Lipid Signal Intensity Research Articles

A novel, sensitive and non-destructive method for quantitative determination of lipid in live Eriocheir sinensis using low-field 1H Nuclear magnetic resonance.

In this study, lipid content of live Eriocheir sinensis has been quickly and accurately determined by low‐field 1H Nuclear magnetic resonance (LF‐1H NMR). The experimental parameters of LF‐1H NMR have been optimized and the validity of the established standard method has been confirmed with traditional Soxhlet extraction method. Results show that the lipid signal intensity is strongly correlated with its content and exhibits a good linear correlation (Y = 0.0376 + 4.899X, R 2 = 0.9999), thus demonstrating favorable accuracy and sensitivity for the quantitative determination of lipid content. In conclusion, the lipid content of live E. Sinensis can be directly obtained based on an established method, indicating a great application potential in food and other fields.

Metabolic Study of Breast MCF-7 Tumor Spheroids after Gamma Irradiation by (1)H NMR Spectroscopy and Microimaging.

Multicellular tumor spheroids are an important model system to investigate the response of tumor cells to radio- and chemotherapy. They share more properties with the original tumor than cells cultured as 2D monolayers do, which helps distinguish the intrinsic properties of monolayer cells from those induced during cell aggregation in 3D spheroids. The paper investigates some metabolic aspects of small tumor spheroids of breast cancer and their originating MCF-7 cells, grown as monolayer, by means of high–resolution (HR) 1H NMR spectroscopy and MR microimaging before and after gamma irradiation. The spectra of spheroids were characterized by higher intensity of mobile lipids, mostly neutral lipids, and glutamine (Gln) signals with respect to their monolayer cells counterpart, mainly owing to the lower oxygen supply in spheroids. Morphological changes of small spheroids after gamma-ray irradiation, such as loss of their regular shape, were observed by MR microimaging. Lipid signal intensity increased after irradiation, as evidenced in both MR localized spectra of the single spheroid and in HR NMR spectra of spheroid suspensions. Furthermore, the intense Gln signal from spectra of irradiated spheroids remained unchanged, while the low Gln signal observed in monolayer cells increased after irradiation. Similar results were observed in cells grown in hypoxic conditions. The different behavior of Gln in 2D monolayers and in 3D spheroids supports the hypothesis that a lower oxygen supply induces both an upregulation of Gln synthetase and a downregulation of glutaminases with the consequent increase in Gln content, as already observed under hypoxic conditions. The data herein indicate that 1H NMR spectroscopy can be a useful tool for monitoring cell response to different constraints. The use of spheroid suspensions seems to be a feasible alternative to localized spectroscopy since similar effects were found after radiation treatment.

Cytoplasmic lipid droplets in nervous system tumour cell lines: Size and lipid species as analysed by 1H nuclear magnetic resonance spectroscopy

Active biogenesis of cytoplasmic lipid droplets (LDs) is reported in different types of cancer cells. LDs are linked to cancer cell proliferation, apoptosis and differentiation. The chemical nature of lipids in LDs is poorly understood and revealing their chemical composition may provide novel information of lipid metabolism in cancers. Gradient ultracentrifugation was performed to isolate LDs from five nervous system tumour cell lines. Nile red staining was used to estimate the size of LDs and validate the isolation procedure. 1H NMR spectroscopy was performed from the chloroform/methanol extracts of whole cells and the isolated LDs. NMR lipid signal intensity from different lipid species was measured to compare the lipid compositions. The average diameter of LDs in cancer cells was 0.21±0.02 μm, with a widely varying size range up to 1.48 μm. 1H NMR spectroscopic analysis revealed that the LDs contain phosphatidylcholine, cholesterol and cholesterol ester with saturated, mono-unsaturated and polyunsaturated fatty acid species. The content of the isolated LDs differed between the tumor cell lines with variability seen in unsaturated fatty acids, cholesterol and lipids containing choline head groups however the mean fatty acid chain length remained similar across the cell lines. The lipid composition of LDs was also found to be different from whole cell extracts. In conclusion, we have shown that the composition of LDs differs between tumour cell lines, suggesting a functional link between these structures and cancer specific pathways.

