The tumor suppressor p53 contributes to maintaining genome stability by inducing a cell cycle arrest or apoptosis in response to conditions that generate DNA damage. Nuclear injection of linearized plasmid DNA, circular DNA with a large gap, or single-stranded circular phagemid is sufficient to induce a p53-dependent arrest. Supercoiled and nicked plasmid DNA, and circular DNA with a small gap were ineffective. Titration experiments indicate that the arrest mechanism in normal human fibroblasts can be activated by very few double strand breaks, and only one may be sufficient.Polymerase chain reaction assays showed that end-joining activity is low in serum-arrested human fibroblasts, and that higher joining activity occurs as cells proceed through G, or into S phase. We propose that the exquisite sensitivity of the p53-dependent G1 arrest is partly due to inefficient repair of certain types of DNA damage in early G1.Normal cells evolve into cancers by a process of clonal evolution involving the accumulation of multiple genetic alterations. Many of these changes are initiated by chromosome breakage. Through induction of apoptosis or cell cycle arrest, a p53-dependent mechanism effectively prevents DNA damage present in G, from being replicated in S phase (1-6). As DNA breakage is likely to be the first step in the process of generating gene amplification, translocations, and deletions, it is understandable why cells with an intact p53 pathway do not produce descendants with such alterations at experimentally measurable rates (7-9). In contrast, inactivation of p53 alone allows immortalized nontumorigenic cells and primary fibroblasts to cycle in the presence of chromosome breaks and to undergo gene amplification at high rates (4, 10, 11). It is not surprising, therefore, that loss of p53 function is highly selected during cancer progression, and that defects in the p53 gene occur in more than 50% of human cancers (12).The specific signals that induce p53-dependent G1 arrest remain to be elucidated. Previous studies showed that ultraviolet light, ionizing radiation, and a variety of chemotherapeutic agents increase p53 levels (3,4,13,14) and alter expression of p53 responsive genes (3,(15)(16)(17)

Pluripotent or multipotent stem cells isolated from human embryos or adult central nervous system (CNS) may provide new neurons to ameliorate neural disorders. A major obstacle, however, is that the majority of such cells do not differentiate into neurons when grafted into non-neurogenic areas of the adult CNS. Here we report a new in vitro priming procedure that generates a nearly pure population of neurons from fetal human neural stem cells (hNSCs) transplanted into adult rat CNS. Furthermore, the grafted cells differentiated by acquiring a cholinergic phenotype in a region-specific manner. This technology may advance stem cell-based therapy to replace lost neurons in neural injury or neurodegenerative disorders.

Sensitization of purinergic P2X receptors is one of the mechanisms responsible for exaggerated pain responses to inflammatory injuries. Prostaglandin E2 (PGE2), produced by inflamed tissues, is known to contribute to abnormal pain states. In a previous study, we showed that PGE2 increases fast inactivating ATP currents that are mediated by homomeric P2X3 receptors in dorsal root ganglion (DRG) neurons isolated from normal rats. Protein kinase A (PKA) is the signalling pathway used by PGE2. Little is known about the action of PGE2 on ATP currents after inflammation, although the information is crucial for understanding the mechanisms underlying inflammation-induced sensitization of P2X receptors. We therefore studied the effects of PGE2 on P2X3 receptor-mediated ATP currents in DRG neurons dissociated from complete Freund's adjuvant (CFA)-induced inflamed rats. We found that PGE2 produces a large increase in ATP currents. PKCε, in addition to PKA, becomes involved in the modulatory action of PGE2. Thus, PGE2 signalling switches from a solely PKA-dependent pathway under normal conditions to both PKA-and PKC-dependent pathways after inflammation. Studying the mechanisms underlying the switch, we demonstrated that cAMP-responsive guanine nucleotide exchange factor 1 (Epac1) is up-regulated after inflammation. The Epac agonist CPT-OMe mimics the potentiating effect of PGE2 and occludes the PKC-mediated PGE2 action on ATP currents. These results suggest that Epac plays a critical role in P2X3 sensitization by activation of de novo PKC-dependent signalling of PGE2 after inflammation and would be a useful therapeutic target for pain therapies.

Starch is a vital energy source for living organisms and is a key raw material and additive in the food and non-food industries. Starch has received continuous attention in multiple research fields. The endosperm of cereals (e.g., rice, corn, wheat, and barley) is the most important site for the synthesis of storage starch. Around 2010, several excellent reviews summarized key progress in various fields of starch research, serving as important references for subsequent research. In the past 10 years, many achievements have been made in the study of starch synthesis and regulation in cereals. The present review provides an update on research progress in starch synthesis of cereal endosperms over the past decade, focusing on new enzymes and non-enzymatic proteins involved in starch synthesis, regulatory networks of starch synthesis, and the use of elite alleles of starch synthesis-related genes in cereal breeding programs. We also provide perspectives on future research directions that will further our understanding of cereal starch biosynthesis and regulation to support the rational design of ideal quality grain.

BackgroundDiabetic neuropathy is a common neuropathy associated with paresthaesia and pain. The mechanisms underlying the painful conditions are not well understood. The aim of this study is to investigate the participation of purinergic P2X3 receptors in painful diabetic neuropathy.ResultsDiabetes was induced by an intraperitoneal injection of streptozotocin (STZ). We showed that mechanical allodynia was induced two weeks after a STZ injection and lasted for at least another seven weeks. The mechanical allodynia was significantly attenuated by peripheral administration of the P2X receptor antagonists, PPADS or TNP-ATP. DiI was subcutaneously injected into the rat hindpaw to label hindpaw-innervated dorsal root ganglion (DRG) neurons. ATP activated fast-inactivating P2X3 receptor-mediated currents in the labeled DRG neurons were studied. ATP responses in STZ-treated rats were ~2-fold larger than those in control rats. Furthermore, the expression of P2X3 receptor proteins in the plasma membrane of L4-6 DRGs of STZ rats was significantly enhanced while the total expression of P2X3 receptors remained unaltered.ConclusionsThese results indicate that a large enhancement of P2X3 receptor activity and an increase in the membrane expression of P2X3 receptors contribute to the development of chronic pain in STZ-induced diabetic rats and suggest a possible target for the treatment of diabetic neuropathic pain.