Iron pnictides as a new setting for quantum criticality

Two major themes in the physics of condensed matter are quantum critical phenomena and unconventional superconductivity. These usually occur in the context of competing interactions in systems of strongly correlated electrons. All this interesting physics comes together in the behavior of the recently discovered iron pnictide compounds that have generated enormous interest because of their moderately high-temperature superconductivity. The ubiquity of antiferromagnetic ordering in their phase diagrams naturally raises the question of the relevance of magnetic quantum criticality, but the answer remains uncertain both theoretically and experimentally. Here, we show that the undoped iron pnictides feature a unique type of magnetic quantum critical point, which results from a competition between electronic localization and itinerancy. Our theory provides a mechanism to understand the experimentally observed variation of the ordered moment among the undoped iron pnictides. We suggest P substitution for As in the undoped iron pnictides as a means to access this example of magnetic quantum criticality in an unmasked fashion. Our findings point to the iron pnictides as a much-needed setting for quantum criticality, one that offers a unique set of control parameters.

Production of cloned miniature pigs by enucleation using the spindle view system

Porcine somatic cell nuclear transfer (NT) has been successfully performed, but its efficiency remains quite low. In this study, we improvised on the enucleation method to enhance the development of NT embryos. Initially, an experiment was performed to determine the location relationship between the metaphase plate and the first polar body, where the results showed that the metaphase plate may frequently be displaced during the varying period of maturation process. When the metaphase plates were removed using the 'blind' enucleation method, the enucleation rate was affected by the maturation time; however, when the spindle view system was used, an enucleation rate of 100% was achieved. In the next experiment, these two methods were used to construct embryos: the fusion efficiency was significantly higher (p < 0.01) in the spindle view system group and the development rates of the reconstructed embryos were significantly higher in the spindle view system group compared with the 'blind' enucleation group (p < 0.01). An average of 174 (141-210) cloned embryos from the spindle view system group were transferred into five surrogate pigs and one piglet was delivered at 114 days after embryo transfer by caesarean section. DNA analysis confirmed that the piglet was genetically identical to the male donor pig. We showed that enucleation by the spindle view system is the another new technique compare the handmade cloning method [Theriogenology 2007: 68, 1104] to promote the development of the reconstructed embryos, and that a full-term cloned pig could be produced using this method.

Testing the druggable endothelial differentiation gene 2 knee osteoarthritis genetic factor for replication in a wide range of sample collections

OBJECTIVES

To replicate a previously reported association with osteoarthritis (OA) of the promoter single nucleotide polymorphism (SNP) rs10980705 in the endothelial differentiation gene 2 (EDG2).

METHODS

Five collections of samples, four from Europe and one from China, were studied. They included patients with 3 OA phenotypes: 1501 with knee OA, 1497 with hip OA and 376 with generalised OA. A total of 2521 controls were also studied. Allele and genotype frequencies of the rs10980705 SNP were analysed in each individual sample collection and in pooled data. In addition, a meta-analysis to incorporate results from the original Japanese report was performed.

RESULTS

The association of the rs10980705 SNP with knee OA was not replicated in any of the five sample collections studied or in their combined analysis (odds ratio (OR) 1.10, 95% CI 0.98 to 1.22; p = 0.10). Meta-analysis of all data, including the original Japanese study, did show association with knee OA (OR 1.15, 95% CI 1.06 to 1.26; p = 0.002) but the effect was accounted for by the Japanese data and was less significant than the original report. No association was found with hip OA or with generalised OA.

CONCLUSIONS

The original report of a promising genetic association between a druggable G-protein coupled receptor, EDG2, and knee OA has not been replicated. This lack of replication could be due to a modest effect of the promoter polymorphism that will require even larger studies (the winners curse) although a more pronounced effect in the Asian population vs Europeans cannot be excluded.

