Quantitative studies are commonly realised in the biomedical research to compare RNA expression in different experimental or clinical conditions. These quantifications are performed through their comparison to the expression of the housekeeping gene transcripts like glyceraldehyde-3-phosphate dehydrogenase (G3PDH), albumin, actins, tubulins, cyclophilin, hypoxantine phosphoribosyltransferase (HRPT), L32. 28S and 18S rRNAs are also used as internal standards. In this paper, it is recalled that the commonly used internal standards can quantitatively vary in response to various factors. Possible variations are illustrated using three experimental examples. Preferred types of internal standards are then proposed for each of these samples and thereafter the general procedure concerning the choice of an internal standard and the way to manage its used are discussed. © 1999 Elsevier Science B.V. All rights reserved.Keywords: Internal standards; Housekeeping genes; RNase protection; RT-PCR www.elsevier.com/locate/jbiotec Quantitative assays widely use housekeeping gene transcripts as b-actin, glyceraldehyde-3-phosphate dehydrogenase (G3PDH) or L32 whose presumed stable expression allows quantification of other expressions, for example those of cytokines, by comparison to this internal standard. In this paper, a series of in vivo and in vitro models are presented using housekeeping genes showing in certain cases the limits at the use of such internal standards. Different possible methods enabling the management of this problem will be discussed.The study of biological regulations is very often correlated to quantification assays, which can be related to proteins or RNA. This paper will discuss the problem of mRNA quantification.Abbre6iations: G3PDH, glyceraldehyde-3-phosphate dehydrogenase; HPRT, hypoxantine phosphoribosyltransferase; PMA, phorbol 10-myristate 13-acetate.

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Abstract. Potential sterilization/disinfection of medical devices (MDs) is investigated using a specific plasma process developed at the Université de Montréal over the last decade. The inactivating medium of the microorganisms is the flowing afterglow of a reduced-pressure N2-O2 discharge, which provides, as the main biocidal agent, photons over a broad ultraviolet (UV) wavelength range. The flowing afterglow is considered less damaging to MDs than the discharge itself. Working at gas pressures in the 400-700 Pa range (a few torr) ensures, through species diffusion, the uniform filling of large volume chambers with the species outflowing from the discharge, possibly allowing batch processing within them. As a rule, bacterial endospores are used as bio-indicators (BI) to validate sterilization processes. Under the present operating conditions, Bacillus atrophaeus is found to be the most resistant one and is therefore utilized as BI. The current paper reviews the main experimental results concerning the operation and characterization of this sterilizer/disinfector, updating and completing some of our previously published papers. It uses modeling results as guidelines, which are particularly useful when the corresponding experimental data are not (yet) available, hopefully leading to more insight into this plasma afterglow system. The species flowing out of the N 2-O2 discharge can be divided into two groups, depending on the time elapsed after they left the discharge zone as they move toward the chamber, namely the early afterglow and the late afterglow. The early flowing afterglow from a pure N2 discharge (also called pink afterglow) is known to be comprised of N + 2 and N + 4 ions. In the present N2-O2 mixture discharge, NO + ions are additionally generated, with a lifetime that extends over a longer period than that of the nitrogen molecular ions. We shall suppose that the disappearance of the NO + ions marks the end of the early afterglow regime, thereby stressing our intent to work in an ion-free process chamber to minimize damage to MDs. Therefore, operating conditions should be set such that the sterilizer/disinfector chamber is predominantly filled by N and O atoms, possibly together with long-lived metastable-state O2( 1 Δg) (singlet-delta) molecules. Various aspects related to the observed survival curves are examined: the actual existence of two "phases" in the inactivation rate, the notion of UV irradiation dose (fluence) and its implications, the UV photon best wavelength range in terms of inactivation efficiency, the influence of substrate temperature and the reduction of UV intensity through surface recombination of N and O atoms on the object/packaging being processed. To preserve their on-shelf sterility, MDs are sealed/wrapped in packaging material. Porous packaging materials utilized in conventional sterilization systems (where MDs are packaged before being subjected to sterilization) were tested and found inadequate for the N 2-O2 afterglow system in contrast to a (non-porous) polyolefin polym...

Interactions between the conceptus and the mother are bi-directional: the feto-placental tissues need nutrition and a suitable environment in homeostatic condition whereas the mother influenced by the placental factors adapts her metabolism and immune system. Many different mechanisms acting locally or at distance ensure tolerance of the semiallogeneic graft by the maternal natural and adaptive immune defences. In front of this tolerance, mechanisms exist ensuring rejection of the conceptus by the mother (spontaneous abortion) through rupture of one or more tolerance mechanisms, notably in stress situations endangering the mother. Thus outcome of a pregnancy is dependent on efficiently working tolerance mechanisms, and rupture of such mechanisms can lead to rejection. The balance of influence leading either to tolerance or rejection is under control of internal (maternal and fetal) and external (environmental) factors. Rejection, if triggered, mainly occurs through immune-induced inflammation, tissue degradation and coagulation. #

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