A human embryonic stem cell is reined in – prevented from giving up its unique characteristics of self-renewal and pluripotency – by the presence of a protein modification that stifles any genes that would prematurely instruct the cell to develop into heart or other specialized tissue. But, thanks to the simultaneous presence of different protein modifications, stem cells are primed and poised, ready to develop into specialized body tissue, Singapore scientists report.

The molecules central to this balancing act, H3K4me3 and H3K27me3, are among the so-called epigenetic modifications that influence the activity patterns of genes in both human embryonic stem (ES) cells and mature human adult cells.

Quantum dots have great promise as light-emitting materials, because the wavelength, or color, of light that the quantum dots give off can be very widely tuned simply by changing the size of the nanoparticles. If a single dot is observed under a microscope, it can be seen to randomly switch between bright and dark states. This flickering, or blinking, behavior has been widely studied, and it has been found that a single dot can blink off for times that can vary between microseconds and several minutes. The causes of the blinking, though, remain the subject of intense study.

In order to learn more about the origins of quantum dot blinking, researchers from the U.S.

two closely related bird species, the collared flycatcher and the pied flycatcher, can reproduce with each other, but the females are more strongly attracted to a male of their own species. This has been shown by an international research team directed by Anna Qvarnström at Uppsala University in today’s Net edition of Science. They demonstrate that the gene for this sexual preference is found on the sex chromosome that is inherited from the father and that only females have a copy of. The discovery sheds new light on how new species are formed.

The formation of new species takes millions of years. It often happens when a population (group of individuals) is divided and separated geographically and then adapts to disparate environments over thousands of generations.

Urologists at Thomas Jefferson University Hospital are studying whether a neo-bladder construct grown from a patient’s own cells can improve bladder function for adult spinal cord injury patients.

Jefferson is only one of six sites in the U.S. enrolling participants in this clinical trial for the lab-grown neo-bladder construct that will involve a total of 10 patients.

“It’s never been done in adults before,” said primary investigator Patrick Shenot, M.D., instructor in Urology, Jefferson Medical College of Thomas Jefferson University, noting that a similar study is being conducted with children with spina bifida.

In a report this week in Cell, researchers have identified a biological basis for why events that happen during heightened states of emotion such as fear, anger and joy are more memorable than less dramatic occurrences: a hormone released during emotional arousal “primes” nerve cells to remember events by increasing their chemical sensitivity at sites where nerves rewire to form new memory circuits.

'Word of mouth' advertising is valuable because marketing groups know that opinions of friends and associates count more than the paid endorsements of strangers. But what kind of opinions matter most? It turns out the negative ones do, even if someone had privately had a positive impression prior to the negative input.

“Consumer attitudes toward products and services are frequently influenced by others around them. Social networks, such as those found on Myspace and Facebook suggest that these influences will continue to be significant drivers of individual consumer attitudes as society becomes more inter-connected,” explain Adam Duhachek, Shuoyang Zhang, and Shanker Krishnan of Indiana University in a Journal of Consumer Research report.