Day: 03/15/2011

CSF amyloid beta38 as a novel diagnostic marker for dementia with Lewy bodies.

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The clinical distinction between Alzheimer`s disease (AD) and dementia with Lewy bodies (DLB) is sometimes difficult, particularly in mild cases. Although CSF markers such as amyloid beta42 (Abeta42) and P-tau can distinguish between AD and normal controls, their ability to distinguish between AD and DLB is not adequate.
OBJECTIVE: This study aims to investigate whether CSF markers, in particular levels of Abeta38, can differentiate between mild AD and DLB.
METHODS: 85 individuals were included after standardised diagnostic procedures: 30 diagnosed as probable AD, 23 probable DLB, 20 probable Parkinson`s disease dementia and 12 non-demented control subjects. CSF levels of Abeta38, Abeta40 and Abeta42 were determined using commercially available ultra-sensitive multi-array kit assay (MSD) for human Abeta peptides. Total tau (T-tau) and phosphorylated tau (P-tau) were analysed using ELISA (Innotest). In addition, combinations (Abeta42/Abeta38, Abeta42/Abeta40, Abeta42/P-tau and Abeta42/Abeta38/P-tau) were assessed.
RESULTS: Significant between group differences were found for all CSF measures, and all except Abeta40, Abeta42 and Abeta42/P-tau differed between AD and DLB. The Abeta42/Abeta38 ratio was the measure that best discriminated between AD and DLB (AUC 0.765; p<0.005), with a sensitivity of 78% and a specificity of 67%.
CONCLUSION: This study suggests that the level of Abeta38 can potentially contribute in the diagnostic distinction between AD and DLB when combined with Abeta42. Single measures had low diagnostic accuracy, suggesting that developing a panel of markers is the most promising strategy. Studies with independent and larger samples and a priori cut-offs are needed to test this hypothesis.

source: journal of neurology, neurosurgery and neuropsyciatry

Intermittent theta-burst transcranial magnetic stimulation for treatment of Parkinson disease

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To investigate the safety and efficacy of intermittent theta-burst stimulation (iTBS) in the treatment of motor symptoms in Parkinson disease (PD).
BACKGROUND: Progression of PD is characterized by the emergence of motor deficits, which eventually respond less to dopaminergic therapy and pose a therapeutic challenge. Repetitive transcranial magnetic stimulation (rTMS) has shown promising results in improving gait, a major cause of disability, and may provide a therapeutic alternative. iTBS is a novel type of rTMS that may be more efficacious than conventional rTMS.
METHODS: In this randomized, double-blind, sham-controlled study, we investigated safety and efficacy of iTBS of the motor and dorsolateral prefrontal cortices in 8 sessions over 2 weeks (evidence Class I). Assessment of safety and clinical efficacy over a 1-month period included timed tests of gait and bradykinesia, Unified Parkinson`s Disease Rating Scale (UPDRS), and additional clinical, neuropsychological, and neurophysiologic measures.
RESULTS: We investigated 26 patients with mild to moderate PD: 13 received iTBS and 13 sham stimulation. We found beneficial effects of iTBS on mood, but no improvement of gait, bradykinesia, UPDRS, and other measures. EEG/EMG monitoring recorded no pathologic increase of cortical excitability or epileptic activity. Few reported discomfort or pain and one experienced tinnitus during real stimulation.
CONCLUSION: iTBS of the motor and prefrontal cortices appears safe and improves mood, but failed to improve motor performance and functional status in PD. Classification of evidence: This study provides Class I evidence that iTBS was not effective for gait, upper extremity bradykinesia, or other motor symptoms in PD.

source: Neurology

Procalcitonin as a Biomarker for Bacterial Infections in Patients With Liver Cirrhosis in the Emergency Department

