Radiation-induced non-targeted response in vivo: role of the TGFβ-TGFBR1-COX-2 signalling pathway

Background:

Previous studies from our group and others have shown that cyclooxygenase-2 (COX-2) has an essential role in radiation-induced non-targeted responses and genomic instability in vivo. However, the signalling pathways involved in such effects remain unclear.

Methods:

A 1 cm² area (1 cm × 1 cm) in the lower abdominal region of gpt delta transgenic mice was irradiated with 5 Gy of 300 keV X-rays. Nimesulide, a selective COX-2 inhibitor, was given to mice for five consecutive days before irradiation. Changes in transforming growth factor-beta (TGF-β) and TGF-β receptor type-1 (TGFBR1) mediated signalling pathways, in the out of radiation field lung and liver tissues were examined.

Results:

While the plasma level of cytokines remained unchanged, the expression of TGF-β and its receptors was elevated in non-targeted lung tissues after partial body irradiation. In contrast to the predominant expression of TGF-β in stromal and alveolar cells, but not in bronchial epithelial cells, TGF-β receptors, especially TGFBR1 were significantly elevated in non-targeted bronchial epithelial cells, which is consistent with the induction of COX-2. The different expression levels of TGFBR1 between liver and lung resulted in a tissue specific induction of COX-2 in these two non-targeted tissues. Multiple TGF-β induced signalling pathways were activated in the non-targeted lung tissues.

Conclusion:

The TGFβ-TGFBR1-COX-2 Signalling Pathway has a critical role in radiation-induced non-targeted response in vivo.

Molecular and cellular regulatory mechanisms of tongue myogenesis

The tongue exerts crucial functions in our daily life. However, we know very little about the regulatory mechanisms of mammalian tongue development. In this review, we summarize recent findings of the molecular and cellular mechanisms that control tissue-tissue interactions during tongue morphogenesis. Specifically, cranial neural crest cells (CNCC) lead the initiation of tongue bud formation and contribute to the interstitial connective tissue, which ultimately compartmentalizes tongue muscles and serves as their attachments. Occipital somite-derived cells migrate into the tongue primordium and give rise to muscle cells in the tongue. The intimate relationship between CNCC- and mesoderm-derived cells, as well as growth and transcription factors that have been shown to be crucial for tongue myogenesis, clearly indicate that tissue-tissue interactions play an important role in regulating tongue morphogenesis.

Tgf-beta-mediated FasL-Fas-Caspase pathway is crucial during palatogenesis

Programmed cell death, or apoptosis, is one of the fates of the medial edge epithelium (MEE) during palatal fusion. Transforming growth factor β (Tgf-β) signaling (such as Tgf-β3) is required for the disappearance of the MEE, but the relationship between Tgf-β3 and apoptosis remains unclear. Here we show that the Fas ligand (FasL)-Fas-Caspase extrinsic apoptosis pathway functions during palatal fusion in wild-type mice, but is not detectable in mice lacking Tgf-β3 (Tgf-β3 (-/-) ) or Tgfβr2 in the MEE (K14-Cre;Tgfbr2 (fl/fl)). Inhibition of the FasL-Fas system results in persistence of the midline epithelial seam (MES) and inhibition of caspase activity during palatal organ culture. Moreover, ectopic FasL protein induces apoptosis in MES of K14-Cre;Tgfbr2 (fl/fl) mice. Thus, we conclude that the FasL-Fas-caspase extrinsic apoptosis pathway is regulated by the Tgf-β3 signaling cascade and is essential for palatal fusion during craniofacial development.

The mechanism of TGF-β signaling during palate development

Cleft palate, a malformation of the secondary palate development, is one of the most common human congenital birth defects. Palate formation is a complex process resulting in the separation of the oral and nasal cavities that involves multiple events, including palatal growth, elevation, and fusion. Recent findings show that transforming growth factor beta (TGF-β) signaling plays crucial roles in regulating palate development in both the palatal epithelium and mesenchyme. Here, we highlight recent advances in our understanding of TGF-β signaling during palate development.

