Lipid droplets

Lipid droplets possess a neutral lipid core containing mainly TAG and cholesterol ester species, surrounded by a monolayer of mainly GPL species and 

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There are striking similarities in the mechanisms of formation of chylomicrons by intestinal cells and of VLDL by hepatic parenchymal cells (Figure 25—2), perhaps because—apart from the mammary gland—the intestine and liver are the only tissues from which particulate lipid is secreted. Newly secreted or nascent chylomicrons and VLDL contain only a small amount of apolipoproteins C and E, and the frill complement is acquired from HDL in the circulation (Figures 25—3 and 25-4). Apo B is essential for chylomicron and VLDL formation. In abetalipoproteinemia (a rare disease), lipoproteins containing apo B are not formed and lipid droplets accumulate in the intestine and liver. 

The bioaccessibility of a compound can be defined as the result of complex processes occurring in the lumen of the gut to transfer the compound from a non-digested form into a potentially absorbable form. For carotenoids, these different processes include the disruption of the food matrix, the disruption of molecular linkage, the uptake in lipid droplets, and finally the formation and uptake in micelles. Thus, the bioaccessibility of carotenoids and other lipophilic pigments from foods can be characterized by the efficiency of their incorporation into the micellar fraction in the gut. The fate of a compound from its presence in food to its absorbable form is affected by many factors that must be known in order to understand and predict the efficiency of a compound s bioaccessibility and bioavailability from a certain meal. ... 

Tyssandier, V., Lyan, B., and Borel, R, Main factors governing the transfer of carotenoids from emulsion lipid droplets to micelles, Biochim. Biophys. Acta, 1533, 285, 2001. 

A 1.2-micron in-line filter should be used for the infusion of 3-in-l PN (i.e., a TNA) because it can remove large and unstable lipid droplets as well as particulate matter.22... 

Unheated carrot juices produced from carrots blanched at 80°C for lOmin were devoid of di-isomers, and further pasteurization or sterilization process formed only 13-d.v-P-carotene, respectively, at 2% and 5% (Marx et al. 2003). However, extensive carrot blanching (100°C for 60min) caused the losses of 26%-29% in total P-carotene content, along with an increased 13-d.s-P-carotene content up to 10% after pasteurization (Tmax 95°C, F = 3) and to 14% after sterilization (Tmax 121°C, F = 5) (Marx et al. 2003). The addition of grape oil to carrot juice before heat treatment enhanced the 13-di-P-carotene formation (18.8%) as compared to the control (6.0%) (Marx et al. 2003). This fact is probably due to the partial dissolution of crystalline carotene, present in the intact carrot in lipid droplets, since the solubilization of carotenes during blanching is a prerequisite for the formation of di-isomers. 

Hayashi, T., Su, T.-P. Sigma-1 receptors (sigma-1 binding sites) form raft-like microdomains and target lipid droplets on the endoplasmic reticulum roles in endoplasmic reticulum lipid compartmen-talization and export. J. Pharmacol. Exp. Ther. 306 718, 2003. 

Free the plug of debris from the sides of the tube by ringing the tube with an applicator stick, and carefully pour the top three layers into a discard container. With the tube still tipped, use a swab to remove debris from the sides of the tube. This step is very important, for lipid droplets which reach the sediment make examination difficult. 

The gravity sensor is unknown in Phycomyces. Statoliths have not been detected. Any particle with a density different from that of the average density of the cytoplasm could be a candidate, e.g., mitochondria, lipid droplets, nuclei or crystals. The work of Dennison (1961) has clearly shown that the gravity sensor must be inside the cell because the response is independent of the density of the medium outside the sporangiophore. 

Chlorella zofingensis cells are transferred to a growth medium, with a low nitrogen concentration (10% of normal concentration). After approximately 6-8 wk they develop a red colour, due to the decomposition of chlorophylls and synthesis of secondary carotenoids (stored in lipid droplets within the cytoplasm of the cells). At this stage the chloroplast are intact, although the surface area of thylacoids is mostly reduced. 

Fig. 6 TEM micrographs of seed coat and aleurone cells of radish control seed 18 h after sowing in water e, epidermis pi, pigment layer al, aleurone layer. (A) Bar = 30 pm Particulars of the aleurone cell showing some organelles nucleus (n), plasmodesmata (pd), protein bodies (pb) and lipid droplets (Id). (B, C). Bar = 5 mm. 

