Home About us Contact
|
Home About us Contact | ||
|
|
||
Signal Components (signal + component)
Selected AbstractsCalcium/calcineurin signaling in primary cortical astrocyte cultures: Rcan1-4 and cyclooxygenase-2 as NFAT target genesGLIA, Issue 7 2008Andrea Canellada Abstract The calcineurin/nuclear factor of activated T cells (NFAT) signaling pathway mediates important cell responses to calcium, but its activity and function in astrocytes have remained unclear. We show that primary cortical astrocyte cultures express the regulatory and catalytic subunits of the phosphatase calcineurin as well as the calcium-regulated NFAT family members (NFATc1, c2, c3, and c4). NFATs are activated by calcium-mobilizing agents in astrocytes, and this activation is blocked by the calcineurin inhibitor cyclosporine A. Microarray screening identified cyclooxygenase-2 (Cox-2), which is implicated in brain injury, and Rcan 1-4, an endogenous calcineurin inhibitor, as genes up-regulated by calcineurin-dependent calcium signals in astrocytes. Mobilization of intracellular calcium with ionophore potently augments the promoter activity and mRNA and protein expression of Rcan 1-4 and Cox-2 induced by combined treatment with phorbol esters. Moreover, Rcan 1-4 expression is efficiently induced by calcium mobilization alone. For both the genes, the calcium signal component is dependent on calcineurin and is replicated by exogenous expression of a constitutively active NFAT, strongly suggesting that the calcium-induced gene activation is mediated by NFATs. Finally, we report that calcineurin-dependent expression of Cox-2 and Rcan 1-4 is induced by physiological calcium mobilizing agents, such as thrombin, agonists of purinergic and glutamate receptors, and L-type voltage-gated calcium channels. These findings provide insights into calcium-initiated gene transcription in astrocytes, and have implications for the regulation of calcium responses in astrocytes. © 2008 Wiley-Liss, Inc. [source] How accurately can parameters from exponential models be estimated?CONCEPTS IN MAGNETIC RESONANCE, Issue 2 2005A Bayesian view Abstract Estimating the amplitudes and decay rate constants of exponentially decaying signals is an important problem in NMR. Understanding how the uncertainty in the parameter estimates depends on the data acquisition parameters and on the "true" but unknown values of the exponential signal parameters is an important step in designing experiments and determining the amount and quality of the data that must be gathered to make good parameter estimates. In this article, Bayesian probability theory is applied to this problem. Explicit relationships between the data acquisition parameters and the "true" but unknown exponential signal parameters are derived for the cases of data containing one and two exponential signal components. Because uniform prior probabilities are purposely employed, the results are broadly applicable to experimental parameter estimation. © 2005 Wiley Periodicals, Inc. Concepts Magn Reson Part A 27A: 73,83, 2005 [source] Effects of Abstinence From Alcohol on the Broad Phospholipid Signal in Human Brain: An In Vivo 31P Magnetic Resonance Spectroscopy StudyALCOHOLISM, Issue 8 2001M. R. Estilaei Background: In vivo phosphorus magnetic resonance spectroscopy (31P MRS) at a magnetic field strength of 1.5 T allows measurement of fairly mobile membrane phospholipids in the human brain. We previously showed that subjects who are heavy drinkers had a smaller signal and a shorter transverse relaxation time (T2) of white matter phospholipids than light drinkers, which suggested lower concentrations and molecular mobility of phospholipids in heavy drinkers. The purpose of the present study was to measure if such chronic alcohol-induced white matter tissue changes are persistent in long-term abstinent alcoholics. Methods: Fourteen abstinent alcoholics (mean age 45 years, seven men and seven women) were studied by localized 31P MRS in the centrum semiovale and were compared with 13 male, alcohol-dependent, heavy drinkers and 23 nondependent light drinkers (17 men, 6 women) of similar age. Methods for measurements of the broad membrane phospholipid signal and its relaxation time were described previously. Results: Phospholipid concentrations and relaxation times in alcoholics abstinent for an average of 31 months were not significantly different from those measured in light drinkers. The contribution of fast and slowly relaxing signal components to the broad phospholipid signal, however, was still different in abstinent alcoholics compared with light drinkers. No effects of sex or of family history of alcoholism were noted on any of our spectroscopic measures within the light-drinking