The size of cytoplasmic lipid droplets varies between tumour cell lines of the nervous system: a 1H NMR spectroscopy study

Cytoplasmic lipid droplets (LDs) are dynamic cellular organelles; their accumulation is associated with several cellular processes, such as cell proliferation, apoptosis and necrosis. (1)H Nuclear Magnetic Resonance (NMR) spectroscopy detects resonances from lipids present in cytoplasmic (LDs); an understanding of the relationship between LD characteristics and NMR lipid signals is important. In this study, five nervous system cancer cell lines were investigated. Nile red staining was used to measure the diameter of LDs. High-resolution magic angle spinning NMR (HR-MAS) was performed on harvested cell pellets to quantify the patterns of lipid signals. LDs were present in all five cell lines with different morphology. An average LD diameter of approximately 0.2 μm was found in all cell types. Diameter of the largest LDs varied across the cell lines. The intensity of NMR lipid signals varied greatly between cell types, and a good correlation was found between total volume of LDs and the proton NMR lipid signal intensity at 0.9 and 1.3 ppm. The correlation implied that little NMR signal is detected from LDs of diameters less than approximately 0.34 μm, most likely due to restriction of rotational motion of the lipids.

3-Tesla MR spectroscopy in patients subjected to bone marrow transplantation: clinical correlations

This study evaluated the usefulness of 3-Tesla magnetic resonance (MR) spectroscopy in patients with non-Hodgkin's lymphoma (NHL) undergoing bone marrow transplantation (BMT). Twelve NHL patients who were candidates for BMT underwent three MR examinations of the lumbosacral spine: before ablative therapy for BMT, 15±4 days and 54±24 days after BMT. The MR study was supplemented by spectroscopic analysis. The lipid content was calculated and expressed as a percentage of lipid signal intensity relative to total signal intensity [fat fraction (FF)]. In the first MR study, the FF was 62.5±7%, in the second it was 70.75±5% and in the third it was 75±1%. We observed a statistically significant difference between FF values calculated at the various MR studies (p=0.02) and between red blood cell count (p=0.017), platelet count (p=0.003) and haematocrit (p<0.001) at the three MR studies. FF had a statistically significant correlation with the number of circulating platelets (p<0.01) MR spectroscopy of the bone marrow of NHL patients undergoing BMT is noninvasive and highly sensitive for characterising and monitoring bone marrow after BMT.

Skeletal muscle lipid concentration quantified by magnetic resonance imaging

Skeletal muscle lipid is associated with obesity and type 2 diabetes and may be altered by diet, physical activity, and weight loss. We explored the utility of magnetic resonance imaging (MRI) for quantifying the lipid concentration of muscle tissue in vivo. Fat-selective MR images of the lower leg were taken in 8 normal-weight [body mass index (in kg/m(2)) < or = 24.9] and 8 obese (body mass index > 29.9) subjects to obtain spatial maps of lipid signal intensity within muscle tissue. Fast-spiral-sequence (echo time = 5.6-13.8 ms, repetition time = 1 s, 8 interleaves) MRI scans were conducted at 3.0 T by using an extremity transmit-receive coil. Lipid concentrations within muscle were determined from manually drawn regions of interest in the tibialis anterior (TA), soleus, and medial head of the gastrocnemius (MHG) muscle groups. There was extremely good agreement (mean R(2) = 0.985) between the fat signal intensity and the actual lipid concentration of standards containing 2.5, 5.0, and 10.0 g lipid/dL, which were placed on the subject's leg during each scan. The lipid content of both the soleus (2.99 +/- 0.37 g/dL) and the MHG (3.80 +/- 0.68 g/dL) was higher (P < 0.05) than that of the TA (1.83 +/- 0.28 g/dL). Lipid content was more than two-fold higher (P < 0.05) in the MHG of obese subjects (5.48 +/- 1.18 g/dL) than in the MHG of normal-weight subjects (2.54 +/- 0.47 g/dL), but did not differ significantly in the TA or soleus. MRI can be used to quantify lipid within human muscle tissue. MRI can also be used to detect differences in muscle lipid content among various muscle groups and between normal-weight and obese subjects.

Water and lipid MRI of the Xenopus oocyte.

Oocytes of Xenopus laevis are large, single cells that provide a promising model system for the exploration of the MR biophysics fundamental to more complex living systems. Previous studies have generally employed 2D spin-echo sequences with an image slice thickness greater than the thickness of the cellular volumes of interest. Also, the large cytoplasmic lipid signal has typically been ignored. This study describes separate, high-resolution 3D measurements of the water and lipid spin densities, T(1) and T(2) relaxation time constants, and the water apparent diffusion rate constant (ADC) in the Xenopus oocyte without significant partial volume artifacts. The lipid spin-density and values for water MR properties varied monotonically from the vegetal to animal poles, indicating that the border between the poles is not sharply demarcated. Regional water MR property values correlated with lipid signal intensity. Lipid-specific imaging is shown for which water suppression is achieved via high diffusion weighting in the imaging sequence.

