Derivation of high-purity definitive endoderm from human parthenogenetic stem cells using an in vitro analog of the primitive streak.

Human parthenogenetic stem cells (hpSCs) are pluripotent stem cells with enormous potential as cell sources for cell-based therapies: hpSCs may have histocompatibilty advantages over human embryonic stem cells (hESCs) and derivation of hpSCs does not require viable blastocyst destruction. For translation of all pluripotent stem cell-based therapies, derivation of differentiated cell products that are not contaminated with undifferentiated cells is a major technical roadblock. We report here a novel method to derive high-purity definitive endoderm (DE) from hpSCs, based on reproducing features of the normal human embryonic microenvironment.

Human parthenogenetic stem cells produce enriched populations of definitive endoderm cells after trichostatin A pretreatment.

Human parthenogenetic stem cells (hpSC) hold great promise as a source of pluripotent stem cells for cell-based transplantation therapy due to their ethical method of derivation as well as the enhanced capacity for immunomatching with significant segments of the human population. We report here the directed differentiation of hpSC to produce enriched populations of definitive endoderm. Moreover, we find that treatment of undifferentiated hpSC by trichostatin A (TSA) before applying the directed differentiation protocol significantly increases the proportion of definitive endoderm cells in the final population.

Vitreoretinal surgery assisted by the 193-nm excimer laser.

Purpose: Ablating and cutting vitreoretinal membranes using a 193-nm excimer laser-based microsurgical system.

Methods: A 193-nm microsurgical system enables delivery of the beam into a fluid medium to cut preretinal and subretinal membranes. Two patients with proliferative diabetic retinopathy and one patient with proliferative vitreoretinopathy were treated with this new device.

Dynamics of ArF excimer laser-induced cavitation bubbles in gel surrounded by a liquid medium.

Background And Objective: Cavitation bubbles have been shown to be the driving force of tissue cutting in 193 nm ArF excimer laser-based vitreoretinal microsurgery. In the present work we investigate the dynamics of cavitation bubbles inside a gelatin gel in a saline environment using fast flash microphotography.

Study Design/materials And Methods: The screening influence of the saline medium was found to restrict the maximal distance between the tip and the tissue at which cavitation bubbles are created to < 100 microns at an energy fluence up to 0.

ArF excimer laser-induced bubble formation during irradiation of NaCl solutions.

During application of the 193 nm excimer laser to vitreoretinal surgery, very deep cutting of the retina of about 100 microm/pulse was detected at the energy fluence in the range of 0.25-0.35 J/cm2/pulse.