Modulation of DNA loop lifetimes by the free energy of loop formation.

Storage and retrieval of the genetic information in cells is a dynamic process that requires the DNA to undergo dramatic structural rearrangements. DNA looping is a prominent example of such a structural rearrangement that is essential for transcriptional regulation in both prokaryotes and eukaryotes, and the speed of such regulations affects the fitness of individuals. Here, we examine the in vitro looping dynamics of the classic Lac repressor gene-regulatory motif. We show that both loop association and loop dissociation at the DNA-repressor junctions depend on the elastic deformation of the DNA and protein, and that both looping and unlooping rates approximately scale with the looping J factor, which reflects the system's deformation free energy. We explain this observation by transition state theory and model the DNA-protein complex as an effective worm-like chain with twist. We introduce a finite protein-DNA binding interaction length, in competition with the characteristic DNA deformation length scale, as the physical origin of the previously unidentified loop dissociation dynamics observed here, and discuss the robustness of this behavior to perturbations in several polymer parameters.

iPreP is a three-dimensional nanofibrillar cellulose hydrogel platform for long-term ex vivo preservation of human islets.

Islet transplantation is an effective therapy for achieving and maintaining normoglycemia in patients with type 1 diabetes mellitus. However, the supply of transplantable human islets is limited. Upon removal from the pancreas, islets rapidly disintegrate and lose function, resulting in a short interval for studies of islet biology and pretransplantation assessment. Here, we developed a biomimetic platform that can sustain human islet physiology for a prolonged period ex vivo. Our approach involved the creation of a multichannel perifusion system to monitor dynamic insulin secretion and intracellular calcium flux simultaneously, enabling the systematic evaluation of glucose-stimulated insulin secretion under multiple conditions. Using this tool, we developed a nanofibrillar cellulose hydrogel-based islet-preserving platform (iPreP) that can preserve islet viability, morphology, and function for nearly 12 weeks ex vivo, and with the ability to ameliorate glucose levels upon transplantation into diabetic hosts. Our platform has potential applications in the prolonged maintenance of human islets, providing an expanded time window for pretransplantation assessment and islet studies.

Venous outflow reconstruction using an expanded polytetrafluoroethylene vascular graft in living-donor liver transplant: a single-center experience.

OBJECTIVES: Limited studies have focused on the feasibility and technical requirements of using expanded polytetrafluoroethylene vessel grafts for venous outflow reconstruction in a living-donor liver transplant using right liver grafts without the middle hepatic vein. MATERIALS AND METHODS: Between August 2007 and December 2012, thirty-two patients who had received an expanded polytetrafluoroethylene vascular graft for outflow reconstruction during a living-donor liver transplant using a right liver graft without the middle hepatic vein were retrospectively reviewed. Preoperative and operative data, complications, and mortality were compared among patients who received the expanded polytetrafluoroethylene grafts with individual anastomoses (n = 18) or confluent anastomoses (n =14). RESULTS: For patients who had received an individual and a confluent anastomosis, graft reconstruction time was 25.8 and 14.9 minutes (P = .000). No cases of graft occlusion occurred during first 72 hours after surgery. Although 5 patients (15.6%) died within 90 days, none of the deaths were associated with the vascular grafts. Operative mortality was not statistically different between patients who had received an individual anastomosis (3/18, 16.7%) and those who had received a confluent anastomosis (2/14, 14.3%) (P = 1.000). CONCLUSIONS: Individual and confluent anastomoses using an expanded polytetrafluoroethylene vascular graft is a feasible approach to venous outflow reconstruction in a living-donor liver transplant using right liver grafts without the middle hepatic vein.

Expression of VP1 protein in the milk of transgenic mice: a potential oral vaccine protects against enterovirus 71 infection.

Enterovirus 71 (EV71) is the most common etiological agent detected in cases of hand-foot-and-mouth disease (HFMD) resulting in incidences of neurological complications and fatality in recent years. The clinical data have already shown the significant increase in recent EV71 epidemic activity throughout the Asia-Pacific region. Due to the lack of an effective antiviral agent, primary prevention of the disease, including the development of an effective vaccine, has been the top priority in terms of control strategies. In this study, we first generated a transgenic animal system to produce the EV71 VP1 capsid protein under the control of alpha-lactalbumin promoter and alpha-casein leader sequences. A high level of recombinant VP1 protein (2.51 mg/ml) was expressed and secreted into the milk of transgenic mice. Mouse pups that received VP1-transgenic milk orally demonstrated relatively better health conditions after challenge with the respective virus as compared with the non-transgenic milk fed group; moreover, the mice fed with the VP1-milk had body weights similar to those of the PBS placebo control groups. According to the serum-neutralization assay and serum antibody detection, the littermates suckling VP1-milk generated antibodies specific to EV71. Our data suggest that EV71 VP1-containing milk is suitable for development as a potential oral vaccine.