			Home About us Contact

Transient Response (transient + response)

Distribution by Scientific Domains

Medical Sciences	36%
Engineering	36%
Life Sciences	20%
2 Other Domains	8%

Distribution within Medical Sciences

Hematology	27%
Hepatology	16%

Selected Abstracts

Transient response of closed-loop MHD experimental facility

ELECTRICAL ENGINEERING IN JAPAN, Issue 1 2007
Hidemasa Takana
Abstract Transient responses of a closed-loop MHD experimental facility from nonpower generation to power generation have been investigated by means of time-dependent quasi-one-dimensional numerical simulations. For the long-time continuous power generation experiment, the time required to obtain the steady state for the power generation is estimated to be approximately 20 hours. By increasing the electrical input power to the heater as an exponential function of time, the temperature increment of ceramics can be moderated. When the duration of the experiment is around 10 minutes, argon gas temperature at the exit of the heater hardly changes because of the large heat capacity of structure materials. It is found that the fluid disturbances are induced at the instant of the power generation and they propagate as they repeatedly reflect at the sudden change of duct shape. Since all of the induced disturbances attenuate approximately 0.4 second after the power generation, the time scale that the disturbances exist in the facility is estimated to be 1 second at most. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(1): 46,52, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20237 [source]

Transient response of cardiac angiosarcoma to paclitaxel

EUROPEAN JOURNAL OF CANCER CARE, Issue 5 2010
E. CASTILLA md
CASTILLA E., PASCUAL I., RONCALÉS F., AGUIRRE E. & RÍO A. DEL (2010) European Journal of Cancer Care19, 699,700 Transient response of cardiac angiosarcoma to paclitaxel Malignant tumours of the heart are a group of tumours with low incidence but very high mortality. Delays in diagnosis are common because of their multiple forms of presentation, and 80% present with metastases, further reducing the possibility for cure. We present here the case of a patient with primary cardiac angiosarcoma that highlights the misdiagnosis at clinical presentation, current diagnostic modalities and a possible new treatment using paclitaxel for cardiac angiosarcoma. [source]

Transient response of closed-loop MHD experimental facility

Investigating static and dynamic characteristics of electromechanical actuators (EMA) with MATLAB GUIs

COMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 2 2010
Gursel Sefkat
Abstract This paper deals with the design of an electromechanical device considering some prescribed performance requirements, and static and dynamic analysis of this device are carried out. In studying the transient response of such a system, as part of dynamic analysis, two methods mostly used finite element method (FEM) and finite differences method (FDM). However, these methods need much CPU time. In this work, a computer simulator program is developed for an EMA. This technique is implemented in the MATLAB-Simulink environment and tested for different design tasks such as electromagnetic valves or electromechanical brakes etc. Furthermore, by using GUIDE tools within MATLAB, a simple useful and user-friendly GUI structure is developed to provide a visual approach to design and analysis process. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 18: 383,396, 2010; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20279 [source]

Dynamic systems with high damping rubber: Nonlinear behaviour and linear approximation

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 13 2008
Andrea Dall'Asta
Abstract High damping rubber (HDR) shows a quite complex constitutive behaviour, which is nonlinear with respect to strain and is dependent on the strain rate. In addition, it exhibits a transient response during which the material properties change (scragging or more generally the Mullins effect). A number of recent works were dedicated to analysing and modelling material behaviour. This paper studies the nonlinear dynamics of systems with restoring force produced by HDR-based devices in order to propose a procedure to define equivalent linear models considering both transient and stationary behaviours. The reliability of these linear models is tested by evaluating the upper and lower bounds of the seismic response of a structural system equipped with HDR-based devices (structural system with dissipative bracings and isolated systems). Copyright © 2008 John Wiley & Sons, Ltd. [source]

Non-parametric,parametric model for random uncertainties in non-linear structural dynamics: application to earthquake engineering

