Effect of sucralfate on gastric mucosal blood flow in rats

Sucralfate possesses site protective and cytoprotective actions and heals ulcers effectively, but its effect on gastric mucosal blood flow is unknown. Using an ex vivo gastric chamber preparation, we studied the effect of sucralfate on gastric mucosal blood flow in rats by laser doppler flowmetry. Under both fasting and fed states, measurements of gastric mucosal blood flow and damage were made in rats after topical application of absolute ethanol alone or after pretreatment with sucralfate. Gastric mucosal damage was assessed by measuring the total area of haemorrhagic mucosal lesions. Ethanol induced gastric mucosal lesions were significantly less with sucralfate pretreatment than without (p less than 0.008). Mucosal blood flow significantly fell after ethanol application (p less than 0.001). The fall was significantly less in fed than in fasted rats (p less than 0.05), and after pretreatment with sucralfate 100 mg or 200 mg than without in both fasted (p less than 0.0008 and 0.00001, respectively) and fed (p less than 0.002 and 0.001, respectively) rats. Graded doses of sucralfate (25-400 mg) resulted in an increase in gastric mucosal blood flow in a dose dependent manner (r = 0.731, p less than 0.001). In conclusion that sucralfate increases gastric mucosal blood flow in rats and lessens the fall in blood flow in rats treated with ethanol, and this action may contribute to its protection against the vascular damage of mucosa by ethanol.published_or_final_versio

Effect of sucralfate on gastric mucosal blood flow in rats

Sucralfate possesses site protective and cytoprotective actions and heals ulcers effectively, but its effect on gastric mucosal blood flow is unknown. Using an ex vivo gastric chamber preparation, we studied the effect of sucralfate on gastric mucosal blood flow in rats by laser doppler flowmetry. Under both fasting and fed states, measurements of gastric mucosal blood flow and damage were made in rats after topical application of absolute ethanol alone or after pretreatment with sucralfate. Gastric mucosal damage was assessed by measuring the total area of haemorrhagic mucosal lesions. Ethanol induced gastric mucosal lesions were significantly less with sucralfate pretreatment than without (p less than 0.008). Mucosal blood flow significantly fell after ethanol application (p less than 0.001). The fall was significantly less in fed than in fasted rats (p less than 0.05), and after pretreatment with sucralfate 100 mg or 200 mg than without in both fasted (p less than 0.0008 and 0.00001, respectively) and fed (p less than 0.002 and 0.001, respectively) rats. Graded doses of sucralfate (25-400 mg) resulted in an increase in gastric mucosal blood flow in a dose dependent manner (r = 0.731, p less than 0.001). In conclusion that sucralfate increases gastric mucosal blood flow in rats and lessens the fall in blood flow in rats treated with ethanol, and this action may contribute to its protection against the vascular damage of mucosa by ethanol.published_or_final_versio

Terahertz detectors based on all-dielectric photoconductive metasurfaces

Performance of terahertz (THz) photoconductive devices, including detectors and emitters, has been improved recently by means of plasmonic nanoantennae and gratings. However, plasmonic nanostructures introduce Ohmic losses, which limit gains in device performance. In this presentation, we discuss an alternative approach, which eliminates the problem of Ohmic losses. We use all-dielectric photoconductive metasurfaces as the active region in THz switches to improve their efficiency. In particular, we discuss two approaches to realize perfect optical absorption in a thin photoconductive layer without introducing metallic elements. In addition to providing perfect optical absorption, the photoconductive channel based on all-dielectric metasurface allows us to engineer desired electrical properties, specifically, fast and efficient conductivity switching with very high contrast. This approach thus promises a new generation of sensitive and efficient THz photoconductive detectors. Here we demonstrate and discuss performance of two practical THz photoconductive detectors with integrated all-dielectric metasurfaces

Efficient Terahertz Detection with Perfectly-Absorbing Metasurface

We demonstrate a unique photoconductive design for terahertz (THz) detection based on a perfectly absorbing, all-dielectric metasurface. Our design exploits Mie resonances in electrically connected cubic resonators fabricated in low-temperature grown (LT) GaAs. Experimentally, the detector achieves very high contrast between ON/OFF conductivity states (107) whilst also requiring extremely low optical power for optimal operation (100 muW). We find that the Mie resonances dissipate sufficiently fast and maintain the detection bandwidth up to 3 THz

Perfect absorption in GaAs metasurfaces near the bandgap edge

Perfect optical absorption occurs in a metasurface that supports two degenerate and critically-coupled modes of opposite symmetry. The challenge in designing a perfectly absorbing metasurface for a desired wavelength and material stems from the fact that satisfying these conditions requires multi-dimensional optimization often with parameters affecting optical resonances in non-trivial ways. This problem comes to the fore in semiconductor metasurfaces operating near the bandgap wavelength, where intrinsic material absorption varies significantly. Here we devise and demonstrate a systematic process by which one can achieve perfect absorption in GaAs metasurfaces for a desired wavelength at different levels of intrinsic material absorption, eliminating the need for trial and error in the design process. Using this method, we show that perfect absorption can be achieved not only at wavelengths where GaAs exhibits high absorption, but also at wavelengths near the bandgap edge. In this region, absorption is enhanced by over one order of magnitude compared a layer of unstructured GaAs of the same thickness

