1,858 research outputs found
Celecoxib decreases prostaglandin E\u3csub\u3e2\u3c/sub\u3e concentrations in nipple aspirate fluid from high risk postmenopausal women and women with breast cancer
Background
Celecoxib inhibits PGE2 production in cancerous tissue. We previously reported that PGE2 levels in nipple aspirate fluid (NAF) and plasma were not decreased in women at increased breast cancer risk who received celecoxib 200 mg twice daily (bid). The endpoints of the current study were to determine if a short course of celecoxib 400 mg bid would decrease PGE2 levels in women 1) at increased breast cancer risk, and 2) with established breast cancer.
Methods
NAF and plasma samples were collected before, 2 weeks after taking celecoxib 400 mg bid, and two weeks after washout from 26 women who were at increased breast cancer risk. From 13 women with newly diagnosed breast cancer, NAF from the incident breast and plasma were collected before and on average 2 weeks after taking celecoxib. Additionally, in nine of the 13 women with breast cancer, NAF was collected from the contralateral breast.
Results
No consistent change in NAF or plasma PGE2 levels was noted in high risk premenopausal women. NAF PGE2 levels decreased after celecoxib administration in postmenopausal high risk women (p = 0.02), and in both the NAF (p = 0.02) and plasma (p = 0.03) of women with breast cancer.
Conclusion
Celecoxib 400 mg bid taken on average for 2 weeks significantly decreased NAF, but not plasma, PGE2 levels in postmenopausal high risk women, and decreased both NAF and plasma PGE2 levels in women with newly diagnosed breast cancer. PGE2 levels may predict celecoxib breast cancer prevention and treatment efficacy. Our observations are preliminary, and larger studies to confirm and extend these findings are warranted
Entropy Cost of "Erasure" in Physically Irreversible Processes
A restricted form of Landauer's Principle, independent of computational
considerations, is shown to hold for thermal systems by reference to the joint
entropy associated with conjugate observables. It is shown that the source of
the compensating entropy for irreversible physical processes is due to the
ontological uncertainty attending values of such mutually incompatible
observables, rather than due to epistemic uncertainty as traditionally assumed
in the information-theoretic approach. In particular, it is explicitly shown
that erasure of logical (epistemic) information via reset operations is not
equivalent to erasure of thermodynamic entropy, so that the traditional,
information-theoretic form of Landauer's Principle is not supported by the
physics. A further implication of the analysis is that there is no Maxwell's
Demon in the real world.Comment: This version clarifies that the traditional, information-theoretic
form of Landauer's Principle is not supported by the physics; however, a
restricted form involving erasure of ontological uncertainty does hol
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