Utilization of Chinic Acid in the Differentiation of the Colon-Aerogenes Groups

Beijerinck in 1911 called attention to the fact that some strains of Bact. aaerogenes produce from chinic acid and a ferric salt, a red to black coloration under aerobic conditions. Strains of Bact. coli, he stated, do not color the medium under similar conditions. Under anaerobic conditions in solutions of chinate salt, a fermentation may occur with some members of the aerogenes group, whereby carbonic, acetic and propionic acids are formed. At the Iowa State College laboratory an attempt was made to duplicate this anaerobic type of fermentation by organisms of the coli-aerogenes group but without success. Both Smith and Durham tubes were used and no gas was detected. However, the coloration produced by Bact. aerogenes when grown on chinate medium was found to be pronounced. This color is soluble and diffuses through the medium, either liquid or solid. The suggestion from this article of Beijerinck\u27s presented an opportunity for the development of a possible differential test for coli and aerogenes strains

Role of Cortisol and Dehydroepiandrosterone on RACK1/PKC Signalling and Consequences in Immunosenescence

Over the past 15 years, it was demonstrated that defective protein kinase C (PKC) signal transduction machinery correlates to the decline of immune functions associated with aging. Experimental evidence suggest that altered PKC signalling results in impaired response to lipopolisaccaride (LPS) stimulation and cytokine release. Such defective signalling is due to reduced expression of receptor for activated C kinase 1 (RACK1) and to age-related alteration of the hormonal balance between cortisol and dehydroepiandrosterone (DHEA): cortisol levels remain substantially unchanged while DHEA levels decline with aging. These aspects are particularly relevant for the functional PKC signalling system because DHEA administration in vivo and in vitro in aged animals and in human cells can reestablish the levels of RACK1 and thus the function of the PKC signalling cascade. There is also evidence that cortisol and DHEA have opposite effect on the transcriptional regulation of the gene encoding for RACK1 and known as GNB2L1. At transcriptional level, cortisol has a peculiar function of a negative regulator of the RACK1 promoter, while the effect of DHEA seems to derive from a complex influence on the functions and post-transcriptional regulation of the glucocorticoid receptor (GR). Here we discuss the role of PKC/RACK1 signalling in the context of immune cells and immunosenescence also focusing on the role of cortisol and DHEA in the regulation of RACK1 expression