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2004
Christophe Desceliers
Abstract This paper deals with the transient response of a non-linear dynamical system with random uncertainties. The non-parametric probabilistic model of random uncertainties recently published and extended to non-linear dynamical system analysis is used in order to model random uncertainties related to the linear part of the finite element model. The non-linearities are due to restoring forces whose parameters are uncertain and are modeled by the parametric approach. Jayne's maximum entropy principle with the constraints defined by the available information allows the probabilistic model of such random variables to be constructed. Therefore, a non-parametric,parametric formulation is developed in order to model all the sources of uncertainties in such a non-linear dynamical system. Finally, a numerical application for earthquake engineering analysis is proposed concerning a reactor cooling system under seismic loads. Copyright © 2003 John Wiley & Sons, Ltd. [source]

A case of hepatosplenic ,,, T-cell lymphoma with a transient response to Fludarabine and Alemtuzumab

EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 6 2006
S. Mittal
Abstract:, Hepatosplenic ,,, T-cell lymphoma is a rare, usually fatal lymphoma and available literature on management is sparse. Allografting is probably the only curative option. We describe a further case with a dramatic, though transient response to Fludarabine and Alemtuzumab combination, following a failure of conventional chemotherapy. Given the dreadful prognosis with conventional chemotherapy, it is a regimen worth pursuing as a disease reduction strategy prior to allograft where appropriate. [source]

Effects of intermediate load on damping of synchronous generator

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2006
P. Aree
Abstract The transfer-function block-diagram model of a single-machine infinite-bus power system, originally developed by Heffron and Phillips, has been a popular analytical tool amongst power system engineers for explanation and assessment of synchronous generator dynamic behaviors. Since this model simply accounts for the generator field circuit with none of the damper circuits, it may not always give a realistic transient response. Moreover, the model considers only a grid-system load without local and intermediate loads. Hence, effects of these loads together with the damper circuits on electromechanical damping have not yet been completely studied. In this paper, the Heffron-Phillips's model has been advanced to incorporate an intermediate load plus one additional damper circuit in the q -axis. The upgraded model demonstrates a great influence of the intermediate load together with the q -axis damper circuit on the electromechanical damping and the dynamic interaction between the field and damper flux linkages. The study shows the key contributions of load to rise and fall of the damping. It appears that the electromechanical damping can be improved with regard to the unity power-factor load through increasing in the natural damping and decreasing in the automatic voltage regulator (AVR) negative damping torques. Nevertheless, the damping is mostly declined, when the load power factor is poor. Moreover, it is markedly changed in relation to various locations of load. The damping characteristics of synchronous generator are investigated using the eigenvalue and frequency response methods. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A wide-band lumped circuit model of the terminal and internal electromagnetic response of coaxially insulated windings mounted on a core

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2003
P. Holmberg
This paper presents a wide-band lumped circuit model of coaxially insulated windings mounted on a core. The polyphase model can be used to simulate the terminal and internal electromagnetic response in DryformerTM, a new oil-free power transformer, and similar electromagnetic power devices. The circuit parameters are based on geometrical and material data. The simulated frequency and transient response of the lumped circuit is compared to measurements on a 20 MVA 140/6.6 kV three-phase transformer of the DryformerTM type. The comparison shows that the model can be used to estimate resonance frequencies and transient overvoltages in the transformer, although the damping is not accurately modelled. The influence of the core is discussed and investigated. [source]

Global climate change and soil carbon stocks; predictions from two contrasting models for the turnover of organic carbon in soil

