Influencing factors on the size uniformity of self-assembled SiGe quantum rings grown by molecular beam epitaxy

The size uniformity of self-assembled SiGe quantum rings, which are formed by capping SiGe quantum dots with a thin Si layer, is found to be greatly influenced by the growth temperature and the areal density of SiGe quantum dots. Higher growth temperature benefits the size uniformity of quantum dots, but results in low Ge concentration as well as asymmetric Ge distribution in the dots, which induces the subsequently formed quantum rings to be asymmetric in shape or even broken somewhere in the ridge of rings. Low growth temperature degrades the size uniformity of quantum dots, and thus that of quantum rings. A high areal density results in the expansion and coalescence of neighboring quantum dots to form a chain, rather than quantum rings. Uniform quantum rings with a size dispersion of 4.6% and an areal density of 7.8×10(8) cm(-2) are obtained at the optimized growth temperature of 640°C.

Circulating endothelial progenitor cells and erectile dysfunction: possibility of nutritional intervention?

To provide an overview of molecular and cellular processes involved in erectile dysfunction (ED) with emphasis on circulating endothelial progenitor cells (EPC) and discuss possible nutraceutical means of intervention. A review of literature on Pubmed related to EPC and ED was conducted. Patients with ED appear to possess a reduced number of circulating EPC, which is associated with poor endothelial function possibly as a result of underlying low-grade inflammation. Several studies support the possibility of improving erectile function by inhibition of inflammation as well as administration of various stem cell types. One particularly interesting approach is nutraceutical supplementation to increase circulating EPC, as demonstrated in the product Stem-Kine. Interventions aimed at increasing circulating EPC may have potential in treatment of vascular ED.

Phase I study of the heat shock protein 90 inhibitor alvespimycin (KOS-1022, 17-DMAG) administered intravenously twice weekly to patients with acute myeloid leukemia

Heat shock protein 90 (Hsp90) is a molecular chaperone with many oncogenic client proteins. The small-molecule Hsp90 inhibitor alvespimycin, a geldanamycin derivative, is being developed for various malignancies. This phase 1 study examined the maximum-tolerated dose (MTD), safety and pharmacokinetic/pharmacodynamic profiles of alvespimycin in patients with advanced acute myeloid leukemia (AML). Patients with advanced AML received escalating doses of intravenous alvespimycin (8-32 mg/m(2)), twice weekly, for 2 of 3 weeks. Dose-limiting toxicities (DLTs) were assessed during cycle 1. A total of 24 enrolled patients were evaluable for toxicity. Alvespimycin was well tolerated; the MTD was 24 mg/m(2) twice weekly. Common toxicities included neutropenic fever, fatigue, nausea and diarrhea. Cardiac DLTs occurred at 32 mg/m(2) (elevated troponin and myocardial infarction). Pharmacokinetics revealed linear increases in C(max) and area under the curve (AUC) from 8 to 32 mg/m(2) and minor accumulation upon repeated doses. Pharmacodynamic analyses on day 15 revealed increased apoptosis and Hsp70 levels when compared with baseline within marrow blasts. Antileukemia activity occurred in 3 of 17 evaluable patients (complete remission with incomplete blood count recovery). The twice-weekly administered alvespimycin was well tolerated in patients with advanced AML, showing linear pharmacokinetics, target inhibition and signs of clinical activity. We determined a recommended phase 2 dose of 24 mg/m(2).

REP-PCR tracking of the origin and spread of airborne Staphylococcus aureus in and around chicken house

Staphylococcus aureus was used as an indicator to study the origin and spread of microbial aerosol in and around chicken houses. Air samples indoor, upwind (10 and 50 m), and downwind (10, 50, 100, 200, and 400 m) of four chicken houses were collected using Andersen-6 stages sampler. The concentrations of S. aureus were determined for every sample site. Isolation of S. aureus from chicken feces was performed according to the standard method. The genetic relationship among the isolates was determined by profiles of PCR-amplified repetitive extragenic palindromic (REP-PCR) elements. The results showed that the concentrations of S. aureus indoor of four chicken houses were higher than those upwind and downwind sites (P < 0.05 or P < 0.01), but there were no significant concentration differences among downwind sites (P > 0.05). The fingerprints and the phylogenetic tree indicated that a part of the S. aureus (55.6%, 10/18) isolates from indoor air had the same REP-PCR fingerprints as feces isolates. Consequently, most isolates (57.1%, 20/35) from downwind 10, 50, 100, 200, even 400 m had the same REP-PCR fingerprints as those from indoor or feces. These data indicated that some isolates from downwind and indoor originated from the chicken feces. However, those isolates from upwind had low similarity (similarity index 0.6-0.87) to those from indoor or feces. Therefore, the isolates upwind were not from the chicken feces or indoor. These results suggest that microbes in chicken feces can be aerosolized and spread indoor and outdoor, especially to downwind of the chicken houses. It should have an important epidemiological and public health significance.