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The objective was to determine the diagnostic accuracy of procalcitonin measurement for bacterial infections in patients with all causes of liver cirrhosis.
METHODS: The authors conducted a cross-sectional study of 98 patients with cirrhosis treated in the emergency department (ED) of Chang-Gung Memorial Hospital, Taiwan. Serum procalcitonin levels and other clinical information were obtained concurrently. Patients were assigned to a sepsis or nonsepsis group after the medical records were reviewed by two emergency physicians blinded to the study. Receiver operating characteristic (ROC) curve analysis was conducted to determine the sensitivity, specificity, likelihood ratio, and suggested cutoff values. The diagnostic accuracy of the C-reactive protein (CRP) level was also determined for comparison.
RESULTS: A total of 98 patients were enrolled for analysis in 1 year. Twenty-seven patients (27.6%) were assigned to the sepsis group. Eleven patients (11.2%) had positive blood cultures. The areas under the ROC curves for procalcitonin and CRP in predicting sepsis were 0.89 (95% confidence interval [CI] = 0.77 to 0.92) and 0.81 (95% CI = 0.72 to 0.89), respectively (p = 0.11). The cutoff that maximized Youden`s index was 0.49 ng/mL for procalcitonin and 24.7 mg/L for CRP. At these cutoffs, the sensitivity and specificity were 81.5 and 87.3% for procalcitonin and 80.0 and 80.3% for CRP. These results suggest that procalcitonin measurement shows at least an equivalent diagnostic accuracy to CRP measurement.
CONCLUSIONS: Procalcitonin provided satisfactory diagnostic accuracy in differentiating bacterial infections in patients with all causes of liver cirrhosis in the ED. A cutoff value of 0.5 ng/mL is suggested for clinical use.

source: academic emergency medicine

Nano fridge

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A silicon heat engine, about the size of a bacterium and thought to be the smallest ever created, has been developed by scientists from NXP Semiconductors in Eindhoven. It is powered by an electrical current that heats an expanding and contracting silicon beam, and offers evidence of the potential for applying heat engines on the micro- and nano-scale.
The study, published in Nature Physics [Steeneken et al Nature Physics (2011) doi: 10.1038/nphys1871], revealed that a tiny silicon crystal can be made to mechanically oscillate when a D.C. current is applied to it. When there is enough current, a 280 nm silicon beam begins to operate as a heat engine similar to that in cars or steam engines.
The researchers have been working on mechanical micro-electro-mechanical system (MEMS) oscillators whose motion is detected by the piezoresistive effect, as they are better than quartz oscillators due to both the mechanical resonator and the transistor amplifier being made in/on silicon crystals. Silicon crystals can also be made much smaller than quartz crystals, as they can be structured using the same lithographic tools used to structure transistors, bringing down costs and allowing for higher resonance frequencies.
The team discovered the new method for generating motion using thermodynamic/thermal expansion forces from the piezoresistive effect; the change of electrical resistance of a material when it is mechanically compressed, for power supply and amplification. With no transistors necessary for amplification, a 1 mW current can be run through a piece of silicon crystal, making it start to vibrate at a very stable frequency, simplifying the production of mechanical oscillators significantly.
They also showed that the heat engines can modify the Brownian motion of a resonator and amplify these Brownian vibrations. And it can also be reversed, reducing the Brownian motion, making it operate as a tiny refrigerator.
When the current is applied to the crystal, it spontaneously oscillates mechanically at a frequency of 1.3 MHz, more than a million times each second. They measured the high-frequency motion by using slow-motion video under a microscope with stroboscopic illumination.
The silicon beam, called the engine beam, was used to drive a larger silicon structure in the shape of a pendulum. When electricity flows through a resistor, it generates heat that makes the resistor’s temperature increase. With the power focused in a silicon resistor beam of very small volume, a huge heating power per volume is generated in the beam.
The oscillation from the heat engine could have applications in smaller, simpler and cheaper watches or other electronic devices, or for use in microscopic clocks or as a sensor. The researchers now hope to demonstrate applications for the oscillator, and improve its performance and operation.
source: materials today

Twenty-first century yarn

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The future of weaving looms into view