Sensitivity and Noise in THz Photoconductive Metasurface Detectors

Photoconductive antenna THz detectors based on highly absorbing LT-GaAs metasurfaces enable high sensitivity and high signal-to-noise ratio (> 106) at optical gate powers as low as 5 μW. By investigating the dependence of detector performance on optical gate power, we compare several metasurface detectors with standard PCAs and develop a general model for quantifying the sensitivity and optimal gate power for detector operation. We also show that the LT-GaAs metasurface can even enhance sub bandgap absorption, enabling the use of these detectors in telecom wavelength systems

Perfectly-absorbing photoconductive metasurfaces for THz applications

Ultrafast switching of photoconductivity is essential for many terahertz (THz) technologies, however this process is inefficient. Recently developed concepts of all-dielectric metasurfaces can improve efficiency of ultrafast switches, overcoming material limitations, reducing the thickness of the photoconductive region and lowering optical power requirements for THz devices. We will consider two types of perfectly absorbing metasurfaces compatible with the photoconductive switch architecture and discuss performance of THz detectors with integrated metasurfaces. We will show that optical power level required for optimum operation for these THz detectors is more than one order of magnitude lower in comparison to devices without metasurfaces

Nonlinear Terahertz Generation in Semiconductor Metasurfaces

We demonstrate ultra-thin semiconductor metasurfaces for generation of THz pulses. By investigating the dependence of the THz amplitude and phase on excitation field polarization and crystal orientation, we deduce that the underlying THz emission mechanism in metasurfaces differs from bulk semiconductor wafers with second order nonlinearity playing a dominant role. The metasurface enables control of the THz phase and can therefore be used to spatially structure the THz emitted field. We use this effect to design and demonstrate a metasurface which simultaneously emits and focusses THz pulses

Mesenchymal stromal cells rescue disc degeneration and function via suppression of fibrotic events

DMM 2011 entitled: Re-engineering Regenerative MedicinePoster Session - Orthopedic Regeneration: no. 92Chronic back pain and neuropathological conditions such as spondylomyelopathy and radiculopathy are associated with degeneration of the intervertebral discs in spinal column. Human and animal studies imply a role of fibrosis in the degeneration process. Mesenchymal stromal cells (MSCs) possess anti-fibrotic activities. We investigated if MSCs elicit disc regeneration through modulating fibrotic events. Skeletally mature rabbits with injury-induced lumbar disc degeneration were randomized to receive intradiscal engraftment of bone marrow-derived MSCs or control vehicle. Disc degeneration status was evaluated by MRI and radiographs. We showed that MSCs regenerated the disc along with a recovery …postprin

Expression of cytokine and chemokine mRNA and secretion of tumor necrosis factor-α by gallbladder epithelial cells: Response to bacterial lipopolysaccharides

BACKGROUND: In addition to immune cells, many other cell types are known to produce cytokines. Cultured normal mouse gallbladder epithelial cells, used as a model system for gallbladder epithelium, were examined for their ability to express the mRNA of various cytokines and chemokines in response to bacterial lipopolysaccharide. The synthesis and secretion of the tumor necrosis factor-α (TNF-α) protein by these cells was also measured. RESULTS: Untreated mouse gallbladder cells expressed mRNA for TNF-α, RANTES, and macrophage inflammatory protein-2 (MIP-2). Upon treatment with lipopolysaccharide, these cells now produced mRNA for Interleukin-1β (IL-1β), IL-6, monocyte chemoattractant protein-1 (MCP-1), and showed increased expression of TNF-α and MIP-2 mRNA. Untreated mouse gallbladder cells did not synthesize TNF-α protein; however, they did synthesize and secrete TNF-α upon treatment with lipopolysaccharide. METHODS: Cells were treated with lipopolysaccharides from 3 strains of bacteria. Qualitative and semi-quantitative RT-PCR, using cytokine or chemokine-specific primers, was used to measure mRNA levels of TNFα, IL-1β, IL-6, IL-10, KC, RANTES, MCP-1, and MIP-2. TNF-α protein was measured by immunoassays. CONCLUSION: This research demonstrates that gallbladder epithelial cells in response to lipopolysaccharide exposure can alter their cytokine and chemokine RNA expression pattern and can synthesize and secrete TNFα protein. This suggests a mechanism whereby gallbladder epithelial cells in vivo may mediate gallbladder secretory function, inflammation and diseases in an autocrine/paracrine fashion by producing and secreting cytokines and/or chemokines during sepsis