GLOBAL CHANGE BIOLOGY, Issue 1 2005
Chris Jones
Abstract Enhanced release of CO2 to the atmosphere from soil organic carbon as a result of increased temperatures may lead to a positive feedback between climate change and the carbon cycle, resulting in much higher CO2 levels and accelerated global warming. However, the magnitude of this effect is uncertain and critically dependent on how the decomposition of soil organic C (heterotrophic respiration) responds to changes in climate. Previous studies with the Hadley Centre's coupled climate,carbon cycle general circulation model (GCM) (HadCM3LC) used a simple, single-pool soil carbon model to simulate the response. Here we present results from numerical simulations that use the more sophisticated ,RothC' multipool soil carbon model, driven with the same climate data. The results show strong similarities in the behaviour of the two models, although RothC tends to simulate slightly smaller changes in global soil carbon stocks for the same forcing. RothC simulates global soil carbon stocks decreasing by 54 Gt C by 2100 in a climate change simulation compared with an 80 Gt C decrease in HadCM3LC. The multipool carbon dynamics of RothC cause it to exhibit a slower magnitude of transient response to both increased organic carbon inputs and changes in climate. We conclude that the projection of a positive feedback between climate and carbon cycle is robust, but the magnitude of the feedback is dependent on the structure of the soil carbon model. [source]

Differential regulation of TGF-, signal in hepatic stellate cells between acute and chronic rat liver injury

HEPATOLOGY, Issue 1 2002
Yoshiya Tahashi
During chronic liver injury, transforming growth factor , (TGF-,) plays a prominent role in stimulating liver fibrogenesis by myofibroblast-like cells derived from hepatic stellate cells (HSCs). On the other hand, Smad 7 was recently shown to antagonize the TGF-,,induced activation of signal-transducing Smads (2 and 3). In this study, we investigated the regulatory mechanisms of the TGF-, signals in rat HSCs during acute liver injury and myofibroblasts (MFBs) during chronic liver injury, focusing on the roles of Smad 2 and antagonistic Smad 7. In acute liver injury, HSC-derived TGF-, increased plasminogen activator inhibitor type 1 (PAI-1) and ,2(I) procollagen (COL1A2) transcripts. Smad 2 in HSCs during liver injury and primary cultured HSCs were activated by an autocrine mechanism, because high levels of Smad 2 phosphorylation and induction of PAI-1 transcript by TGF-, were observed in HSCs. Thereafter, Smad 7 induced by TGF-, negatively regulated the Smad 2 action. These results indicated that endogenous TGF,,mediated Smad 7 in HSCs terminated the fibrotic signals mediated by signal-transducing Smads, and might be involved in the transient response to autocrine TGF-, signal after acute liver injury. By contrast, Smad 7 was not induced by the autocrine TGF-, signal, and constitutive Smad 2 activation was observed in MFBs throughout chronic liver injury, although Smad 7 could inhibit the TGF-, signal requiring Smad 2 phosphorylation by activated TGF-, receptor in cultured MFBs. This constitutive phosphorylation of Smad 2 by endogenous TGF-, under a low level of Smad 7 could be involved in the progression of liver fibrosis. [source]

Effect of interferon ,-2b plus ribavirin therapy on incidence of hepatocellular carcinoma in patients with chronic hepatitis

HEPATOLOGY RESEARCH, Issue 5 2009
Mika Kurokawa
Aim:, The objective of this study was to elucidate the long-term effects of interferon (IFN),-2b plus ribavirin combination therapy and to clarify whether this therapy can reduce the incidence of hepatocellular carcinoma (HCC) in patients with chronic hepatitis C. Methods:, A total of 403 patients infected with hepatitis C virus (HCV) were enrolled in a multicenter trial. All patients were treated with a combination of IFN-,-2b plus ribavirin therapy. We examined the incidence of HCC after combination therapy and analyzed the risk factors for liver carcinogenesis. Results:, A sustained virological response (SVR) was achieved by 139 (34%) of the patients. The cumulative rate of incidence of HCC was significantly lower in SVR patients than in non-SVR patients (P = 0.03), while there was no difference in the cumulative incidence of HCC between the transient response (TR) group and the no response (NR) group. Cox's regression analysis indicated the following risk factors as independently significant in relation to the development of HCC: age being > 60 years (P = 0.006), advanced histological staging (P = 0.033), non-SVR to IFN therapy (P = 0.044). The cumulative incidence rate of HCC was significantly lower in patients who had average serum alanine aminotransferase (ALT) levels of < 40 IU/L than in those who showed average serum ALT levels of , 40 IU/L after the combination therapy (P = 0.021). Conclusions:, These results suggest that the attainment of SVR or continuous normalization of ALT levels after IFN therapy can affect patients apart from HCC development. [source]