Medical physics aspects of cancer care in the Asia Pacific region

Medical physics plays an essential role in modern medicine. This is particularly evident in cancer care where medical physicists are involved in radiotherapy treatment planning and quality assurance as well as in imaging and radiation protection. Due to the large variety of tasks and interests, medical physics is often subdivided into specialties such as radiology, nuclear medicine and radiation oncology medical physics. However, even within their specialty, the role of radiation oncology medical physicists (ROMPs) is diverse and varies between different societies. Therefore, a questionnaire was sent to leading medical physicists in most countries/areas in the Asia/Pacific region to determine the education, role and status of medical physicists.Answers were received from 17 countries/areas representing nearly 2800 radiation oncology medical physicists. There was general agreement that medical physicists should have both academic (typically at MSc level) and clinical (typically at least 2 years) training. ROMPs spent most of their time working in radiotherapy treatment planning (average 17 hours per week); however radiation protection and engineering tasks were also common. Typically, only physicists in large centres are involved in research and teaching. Most respondents thought that the workload of physicists was high, with more than 500 patients per year per physicist, less than one ROMP per two oncologists being the norm, and on average, one megavoltage treatment unit per medical physicist.There was also a clear indication of increased complexity of technology in the region with many countries/areas reporting to have installed helical tomotherapy, IMRT (Intensity Modulated Radiation Therapy), IGRT (Image Guided Radiation Therapy), Gamma-knife and Cyber-knife units. This and the continued workload from brachytherapy will require growing expertise and numbers in the medical physics workforce. Addressing these needs will be an important challenge for the future.

Olfactory ensheathing cells promote proliferation and inhibit neuronal differentiation of neural progenitor cells through activation of Notch signaling

A population of neural progenitor cells (NPCs) has been known to exist in adult spinal cord and migrate toward the lesion regions during spinal cord injury (SCI). Although there are some positive effects of the transplanted olfactory ensheathing cells (OECs) on axonal regeneration in SCI, little is known about the effects and the underlying mechanism of these grafted OECs on NPCs. In this study, we have investigated how soluble factors derived from rat OECs regulate the proliferation and differentiation of rat NPCs. The conditioned medium from cultured OECs showed its ability to promote proliferation and inhibit neuronal differentiation of NPCs. Notch signaling was apparently involved in this process. With the addition of DAPT, which inhibited Notch signaling, the effects of OEC-conditioned medium on NPCs were blocked. We thus conclude that diffusible factors released from OECs activate the Notch signaling pathway to stimulate the proliferation and suppress neuronal differentiation of NPCs. These findings reveal the likely limitation of using OECs transplantation for SCI repair.

Rigorous solution of the spin-1 quantum Ising model with single-ion anisotropy

We solve the spin-1 quantum Ising model with single-ion anisotropy by mapping it onto a series of segmented spin-1/2 transverse Ising chains, separated by the S(z)=0 states called holes. A recursion formula is derived for the partition function to simplify the summation of hole configurations. This allows the thermodynamic quantities of this model to be rigorously determined in the thermodynamic limit. The low temperature behavior is governed by the interplay between the hole excitations and the fermionic excitations within each spin-1/2 Ising segment. The quantum critical fluctuations around the Ising critical point of the transverse Ising model are strongly suppressed by the hole excitations.

VEGF: an essential mediator of both angiogenesis and endochondral ossification

During bone growth, development, and remodeling, angiogenesis as well as osteogenesis are closely associated processes, sharing some essential mediators. Vascular endothelial growth factor (VEGF) was initially recognized as the best-characterized endothelial-specific growth factor, which increased vascular permeability and angiogenesis, and it is now apparent that this cytokine regulates multiple biological functions in the endochondral ossification of mandibular condylar growth, as well as long bone formation. The complexity of VEGF biology is paralleled by the emerging complexity of interactions between VEGF ligands and their receptors. This narrative review summarizes the family of VEGF-related molecules, including 7 mammalian members, namely, VEGF, placenta growth factor (PLGF), and VEGF-B, -C, -D, -E, and -F. The biological functions of VEGF are mediated by at least 3 corresponding receptors: VEGFR-1/Flt-1, VEGFR-2/Flk-1, VEGFR-3/Flt-4 and 2 co-receptors of neuropilin (NRP) and heparan sulfate proteoglycans (HSPGs). Current findings on endochondral ossification are also discussed, with emphasis on VEGF-A action in osteoblasts, chondroblasts, and chondroclasts/osteoclasts and regulatory mechanisms involving oxygen tension, and some growth factors and hormones. Furthermore, the therapeutic implications of recombinant VEGF-A protein therapy and VEGF-A gene therapy are evaluated. Abbreviations used: VEGF, Vascular endothelial growth factor; PLGF, placenta growth factor; NRP, neuropilin; HSPGs, heparan sulfate proteoglycans; FGF, fibroblast growth factor; TGF, transforming growth factor; HGF, hepatocyte growth factor; TNF, tumor necrosis factor; ECM, extracellular matrix; RTKs, receptor tyrosine kinases; ERK, extracellular signal kinases; HIF, hypoxia-inducible factor.

