Single-Molecule Analysis of Epidermal Growth Factor Signaling that Leads to Ultrasensitive Calcium Response

AbstractQuantitative relationships between inputs and outputs of signaling systems are fundamental information for the understanding of the mechanism of signal transduction. Here we report the correlation between the number of epidermal growth factor (EGF) bindings and the response probability of intracellular calcium elevation. Binding of EGF molecules and changes of intracellular calcium concentration were measured for identical HeLa human epithelial cells. It was found that 300 molecules of EGF were enough to induce calcium response in half of the cells. This number is quite small compared to the number of EGF receptors (EGFR) expressed on the cell surface (50,000). There was a sigmoidal correlation between the response probability and the number of EGF bindings, meaning an ultrasensitive reaction. Analysis of the cluster size distribution of EGF demonstrated that dimerization of EGFR contributes to this switch-like ultrasensitive response. Single-molecule analysis revealed that EGF bound faster to clusters of EGFR than to monomers. This property should be important for effective formation of signaling dimers of EGFR under very small numbers of EGF bindings and suggests that the expression of excess amounts of EGFR on the cell surface is required to prepare predimers of EGFR with a large association rate constant to EGF

Laparoscopic Rectosigmoid Colon Vaginoplasty in Male-to-Female Transsexuals: Experience in Japan

Intestinal vaginoplasty has several advantageous features, such as scarless surgery, low incidence of contraction of the reconstructed vagina, maintenance of vaginal depth, spontaneous mucus production, and a low rate of complications. Therefore, this technique is becoming popular in many countries. Following the global trend, the demand for intestinal vaginoplasty for transsexuals is also increasing in Japan. However, there are few reports on intestinal vaginoplasty in Japan. In this study, we examined the safety and effectiveness of rectosigmoid colon vaginoplasty in the Japanese population. We retrospectively surveyed 18 male-to-female transsexuals who underwent laparoscopic rectosigmoid colon vaginoplasty at the Okayama University Hospital Gender Center between October 2012 and December 2017. One patient had developed an anastomotic leak and 2 patients experienced vaginal prolapse, which needed revision surgery. Both adverse outcomes were comparable with those from previous studies. The anastomotic leak was managed adequately with conservative treatment. To avoid vaginal prolapse, it is important to decide the length of the rectosigmoid segment so that a pull on it does not cause it to become lax, while excessive stress on the feeder vessels is avoided. Based on our study, we concluded that rectosigmoid vaginoplasty was a reliable technique in the Japanese population