Enhanced radiation sensitivity and radiation recall dermatitis (RRD) after hypericin therapy – case report and review of literature

BACKGROUND: Modern radiotherapy (RT) reduces the side effects at organ at risk. However, skin toxicity is still a major problem in many entities, especially head and neck cancer. Some substances like chemotherapy provide a risk of increased side effects or can induce a "recall phenomenon" imitating acute RT-reactions months after RT. Moreover, some phototoxic drugs seem to enhance side effects of radiotherapy while others do not. We report a case of "radiation recall dermatitis" (RRD) one year after RT as a result of taking hypericin (St. John's wort). CASE REPORT: A 65 year old man with completely resected squamous cell carcinoma of the epiglottis received an adjuvant locoregional RT up to a dose of 64.8 Gy. The patient took hypericin during and months after RT without informing the physician. During radiotherapy the patient developed unusual intensive skin reactions. Five months after RT the skin was completely bland at the first follow up. However, half a year later the patient presented erythema, but only within the area of previously irradiated skin. After local application of a steroid cream the symptoms diminished but returned after the end of steroid therapy. The anamnesis disclosed that the patient took hypericin because of depressive mood. We recommended to discontinue hypericin and the symptoms disappeared afterward. CONCLUSION: Several drugs are able to enhance skin toxicity of RT. Furthermore, the effect of RRD is well known especially for chemotherapy agents such as taxans. However, the underlying mechanisms are not known in detail so far. Moreover, it is unknown whether photosensitising drugs can also be considered to increase radiation sensitivity and whether a recall phenomenon is possible. The first report of a hypericin induced RRD and review of the literature are presented. In clinical practise many interactions between drugs and radiotherapy were not noticed and if registered not published. We recommend to ask especially for complementary or alternative drugs because patients tend to conceal such medication as harmless

Application to light-induced control of open quantum systems

In linear control, balanced truncation is known as a powerful technique to reduce the state-space dimension of a system. Its basic principle is to identify a subspace of jointly easily controllable and observable states and then to restrict the dynamics to this subspace without changing the overall response of the system. This work deals with a first application of balanced truncation to the control of open quantum systems which are modeled by the Liouville-von Neumann equation within the Lindblad formalism. Generalization of the linear theory has been proposed to cope with the bilinear terms arising from the coupling between the control field and the quantum system. As an example we choose the dissipative quantum dynamics of a particle in an asymmetric double well potential driven by an external control field, monitoring population transfer between the potential wells as a control target. The accuracy of dimension reduction is investigated by comparing the populations obtained for the truncated system versus those for the original system. The dimension of the model system can be reduced very efficiently where the degree of reduction depends on temperature and relaxation rate

Nucleosynthesis and the variation of fundamental couplings

We determine the influence of a variation of the fundamental ``constants'' on the predicted helium abundance in Big Bang Nucleosynthesis. The analytic estimate is performed in two parts: the first step determines the dependence of the helium abundance on the nuclear physics parameters, while the second step relates those parameters to the fundamental couplings of particle physics. This procedure can incorporate in a flexible way the time variation of several couplings within a grand unified theory while keeping the nuclear physics computation separate from any model-dependent assumptions.Comment: 8 pages, no figure

Higgs description of two-flavor QCD vacuum

A Higgs description for the QCD vacuum in the limit of two quark flavors is proposed. Complete ``spontaneous breaking'' of color symmetry is realized by condensation of an adjoint quark-antiquark and a quark-quark pair. The vacuum is invariant under isospin symmetry applying color and flavor transformations simultaneously. All elementary excitations acquire integral charges. The dressed microscopic quark and gluon degrees of freedom can be identified with the macroscopic baryon and vector meson degrees of freedom. In addition to the nucleons we find soliton--type fermions with integer isospin. Their presence provides an important test accessible to lattice QCD simulations.Comment: 4 page

Gemcitabine Functions Epigenetically by Inhibiting Repair Mediated DNA Demethylation

Gemcitabine is a cytotoxic cytidine analog, which is widely used in anti-cancer therapy. One mechanism by which gemcitabine acts is by inhibiting nucleotide excision repair (NER). Recently NER was implicated in Gadd45 mediated DNA demethylation and epigenetic gene activation. Here we analyzed the effect of gemcitabine on DNA demethylation. We find that gemcitabine inhibits specifically Gadd45a mediated reporter gene activation and DNA demethylation, similar to the topoisomerase I inhibitor camptothecin, which also inhibits NER. In contrast, base excision repair inhibitors had no effect on DNA demethylation. In Xenopus oocytes, gemcitabine inhibits DNA repair synthesis accompanying demethylation of oct4. In mammalian cells, gemcitabine induces DNA hypermethylation and silencing of MLH1. The results indicate that gemcitabine induces epigenetic gene silencing by inhibiting repair mediated DNA demethylation. Thus, gemcitabine can function epigenetically and provides a tool to manipulate DNA methylation

Excited hadrons on the lattice: Mesons

We present results for masses of excited mesons from quenched calculations using chirally improved quarks at pion masses down to 350 MeV. The key features of our analysis are the use of a matrix of correlators from various source and sink operators and a basis which includes quark sources with different spatial widths, thereby improving overlap with states exhibiting radial excitations.Comment: 8 pages, 8 figures; version accepted to PR