Recombinant AAV-mediated VEGF gene therapy induces mandibular condylar growth

Craniofacial anomalies resulting from impaired growth of mandibular condyles require multidisciplinary interventions, which impose a substantial burden on patients and their families. So far, correcting such deformities with an alternative strategy - gene therapy - is still an uncharted territory. Here, we established an effective in vivo gene delivery system with recombinant adeno-associated virus (rAAV)-mediated vascular endothelial growth factor (VEGF) to enhance mandibular condylar growth. With in situ hybridization, RT-PCR, immunostaining and Western blot, transgene expression was clearly detected in the mandibular condyles during the whole experiment periods. At defined time points, specific osteogenetic markers (alkaline phosphatase and osteocalcin) and chondrogenetic markers (collagen type II and collagen type X) were assessed by means of biochemical analysis and their expression significantly changed from day 30. Proliferation index by proliferating cell nuclear antigen staining showed also a significant increase in cell proliferation. Morphological measurement identified that the size of mandibular condyle significantly increased from day 30. Taken together, rAAV-VEGF was successfully established as an efficient delivery system to induce mandibular condylar growth, which provides the basis for future gene therapy to treat patients with craniofacial deformities.

A study on Notch signaling in human breast cancer

Breast cancer is one of the leading causes of cancer death in women. The Notch family of proteins plays crucial roles in determining cell fates such as proliferation, differentiation and apoptosis. A role for Notch signaling in human breast cancer has been suggested by the development of adenocarcinomas in the murine mammary gland. However, it is not clear currently whether Notch signaling is frequently expressed and activated in breast cancers. Here we show that Notch signaling is overexpressed and highly activated in breast cancers. More significantly, the attenuation of Notch signaling by gamma-secretase inhibitor can inhibit the proliferation of breast cancer cells by both causing cell cycle arrest and apoptosis. Thus, targeting Notch signaling may be of therapeutic value in breast cancers.

Identification of three FGA mutations in two Chinese families with congenital afibrinogenaemia

Congenital afibrinogenaemia is a rare autosomal recessive disorder, characterized by the complete absence or extremely reduced level of fibrinogen (Fg). We attempted to analyse the phenotype and genotype in two Chinese families with congenital afibrinogenaemia. Coagulation studies including activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT) and Fg were performed in the patients and other family members. All the exons, exon-intron boundaries and promoter regions of three Fg genes (FGA, FGB and FGG) were screened by direct sequencing. Three patients in two families suffered from moderate to severe haemorrhage. Their APTT, PT and TT were extremely prolonged and plasma Fg levels were undetectable by Clauss method and extremely reduced by immunoassay. Genetic analysis revealed three FGA mutations in three patients including one novel mutation. In family 1, patient 1 was detected compound heterozygous mutations in FGA, g.1892-1899delAGTA/GTAA from her patriline and g.1978-g.3215del1238 bp from her matriline. In family 2, a homozygous Gln203X in Aalpha-chain was found in both patients 2 and 3 due to consanguineous marriage. All these mutations were null mutations, which could produce premature stop codons in FGA. It can be indicated that with more genetic analysis performed on afibrinogenaemia patients all over the world, there is no distinct difference in geographical distribution of Fg gene mutations. Gln203X in Aalpha-chain was first reported in this study, which may help to further understand the function of Aalpha-chain.