Low-dose tamoxifen treatment in juvenile males has long-term adverse effects on the reproductive system: implications for inducible transgenics

The tamoxifen-inducible Cre system is a popular transgenic method for controlling the induction of recombination by Cre at a specific time and in a specific cell type. However, tamoxifen is not an inert inducer of recombination, but an established endocrine disruptor with mixed agonist/antagonist activity acting via endogenous estrogen receptors. Such potentially confounding effects should be controlled for, but >40% of publications that have used tamoxifen to generate conditional knockouts have not reported even the minimum appropriate controls. To highlight the importance of this issue, the present study investigated the long-term impacts of different doses of a single systemic tamoxifen injection on the testis and the wider endocrine system. We found that a single dose of tamoxifen less than 10% of the mean dose used for recombination induction, caused adverse effects to the testis and to the reproductive endocrine system that persisted long-term. These data raise significant concerns about the widespread use of tamoxifen induction of recombination, and highlight the importance of including appropriate controls in all pathophysiological studies using this means of induction

Molecular structure of lipopolysaccharides of cold-adapted bacteria

Cold-adapted Gram-negative bacteria inhabit snow, ice water, and frozen grounds and are perfectly adapted to live at very low temperatures. They have evolved several adaptation strategies, some of which concern the cellular membrane. Bacterial outer membrane, that functions as a selective barrier allowing the influx of nutrients and confers protection to the cell, is also considered a primary sensor of the cold. It is well known that one of the main responses to cold concerning the cell membrane is the increment of fluidity and the upregulation of genes encoding for proteins and membrane transporters. In this context, also the lipopolysaccharides, macromolecules constituting approximately 75% of the outer surface, may be modified in their structure in response to the conditions prevailing in the environment. In this chapter, for the first time, the role played by lipopolysaccharides structures in response to cold adaptation is analyzed. Some structural features of the lipopolysaccharides are modified as a consequence of living at low temperatures, thus confirming that all the outer membrane components are involved in adaptation and survival molecular mechanisms