33 research outputs found
Calcium confusion--is the variability in calcium response by Sertoli cells to specific hormones meaningful or simply redundant?
When results of more than ten different studies on hormone-induced calcium
signals in Sertoli cells are taken together, a wide variety of responses
emerges. The reported changes range from increased concentrations, via no
response at all, to decreased calcium concentrations. Minor variations in
cell isolation techniques, culture conditions, or techniques for measuring
the intracellular calcium could explain some of these differences.
However, erratic variations in response are also observed within research
groups under very similar experimental conditions. Such 'negative'
findings are mainly reported orally and do not further penetrate the
scientific community. As hormone-dependent calcium responses evidently may
depend very much on the context of the cells, calcium transients would
appear to be unreliable bioassay principles with which to detect the
primary actions of FSH and effectors such as androgens on Sertoli cells. A
more important biological question is whether these sometimes opposed
calcium transients are connected with a particular cellular response. To
date there is no evidence for such a tight coupling in Sertoli cells,
implying that, at least under in vitro conditions, calcium signals might
even be redundant altogether. Such calcium variability is probably not
unique to Sertoli cells, and the aim of this commentary is to promote an
open debate that may help to transform the current state of 'calcium
confusion' into a better understanding of the intracellular calcium
language
The micronucleus test methodological aspects
Changes in the cellular compositiion of bone marrow were studied in relation to dose of Trenimon® and time after treatment. Strong mutagenic effects caused a partial depletion of the marrow cavities of nucleated blood cell precursors, with subsequent retention of newly formed erythrocytes and inundation with peripheral blood. The influence of these changes on the results of micronucleus scoring was investigated in a time-effect and a dose-effect study using three different methods of evaluation, relating the incidence of micronuclei to (a) nucleated cells, (b) all erythrocytes, and (c) polychromatic erythrocytes. Conclusions are drawn on the practical use of the micronucleus test system. The simplest scoring procedure, namely relating micronucleated polychromatic erythrocytes to a given total number of erythrocytes, was very efficient in the range of low mutagenic effects and therefore well suited for safety screening wherease dose-effect studies comprising very high mutagenic effects required the application of a modified method of scoring
Agricultural Market Performance in the EU after the 2000 and 2003 CAP Reform An Ex-post Evaluation based on AGMEMOD
The paper investigates the CAP impacts on the EU agriculture by means of policy simulations conducted with the AGMEMOD model. To isolate the policy effects in the historical period 2000-2005, counterfactual simulations for this period are run. To simulate the response of the EU agriculture on different policy changes in the period 2006-2020, a ‘no-policy change’ baseline scenario is developed and then policy experiments are conducted such as the abolition of milk quota, the implementation of the regional payments and some budget cuts. To identify the policy effects, the policy scenarios are compared with the ‘no-policy change’ baseline