Impaired osteoclast homeostasis in the cystatin B-deficient mouse model of progressive myoclonus epilepsy.

Progressive myoclonus epilepsy of Unverricht-Lundborg type (EPM1) is an autosomal recessively inherited disorder characterized by incapacitating stimulus-sensitive myoclonus and tonic-clonic epileptic seizures with onset at the age of 6 to 16 years. EPM1 patients also exhibit a range of skeletal changes, e.g., thickened frontal cranial bone, arachnodactyly and scoliosis. Mutations in the gene encoding cystatin B (CSTB) underlie EPM1. CSTB is an inhibitor of cysteine cathepsins, including cathepsin K, a key enzyme in bone resorption by osteoclasts. CSTB has previously been shown to protect osteoclasts from experimentally induced apoptosis and to modulate bone resorption in vitro. Nevertheless, its physiological function in bone and the cause of the bone changes in patients remain unknown. Here we used the CSTB-deficient mouse (Cstb-/-) model of EPM1 to evaluate the contribution of defective CSTB protein function on bone pathology and osteoclast differentiation and function. Micro-computed tomography of hind limbs revealed thicker trabeculae and elevated bone mineral density in the trabecular bone of Cstb-/- mice. Histology from Cstb-/- mouse bones showed lower osteoclast count and thinner growth plates in long bones. Bone marrow-derived osteoclast cultures revealed lower osteoclast number and size in the Cstb-/- group. Cstb-/- osteoclasts formed less and smaller resorption pits in an in vitro assay. This impaired resorptive capacity was likely due to a decrease in osteoclast numbers and size. These data imply that the skeletal changes in Cstb-/- mice and in EPM1 patients are a result of CSTB deficiency leading to impaired osteoclast formation and consequently compromised resorptive capacity. These results suggest that the role of CSTB in osteoclast homeostasis and modulation of bone metabolism extends beyond cathepsin K regulation.

Visualizing water-filled versus embolized status of xylem conduits by desktop x-ray microtomography.

BACKGROUND: The hydraulic conductivity of the stem is a major factor limiting the capability of trees to transport water from the soil to transpiring leaves. During drought conditions, the conducting capacity of xylem can be reduced by some conduits being filled with gas, i.e. embolized. In order to understand the dynamics of embolism formation and repair, considerable attention has been given to developing reliable and accurate methods for quantifying the phenomenon. In the past decade, non-destructive imaging of embolism formation in living plants has become possible. Magnetic resonance imaging has been used to visualize the distribution of water within the stem, but in most cases it is not possible to resolve individual cells. Recently, high-resolution synchrotron x-ray microtomography has been introduced as a tool to visualize the water contents of individual cells in vivo, providing unprecedented insight into the dynamics of embolism repair. We have investigated the potential of an x-ray tube -based microtomography setup to visualize and quantify xylem embolism and embolism repair in water-stressed young saplings and shoot tips of Silver and Curly birch (Betula pendula and B. pendula var. carelica). RESULTS: From the microtomography images, the water-filled versus gas-filled status of individual xylem conduits can be seen, and the proportion of stem cross-section that consists of embolized tissue can be calculated. Measuring the number of embolized vessels in the imaged area is a simple counting experiment. In the samples investigated, wood fibers were cavitated in a large proportion of the xylem cross-section shortly after watering of the plant was stopped, but the number of embolized vessels remained low several days into a drought period. Under conditions of low evaporative demand, also refilling of previously embolized conduits was observed. CONCLUSIONS: Desktop x-ray microtomography is shown to be an effective method for evaluating the water-filled versus embolized status of the stem xylem in a small living sapling. Due to its non-destructive nature, the risk of inducing embolisms during sampling is greatly reduced. Compared with synchrotron imaging beamlines, desktop microtomography offers easier accessibility, while maintaining sufficient resolution to visualize the water contents of individual cells.

Tablet preformulations of indomethacin-loaded mesoporous silicon microparticles.

In this study, indomethacin-loaded thermally oxidized mesoporous silicon microparticles (TOPSi-IMC) were formulated into tablets with excipients in order to improve the dissolution and permeability properties of the poorly soluble drug. Formulations of TOPSi-IMC particles and excipients were prepared at different TOPSi-IMC particle ratios (25, 30 and 35%). The formulations were compressed by direct compression technique with a single punch tablet machine. For comparison, a formulation containing the bulk IMC (indomethacin) and the same excipients without thermally oxidized mesoporous silicon microparticles particles (TOPSi) was prepared and compressed into tablets. The TOPSi-IMC tablets were characterised according to weight, thickness, crushing strength, disintegration time and dissolution rate. The results of this study show that TOPSi-IMC particles can be compressed to a conventional tablet. The release rate of the drug and its permeation across intestinal cells model (Caco-2) from TOPSi-IMC tablets was improved compared to the bulk IMC tablets. The dissolution rate and permeability of IMC from the tablets decreased with increasing ratio of the TOPSi-IMC particles in the formulation. The phenomenon is, presumably, a result of the loss of unique pore structure of the particles due to deformation of the particles under the compression load.

