Give a shell a break

Sall4 won’t give stem cells a break

A protein that helps embryonic stem cells (ESCs) retain their identity also induces the cells to repair DNA damage, Xiong et al. report. Fixing broken DNA is particularly important for ESCs because they pass on any mutations to their differentiated descendants. Mouse ESCs are adept at making repairs—they carry far fewer mutations than do differentiated cells—but how they achieve this isn’t clea...

Immortal Strands? Give Me a Break

The "immortal strand" hypothesis proposes that asymmetrically dividing stem cells selectively retain chromosomes containing "old" DNA to prevent accumulation of mutations. As I describe in this Essay, such a possibility seems unlikely. An alternative explanation is that asymmetric cell divisions and cell fate are codirected by epigenetic differences between sister chromatids.

Fetal dendritic cells give mum a break.

Give me a break: how telomeres suppress the DNA damage response.

Linear organization of the genome requires mechanisms to protect and replicate chromosome ends. To this end eukaryotic cells evolved telomeres, specialized nucleoproteic complexes, and telomerase, the enzyme that maintains the telomeric DNA. Telomeres allow cells to distinguish chromosome ends from sites of DNA damage. In mammalian cells this is accomplished by a protein complex, termed shelter...

Dynamic stress concentration in a hybrid composite laminate subjected to a sudden internal break

In this work, transient dynamic stress concentration in a hybrid composite laminate subjected to a sudden internal crack is examined. It is assumed that all fibers lie in one direction and the applied load acts along direction of fibers. Two types arrangements are considered for the fiber; square and hexagonal arrangement. Using shear lag model, equilibrium equations are deduced and upon proper...