An operator-split ALE model for large deformation analysis of geomaterials

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 12 2007
Y. Di
Abstract Analysis of large deformation of geomaterials subjected to time-varying load poses a very difficult problem for the geotechnical profession. Conventional finite element schemes using the updated Lagrangian formulation may suffer from serious numerical difficulties when the deformation of geomaterials is significantly large such that the discretized elements are severely distorted. In this paper, an operator-split arbitrary Lagrangian,Eulerian (ALE) finite element model is proposed for large deformation analysis of a soil mass subjected to either static or dynamic loading, where the soil is modelled as a saturated porous material with solid,fluid coupling and strong material non-linearity. Each time step of the operator-split ALE algorithm consists of a Lagrangian step and an Eulerian step. In the Lagrangian step, the equilibrium equation and continuity equation of the saturated soil are solved by the updated Lagrangian method. In the Eulerian step, mesh smoothing is performed for the deformed body and the state variables obtained in the updated Lagrangian step are then transferred to the new mesh system. The accuracy and efficiency of the proposed ALE method are verified by comparison of its results with the results produced by an analytical solution for one-dimensional finite elastic consolidation of a soil column and with the results from the small strain finite element analysis and the updated Lagrangian analysis. Its performance is further illustrated by simulation of a complex problem involving the transient response of an embankment subjected to earthquake loading. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Current management of adult idiopathic thrombocytopenic purpura in practice: a cohort study of 201 patients from a single center,

INTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 2 2004
J. Zimmer
Summary To define usefulness and response to therapy and outcome in adults with idiopathic thrombocytopenic purpura (ITP) in clinical practice. We retrospectively reviewed a cohort of 201 consecutive patients with ITP, diagnosed between 1985 and 1994. In particular, we analyzed the therapies used, their response rates, prognostic indicators of response and outcome. In 62 patients, with minor bleeding episodes and a mean (±SD) platelet count of 88 ± 23 × 109/l, no treatment was used and chronic ITP was diagnosed in 59%. A total of 139 patients, with bleeding episodes in 71.2% cases and a mean platelet count of 20 ± 13 × 109/l, received at least one treatment. Three patients died (1.5% of the series). Corticosteroids were used in 118 patients, with an initial response rate of 82.2% and a long-term complete response (CR) of only 22.9%. Intravenous immunoglobulin was used in 26 patients, with an initial transient response in more than 60%. A splenectomy was performed in 55 patients, with an initial response rate of 92.5% and a long-term CR in 60%. Young age and prior response to corticosteroids were significant predictors of a durable response to splenectomy. Danazol was given in 37 patients, with a favorable response in 73% of cases. Our results illustrate the guidelines of the American Society of Hematology. Patients with moderate thrombocytopenia do not require treatment. In severe cases, splenectomy is the only treatment giving durable cures in a significant proportion of patients. Despite frequent chronicity, ITP is life-threatening only in a minor subset of patients. [source]

Influence of the carrier diffusion process on the transient response of vertical-cavity surface-emitting lasers

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1 2003
M. S. Torre
Abstract We investigate the transverse mode dynamics of weakly index-guided vertical-cavity surface-emitting lasers (VCSEL). The turn-on time of transverse modes are calculated by implementing a model for the VCSEL dynamics including diffusion and transport/capture phenomena. It takes into account the spatial dependence of the two carrier density profiles associated with the confined carriers in the quantum wells, and with the unconfined carriers in the barrier region. Devices of different aperture diameter under different excitation conditions are also studied. The model displays the correct turn-on time dependence on the injection current density when compared with the experimental data available. We show that the turn-on time of the modes increases when capture time increases and escape time decreases and also when diffusion increases. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Chattering-free sliding mode control for a class of nonlinear mechanical systems