Changes in submicrometer structure of enzymatically hydrolyzed microcrystalline cellulose.

To understand the limitations occurring during enzymatic hydrolysis of cellulosic materials in renewable energy production, we used wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), X-ray microtomography, and transmission electron microscopy (TEM) to characterize submicrometer changes in the structure of microcrystalline cellulose (Avicel) digested with the Trichoderma reesei enzyme system. The microtomography measurements showed a clear decrease in particle size in scale of tens of micrometers. In all the TEM pictures, similar elongated and partly ramified structures were observed, independent of the hydrolysis time. The SAXS results of rewetted samples suggested a slight change in the structure in scale of 10-20 nm, whereas the WAXS results confirmed that the degree of crystallinity and the crystal sizes remained unchanged. This indicates that the enzymes act on the surface of cellulose bundles and are unable to penetrate into the nanopores of wet cellulose.

Comparison of microencapsulation properties of spruce galactoglucomannans and arabic gum using a model hydrophobic core compound.

In the present study, microencapsulation and the physical properties of spruce ( Picea abies ) Omicron-acetyl-galactoglucomannans (GGM) were investigated and compared to those of arabic gum (AG). Microcapsules were obtained by freeze-drying oil-in-water emulsions containing 10 wt % capsule materials (AG, GGM, or a 1:1 mixture of GGM-AG) and 2 wt % alpha-tocopherol (a model hydrophobic core compound that oxidizes easily). Microcapsules were stored at relative humidity (RH) of 0, 33, and 66% at 25 degrees C for different time periods, and their alpha-tocopherol content was determined by HPLC. X-ray microtomography analyses showed that the freeze-dried emulsions of GGM had the highest and those of AG the lowest degree of porosity. According to X-ray diffraction patterns, both freeze-dried AG and GGM showed an amorphous nature. The storage test showed that anhydrous AG microcapsules had higher alpha-tocopherol content than GGM-containing capsules, whereas under 33 and 66% RH conditions GGM was superior in relation to the retention of alpha-tocopherol. The good protection ability of GGM was related to its ability to form thicker walls to microcapsules and better physical stability compared to AG. The glass transition temperature of AG was close to the storage temperature (25 degrees C) at RH of 66%, which explains the remarkable losses of alpha-tocopherol in the microcapsules under those conditions.

Effect of amylose content on physical and mechanical properties of potato-starch-based edible films.

The present study investigated the amylose content and the gelatinization properties of various potato starches extracted from different potato cultivars. These potato starches were used to prepare edible films. Physical and mechanical properties of the films were investigated. The crystallinity of selected native starches and edible films made of the same starches were determined by X-ray diffraction. The amylose content of potato starches varied between 11.9 and 20.1%. Gelatinization of potato starches in excess water occurred at temperatures ranging from 58 to 69 degrees C independently of the amylose content. The relative crystallinity was found to be around 10-13% in selected native potato starches with low, medium, and high amylose content. Instead, films prepared from the same potato starches were found to be practically amorphous having the relative crystallinity of 0-4%. The mechanical properties and the water vapor permeability of the films were found to be independent of the amylose content.

Negative Poisson ratio of crystalline cellulose in kraft cooked Norway spruce.

The tensile properties of kraft cooked Norway spruce were studied by tensile testing with in situ X-ray diffraction (XRD). Samples were of earlywood, cooked for varying times. The total lignin content of the samples was between 21.7% and 9.3%. Tensile tests with XRD were performed on wet samples, without XRD on dry samples. The tensile strength, the modulus of elasticity (MOE), and the elongation at fracture/yield were determined. X-ray diffraction was used to determine the microfibril angle (MFA) and the deformation of crystalline cellulose by monitoring the reflections 200 and 004. The (X-ray) Poisson ratio of crystalline cellulose was calculated, both before and after the yield point. The tensile strength and the MOE of the wet samples were significantly lower than in the dry samples. The tensile properties of dry samples were similar to dry earlywood samples of untreated Norway spruce. The MFA only showed notable changes due to strain when it was initially large, when a diminishing effect was observed. The Poisson ratio of crystalline cellulose was negative. The average values ranged between -0.26 and -1.17 before the yield point and between -0.86 and -1.05 after the yield point.