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Rapid Release (rapid + release)
Selected AbstractsPrediction of the behaviour of landslide dams using a geomorphological dimensionless indexEARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2003L. Ermini Abstract Landslide dams are a common phenomenon. They form when a landslide reaches the bottom of a river valley causing a blockage. The first effect of such a dam is the infilling of a lake that inundates the areas upstream, while the possibility of a sudden dam collapse, with a rapid release of the impounded waters, poses a higher flood risk to the downstream areas. The results of the main inventories carried out to date on landslide dams, have been examined to determine criteria for forecasting landslide dam evolution with particular emphasis on the assessment of dam stability. Not all landslides result in the blockage of a river channel. This only occurs with ones that can move a large amount of material with moderate or high-velocities. In most cases, these landslides are triggered by rainfall events or high magnitude earthquakes. A relationship also exists between the volume of the displaced material and the landslide dam stability. Several authors have proposed that landslide dam behaviour can be forecast by defining various geomorphological indexes, that result from the combination of variables identifying both the dam and the dammed river channel. Further developments of this geomorphological approach are presented in this paper by the definition of a dimensionless blockage index. Starting with an analysis of 84 episodes selected worldwide, it proved to be a useful tool for making accurate predictions concerning the fate of a landslide dam. Copyright © 2002 John Wiley & Sons, Ltd. [source] Comparative efficacy of rapid-release nicotine gum versus nicotine polacrilex gum in relieving smoking cue-provoked cravingADDICTION, Issue 11 2005Raymond Niaura ABSTRACT Aims Most relapse episodes occur when smokers are confronted with craving provoked by situational cues. Current nicotine gum can help relieve cue-provoked cravings, but faster effects may result in more rapid relief. We tested a prototype formulation of a new rapid-release nicotine gum (RRNG) that provides more rapid release and absorption of nicotine, for its ability to provide faster and better craving relief compared to current nicotine polacrilex gum (NPG). Design Random assignment to RRNG or NPG, used during a smoking cue provocation procedure. Participants and setting A total of 319 smokers were exposed to a smoking cue in the laboratory by being asked to light but not smoke a cigarette of their preferred brand. Subjects then chewed a piece of 2 mg RRNG (n = 159) or 2 mg NPG (n = 160) according to randomized assignment. Measurements Craving assessments were completed at regular intervals before and after cue exposure (baseline, pre-cue, and 3, 6, 9, 12, 15, 18, 21, 25, 30 and 35 minutes after the cue). Findings Smokers chewing RRNG showed significantly lower craving than NPG subjects starting with the first assessment at 3 minutes (P < 0.025). Repeated-measures ANOVA revealed a significant treatment × time interaction (P < 0.05),craving scores dropped more rapidly in RRNG subjects compared to NPG subjects. Survival analyses also indicated superiority of RRNG in achieving more rapid self-reported meaningful relief (P < 0.05) and complete relief (P < 0.05) of craving. Conclusions Rapid-release nicotine gum reduced cue-provoked craving more rapidly compared to NPG, and thus merits further study in cessation efficacy trials. [source] Voltage- and Ca2+ -activated potassium channels in Ca2+ store control Ca2+ releaseFEBS JOURNAL, Issue 15 2006Masayuki Yamashita Ca2+ release from Ca2+ stores is a ,quantal' process; it terminates after a rapid release of stored Ca2+. To explain the quantal nature, it has been supposed that a decrease in luminal Ca2+ acts as a ,brake' on store release. However, the mechanism for the attenuation of Ca2+ efflux remains unknown. We show that Ca2+ release is controlled by voltage- and Ca2+ -activated potassium channels in the Ca2+ store. The potassium channel was identified as the big or maxi-K (BK)-type, and was activated by positive shifts in luminal potential and luminal Ca2+ increases, as revealed by patch-clamp recordings from an exposed nuclear envelope. The blockage or closure of the store BK channel due to Ca2+ efflux developed lumen-negative potentials, as revealed with an organelle-specific voltage-sensitive dye [DiOC5(3); 3,3'-dipentyloxacarbocyanine iodide], and suppressed Ca2+ release. The store BK channels are reactivated by Ca2+ uptake by Ca2+ pumps regeneratively with K+ entry to allow repetitive Ca2+ release. Indeed, the luminal potential oscillated bistably by ,45 mV in amplitude. Our study suggests that Ca2+ efflux-induced store BK channel closures attenuate Ca2+ release with decreases in counter-influx