A microPET/CT system for in vivo small animal imaging

A microCT scanner was designed, fabricated and integrated with a previously reported microPET II scanner (Tai et al 2003 Phys. Med. Biol. 48 1519, Yang et al 2004 Phys. Med. Biol. 49 2527), forming a dual modality system for in vivo anatomic and molecular imaging of the mouse. The system was designed to achieve high-spatial-resolution and high-sensitivity PET images with adequate CT image quality for anatomic localization and attenuation correction with low x-ray dose. The system also has relatively high throughput for screening, and a flexible gantry and user interface. X-rays were produced by a 50 kVp, 1.5 mA fixed tungsten anode tube, with a focal spot size of 70 microm. The detector was a 5 x 5 cm(2) photodiode detector incorporating 48 microm pixels on a CMOS array and a fast gadolinium oxysulfide (GOS) intensifying screen. The microCT system has a flexible C-arm gantry design with adjustable detector positioning, which acquires CT projection images around the common microPET/CT bed. The design and the initial characterization of the microCT system is described, and images of the first mouse scans with microPET/CT scanning protocols are shown.

First-principles investigations of the pressure-induced structural transitions in Mg(AlH(4))(2)

A systematic investigation is presented of the high-pressure structural stability of Mg(AlH(4))(2) using a plane-wave pseudo-potential method. The total-energy calculations show that under ambient pressure the structure of α-Mg(AlH(4))(2) found by experiments is more stable than the other proposed structures, and with pressure increasing the α to β (δ-Zr(MoO(4))(2)-type structure) and β to γ (Ca(BF(4))(2)-type structure) transitions occur at 0.67 and 10.28 GPa respectively, accompanied with volume reductions of 6.6% and 8.7%. A detailed study of the electronic structures reveals the bonding characteristics between Al and H and between Mg and H as well as the nonmetallic features of α, β, and γ phases under pressure of up to 20.0 GPa. Their electronic structures are mainly responsible for the relative high-pressure stability of the three phases. Finally, an analysis of their structural relations indicates that it is possible to produce the [Formula: see text] structural transition by applying pressure.

Tumor progression in Apc(1638N) mice with Exo1 and Fen1 deficiencies

Flap endonuclease 1 (Fen1) and exonuclease 1 (Exo1) have sequence homology and similar nuclease capabilities. Both function in multiple pathways of DNA metabolism, but appear to have distinct in vivo nucleic acid substrates, and therefore distinct metabolic roles. When combined with Apc(1638N), Fen1 promotes tumor progression. Because of functional similarity to Fen1, and because Exo1 is involved in DNA mismatch repair (MMR) by interaction with Msh2 and Mlh1, genes that cause hereditary nonpolyposis colorectal cancer (HNPCC), we investigated the possibility that Exo1 might also act as a modifier to Apc(1638N). We present evidence that mice with combined mutations in Apc(1638N) and Exo1 and Apc(1638N), Exo1 and Fen1 genes show moderate increased tumor incidence and multiplicity in comparison to Apc(1638N) siblings, implying a low penetrance role for Exo1 in early gastrointestinal (GI) tumorigenesis. Despite a decrease in median survival (10 months) in Apc(1638N) Exo1 mice, their tumors do not progress any more rapidly than those of Apc(1638N). Instead these animals die from infections that are the result of impaired immune response. Apc(1638N) Exo1 Fen1 mice survive longer (18 months), and therefore appear relatively immune competent. They die of invasive GI tumors that display microsatellite instability (MSI). Our results show that Exo1 has a modest tumor suppressor function.

High-energy scale revival and giant kink in the dispersion of a cuprate superconductor

In the present photoemission study of a cuprate superconductor Bi1.74Pb0.38Sr1.88CuO6+delta, we discovered a large scale dispersion of the lowest band, which unexpectedly follows the band structure calculation very well. Similar behavior observed in blue bronze and the Mott insulator Ca2CuO2Cl2 suggests that the origin of hopping-dominated dispersion in an overdoped cuprate might be quite complicated. A giant kink in the dispersion is observed, and the complete self-energy containing all interaction information is extracted for a doped cuprate. These results recovered significant missing pieces in our current understanding of the electronic structure of cuprates.

Inelastic x-ray scattering study of exciton properties in an organic molecular crystal

Excitons in a complex organic molecular crystal were studied by inelastic x-ray scattering (IXS) for the first time. The dynamic dielectric response function is measured over a large momentum transfer region, from which an exciton dispersion of 130 meV is observed. Semiempirical quantum chemical calculations reproduce well the momentum dependence of the measured dynamic dielectric responses, and thus unambiguously indicate that the lowest Frenkel exciton is confined within a fraction of the complex molecule. Our results demonstrate that IXS is a powerful tool for studying excitons in complex organic molecular systems. Besides the energy position, the IXS spectra provide a stringent test on the validity of the theoretically calculated exciton wave functions.