PRACTICAL IMPLICATIONS

Thus, the use of S. aureus as an indicator to study the origin and spread of airborne pathogens from chicken houses is potentially useful for enhancing public health and understanding the airborne epidemiology of this pathogen. Meanwhile it can provide evidence for studying the spreading model of airborne pathogens.

Repeated Intrathecal Administration of Ropivacaine Causes Neurotoxicity in Rats

Previous studies suggest that ropivacaine causes the least neurotoxicity among local anaesthetics. Most data derive from a single injection of ropivacaine into the subarachnoid space. The histological changes and behavioural effects of repeated intrathecal administration have yet to be studied. We examined the possible neurotoxicity of multiple doses of intrathecal ropivacaine in rats.

Rats received 0.12 ml/kg body weight ropivacaine in normal saline at concentrations of 0.25%, 0.5%, 0.75% and 1.0% at 90-minute intervals via an implanted intrathecal catheter (ID 0.12 mm, OD 0.35 mm) for 48 hours. At L3, the spinal cord and posterior roots were examined by light and electron microscopy. We performed in situ TUNEL assay to evaluate apoptosis in the spinal cord. Sensory threshold to noxious stimulation along with behavioural change were also studied.

Both 0.75% and 1.0% ropivacaine induced neuronal injury characterised by infiltration of inflammatory cells, vacuolation of myelin sheaths and axons, abnormal morphology of neurons and apoptosis in the spinal cord, mainly in posterior roots and the adjacent posterior white matter. Compared to controls, the percentage of maximum possible effect did not show any significant differences between the rats treated with variable concentrations of ropivacaine or tested with either heat or mechanical stimulation. As expected, the recovery time to normal ambulation was prolonged as the ropivacaine concentration was increased.

Ropivacaine can induce neurotoxicity and trigger apoptosis in a dose-dependent manner after repeated intrathecal administration. Although the clinical safety profile of ropivacaine appears favourable compared with other local anaesthetics, it is possible our findings have clinical significance.

Comparison of diffraction-enhanced computed tomography and monochromatic synchrotron radiation computed tomography of human trabecular bone

Diffraction-enhanced imaging (DEI) is an x-ray-based medical imaging modality that, when used in tomography mode (DECT), can generate a three-dimensional map of both the apparent absorption coefficient and the out-of-plane gradient of the index of refraction of the sample. DECT is known to have contrast gains over monochromatic synchrotron radiation CT (SRCT) for soft tissue structures. The goal of this experiment was to compare contrast-to-noise ratio (CNR) and resolution in images of human trabecular bone acquired using SRCT with images acquired using DECT. All images were acquired at the National Synchrotron Light Source (Upton, NY, USA) at beamline X15 A at an x-ray energy of 40 keV and the silicon [3 3 3] reflection. SRCT, apparent absorption DECT and refraction DECT slice images of the trabecular bone were created. The apparent absorption DECT images have significantly higher spatial resolution and CNR than the corresponding SRCT images. Thus, DECT will prove to be a useful tool for imaging applications in which high contrast and high spatial resolution are required for both soft tissue features and bone.

Enhancer deletions of the SHOX gene as a frequent cause of short stature: the essential role of a 250 kb downstream regulatory domain

Background:

Mutations and deletions of the homeobox transcription factor gene SHOX are known to cause short stature. The authors have analysed SHOX enhancer regions in a large cohort of short stature patients to study the importance of regulatory regions in developmentally relevant genes like SHOX.

