization of the cytoskeleton. In these latter preparations, it is also observed that EGF receptor-coupled gold particles remain associated with cytoskeletal elements. Moreover, Triton extraction performed before immunogold labeling of EGF receptors demonstrates that isolated cytoskeletons contained binding sites for anti-EGF receptor antibodies. Using stereo micrographs of replica's obtained from these isolated cytoskeletons, it is shown that gold-labeled EGF receptors are exclusively present on the cortical membrane-associated region of the cytoskeleton and not on more intracellular-located filaments.Scatchard analysis of EGF binding to cells fixed with glutaraldehyde and treated with Triton X-100 before and after EGF binding indicates that a high affinity EGF binding site is associated with the Triton X-100 insoluble cytoskeleton.PIDERMAL growth factor (EGF) 1 is one of the most intensively studied polypeptide growth factors, and detailed knowledge has been obtained of the various effects of EGF in its target cells as well as of the molecular characteristics of EGF and EGF receptor (for reviews see references 7, 10, 27). Among the effects of EGF in its target cells are morphological changes, such as rounding up of cells (9) and induction of membrane ruffling and extension of filopodia (8). Furthermore, it has been shown that EGF causes alterations in the distribution of actin and tt-actinin (26). Since morphology and dynamics of the cell are largely maintained by an integrated action of cytoskeletal systems (2, 12), these observations suggest that EGF causes changes in the organization of the cytoskeleton via a direct or indirect coupling. Interestingly, an association of the EGF receptor kinase with the Triton X-100-insoluble cytoskeleton of A431 cells has been described recently (17). Furthermore, an enhanced phosphorylation of high molecular weight cytoskeletal proteins was determined as a consequence of EGFinduced kinase activity (17). In addition to the A431 cells, binding of EGF to purified cytoskeleton of the pheochromocytoma cell line PC12 has also been demonstrated (29).1. Abbreviation used in this paper: EGF, epidermal growth factor. So far, no morphological evidence at the ultrastructural level has been presented for an interaction of EGF receptors with the cytoskele...

IntroductionThe biological action of ultra high dilutions is controversial [1,2]. Inhibition of anti-IgE induced basophil degranulation by successive histamine dilutions is of interest, as it studies a chemically defined compound (histamine) which exerts a negative feed back effect via the histamine H 2 receptor. The biological activity is measured using the human basophil degranulation test, which is relatively simple to perform and does not require specialised equipment. Inhibition of basophil degranulation was observed with histamine dilutions ranging between the 15 th and 19 th centesimal dilutions. Since most data were originally obtained from only one laboratory, this study aimed to verify these results in a multi-centre trial. Materials and methods LaboratoriesFour independent laboratories agreed to participate in the trial. Prior to the start of the trial, participants underwent a training period and their results were verified by the French laboratory. Study protocolThe study was co-ordinated in Brussels and all histamine dilutions were coded randomly by the coordinator, who did not perform any of the tests. The dilutions were prepared in 3 separate laboratories, which did not participate in the trial. The samples were then posted to the trial laboratories. All reagents, including antibodies, histamine, staining solutions, microtitre plates etc., were from the same source. Data were returned to the co-ordinator and analysed independently by a biostatistician, who was not involved in any other part of the trial. Preparation of histamine dilutionsHistamine hydrochloride (50 mg, Sigma) was dissolved in distilled water (5 ml), diluted (1/10, v/v) in distilled water and vortexed for 15 s (full speed). To obtain the dilutions for the trial, this solution was serially diluted (1/100 v/v) up to 19 times, always with vortexing as described. The dilutions 15, 16, 17, 18 and 19 were coded by the coordinator. In parallel, dilutions of distilled water alone were prepared in an identical manner and coded (controls). On receipt of the dilutions, each participating laboratory stored them at 4°C. Prior to use, the solutions were made isotonic by dilution (1/10 v/v) in HEPES buffer (NaCl 127 mM, KCl 5 mM, HEPES 20 mM, pH 7.4). Human basophil degranulation testThe methods for the selection of volunteers, preincubation of cellular suspensions with the test dilutions and anti-IgE induced basophil degranulation have been described previously [3]. Cell suspensions (250 ml) were mixed with the test dilution (250 ml) and incubated at room temperature for 30 min. After mixing (3 s, medium vortex speed), aliquots (20 ml) were placed in the wells of a microtitre plate and mixed with anti-IgE (polyclonal anti-IgE affinity purified ATAB, USA, 20 ml; 1, 0.2, 0.04 mg/ml). The plates were then covered with a sealer tape (Dynatech Laboratories) and incubated for 30 min at 37°C. Thereafter, alcian blue (100 ml) was added to each well. Stained basophils (not activated) were counted using a haemocytometer (Fuchs Rosenthal). Approximately 80...