Symmetry Protected Topological Order in Open Quantum Systems

We systematically investigate the robustness of symmetry protected topological (SPT) order in open quantum systems by studying the evolution of string order parameters and other probes under noisy channels. We find that one-dimensional SPT order is robust against noisy couplings to the environment that satisfy a strong symmetry condition, while it is destabilized by noise that satisfies only a weak symmetry condition, which generalizes the notion of symmetry for closed systems. We also discuss "transmutation" of SPT phases into other SPT phases of equal or lesser complexity, under noisy channels that satisfy twisted versions of the strong symmetry condition

Activin modulates differential effects of estradiol on synthesis and secretion of follicle-stimulating hormone in ovine pituitary cells

In several physiological paradigms, secretion of FSH and LH are not coordinately regulated. Because these hormones appear to be produced by a single cell type in the anterior pituitary gland, their discordant regulation must be related to differential intracellular responses to various stimuli. Estradiol-17β (estradiol) has been shown to influence secretion of both FSH and LH and some of its effects are mediated directly on the gonadotrope. Changes in expression of intrapituitary factors such as activin and follistatin may mediate effects of estradiol and account for discordant patterns of FSH and LH. The aims of this study were 1) to determine if estradiol alters expression of genes encoding activin, follistatin, or both in ovine pituitary cells; and 2) to observe the effects of immunoneutralizing activin B in vitro on gonadotropin secretion. Pituitary cells from five ewes in the anestrous season were cultured for 24 h with estradiol (0.01 or 1.0 nM). Estradiol reduced basal secretion of FSH in a dose-dependent manner (P < 0.001) and simultaneously increased basal secretion of LH (P < 0.001). Decreased secretion of FSH in estradiol-treated cultures was accompanied by suppressed levels of FSHβ subunit mRNA (P < 0.001). Amounts of mRNA for activin βBwere reduced in a dose-dependent manner by estradiol (27% ± 4.9% at 0.01 nM, P < 0.02; and 46% ± 3.9% at 1.0 nM, P < 0.002). In contrast, mRNA for follistatin was not affected by treatment with estradiol. Treatment of pituitary cells with an antibody to activin B reduced secretion of FSH by 50% (P < 0.01) without influencing secretion of LH. These data lead us to conclude that discordant secretion of gonadotropins can be induced by estradiol acting directly at the pituitary level. The inhibitory effect of estradiol on FSH secretion may be mediated indirectly through decreased pituitary expression of the activin gene