Lipid signal

Nishizuka, Y., Protein kinase C and lipid signaling for sustained cellular responses. FASEB J., 7, 484-496, 1995. 

Bazan, N. G. Synaptic lipid signaling significance of polyunsaturated fatty acids and platelet-activating factor. /. Lipid Res. 44 2221-2233, 2003. 

Rodriguez de Turco, E. B., Tan, W., Topham, M. K., Sakane, F., Marcheselli, V. L., Chen, C., Taketomi, A., Prescott, S. and Bazan N. G. Diacylglycerol kinase epsilon regulates seizures susceptibility and long-term potentiation through inositol lipid signaling. Proc. Natl Acad. Sci. U.S.A. 98 4740-4745, 2001. 

Two principles are usually applied to clinical water or fat selective imaging on the one hand, water and lipid signals show different longitudinal relaxation times T and, on the other hand, they are recorded at slightly different Larmor frequencies due to their different chemical shifts. 

The first peculiarity of muscle spectra is the possibility to differentiate two lipid compartments. Furthermore, the characteristics of the lipid signals depend on the chosen particular muscle and its orientation with respect to the magnetic field. Figure 15 shows a typical spectrum of the tibialis anterior muscle (TA) in comparison with a spectrum from the fatty bone marrow of... 

Fig. 15. Comparison of a water suppressed muscle spectrum and a spectrum from yellow bone marrow containing almost pure fat (triglycerides). Measurement parameters STEAM sequence, TE=10 ms, TM=15 ms, TR = 2 s, 40 acq., VOI (11 X 11 X 20) mm. (a) Spectrum from TA muscle recorded after careful positioning of the VOI, avoiding inclusion of macroscopic fatty septa allows separation of extramyocellular (EMCL, broken lines) and intramyocellular lipid signals (IMCL, dotted lines) based on susceptibility differences. For this reason characteristic signals from fatty acids occur double. Signals of creatine (methyl, Crs, and methylene, Cr2) show triplet and doublet structure, respectively, due to dipolar coupling effects. Further signals of TMA (including carnitine and choline compartments), Taurine (Tau), esters, unsaturated fatty acids (-HC=CH-), and residual water are indicated, (b) Spectrum from yellow fatty bone marrow of the tibia with identical measuring parameters, but different amplitude scale.

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