Methods:

The authors tested for the presence of copy number variations in the pseudoautosomal region of the sex chromosomes in 735 individuals with idiopathic short stature and compared the results to 58 cases with Leri–Weill syndrome and 100 normal height controls, using fluorescence in situ hybridisation (FISH), single nucleotide polymorphism (SNP), microsatellites, and multiplex ligand dependent probe amplification (MLPA) analysis.

Results:

A total of 31/735 (4.2%) microdeletions were identified in the pseudoautosomal region in patients with idiopathic short stature; eight of these microdeletions (8/31; 26%) involved only enhancer sequences residing a considerable distance away from the gene. In 58 Leri–Weill syndrome patients, a total of 29 microdeletions were identified; almost half of these (13/29; 45%) involve enhancer sequences and leave the SHOX gene intact. These deletions were absent in 100 control persons.

Conclusion:

The authors conclude that enhancer deletions in the SHOX gene region are a relatively frequent cause of growth failure in patients with idiopathic short stature and Leri–Weill syndrome. The data highlights the growing recognition that regulatory sequences are of crucial importance in the genome when diagnosing and understanding the aetiology of disease.

Characterization of diffraction-enhanced imaging contrast in breast cancer

Diffraction-enhanced imaging (DEI) is a new x-ray imaging modality that has been shown to enhance contrast between normal and cancerous breast tissues. In this study, diffraction-enhanced imaging in computed tomography (DEI-CT) mode was used to quantitatively characterize the refraction contrasts of the organized structures associated with invasive human breast cancer. Using a high-sensitivity Si (3 3 3) reflection, the individual features of breast cancer, including masses, calcifications and spiculations, were observed. DEI-CT yields 14, 5 and 7 times higher CT numbers and 10, 9 and 6 times higher signal-to-noise ratios (SNR) for masses, calcifications and spiculations, respectively, as compared to conventional CT of the same specimen performed using the same detector, x-ray energy and dose. Furthermore, DEI-CT at ten times lower dose yields better SNR than conventional CT. In light of the recent development of a compact DEI prototype using an x-ray tube as its source, these results, acquired at a clinically relevant x-ray energy for which a pre-clinical DEI prototype currently exists, suggest the potential of clinical implementation of mammography with DEI-CT to provide high-contrast, high-resolution images of breast cancer (Parham 2006 PhD Dissertation University of North Carolina at Chapel Hill).

High-energy X-ray diffuse scattering

Diffuse X-ray scattering has been an important tool for understanding the atomic structure of binary systems for more than 50 years. The majority of studies have used laboratory-based sources providing 8 keV photons or synchrotron radiation with similar energies. Diffuse scattering is weak, with the scattering volume determined by the X-ray absorption length. In the case of 8 keV photons, this is not significantly different from the typical extinction length for Bragg scattering. If, however, one goes to energies of the order of 100 keV the scattering volume for the diffuse scattering increases up to three orders of magnitude while the extinction length increases by only one order of magnitude. This leads to a gain of two orders of magnitude in the relative intensity of the diffuse scattering compared with the Bragg peaks. This gain, combined with the possibility of recording the intensity from an entire plane in reciprocal space using a two-dimensional X-ray detector, permits time-resolved diffuse scattering studies in many systems. On the other hand, diffraction features that are usually neglected, such as multiple scattering, come into play. Four types of multiple scattering phenomena are discussed, and the manner in which they appear in high-energy diffraction experiments is considered.

C-Jun N-terminal kinase 2 promotes graft injury via the mitochondrial permeability transition after mouse liver transplantation

The c-Jun N-terminal kinase (JNK) pathway enhances graft injury after liver transplantation (LT). We hypothesized that the JNK2 isoform promotes graft injury via the mitochondrial permeability transition (MPT). Livers of C57BL/6J (wild-type, WT) and JNK2 knockout (KO) mice were transplanted into WT recipients after 30 h of cold storage in UW solution. Injury after implantation was assessed by serum ALT, histological necrosis, TUNEL, Caspase 3 activity, 30-day survival, and cytochrome c and 4-hydroxynonenal immunostaining. Multiphoton microscopy after LT monitored mitochondrial membrane potential in vivo. After LT, ALT increased three times more in WT compared to KO (p < 0.05). Necrosis and TUNEL were more than two times greater in WT than KO (p < 0.05). Immunostaining showed a >80% decrease of mitochondrial cytochrome c release in KO compared to WT (p < 0.01). Lipid peroxidation was similarly decreased. Every KO graft but one survived longer than all WT grafts (p < 0.05, Kaplan-Meier). After LT, depolarization of mitochondria occurred in 73% of WT hepatocytes, which decreased to 28% in KO (p < 0.05). In conclusion, donor JNK2 promotes injury after mouse LT via the MPT. MPT inhibition using specific JNK2 inhibitors may be useful in protecting grafts against adverse outcomes from ischemia/reperfusion injury.