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 12 2001
Vicente Parra-Vega
Abstract Second-order sliding mode control (2-smc) and dynamic sliding mode control (dsmc) eliminate the disturbing characteristic of chattering in static sliding mode control under the assumption that the derivative of the sliding surface is available or complex inequalities at the acceleration level can be constructed. In this paper, passivity-based adaptive and non-adaptive chattering-free sliding mode controllers are proposed assuming that the upper bound of the norm of the derivative of the sliding surface is available, a weaker and easy to implement assumption in comparison to those of 2-smc and dsmc. The closed-loop system accounts explicitly for the invariance condition without reaching phase, and therefore for a desired transient response with global exponential convergence of tracking errors. Preliminary experiments are presented. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Collagen promotes sustained glycoprotein VI signaling in platelets and cell lines

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 11 2007
M. G. TOMLINSON
Summary. Background:,Glycoprotein (GP)VI is the major signaling receptor for collagen on platelets and signals via the associated FcR,-chain, which has an immunoreceptor tyrosine-containing activation motif (ITAM). Objective:,To determine why GPVI,FcR, signals poorly, or not at all, in response to collagen in hematopoietic cell lines, despite robust responses to the GPVI-reactive snake venom toxin convulxin. Methods and results:,Using a nuclear factor of activated T-cells (NFAT) transcriptional reporter assay, a sensitive readout for sustained ITAM signaling, we demonstrate collagen-induced GPVI,FcR, signaling in hematopoietic cell lines. This is accompanied by relatively weak but sustained protein tyrosine phosphorylation, in contrast to the stronger but transient response to convulxin. Sustained signaling by collagen is also observed in platelets and is necessary for the maintenance of spreading on collagen. Finally, in cell lines, the inhibitory collagen receptor leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1), which is not expressed on platelets but is present on most hematopoietic cells, inhibits GPVI responses to collagen but not convulxin. Conclusion:,The inability of previous studies to readily detect GPVI collagen signaling in cell lines is probably because of the weak but sustained nature of the signal and the presence of the inhibitory collagen receptor LAIR-1. In platelets, we propose that GPVI,FcR, has evolved to transmit sustained signals in order to maintain spreading over several hours, as well as facilitating rapid activation through release of feedback agonists and integrin activation. The establishment of a cell line NFAT assay will facilitate the molecular dissection of GPVI signaling and the identification of GPVI antagonists in drug discovery. [source]

A simple spice model for traveling wave semiconductor laser amplifier

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2007
Abhirup Das Barman
Abstract An equivalent lumped element electric circuit model for traveling wave semiconductor laser amplifier has been developed using the rate equation for carriers. SPICE simulation of the circuits gives results in close agreement with the experimental data and values from sophisticated analyses. The modulation bandwidth and transient response were examined by including parasitic elements in the intrinsic model. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1558,1561, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22483 [source]

Oxytocin receptor expressed on the smooth muscle mediates the excitatory effect of oxytocin on gastric motility in rats

NEUROGASTROENTEROLOGY & MOTILITY, Issue 4 2009
J. Qin
Abstract, The aim of this study was to localize oxytocin receptor (OTR) in the stomach and to investigate the effect of OT on gastric motility in rats. Western blot and immunohistochemistry methods were used to localize OTR in stomach. The motility of stomach was recorded in vivo (recording of the intragastric pressure), in vitro (recording of the contraction of muscle strips) and on isolated smooth muscle cells. OTR was expressed on cells of both circular and longitudinal muscle of stomach. Systemic administration of OT induced an early transient decrease and a subsequent increase on intragastric pressure. Devazepide (1 mg kg,1, i.v.), a cholecystokinin-1 (CCK1) receptor antagonist, completely abolished the transient response but did not influence the subsequent one. OT (10,9,10,6 mol L,1) dose-dependently increased the contraction of the muscle strips of gastric body, antrum, and pyloric sphincter, and decreased the average cell length of isolated smooth muscle cells. Tetrodotoxin and atropine did not influence the effect of OT on muscle strips. Pretreatment with atosiban, an OTR antagonist, inhibited the spontaneous contraction of muscle strips and abolished the excitatory effect of OT on the muscle strips and the isolated cells. These results suggest that the OTR is expressed on the smooth muscle of the stomach and mediates excitatory effect of OT on gastric motility. [source]