Some of the most interesting and potentially useful materials are restricted in their application due to the limited manner in which they may be processed. For example it is not uncommon for useful materials to be produced in a powder form, when a single crystal or flexible wire morphology would be much more practical. Fortunately a team of researchers working at the University of Texas at Dallas have developed a method of producing yarn that contains high powder concentrations such that functional fibers can be produced for weaving, sewing, knotting, and braiding [Lima et al., Science (2011) 331, 51].
Previous methods used to produce yarns from functional powders have relied on dispersing the powder within a fiber, or by incorporating the powder onto the fiber surface. However these methods are not ideal as the concentrations of the powder are typically low, and the material is not functionally robust. Now Prof. Ray H. Baughman and colleagues have demonstrated that durable and functional yarns can be produced by biscrolling nanotube sheets. That is to say, the functional guest powder is placed on top of a host nanotube sheet which is then twisted to form a yarn. Even though the powders are not bonded to the surface, these new yarns can be washed in a conventional washing machine without losing a measurable amount of guest material. The carbon nanotube sheets are light and thin, and so the yarn is actually 95 % powder by weight. Thus, the resulting material retains the properties of the guest powder.
The sheets are drawn “at up to 2 m/s from special forests of carbon nanotubes” Baughman explained. “There are no inherent limitations on either sheet width or length, and no special difficulties in maintaining sheet quality during the draw. In fact we have already produced kilometer long yarns by twisting the narrow sheets as they are drawn from a forest”.
The sheets are just 50 nm thick, and thanks to the conductive nature of CNTs it is possible for the powder to be electrically connected. However, the authors point out that insulating hosts such as SiO2 and Si3N4 nanotubes could be also be used, depending on the situation.
To demonstrate the effectiveness of their method, the team produced several functional yarns. By biscrolling boron and magnesium powders, and then treating the yarn with magnesium vapor, they created a superconducting MgB2 yarn. The resulting material was thus far easier to produce than conventional MgB2 wires. By using LiFePO4 the researchers produced flexible Li-ion battery cathodes that were far lighter than conventional cathodes. The team is continuing their work in this area, and are working with researchers at Hanyang University, Korea to produce “flexible fuel cells, biofuel cells, and batteries using biscrolled yarns that are woven or sewn into fabrics.
source:materials today

Nanomaterial biomagnification

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The notion of nanotechnology escaping into the environment is not only a staple of science fiction, but also a concern raised by the general public. However, reality is far less terrifying than that portrayed in film and literature, as rather than nano-robots wreaking havoc the worst we currently have to contend with are nanoparticles.
Of course there are many types of nanoparticle, some of which can be harmful. Until recently it was known that nanoparticles could be passed up the food chain, from prey to predator; however, it was unclear as to whether these materials could be biomagnified. That is, could the concentration of the particles be increased on moving up the food chain. Researchers at the University of California, Santa Barbara, have recently demonstrated that such biomagnification can occur within a simple food chain [Werlin et al., Nature Nanotechnol (2010) 6, 65].
The team cultivated Pseudomonas aeruginosa bacteria in an environment of CdSe quantum dots (QDs), along with a separate control batch and bacteria in a cadmium acetate solution. After allowing the bacteria to internalize the surrounding contaminates, they were then washed and placed with the predatory Tetrahymena thermophilia protozoa. While the initial behavior of the three batches of protozoa was similar, differences soon became apparent. The growth rate of the protozoa feeding on the cadmium acetate fed bacteria dropped to zero after the first doubling, and even after being transferred to a healthy environment they were unable to resume growth. This was apparently due to the toxic effect of the cadmium. The protozoa feeding on the QD fed bacteria fared slightly better, with protozoa remaining mobile for longer, and maintaining some growth once placed in a healthy medium.
Examination of the protozoa revealed that those that had fed on the quantum dots possessed large (approximately 5 micron) food vacuoles that contained undigested bacteria. Thus the QD fed bacteria inhibited their own digestion. As digestion is needed to free the QDs into the vacuole, this inhibition actually helps the protozoa survive longer than the cadmium acetate fed protozoa, as they do not succumb to the toxic effects of cadmium so quickly. This delayed death means that as the protozoa continue to survive, and feed, the QDs are biomagnifed.
Prof. Holden explained that their research into this area continues. “We are interested in the possibility for further trophic transfer, but also are very interested in understanding more about the QD effects observed in this trophic transfer study”. “We are trying to do research to understand better how nanoparticles, including QDs, change in cells over time.”

source: materials today