of K+. [source] Tailoring Macromolecular Expression at Polymersome SurfacesADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Adam Blanazs Abstract A series of amphiphilic ABC triblock copolymers are synthesized by atom transfer radical polymerization, wherein the ,A' and ,C' blocks are hydrophilic and the pH-sensitive ,B' block can be switched from hydrophilic in acidic solution to hydrophobic at pH 7. Careful addition of base to the molecularly dissolved copolymer in acidic solution readily induces the self-assembly of such triblock copolymers at around neutral pH to form pH-sensitive polymersomes (a.k.a. vesicles) with asymmetric membranes. By systematic variation of the relative volume fractions of the ,A' and ,C' blocks, the chemical nature of the polymer chains expressed at the interior or exterior corona of the polymersomes can be selected. Treatment of primary human dermal fibroblast cells with these asymmetric polymersomes demonstrates the biological consequences of such spatial segregation, with both polymersome cytotoxicity and endocytosis rates being dictated by the nature of the polymersome surface chemistry. The pH-sensitive nature of the polymersomes readily facilitates their dissociation after endocytosis due to the relatively low endosomal pH, which results in the rapid release of an encapsulated dye. Selective binding of anionic substrates such as DNA within the inner cationic polymersome volume, coupled with a biocompatible exterior, leads to potential gene delivery applications for these pH-sensitive asymmetric nanovectors. [source] Experimental study of stick-slip behaviourINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2004Florence Adjemian Abstract Simple axi-symmetric uni-axial compression tests have been realized on dry loose samples of glass beads (diameters d: d=0.2 ± 0.05 mm, 0.75 ± 0.1 mm, or 3 mm) and on Hostun sand under small lateral confinement, ,3<60 kPa, using different sample sizes. The experiments with the two smallest spheres (d=0.2 and 0.75 mm) exhibit stick-slips, which are characterized by (i) a rapid release ,q of the deviatoric stress q and by (ii) the strain ,,1 separating two events. The samples which exhibit stick-slip also present a weakening of strength q(,1) as the rate of deformation d,1/dt is increased. No stick-slip is generated during the first part of the q,,1 curve, i.e. when q grows fast with ,1. Four different parameters helped us determine the statistics of ,q and ,,: the lateral pressure ,3,, the rate of deformation d,1/dt, the sample height H, and the diameter D. The statistics do not depend on rate history. They look like exponentials in small samples and/or in (large sample+fast d,1/dt), and they look like Poissonian or Gaussian in (Large sample+small d,1/dt). This change in statistics is attributed to a varying of triggering process starting from a single random event in small samples to multiple random events. We have interpreted this change of statistics as due to some finite size effect so that the representative elementary volume shall contain at least (200)3 grains. Localization of deformation is visible at the end of compression but cannot be detected from stick-slip statistics nor from q vs , curve. Copyright © 2004 John Wiley & Sons, Ltd. [source] In vitro release of complexed pDNA from biodegradable polymer filmsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Y. Ramgopal Abstract The controlled delivery of low-molecular weight drugs and proteins from biodegradable polymers has received considerable attention. However, controlled release studies of pDNA from such polymers have not been reported to date. In this study, a plasmid DNA was complexed with the cationic polymer called polyethylenimine (PEI). This gene vector has been shown to be very effective in transfecting cells. The complexed DNA were then incorporated into different types of poly-lactic- co -glycolic acid (PLGA) film; PLGA 53/47 (Mw 90 kDa), 50/50 (Mw 11 kDa, end group is lauryl ester) and 75/25 (Mw 120 kDa). Their release profiles from a buffer solution were studied. An initial (small) burst release of PEI-DNA from film was observed in PLGA 53/47 and 50/50, followed by a plateau phase and finally a rapid erosion-controlled release. For PLGA 50/50, the rapid release started after 14 days; erosion-controlled release for PLGA 53/47 started after 9 days; for PLGA 75/25, the release rate was governed by an initial burst release (10%) followed by a slow release controlled by diffusion. No obvious erosion-controlled release rate was observed for this polymer up to 27 days. Thus, the controlled release of complexed DNA follows the general features exhibited by lower- Mw drugs. This is of significance in designing gene vector matrices that offer the promise of more lasting gene therapy compared with particulate formulations. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Osteoblast interactions with various hydroxyapatite based biomaterials consolidated using a spark plasma sintering techniqueJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008J. L. Xu Abstract This study investigated the osteoblast behaviors on various hydroxyapatite based biomaterials that were consolidated at 1100°C for 3 min by a spark plasma sintering technique. The osteoblasts from human fetal osteoblast cell line were cultured in the medium on the various biomaterials surfaces (HA, RF21, 1SiHA, and 5SiHA) to assess the cell morphology and proliferation as well as cell differentiation (alkaline phosphatase activity). Moreover, the bone ,-carboxyglutamic protein or osteocalcin in the medium were determined at different periods of culture. The present results indicated that the amount of osteocalcin in the medium decreased during the periods of culture. The highest osteocalcin production obtained from the biomaterial 5SiHA after cell culture for 2 days demonstrated that the presence of silica in the biomaterials enhanced the cell differentiation by the rapid release of silicate and calcium ions. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008 [source] Development and in-vivo evaluation of insulin-loaded chitosan phthalate microspheres for oral deliveryJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 10 2007Udhumansha Ubaidulla Novel chitosan phthalate microspheres containing insulin were prepared by emulsion cross-linking technique. The feasibility of these microspheres as oral insulin delivery carriers was evaluated. The pH-responsive release behaviour of insulin from microspheres was analysed. The ability of chitosan phthalate-insulin microspheres to enhance intestinal absorption and improve the relative pharmacological availability of insulin was investigated by monitoring the plasma glucose and insulin level of streptozotocin-induced diabetic rats after oral administration of microspheres at insulin dose of 20 IU kg,1. In simulated gastric fluid (pH 2.0), insulin release from the microspheres was very slow. However, as the pH of the medium was changed to simulated intestinal fluid (pH 7.4), a rapid release of insulin occurred. The relative pharmacological efficacy for chitosan phthalate microspheres (18.66 ± 3.84%) was almost four-fold higher than the efficacy of the chitosan phthalate-insulin solution administration (4.08 ± 1.52%). Chitosan phthalate microspheres sustained the plasma glucose at pre-diabetic level for at least 16 h. These findings suggest that the microsphere is a promising carrier as oral insulin delivery system. [source] Reduction-Sensitive Reversibly Crosslinked Biodegradable Micelles for Triggered Release of DoxorubicinMACROMOLECULAR BIOSCIENCE, Issue 12 2009Yanmin Xu Abstract Reduction-responsive reversibly crosslinked biodegradable micelles were developed and applied for triggered release of doxorubicin (DOX). An amphiphilic block copolymer of poly(ethylene glycol) (PEG) and poly(, -caprolactone) (PCL) that contains two lipoyl functional groups at their interface (PEG-L2 -PCL) has been synthesized. 1H NMR spectroscopy and gel permeation chromatography (GPC) measurements show that the PEG-L2 -PCL block copolymer had a controlled composition (PEG 5 kDa and PCL 5.4 kDa) and a polydispersity index (PDI) of 1.36. PEG-L2 -PCL formed micelles with sizes that ranged from 20 to 150,nm in aqueous solutions, wherein a critical micelle concentration (CMC) of 16,mg·L,1 was determined. The micelles were readily crosslinked by adding 7.6,mol % of dithiothreitol (DTT) relative to the lipoyl groups. Notably, micelles after crosslinking demonstrated a markedly enhanced stability against dilution, physiological salt concentration, and organic solvent. In the presence of 10,×,10,3,M DTT, however, micelles were subject to rapid de-crosslinking. In vitro release studies showed minimal release of DOX from crosslinked micelles at a concentration of 10,mg,L,1 (C,<,CMC, analogous to intravenous injection), wherein less than 15% of the DOX was released in 10,h. In contrast, rapid release of DOX was observed for DOX-loaded non-crosslinked micelles under otherwise the same conditions (,80% release in 0.5,h). In the presence of 10,×,10,3,M DTT mimicking an intracellular reductive environment, sustained release of DOX from crosslinked micelles was achieved, in which 75% of the DOX was released in 9,h. These novel reduction-sensitive reversibly crosslinked biodegradable micelles are highly promising for targeted intracellular delivery of anticancer drugs. [source] The Binding Characteristics and Intracellular Localization of Temoporfin (mTHPC) in Myeloid Leukemia Cells: Phototoxicity and Mitochondrial Damage,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2000J. Y. Chen ABSTRACT The state of aggregation of the photosensitizer meso -tetrahydroxyphenylchlorin (mTHPC) in both cell free and intracellular environment was elucidated by comparing its absorption and excitation spectra. In