or abstinent groups. Conclusions: Most of our results suggest at least partial recovery of chronic alcohol-induced white matter phospholipid damage with long-term abstinence. They offer myelination changes and/or dendritic rearborization as a possible mechanism for the commonly observed white matter volume gain with prolonged abstinence. But the results also suggest a persistent abnormality in the nature and/or physical properties of white matter phospholipids in long-term abstinent alcoholics. [source] Chemical cues and binary individual recognition in the hermit crab Pagurus longicarpusJOURNAL OF ZOOLOGY, Issue 1 2004Francesca Gherardi Abstract The behaviour exhibited by the hermit crab Pagurus longicarpus in response to an empty shell varied in the presence of cues from conspecific individuals according to its familiarity or not with them. This binary discrimination was independent of the conspecific's relative size and was based on chemical signatures, an ability that this species shares with a few other aquatic invertebrates. From our results, olfaction appeared to be the dominant sensory channel in P. longicarpus' binary discrimination, but the combination of two signal components from visual and olfactory channels resulted in the enhancement of the response displayed by the receiver. Besides, crabs reacted differently when exposed to their own odour than to the odour of familiar (as well as unfamiliar) conspecifics, suggesting that recognition in this species can be more refined than a binary discrimination and that chemical ,badges' may be attributes of individual crabs. [source] MRI of muscular fatMAGNETIC RESONANCE IN MEDICINE, Issue 4 2002Fritz Schick Abstract An MRI technique with high selectivity and sensitivity to the signal components in the chemical shift range of methylene and methyl protons of fatty acids has been developed for noninvasive assessment of muscular fat in vivo. A spoiled gradient-echo sequence with spatial-spectral excitation by six equidistant pulses with 2°-(,9°)-17°-(,17°)-9°-(,2°) and a multi-echo train (TE = 16, 36, 56, 76, 96, and 116 ms) allowed a series of images to be recorded with a receiver bandwidth of 78 Hz per pixel. SIs from phantoms with lipid contents between 0.1% and 100% were compared to those from pure water. Thirty healthy volunteers underwent fat-selective imaging of their lower leg, and parallel localized proton spectroscopy of the tibialis anterior and the soleus muscle by a single-voxel stimulated echo acquisition mode (STEAM) technique (TR = 2 s, TE = 10 ms, TM = 15 ms). Results show a high correlation (r = 0.91) between fat imaging and the spectroscopic approach in the soleus muscle, considering the percentage total fat content of musculature. The correlation coefficient was clearly lower (r = 0.55) in the tibialis anterior muscle due to signal contaminations from adjacent subcutaneous fat in the images, inhomogeneous fat distribution, and generally lower lipid content in this muscle. Applications of the new imaging technique showed marked intra- and interindividual variability in the spatial distribution of lipids in the musculature of the lower leg. No significant correlation of the muscular fat with the thickness of the subcutaneous fat layer was found. In addition, the body mass index does not appear to determine muscular fat content, except in very obese cases. Magn Reson Med 47:720,727, 2002. © 2002 Wiley-Liss, Inc. [source] Compartmental relaxation and diffusion tensor imaging measurements in vivo in ,-carrageenan-induced edema in rat skeletal muscle,NMR IN BIOMEDICINE, Issue 6 2008Reuben H. Fan Abstract Integrated diffusion tensor T2 measurements were made on normal and edematous rat muscle, and the data were fitted with one- and two-compartment models, respectively. Edematous muscle exhibited a short-lived component (T2,=,28,±,6,ms), with diffusion characteristics similar to that of normal muscle, and a long-lived component (T2,=,96,±,27,ms), with greater mean apparent diffusion coefficient (ADC) and lower fractional anisotropy (FA). With this two-component description of diffusion and relaxation, values of ADC and FA estimated with a conventional pulsed-gradient spin-echo sequence will depend on the echo time, relative fraction of short-lived and long-lived water signals, and the intrinsic ADC and FA values within the tissue. On the basis of the relative differences in water diffusion properties between long-lived and short-lived water signals, as well as the similarities between the short-lived component and normal tissue, it is postulated that these two signal components largely reflect intracellular and extracellular water. Copyright © 2007 John Wiley & Sons, Ltd. [source] | |||||||||||||