Double dynamical regime of confined water

The Van Hove self correlation function of water confined in a silica pore is calculated from Molecular Dynamics trajectories upon supercooling. At long time in the $\alpha$ relaxation region we found that the behaviour of the real space time dependent correlators can be decomposed in a very slow, almost frozen, dynamics due to the bound water close to the substrate and a faster dynamics of the free water which resides far from the confining surface. For free water we confirm the evidences of an approach to a crossover mode coupling transition, previously found in Q space. In the short time region we found that the two dynamical regimes are overimposed and cannot be distinguished. This shows that the interplay between the slower and the faster dynamics emerges in going from early times to the $\alpha$ relaxation region, where a layer analysis of the dynamical properties can be performed.Comment: 6 pages with 9 figures. RevTeX. Accepted for pulbication in J. Phys. Cond. Mat

Supercooled confined water and the Mode Coupling crossover temperature

We present a Molecular Dynamics study of the single particle dynamics of supercooled water confined in a silica pore. Two dynamical regimes are found: close to the hydrophilic substrate molecules are below the Mode Coupling crossover temperature, $T_C$, already at ambient temperature. The water closer to the center of the pore (free water) approaches upon supercooling $T_C$ as predicted by Mode Coupling Theories. For free water the crossover temperature and crossover exponent $\gamma$ are extracted from power-law fits to both the diffusion coefficient and the relaxation time of the late $\alpha$ region.Comment: To be published, Phys. Rev. Lett., 4 pages, 3 figures, revTeX, minor changes in the figures, references added, changes in the tex

The changes of standard DXA measurements and TBS depending on outcomes of neurosurgical treatment in patients with Cushing's disease

BACKGROUND:Patients with endogenous hypercortisolism have reduced bone mineral density (BMD) and trabecular bone score (TBS) that are the causes of secondary osteoporosis and low-traumatic fractures. It is well known that radical treatment (neurosurgery or radiosurgery) of Cushings disease leads to a decline of cortisol levels in all body fluids to normal values. However, it is still uncertain whether bone tissue structure, and particularly its microarchitecture, does recover in remission of the disease. AIMS:To evaluate an influence of hormone activity (presence or absence of remission) in patients with Cushing's disease on changes of bone structure measurements in accordance with DXA values (TBS, BMD, T- and Z-scores), as well as significance of such changes in 12 and 24 months after neurosurgical treatment. MATERIALS AND METHODS:In patients with confirmed active Cushing's disease (ACTH-producing pituitary adenoma) (n = 44) and in control group of healthy volunteers (n = 40), BMD in lumbar spine (L1-L4) and simultaneously TBS, in cut-off points before neurosurgical treatment (in both groups) and in 12 and 24 months after it (only in patients), were assessed. We diagnosed presence or absence of disease remission at cut-offs. All measurements were performed using a GE iDXA device (GE Healthcare Lunar, Madison, Wisconsin, USA). The TBS was calculated simultaneously from taken BMD scans, blinded to clinical outcome using TBS iNsight software v2.1 (Medimaps, Merignac, France). The activity of Cushings disease was evaluated using late-night salivary cortisol (LNSC, at 23:00). To determine the differences in DXA and TBS values before and after neurosurgical intervention depending on remission occurrence, covariate analysis (ANCOVA) was applied. RESULTS:There were found significant changes in TBS, BMD and T-score values in 12 months after neurosurgical treatment associated with presence or absence of disease remission (p = 0.039, 0.046 and 0.048, respectively). No differences in Z-score as well as in all measurements in 24 months, that might be associated with remission occurrence, were revealed. The gain in all DXA measurements (including TBS) during 24 months of observation period was statistically significant when analyzing data using Students paired t-test. However, the values corresponding to the age references had not been achieved for the specified time interval. CONCLUSIONS:Patients with Cushings disease have lower TBS values. In remission conditions TBS is getting significantly higher. The increase in BMD and TBS occurs during 24 months after achieving remission of Cushings disease but doesnt lead to a full restoration of normal bone mass and microstructure throughout observation period of 24 months

Po materialam klinicheskikh rekomendatsiy po vedeniyu bol'nykh s differentsirovannymi neyroendokrinnymi opukholyami ileoeyunal'noy lokalizatsii

Полный текст рекомендаций: B. Eriksson, G. Kloppel, E. Krennin, H. Ahlman, U. Phckinger, B. Wiedenmann, R. Arnold, C. Auernhammer, M. Когжг, G. Rindi, S. Wildi et al. Neuroendocrinology 2008, 87, р. 8-1

TRABECULAR BONE SCORE – A NON-INVASIVE ANALYTICAL METHOD TO EVALUATE BONE QUALITY BASED ON ROUTINE DUAL-ENERGY ABSORPTIOMETRY. PERSPECTIVES OF ITS USE IN CLINICAL PRACTICE

Two-dimensional dual-energy X-ray absorptiometry (DXA, osteodensitometry) is currently considered as the gold standard for diagnosis of osteoporosis. However, despite good operational characteristics, this type of investigation cannot help to assess bone microarchitecture and the degree of its derangement in osteoporosis. Therefore, trabecular bone score (TBS) has been developed as a  non-invasive method of indirect description of bone microarchitecture based on data derived from a  standard DXA of the lumbar spine. Not being a direct mapping of the physical measurements of trabecular microarchitecture, TBS nevertheless shows a positive correlation with quantitative values obtained from micro-computed tomography and high resolution peripheral quantitative computed tomography, i.e. with the bone volume fraction, junction density, trabecular numbers and their disintegration. There is also an association between the ability of the bone tissue to resist stress in experimental studies ex vivo and TBS measurement. Due to TBS, there is a possibility to detect bone microarchitecture impairment even in individuals with normal bone mineral density (BMD), i.e. higher TBS values correlate with improved bone microstructure, whereas a  reduced TBS shows its deterioration. Limitation of TBS use are primarily related to the DXA image quality: image faults caused either by technical reasons or by too low or too high body mass index can lead to an overestimation/underestimation of the index. Assessment of the lumbar TBS has been repeatedly performed in cross-sectional and prospective studies in representative patient samples (mainly postmenopausal women) and significant numbers of healthy subjects, and proved to be a predictor (independent of BMD) of fracture risk. An evaluation of the possibility to use TBS for early diagnosis of secondary osteoporosis (related to various endocrine disorders)  would be of great interest, as BMD, as known from clinical practice, is not always a  reliable measurement of the bone endurance, especially in diabetes, steroid osteoporosis and acromegaly.  The use of TBS along with BMD as a  marker of efficacy of current treatment for secondary osteoporosis is also possible, but it is not yet evidence-based; therefore, research has to be continued