Successful treatment of pure red cell aplasia with autologous stem cell transplantation

AMERICAN JOURNAL OF HEMATOLOGY, Issue 9 2007
Jae H. Park
We report a case of 64-year-old patient with pure red cell aplasia (PRCA) who was intolerant of conventional immunosuppressive therapies but achieved a complete long-term remission following autologous hematologic stem cell transplant (HSCT). The patient was initially treated with high-dose prednisone, cyclophosphamide, cyclosporine, antithymocyte globulin, and then rituximab. With the exception of rituximab, all of the above regimens achieved a transient response. However, because of the persistent requirement for red blood cell transfusions and intolerance to the multiple immunosuppressive therapies, autologous HSCT was eventually performed. The patient remains in complete remission and on no other therapy for 36 months following the autologous HSCT. Am. J. Hematol., 2007. © 2007 Wiley-Liss, Inc. [source]

Fast, transient and specific intracellular ROS changes in living root hair cells responding to Nod factors (NFs)

THE PLANT JOURNAL, Issue 5 2008
Luis Cárdenas
Summary The role of reactive oxygen species (ROS) in root-nodule development and metabolism has been extensively studied. However, there is limited evidence showing ROS changes during the earliest stages of the interaction between legumes and rhizobia. Herein, using ratio-imaging analysis, increasing and transient ROS levels were detected at the tips of actively growing root hair cells within seconds after addition of Nod factors (NFs). This transient response (which lasted up to 3 min) was Nod-factor-specific, as chitin oligomers (pentamers) failed to induce a similar response. When chitosan, a fungal elicitor, or ATP was used instead, a sustained increasing signal was observed. As ROS levels are transiently elevated after the perception of NFs, we propose that this ROS response is characteristic of the symbiotic interaction. Furthermore, we discuss the remarkable spatial and temporal coincidences between ROS and transiently increased calcium levels observed in root hair cells immediately after the detection of NFs. [source]

The response of the coupled tropical ocean,atmosphere to westerly wind bursts

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 579 2002
Alexey V. Fedorov
Abstract Two different perspectives on El Niño are dominant in the literature: it is viewed either as one phase of a continual southern oscillation (SO), or alternatively as the transient response to the sudden onset of westerly wind bursts (WWBs). Occasionally those bursts do indeed have a substantial effect on the SO,the unusual strength of El Niño of 1997/98 appears to be related to a sequence of bursts,but frequently the bursts have little or no impact. What processes cause some bursts to be important, while others remain insignificant? The question is addressed by using a simple coupled tropical ocean,atmosphere model that simulates a continual, possibly attenuating, oscillation to study the response to WWBs. The results show that the impact of WWBs depends crucially on two factors: (i) the background state of the system as described by the mean depth of the thermocline and intensity of the mean winds, and (ii) the timing of the bursts with respect to the phase of the SO. Changes in the background conditions alter the sensitivity of the system, so that the impact of the bursts on El Niño may be larger during some decades than others. Changes in the timing of WWBs affect the magnitude and other characteristics of the SO by modifying the energetics of the ocean,atmosphere interactions. A reasonable analogy is a swinging pendulum subject to modest blows at random times,those blows can either magnify or diminish the amplitude, depending on their timing. It is demonstrated that a WWB can increase the strength of El Niño significantly, if it occurs 6 to 10 months before the peak of warming, or can reduce the intensity of the subsequent El Niño, if it occurs during the cold phase of the continual SO. Copyright © 2002 Royal Meteorological Society. [source]

Modulation of lubricin biosynthesis and tissue surface properties following cartilage mechanical injury