Carbon ARC Generation of C60

Generation of C60 at a rate of more than 10 grams per day has been accomplished by operation of a carbon arc in an atmosphere of helium. Optimum yield of 15% was found to occur near 100–200 torr, but yields greater than 3% were found throughout the range between 50 and 760 torr. A model is proposed to explain the observed behavior based on competition between annealing of graphitic sheets to curve so that they minimize dangling bonds, and further rapid growth of these sheets in the gas phase to form giant fullerenes. In agreement with predictions of this model, laser vaporization of graphite targets was found to produce macroscopic quantities of C60 only when performed in an oven above 1000 C.

Uranium stabilization of c28: a tetravalent fullerene

Laser vaporization experiments with graphite in a supersonic cluster beam apparatus indicate that the smallest fullerene to form in substantial abundance is C(28). Although ab initio quantum chemical calculations predict that this cluster will favor a tetrahedral cage structure, it is electronically open shell. Further calculations reveal that C(28) in this structure should behave as a sort of hollow superatom with an effective valence of 4. This tetravalence should be exhibited toward chemical bonding both on the outside and on the inside of the cage. Thus, stable closed-shell derivatives of C(28) with large highest occupied molecular orbital-lowest unoccupied molecular orbital gaps should be attainable either by reacting at the four tetrahedral vertices on the outside of the C(28) cage to make, for example, C(28)H(4), or by trapping a tetravalent atom inside the cage to make endothedral fullerenes such as Ti@C(28). An example of this second, inside route to C(28) stabilization is reported here: the laser and carbon-arc production of U@C(28).

Vision-Related Quality of Life and Emotional Impact in Children with Strabismus: A Prospective Study

The potential impact of the surgical correction of strabismus on vision-related quality of life (VRQOL) and the symptoms of anxiety and depression in children with strabismus remain unclear. The present study included 60 children with strabismus: 30 with heterophoria and 30 with heterotropia. A healthy age-and gender-matched control group ( n = 60) was also recruited. The psychological instruments that were used were the short-form 25-item National Eye Institute Visual Functioning Questionnaire (NEI-VFQ-25) and the Hospital Anxiety and Depression Scale (HADS). The results demonstrated that eight of the 12 NEI-VFQ-25 subscales were significantly impaired in children with strabismus compared with matched controls. Compared with pre-operative values, significant improvements were noted after surgery in the NEI-VFQ-25 summary score, and the anxiety and depression scores. This study demonstrated that the NEI-VFQ-25 instrument can be used in strabismus children and that surgical interventions can improve VRQOL, anxiety and depression in strabismus patients.

Amyloid-beta induces a caspase-mediated cleavage of P2X4 to promote purinotoxicity

Overproduction of the beta-amyloid fragment 1-42 (A beta(1-42)) is thought to contribute to synaptic dysfunction and neuronal death in Alzheimer's disease. Mounting evidence suggests that purinergic receptors play critical roles in synaptic plasticity and neuronal survival, but the potential involvement of these receptors in A beta(1-42)-induced synaptic dysfunction and neuronal death has not been addressed. Here we report that A beta(1-42) promoted accumulation of the calcium-permeable purinergic receptor P2X4 in neurons. We also report evidence that A beta(1-42) induced a caspase-3-mediated cleavage of the receptor that slowed channel closure times and prevented agonist-induced internalization of the receptor. Molecular interference to reduce the expression of P2X4 in primary rodent neurons attenuated A beta(1-42)-induced neuronal death while induced expression of P2X4 in a neuronal cell line that does not normally express P2-receptors enhanced the toxic effect of A beta(1-42). Together these findings suggest that A beta(1-42)-induced synaptic dysfunction and neuronal death may involve perturbations in P2X4 purinergic receptors.

Carbon nanotube thermal interface material for high-brightness light-emitting-diode cooling

Aligned carbon nanotube (CNT) arrays were fabricated from a multilayer catalyst configuration by microwave plasma-enhanced chemical vapor deposition (PECVD). The effects of the thickness and annealing of the aluminum layer on the CNT synthesis and thermal performance were investigated. An experimental study of thermal resistance across the CNT array interface using the modified ASTM D5470 standard was conducted. It was demonstrated that the CNT-thermal interface material (CNT-TIM) reduced the thermal interfacial resistance significantly compared with the state-of-art commercial TIM. The optimized thermal resistance of the CNT arrays is as low as 7 mm(2) K W(-1). The light performance of high-brightness light-emitting diode (HB-LED) packages using the aligned CNT-TIM was tested. The results indicated that the light output power was greatly improved with the use of the CNT-TIM. The usage of the CNT-TIM can be also extended to other microelectronics thermal management applications.