Analyzer-based imaging of spinal fusion in an animal model

Analyzer-based imaging (ABI) utilizes synchrotron radiation sources to create collimated monochromatic x-rays. In addition to x-ray absorption, this technique uses refraction and scatter rejection to create images. ABI provides dramatically improved contrast over standard imaging techniques. Twenty-one adult male Wistar rats were divided into four experimental groups to undergo the following interventions: (1) non-injured control, (2) decortication alone, (3) decortication with iliac crest bone grafting and (4) decortication with iliac crest bone grafting and interspinous wiring. Surgical procedures were performed at the L5-6 level. Animals were killed at 2, 4 and 6 weeks after the intervention and the spine muscle blocks were excised. Specimens were assessed for the presence of fusion by (1) manual testing, (2) conventional absorption radiography and (3) ABI. ABI showed no evidence of bone fusion in groups 1 and 2 and showed solid or possibly solid fusion in subjects from groups 3 and 4 at 6 weeks. Metal artifacts were not present in any of the ABI images. Conventional absorption radiographs did not provide diagnostic quality imaging of either the graft material or fusion masses in any of the specimens in any of the groups. Synchrotron-based ABI represents a novel imaging technique which can be used to assess spinal fusion in a small animal model. ABI produces superior image quality when compared to conventional radiographs.

A Study of the Regulating Gene of femA from Methicillin-resistant Staphylococcus aureus Clinical Isolates

The regulating gene of femA was studied in methicillin-resistant Staphylococcus aureus (MRSA). High-level MRSA, low-level MRSA and methicillin-sensitive S. aureus (MSSA) were identified by agar diffusion. β-Lactamases were detected by nitrocephin and the presence of the mecA gene was determined by polymerase chain reaction (PCR). Only isolates that were both β-lactamase-negative and mecA-positive were used. The femA gene and its 250 base pair (bp) upstream sequence were amplified by PCR and expression was determined by real-time fluorescent quantitative PCR. The 250 bp upstream sequence was labelled by BrightStar€ Psoralen–Biotin and detected by electrophoretic mobility shift assay (EMSA). Expression levels of femA in MSSA, low-level MRSA and high-level MRSA were 3.53 × 10−3%–29.91%, 5.54 × 10−3%–3.1 × 102% and 13.88–5.50 × 104%, respectively. EMSA detected a signal shift in 57 high-level MRSA isolates but not in four low-level MRSA and four MSSA strains. Expression of femA in high-level MRSA (non-β-lactamase-producing) was higher than in low-level MRSA and MSSA. The femA regulating gene probably lies in the 250 bp upstream sequence in MRSA and high-level expression is essential for high-level methicillin resistance.

Selective oxidation of CO in the presence of air over gold-based catalysts Au/TiO2/C (sonochemistry) and Au/TiO2/C (microwave)

Two model catalysts, Au/TiO2/C (S) (sonochemically derived) and Au/TiO2/C (M) (microwave derived), were produced by employing ultrasound irradiation and microwave irradiation, respectively. The deposition of gold colloids onto the support powders, TiO2/C, was accomplished by using a solvated metal atom impregnation (SMAI) method. The SMAI technique provides highly-dispersed gold particles on the TiO2/C support. The catalytic performance of Au based catalysts 1 wt% Au-TiO2/C (S) and 1 wt%Au-TiO2(M)/C (M) have been tested for the oxidation of CO in the temperature range of 0-300 degrees C and compared to that of 1 wt% Au-TiO2 (Degussa-P25). A boost in the conversion of CO was observed for the sonochemically-derived catalyst, Au/TiO2/C (S), at low temperature. Hence, the reactivity order found for CO oxidation is (Au/TiO2/C (S)>Au/TiO2 (P25)>Au/TiO2/C (M)).