methanol, mTHPC existed as monomers and strongly fluoresced. In aqueous solutions such as phosphate-buffered saline (PBS), mTHPC formed nonfluorescent aggregates. Some portion of mTHPC monomerized in the presence of 10% fetal calf serum PBS. In murine myeloid leukemia M1 and WEHI-3B (JCS) cells, cytoplasmic mTHPC were monomeric. By using organelle-specific fluorescent probes, it was found that mTHPC localized preferentially at the mitochondria and the perinuclear region. Photodynamic treatment of mTHPC-sensitized leukemia cells caused rapid appearance of the apoptogenic protein cytochrome c in the cytosol. Results from flow cytometric analysis showed that the release of cytochrome c was especially pronounced in JCS cells, and well correlated with the extent of apoptotic cell death as reported earlier. Electron microscopy revealed the loss of integrity of the mitochondrial membrane and the appearance of chromatin condensation as early as 1 h after light irradiation. We conclude that rapid release of cytochrome c from photodamaged mitochondria is responsible for the mTHPC-induced apoptosis in the myeloid leukemia JCS and M1 cells. [source] Mechano-biology of skeletal muscle hypertrophy and regeneration: Possible mechanism of stretch-induced activation of resident myogenic stem cellsANIMAL SCIENCE JOURNAL, Issue 1 2010Ryuichi TATSUMI ABSTRACT In undamaged postnatal muscle fibers with normal contraction and relaxation activities, quiescent satellite cells of resident myogenic stem cells are interposed between the overlying external lamina and the sarcolemma of a subjacent mature muscle fiber. When muscle is injured, exercised, overused or mechanically stretched, these cells are activated to enter the cell proliferation cycle, divide, differentiate, and fuse with the adjacent muscle fiber, and are responsible for regeneration and work-induced hypertrophy of muscle fibers. Therefore, a mechanism must exist to translate mechanical changes in muscle tissue into chemical signals that can activate satellite cells. Recent studies of satellite cells or single muscle fibers in culture and in vivo demonstrated the essential role of hepatocyte growth factor (HGF) and nitric oxide (NO) radical in the activation pathway. These experiments have also reported that mechanically stretching satellite cells or living skeletal muscles triggers the activation by rapid release of HGF from its extracellular tethering and the subsequent presentation to the receptor c-met. HGF release has been shown to rely on calcium-calmodulin formation and NO radical production in satellite cells and/or muscle fibers in response to the mechanical perturbation, and depend on the subsequent up-regulation of matrix metalloproteinase (MMP) activity. These results indicate that the activation mechanism is a cascade of events including calcium ion influx, calcium-calmodulin formation, NO synthase activation, NO radical production, MMP activation, HGF release and binding to c-met. Better understanding of ,mechano-biology' on the satellite cell activation is essential for designing procedures that could enhance muscle growth and repair activities in meat-animal agriculture and also in neuromuscular disease and aging in humans. [source] Tricalcium phosphate nanoparticles enable rapid purification, increase transduction kinetics, and modify the tropism of mammalian virusesBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2009Imke A.J. Dreesen Abstract Adenoviral, adeno-associated viral, and retroviral particles are chosen as gene delivery shuttles in more than 50% of all gene therapy clinical trials. Bulk availability of clinical-grade viral particles and their efficiency to transduce the therapeutic cargo into specific target cells remain the most critical bottlenecks in gene therapy applications to date. Capitalizing on the flame-spray technology for the reproducible economic large-scale production of amorphous tricalcium phosphate nanoparticulate powders (ATCP), we designed a scalable ready-to-use gravity-flow column set-up for the straightforward concentration and purification of transgenic adenoviral, adeno-associated viral, and lentiviral particles. Specific elution buffers enabled rapid release of viral particles from the ATCP matrix of the column and provided high-titer virus preparations in an unsurpassed period of time. The interaction of ATCP with adenoviral, adeno-associated viral, and lentiviral particles in solution increased the transduction kinetics of several mammalian cell lines in culture. The nanoparticles were also able to modify the tropism of murine leukemia virus (MLV) towards transduction of human cells. Based on these findings, we believe that the use of flame-spray tricalcium phosphate nanoparticles will lead to important progress in the development of future gene therapy initiatives. Biotechnol. Bioeng. 2009;102: 1197,1208. © 2008 Wiley Periodicals, Inc. [source] | ||||||||||||||||