Epithelial fibroblast growth factor receptor 1 regulates enamel formation

The interaction between epithelial and mesenchymal tissues plays a critical role in the development of organs such as teeth, lungs, and hair. During tooth development, fibroblast growth factor (FGF) signaling is critical for regulating reciprocal epithelial and mesenchymal interactions. FGF signaling requires FGF ligands and their receptors (FGFRs). In this study, we investigated the role of epithelial FGF signaling in tooth development, using the Cre-loxp system to create tissue-specific inactivation of Fgfr1 in mice. In K14-Cre;Fgfr1(fl/fl) mice, the apical sides of enamel-secreting ameloblasts failed to adhere properly to each other, although ameloblast differentiation was unaffected at early stages. Prior to eruption, enamel structure was compromised in the K14-Cre;Fgfr1(fl/fl) mice and displayed severe enamel defects that mimic amelogenesis imperfecta (AI), with a rough, irregular enamel surface. These results suggest that there is a cell-autonomous requirement for FGF signaling in the dental epithelium during enamel formation. Loss of Fgfr1 affects ameloblast organization at the enamel-secretory stage and, hence, the formation of enamel.

TGF-beta receptor II in epithelia versus mesenchyme plays distinct roles in the developing lung

Transforming growth factor (TGF)-beta signalling plays important roles in regulating lung development. However, the specific regulatory functions of TGF-beta signalling in developing lung epithelial versus mesenchymal cells are still unknown. By immunostaining, the expression pattern of the TGF-beta type II receptor (TbetaRII) was first determined in the developing mouse lung. The functions of TbetaRII in developing lung were then determined by conditionally knocking out TbetaRII in the lung epithelium of floxed-TbetaRII/surfactant protein C-reverse tetracycline transactivator/TetO-Cre mice versus mesenchyme of floxed-TbetaRII/Dermo1-Cre mice. TbetaRII was expressed only in distal airway epithelium at early gestation (embryonic day (E)11.5), but in both airway epithelium and mesenchyme from mid-gestation (E14.5) to post-natal day 14. Abrogation of TbetaRII in mouse lung epithelium resulted in retardation of post-natal lung alveolarisation, with markedly decreased type I alveolar epithelial cells, while no abnormality in prenatal lung development was observed. In contrast, blockade of TbetaRII in mesoderm-derived tissues, including lung mesenchyme, resulted in mildly abnormal lung branching and reduced cell proliferation after mid-gestation, accompanied by multiple defects in other organs, including diaphragmatic hernia. The primary lung branching defect was verified in embryonic lung explant culture. The novel findings of the present study suggest that transforming growth factor-beta type II receptor-mediated transforming growth factor-beta signalling plays distinct roles in lung epithelium versus mesenchyme to differentially control specific stages of lung development.

Functional modulation of the ATP-sensitive potassium channel by extracellular signal-regulated kinase-mediated phosphorylation

ATP-sensitive potassium (K(ATP)) channels play an important role in controlling insulin secretion and vascular tone as well as protecting neurons under metabolic stress. We have previously demonstrated that stimulation of the K(ATP) channel by nitric oxide (NO) requires activation of Ras- and extracellular signal-regulated kinase (ERK) of the mitogen-activated protein kinase (MAPK) family. However, the mechanistic link between ERK and the K(atp) channel remained unknown. To investigate how ERK modulates the function of K(ATP) channels, we performed single-channel recordings in combination with site-directed mutagenesis. The Kir6.2/SUR1 channel, a neuronal K(ATP) channel isoform, was expressed in human embryonic kidney (HEK) 293 cells by transient transfection. Direct application of the activated ERK2 to the cytoplasmic surface of excised, inside-out patches markedly enhanced the single-channel activity of Kir6.2/SUR1 channels. The normalized open probability (NPo) and opening frequency were significantly increased, whereas the mean closed duration was reduced. The single-channel conductance level was not affected. The ERK2-induced stimulation of Kir6.2/SUR1 channels was prevented by heat-inactivation of the enzyme. Furthermore, alanine substitutions of T341 and S385 to disrupt the potential ERK phosphorylation sites present in the Kir6.2 subunit significantly abrogated the stimulatory effects of ERK2, while aspartate substitutions of T341 and S385 to mimic the (negative) charge effect of phosphorylation rendered a small yet significant reduction in the ATP sensitivity of the channel. Taken together, here we report for the first time that ERK2/MAPK activates neuronal-type K(ATP) channels, and this stimulation requires ERK phosphorylation of the Kir6.2 subunit at T341 and S385 residues. The ERK2-induced K(ATP) channel stimulation can be accounted for by changes in channel gating that destabilize the closed states and by reduction in the ATP sensitivity. As Kir6.2 is the pore-forming subunit of K(ATP) channels, ERK2-mediated phosphorylation may represent a common mechanism for K(ATP) channel regulation in different tissues.