Potent antitumor efficacy of XAF1 delivered by conditionally replicative adenovirus vector via caspase-independent apoptosis

XAF1 is a newly identified tumor-suppressor gene that can antagonize XIAP and sensitize cells to other cell death triggers. In this study, we utilized ZD55, a conditionally replicative adenovirus (CRAd) similar to ONYX-015 as the vector to transfer XAF1 into the tumor cells to evaluate its antitumor efficacy in vitro and in vivo. Potent and specific cytopathic effect (CPE) was observed upon infection with ZD55-XAF1 in tumor cell lines. Importantly, ZD55-XAF1 exhibited a superior suppression of tumor growth in an animal model of colorectal carcinoma in nude mice compared with Ad-XAF1 (E1-deleted replication-defective viral) and ONYX-015. Complete eradication of the established tumors was observed in four of eight mice. Our data also showed that infection with ZD55-XAF1 resulted in caspase-independent apoptosis. Although caspase-3, poly(ADP-ribose) polymerase were mildly activated in response to ZD55-XAF1 infection, pretreatment with pan-caspase inhibitor hardly influence its apoptosis-inducing activity. In summary, our study strongly suggested that ZD55-XAF1 could serve as an effective gene-virotherapy strategy and has highly potential against human cancers.

Cloning and Expression of Human Stem Cell Factor Fused with Thrombopoietin Mimetic Peptide in Escherichia coli

Thrombopoietin (TPO) acts synergistically with stem cell factor (SCF) in hematopoiesis and megakaryopoiesis. In this work, we designed the expression of SCF fused with the monomer or the dimer of TPO mimetic peptide through a flexible peptide linker. The recombinant fusion proteins were produced in E. coli DH5alpha at up to 25% of total cell proteins. The resultant inclusion bodies were refolded by dilution and purified by ion-exchange chromatography. Subsequent biological activity assays showed that the fusion proteins exhibited higher potency than recombinant human SCF, indicating that they have a potential role for pharmaceutical applications.

The effect of bi-level positive airway pressure mechanical ventilation on gas exchange during general anaesthesia

BACKGROUND

Atelectasis may occur and ventilation-perfusion mismatch may increase during general anaesthesia with neuromuscular paralysis and mechanical ventilation, though preservation of some intermittent muscle contraction might mitigate this process. There is still no ideal manoeuvre to minimize such mismatch or atelectasis. Bi-level positive airway pressure (BiPAP) ventilation adjusts to extra breaths and improves gas exchange during recovery of diaphragm function after neuromuscular paralysis. We hypothesize that BiPAP ventilation may limit the development of pulmonary shunt and may improve ventilation-perfusion mismatch when compared with standard IPPV, with or without PEEP when neuromuscular paralysis has been used during surgery.

METHODS

Twenty ventilated patients either on BiPAP or IPPV with or without PEEP were studied randomly using the multiple inert gas elimination technique (MIGET) at 60 and 120 min after rocuronium at induction and after 60 min. Non-invasive cardiac output (NICO) monitoring and plasma concentrations of rocuronium were measured. We compared the data of MIGET, gas exchange, haemodynamic variables and pulmonary mechanics measurements between the different ventilatory modes.

RESULTS

Intrapulmonary shunt (blood flow to V(A)/Q < 0.005) did not increase at 60 min of anaesthesia in any of the different ventilation modes compared with the shunt value before anaesthesia. Log standard deviation of perfusion increased in IPPV, with and without PEEP groups, compared with the baseline (P< 0.05) but did not increase in the BiPAP group. BiPAP ventilation generated a higher level of Pa(O2)than IPPV with or without PEEP (P<0.05).

CONCLUSION

BiPAP ventilation was beneficial in decreasing ventilation-perfusion mismatch and improving oxygenation when compared with conventional IPPV (with or without PEEP).

Hypoxia blocks 11beta-hydroxysteroid dehydrogenase type 2 induction in human trophoblast cells during differentiation by a time-dependent mechanism that involves both translation and transcription

The present study was undertaken to determine (1) if hypoxia-induced down-regulation of placental 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2; encoded by HSD11B2 gene) activity and protein in human trophoblast cells during in vitro differentiation was mediated at the level of HSD11B2 gene transcription; and (2) whether the reduced placental 11beta-HSD2 in pregnancies complicated with fetal growth restriction (FGR) was a consequence of intrinsic abnormalities in trophoblast cells. Trophoblast cells were isolated from uncomplicated pregnancies and those complicated with FGR at term, and cultured for up to 72 h under normoxic (20% oxygen) or hypoxic (1% oxygen) conditions. Under normoxia, 11beta-HSD2 activity and protein increased progressively over the 72 h culture period, which was accompanied by a corresponding rise in 11beta-HSD2 mRNA. As demonstrated previously, hypoxia blocked the increase in levels of both 11beta-HSD2 activity and protein within the first 24h. In contrast, although hypoxia also prevented the rise in 11beta-HSD2 mRNA, it did not do so until 48 h. This time-dependent effect of hypoxia on placental 11beta-HSD2 activity/protein and mRNA suggests a dual mechanism of action whereby hypoxia may induce a rapid down-regulation of 11beta-HSD2 protein synthesis, which occurs initially at the level of translation, and later extends to the level of transcription. Indeed, transient transfection studies demonstrated that hypoxia diminished HSD11B2 promoter activity. When trophoblast cells isolated from FGR placentas were cultured and allowed to differentiate under the same conditions, they not only exhibited a similar pattern of 11beta-HSD2 activity and mRNA expression but also responded to hypoxia similarly to those from normal placentas. This suggests that the reduced placental 11beta-HSD2 in FGR is not due to intrinsic abnormalities in trophoblast cells, but likely a result of extrinsic factors associated with FGR.