ARTHRITIS & RHEUMATISM, Issue 1 2009
Aled R. C. Jones
Objective To evaluate the effects of injurious compression on the biosynthesis of lubricin at different depths within articular cartilage and to examine alterations in structure and function of the articular surface following mechanical injury. Methods Bovine cartilage explants were subdivided into level 1, with intact articular surface, and level 2, containing middle and deep zone cartilage. Following mechanical injury, lubricin messenger RNA (mRNA) levels were monitored by quantitative reverse transcriptase,polymerase chain reaction, and soluble or cartilage-associated lubricin protein was analyzed by Western blotting and immunohistochemistry. Cartilage morphology was assessed by histologic staining, and tissue functionality was assessed by friction testing. Results Two days after injury, lubricin mRNA expression was up-regulated ,3-fold for level 1 explants and was down-regulated for level 2 explants. Lubricin expression in level 1 cartilage returned to control levels after 6 days in culture. Similarly, lubricin protein synthesis and secretion increased in response to injury for level 1 explants and decreased for level 2 cartilage. Histologic staining revealed changes in the articular surface of level 1 explants following injury, with respect to glycosaminoglycan and collagen content. Injured level 1 explants displayed an increased coefficient of friction relative to controls. Conclusion Our findings indicate that increased lubricin biosynthesis appears to be an early transient response of surface-layer cartilage to injurious compression. However, distinct morphologic changes occur with injury that appear to compromise the frictional properties of the tissue. [source]

Millimeter wave effects on electrical responses of the sural nerve in vivo

BIOELECTROMAGNETICS, Issue 3 2010
Stanislav I. Alekseev
Abstract Millimeter wave (MMW, 42.25,GHz)-induced changes in electrical activity of the murine sural nerve were studied in vivo using external electrode recordings. MMW were applied to the receptive field of the sural nerve in the hind paw. We found two types of responses of the sural nerve to MMW exposure. First, MMW exposure at the incident power density ,45,mW/cm2 inhibited the spontaneous electrical activity. Exposure with lower intensities (10,30,mW/cm2) produced no detectable changes in the firing rate. Second, the nerve responded to the cessation of MMW exposure with a transient increase in the firing rate. The effect lasted 20,40,s. The threshold intensity for this effect was 160,mW/cm2. Radiant heat exposure reproduced only the inhibitory effect of MMW but not the transient excitatory response. Depletion of mast cells by compound 48/80 eliminated the transient response of the nerve. It was suggested that the cold sensitive fibers were responsible for the inhibitory effect of MMW and radiant heat exposures. However, the receptors and mechanisms involved in inducing the transient response to MMW exposure are not clear. The hypothesis of mast cell involvement was discussed. Bioelectromagnetics 31:180,190, 2010. © 2009 Wiley-Liss, Inc. [source]

Accurate control of oxygen level in cells during culture on silicone rubber membranes with application to stem cell differentiation

BIOTECHNOLOGY PROGRESS, Issue 3 2010
Daryl E. Powers
Abstract Oxygen level in mammalian cell culture is often controlled by placing culture vessels in humidified incubators with a defined gas phase partial pressure of oxygen (pO2gas). Because the cells are consuming oxygen supplied by diffusion, a difference between pO2gas and that experienced by the cells (pO2cell) arises, which is maximal when cells are cultured in vessels with little or no oxygen permeability. Here, we demonstrate theoretically that highly oxygen-permeable silicone rubber membranes can be used to control pO2cell during culture of cells in monolayers and aggregates much more accurately and can achieve more rapid transient response following a disturbance than on polystyrene and fluorinated ethylene-propylene copolymer membranes. Cell attachment on silicone rubber was achieved by physical adsorption of fibronectin or Matrigel. We use these membranes for the differentiation of mouse embryonic stem cells to cardiomyocytes and compare the results with culture on polystyrene or on silicone rubber on top of polystyrene. The fraction of cells that are cardiomyocyte-like increases with decreasing pO2 only when using oxygen-permeable silicone membrane-based dishs, which contract on silicone rubber but not polystyrene. The high permeability of silicone rubber results in pO2cell being equal to pO2gas at the tissue-membrane interface. This, together with geometric information from histological sections, facilitates development of a model from which the pO2 distribution within the resulting aggregates is computed. Silicone rubber membranes have significant advantages over polystyrene in controlling pO2cell, and these results suggest they are a valuable tool for investigating pO2 effects in many applications, such as stem cell differentiation. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source]