Gate voltage dependent characteristics of p-n diodes and bipolar transistors based on multiwall CN(x)/carbon nanotube intramolecular junctions

The electrical transport characteristics of multiwall CN(x)/carbon nanotube intramolecular junctions were studied. The junctions could be used as diodes. We found that the rectification resulted from p-n junctions, not from metal-semiconductor junctions. The gate effect was very weak when the diodes were reverse biased. At forward bias, however, some of the p-n diodes could be n-type transistors. Experimental results supported the opinion that the gate voltage dependent property is derived from the Schottky barrier between the CN(x) part and the electrode. Using p-n diodes, a bipolar transistor with nanoscale components was built, whose behavior was very similar to that of a conventional planar bipolar transistor.

Nanodiode based on a multiwall CN(x)/carbon nanotube intramolecular junction

We prepared multiwall carbon nanotubes (MWCNTs) from the pyrolysis of ferrocene, and CN(x) nanotubes from a mixture of ferrocene and melamine. Under well chosen synthesis conditions, massive multiwall CN(x)/carbon nanotube intramolecular junctions were successfully fabricated. The individual nanotubes were used as conductance channels to obtain their transport characteristic information. Measurement results showed that the current-voltage (I-V) curve of the CN(x)/CNT junction is highly asymmetric, behaving like a diode. Moreover, the devices are very stable in ambient environment. We attribute this nonlinear property of the CN(x)/CNT junctions to their two different atomic and electronic sections.

[Identification and characterization of differentially expressed ESTs of Gossypium barbadense infected by Verticillium dahliae with suppression subtractive hybridization]

Cotton wilt defense reaction is a complicated continuous process and involves a battery of genes. In this study, we adopted suppression subtractive hybridization (SSH) technique to isolate differentially expressed ESTs from Gossypium barbadense variety 7124 during Verticillium wilt defense process. An array of 1165 clones from the subtractive library has been screened with reverse northern blotting, of which 131 ESTs were considered as over-expressed and 16 ESTs were down-regulated. Sequence analysis and blast search showed that 83 ESTs were homologous to 45 unique sequences in the databases. Among all these differentially expressed ESTs, at least three kinds of genes were characterized. The majority of ESTs with deduced identity to aerobic metabolism enzymes strongly expressed in the infection process. Likewise, ESTs similar to those reported for pathogen-related protein genes were also picked out in this study. These ESTs in combination with other kinase-like genes and a defensin-like EST constituted an assembly of genes responded during pathogens' infection. These results imply that sea-island cotton undergoes strong oxidative stress and results in a series of defense responses when attacked by V. dahliae. To our knowledge, this is the first report on the isolation of global ESTs during sea-island cotton defense reaction.

TGF-beta signaling and its functional significance in regulating the fate of cranial neural crest cells

Members of the transforming growth factor-beta (TGF-beta) superfamily regulate cell proliferation, differentiation, and apoptosis, and control the development and maintenance of most tissues. TGF-beta signal is transmitted through the phosphorylation of Smad proteins by TGF-beta receptor serine/threonine kinase. During craniofacial development, TGF-beta may regulate the fate specification of cranial neural crest cells. These cells are multipotent progenitors and capable of producing diverse cell types upon differentiation. Here we summarize evidence that TGF-beta ligands and their signaling intermediates have significant roles in patterning and specification of cranial neural crest cells. The biological function of TGF-beta is carried out through the regulation of transcriptional factors during embryogenesis.