Double-wave reentry in excitable media.

A monolayer of chick embryo cardiac cells grown in an annular geometry supports two simultaneous reentrant excitation waves that circulate as a doublet. We propose a mechanism that can lead to such behavior. The velocity restitution gives the instantaneous velocity of a wave as a function of the time since the passage of the previous wave at a given point in space. Nonmonotonic restitution relationships will lead to situations in which various spacings between circulating waves are possible. In cardiology, the situation in which two waves travel in an anatomically defined circuit is referred to as double-wave reentry. Since double-wave reentry may arise as a consequence of pacing during cardiac arrhythmias, understanding the dynamic features of double-wave reentry may be helpful in understanding the physiological properties of cardiac tissue and in the design of therapy.

Cutaneous Apocrine Carcinoma With an In Situ Component and Histiocytoid and Signet-Ring Cells.

We present a case of cutaneous apocrine carcinoma arising in the axilla of a 71-year-old man. The tumor had a significant component of histiocytoid and signet-ring cells as well as in situ carcinoma within the apocrine glands. The cells expressed GATA3, gross cystic disease fluid protein 15, androgen receptor, and E-cadherin. Estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 were negative. Clinical correlation was required to rule out a metastasis from the breast or the gastrointestinal tract. Although most cutaneous apocrine carcinomas do not behave aggressively, our patient developed bone metastases and eventually died of his disease. It is debated whether histiocytoid and signet-ring cell cutaneous carcinomas should be classified as apocrine neoplasm. The presence of in situ carcinoma associated with this kind of tumor has been reported only once in the literature. This characteristic and the immunohistochemical profile are in favor of apocrine differentiation.

Chitosan-Sodium Tetradecyl Sulfate Hydrogel: Characterization and Preclinical Evaluation of a Novel Sclerosing Embolizing Agent for the Treatment of Endoleaks.

PURPOSE: To compare the efficacy of an embolization agent with sclerosing properties (made of chitosan and sodium tetradecyl sulfate, CH-STS) with a similar embolization agent but without sclerosing properties (made of chitosan, CH) in treating endoleaks in a canine endovascular aneurysm repair model. METHODS: Two chitosan-based radiopaque hydrogels were prepared, one with STS and one without STS. Their rheological, injectability, and embolizing properties were assessed in vitro; afterwards, their efficacy in occluding endoleaks was compared in a canine bilateral aneurysm model reproducing type I endoleaks (n = 9 each). The primary endpoint was endoleak persistence at 3 or 6 months, assessed on a CT scan and macroscopic examination. Secondary endpoints were the occurrence of stent-graft (SG) thrombosis, the evolution of the aneurysm mean diameter, as well as aneurysm healing and inflammation scores in pathology examinations. RESULTS: In vitro experiments showed that both products gelled rapidly and presented initial storage moduli greater than 800 Pa, which increased with time. Both gels were compatible with microcatheter injection and occlude flow up to physiological pressure in vitro. In a type I endoleak model, the injection of CH-STS sclerosing gel tended to reduce the risk of occurrence of endoleaks, compared to CH non-sclerosing agent (2/9 vs. 6/9, p = 0.069). No case of SG thrombosis was observed. Moderate inflammation was found around both gels, with a comparable intensity score in both CH and CH-STS groups (2.6 ± 0.9 and 2.7 ± 0.9, respectively; p = 0.789). CONCLUSIONS: Flow occlusion combined with chemical endothelial denudation appears promising for the treatment of endoleaks. LEVEL OF EVIDENCE: N/A.