Abnormal lipid profile of dystrophic cardiac tissue as demonstrated by one- and two-dimensional magic-angle spinning (1)H NMR spectroscopy.

Dystrophin, a protein associated with sarcolemma and cell membranes, is not expressed in sufferers of Duchenne muscular dystrophy (DMD), or in the mdx mouse. DMD is a fatal disorder, with a significant proportion of fatalities associated with cardiac failure ( approximately 40% having dilated cardiomyopathy and >90% clinically significant cardiac defects at death). In this study, the metabolic composition of intact dystrophic cardiac tissue was investigated using high-resolution magic-angle spinning (HRMAS) (1)H NMR spectroscopy with both 1- and 2D pulse sequences coupled with pattern recognition (PR). While conventional solvent presaturation spectra indicated increases in CH(2) chain length in lipids, PR analysis of correlation spectroscopy (COSY) spectra demonstrated that this was also accompanied by an increase in concentration of lactate or threonine along with a relative decrease in CH = CHCH(2)CO groups in these lipids. To investigate the physical environment of these lipids, T(2)- and diffusion-weighted (1)H MAS NMR spectra were acquired on whole-tissue samples. The relatively increased lipid signal intensity in dystrophic tissue was due to an increase in molecules with long T(2) and short diffusion rates. The use of a range of pulse programs allowed the direct probing of the biochemical environment in which the lipid infiltration occurred, and by coupling the experiments to PR the significance of lipid infiltration and accumulation was also assessed.

1H‐MRS lipid signal modulation and morphological and ultrastructural changes related to tumor cell proliferation

Changes in signal intensity of 1H-MRS mobile lipids, mostly triglycerides, have been observed in cultured HeLa cells during exponential growth. Signals were intense in the first days after seeding and almost disappeared after a few days in culture. Choline-based metabolites were not affected by growth. Treatment with the antitumor drug lonidamine, which blocks cell proliferation and cell progression through cycle, increased lipid signal intensity. Morphological changes in the organization of the cell surface were detected by scanning electron microscopy during exponential growth, and were confirmed by freeze fracture analysis. The observed metabolic and structural modifications during cell growth were correlated to cell cycle progression of HeLa cells, as high-intensity lipid signals were typical of cells with a high percentage of S- and G2 + M-phases, while cells with a high frequency in G1-phase were characterized by mobile lipid signals of very low intensity. Magn Reson Med 42:248–257, 1999. © 1999 Wiley-Liss, Inc.

1H-MRS lipid signal modulation and morphological and ultrastructural changes related to tumor cell proliferation.

Changes in signal intensity of (1)H-MRS mobile lipids, mostly triglycerides, have been observed in cultured HeLa cells during exponential growth. Signals were intense in the first days after seeding and almost disappeared after a few days in culture. Choline-based metabolites were not affected by growth. Treatment with the antitumor drug lonidamine, which blocks cell proliferation and cell progression through cycle, increased lipid signal intensity. Morphological changes in the organization of the cell surface were detected by scanning electron microscopy during exponential growth, and were confirmed by freeze fracture analysis. The observed metabolic and structural modifications during cell growth were correlated to cell cycle progression of HeLa cells, as high-intensity lipid signals were typical of cells with a high percentage of S- and( )G(2) + M-phases, while cells with a high frequency in G(1)-phase were characterized by mobile lipid signals of very low intensity. Magn Reson Med 42:248-257, 1999.

Magnetic resonance imaging of lipid deposits in human atheroma via a stimulated‐echo diffusion‐weighted technique

NMR images of subintimal lipid deposits within the vessel walls of atherosclerotic human aortas were obtained at 37 and 27 degrees C at 4.7 T. A combination of a stimulated-echo and pulsed-field gradients was used for suppressing the mobile tissue water relative to the less mobile tissue lipids. At 27 degrees C there was also a substantial reduction of the subintimal lipid signal intensity, which is consistent with the characteristic phase transition of cholesteryl esters in human atheroma. These results represent the first direct detection of lipid deposits in nonprotruding atherosclerotic lesions with NMR imaging.

NMR imaging of 13C in animal tissues.

Natural-abundance 13C NMR imaging of animal tissues is demonstrated using high-field (4.7-T) and surface coil techniques. Undecoupled images of an unfertilized egg yolk and an oxtail are presented. Analysis indicates the images map mainly methylene carbon or lipid signal intensity.