Borel P, Grolier P, Armand M, Partier A, Lafont H, Lairon D and Azais-Braesco V. 1996. Carotenoids in biological emulsions solubility, surface-to-core distribution, and release from lipid droplets. J Lipid Res 37 250-260. 

Glutaric aciduria type II, which is a defect of P-oxida-tion, may affect muscle exclusively or in conjunction with other tissues. Glutaric aciduria type II, also termed multiple acyl-CoA dehydrogenase deficiency (Fig. 42-2), usually causes respiratory distress, hypoglycemia, hyperammonemia, systemic carnitine deficiency, nonketotic metabolic acidosis in the neonatal period and death within the first week. A few patients with onset in childhood or adult life showed lipid-storage myopathy, with weakness or premature fatigue [4]. Short-chain acyl-CoA deficiency (Fig. 42-2) was described in one woman with proximal limb weakness and exercise intolerance. Muscle biopsy showed marked accumulation of lipid droplets. Although... 

Lead citrate/uranyl acetate6 Step 1 Float or immerse sections for 10-30 min on filtered 1-2% aqueous uranyl acetate (or in EtOH) wash with ultrapure H20 (three beakers of 50 mL each) by dipping grids held with a forceps dry for 5 min Step 2 Place drops of lead citrate (lead carbonate free) onto a wax surface (parafilm or dental wax) in a Petri dish line edges of dish with pellets of KOH float grid with sections (sections face down) for 4-5 min (if overstained 2-3 min and dilute stain) wash grids with sections in ultrapure H20 Nonselective enhancement of membrane contrast, ribosomes, and nuclear material proteins and lipid droplets... 

The relatively nonpolar squaraine rotaxane 14c was found to interact with cells in a very similar way to the well-known lipophilic dye Nile Red this probe rapidly accumulates at lipophilic sites inside a living cell, such as the endoplasmic reticulum and intracellular lipid droplets [55], The red emission band for probe 14c is quite narrow and permits the acquisition of multicolor images. It displayed high chemical stability and low toxicity. 

Muscle biopsy shows elevated musde triglyceride detected as lipid droplets in cytoplasm... 

Fig. 4. Electron myograph of skeletal muscle. The band structure caused by the sarcomeres, two capillaries (1) and several small lipid droplets (2) are shown. The intramyocellular lipid droplets (size approximately 0.1-1 pm) make up the IMCL content mentioned in the context.

Fatty acids are clearly larger in size and show markedly slower diffusion velocity than the small water (or creatine) molecules which have been examined so far by diffusion weighted NMR spectroscopy. However, assessment of diffusion properties of lipids could be a key step for further experimental studies of skeletal muscle lipid metabolism. Diffusion properties of FFA and triglycerides are likely different due to differences in molecular weight. In addition, effects of temperature, chemical surroundings, and the mobility of small lipid droplets in the cytosol may also lead to measurable differences in the diffusion characteristics. 

Figure 7.5 An interference contrast photograph of a white adipose tissue celt Note the spherical lipid droplet fills most of the cell.

Beauveriolides I (19) and III (20), two fungal (Beauveria Spp) metabolites, have been found to be specific inhibitors of lipid droplet formation in mouse macrophages. It has been recently observed that the metabolisms of A[3 proteins and cholesterol esters are closely linked. One of the... 

Cholesterol can be derived from two sources—food or endogenous synthesis from ace-tyl-CoA. A substantial percentage of endogenous cholesterol synthesis takes place in the liver. Some cholesterol is required for the synthesis of bile acids (see p. 314). In addition, it serves as a building block for cell membranes (see p. 216), or can be esterified with fatty acids and stored in lipid droplets. The rest is released together into the blood in the form of lipoprotein complexes (VLDLs) and supplies other tissues. The liver also contributes to the cholesterol metabolism by taking up from the blood and breaking down lipoproteins that contain cholesterol and cholesterol esters (HDLs, IDLs, LDLs see p.278). 

The cholesterol required for biosynthesis of the steroid hormones is obtained from various sources, it is either taken up as a constituent of LDL lipoproteins (see p. 278) into the hormone-synthesizing glandular cells, or synthesized by glandular cells themselves from acetyl-CoA (see p. 172). Excess cholesterol is stored in the form of fatty acid esters in lipid droplets. Hydrolysis allows rapid mobilization of the cholesterol from this reserve again. 

Emulsification breaks lipid droplets into smaller-sized structures, which increases their overall surface area. 

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