Transient Cooling of Heat-Generating Materials with Thermoelectric Coolers

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2006
Y. Makino
Abstract The transient cooling of heat-generating materials contacted with a thermoelectric microcooler was discussed, and the operation of a fixed electric current was proposed as an alternative to the conventional operation of a variable electric current to obtain the maximum heat flux of cooling. The changes in temperature of the materials cooled by the thermoelectric cooler were obtained by numerical calculation of the unsteady one-dimensional energy equation. The proposed operation of a fixed current was found to be a useful alternative to the conventional operation. An approximate analysis was made on the basis of the results of the numerical calculation. The results showed that the transient response of cooling of material without heat generation could be expressed by the first-order delay. Comparisons with the numerical calculation indicated that the expression by the first-order delay is also applicable to the cooling of material with heat generation and that the time constant decreases with increasing rate of heat generation from the material. [source]

Search for cerebral G cluster neurons responding to taste stimulation with seaweed in Aplysia kurodai by the use of calcium imaging

DEVELOPMENTAL NEUROBIOLOGY, Issue 3 2003
Ryusuke Yoshida
Abstract The calcium imaging method can detect the spike activities of many neurons simultaneously. In the present experiments, this method was used to search for unique neurons contributing to feeding behavior in the cerebral ganglia of Aplysia kurodai. We mainly explored the neurons whose cell bodies were located in the G cluster and the neuropile region posterior to this cluster on the ventral surface of the cerebral ganglia. When the extract of the food seaweed Ulva was applied to the tentacle-lip region, many neurons stained with a calcium-sensitive dye, Calcium Green-1, showed changes in fluorescence. Some neurons showed rhythmic responses and others showed transient responses, suggesting that these neurons may be partly involved in the feeding circuits. We also identified three motor neurons among these neurons that showed rhythmic fluorescence responses to the taste stimulation. One of them was a motor neuron shortening the anterior tentacle (ATS), and the other two were motor neurons producing lip opening-like (LOG) and closing-like (LCG) movements, respectively. Application of the Ulva extract to the tentacle-lip region induced phase-locked rhythmic firing activity in these motor neurons, suggesting that these neurons may contribute to the rhythmic patterned movements of the anterior tentacles and lips during the ingestion of seaweed. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 299,314, 2003 [source]

Ca2+ -independent phospholipase A2-dependent sustained Rho-kinase activation exhibits all-or-none response

GENES TO CELLS, Issue 9 2006
Akio Maeda
Sustained contraction of cells depends on sustained Rho-associated kinase (Rho-kinase) activation. We developed a computational model of the Rho-kinase pathway to understand the systems characteristics. Thrombin-dependent in vivo transient responses of Rho activation and Ca2+ increase could be reproduced in silico. Low and high thrombin stimulation induced transient and sustained phosphorylation, respectively, of myosin light chain (MLC) and myosin phosphatase targeting subunit 1 (MYPT1) in vivo. The transient phosphorylation of MLC and MYPT1 could be reproduced in silico, but their sustained phosphorylation could not. This discrepancy between in vivo and in silico in the sustained responses downstream of Rho-kinase indicates that a missing pathway(s) may be responsible for the sustained Rho-kinase activation. We found, experimentally, that the sustained phosphorylation of MLC and MYPT1 exhibit all-or-none responses. Bromoenol lactone, a specific inhibitor of Ca2+ -independent phospholipase A2 (iPLA2), inhibited sustained phosphorylation of MLC and MYPT1, which indicates that sustained Rho-kinase activation requires iPLA2 activity. Thus, the systems analysis of the Rho-kinase pathway identified a novel iPLA2-dependent mechanism of the sustained Rho-kinase activation, which exhibits an all-or-none response. [source]