Phospholipid Content

Intravenous lipid emulsions differ in their concentration (10%, 20%, and 30%), caloric density, natural source of lipids, and ratio of phospholipids to triglycerides (PL TG). Table 97-2 shows a comparison of commercially available intravenous lipid emulsions in the United States. The 10%, 20%, and 30% lipid emulsions provide 1.1 kcal/mL (4.6 kJ/mL), 2 kcal/mL (8.4 kJ/mL), and 3 kcal/mL (12.6 kJ/mL) with a PL TG of 0.12, 0.06 and 0.04 respectively. The lower PL TG indicates a lower phospholipid content and translates to abetter clearance of the 20% and 30% lipid emulsions compared with the 10% lipid emulsion.9 The 30% lipid emulsion is only approved for infusion in a TNA and should not be infused directly into patients. 

Hydrogen bonding and electrostatic interactions between the sample molecules and the phospholipid bilayer membranes are thought to play a key role in the transport of such solute molecules. When dilute 2% phospholipid in alkane is used in the artificial membrane [25,556], the effect of hydrogen bonding and electrostatic effects may be underestimated. We thus explored the effects of higher phospholipid content in alkane solutions. Egg and soy lecithins were selected for this purpose, since multicomponent mixtures such as model 11.0 are very costly, even at levels of 2% wt/vol in dodecane. The costs of components in 74% wt/vol (see below) levels would have been prohibitive. 

The permeabilities of the acid examples rise with increasing phospholipid content, up to 20% lipid, with rank ordering preserved. Naproxen and ketoprofen... 

The nonionizable molecules respond to the changes in the phospholipid content. Griseofulvin has the highest permeability in the lowest phospholipid-containing membranes. The most remarkable change of properties in going from 2% to 10%... 

Neutral molecules show a range of retention properties between those of acids and bases. Progesterone membrane retention is very high in all cases. Griseofulvin and carbamazepine retention steeply increase with phospholipid content. The patterns of retention follow the lipophilicity properties of the molecules, as indicated by octanol-water apparent partition coefficients (Table 7.4). 

Lipophilicity and Decrease in Permeability with Increased Phospholipid Content in Dodecane... 

The permeabilities of the acid examples rise with increasing phospholipid content, up to 20% lipid, with rank ordering preserved (data not shown). Naproxen and ketoprofen show the most dramatic increases in going from 2% to 10% lipid membranes - somewhat higher in soy than in egg. Piroxicam shows less... 

Summary Increasing Phospholipid Content in the Absence of Sink Conditions... 

Mercuric chloride after i.p. administration in mice significantly increases the phospholipid content in mouse liver, while the content in kidney is reduced... 

Infants require a substantial supplementation of AA, which is normally supplied through breast milk. Almost 10% of the membrane phospholipid content of breast fed infants was found to be AA in one study (Koletzko et ah, 1996). A crucial factor of the developing infant brain is the amount and type of polyunsaturated fatty acids they receive from their diet. That is, the ratio of dietary n-3 fatty acids (those in which the unsaturation begins 3 carbons from the terminal carbon) to n-6 fatty acids can be optimized to... 

In addition to the differences in phospholipid content between microbial and host cell membranes, it has been demonstrated that disparity exists between the transmembrane potentials of both organisms. The transmembrane potential is defined by the proton flux between the inner and outer bilayers of the cytoplasmic membrane and ranges from —90 to —110 mV in normal mammalian cells in contrast to transmembrane potentials of —130 to —150mV for logarithmic phase microbes. The differences in these electrochemical gradients have been postulated to drive the influx of peptides into the cell and thus act as a crucial barrier for defining host defense peptide selectivity. ... 

Table 3.4 Total fat and phospholipid content of some milk products...

The rate of extraction can be increased significantly by using ethyl alcohol as entrainer. The extraction curves, in which the total extraction yields are plotted against the specific CO2-solvent-mass passed through the raw material, are shown in Figure 9.6-12. Increasing the alcohol concentration in CO2 from 0% to 10% significantly improved the solubility of phospholipids (phospholipid content of oils increased from 0.026 wt.% to 0.756 wt.%). The use of alcohol as a co-solvent also improved the functionality of protein materials [103]. 

Most dry buttermilk is prepared from sweet cream buttermilk, and is produced in a manner similar to that of nonfat dry milk. Dry buttermilk has a higher phospholipid content than other dry milk products and therefore is a natural emulsifier for use in the dairy and baking industries and for dry mixes and other foods. A dry, high-acid buttermilk can be produced from milk fermented by L. bulgaricus. It is difficult to dry, however, and has found only limited use in the baking industry. There are no United States and FAO standards for this product, although typically the moisture content is less than 5%. 

The phospholipid content of milk and milk products is given in Table 4.5 (Kurtz 1974). Total phospholipid is usually determined by measuring the lipid phosphorus content of the product and multiplying by 26 (AOCS 1975). As the total milk lipid increases in a milk product, so does the phospholipid concentration. However, the ratio of phospholipid to total lipid varies greatly. Referring to Table 4.5 skim milk contains the smallest concentration of phospholipid but the highest ratio of phospholipid to total lipid. The opposite relationship is seen in cream and butter. 

Table 4.5. Percent Phospholipid Content of Milk and Milk Products.

The percentage of phospholipid content of tissues varies little under normal physiological conditions, thus giving rise to the term element constant, in contrast to the triglycerides, which have been called the element variable. 

Analysis of the phospholipid fractions can also provide useful information on the quality of oilseeds as affected by stress due to environmental conditions in the field and during storage. Mounts and Nash found that the FFA content increased and the overall phospholipid content decreased as stress was applied (49). As far as individual PL classes were concerned, the content of PC and PI decreased significantly, while the PA and PE content increased, thus giving rise to an increased nonhydratable phospholipid (NHP) content in the crude oil. The NHPs refer to the phosphatides that, during degumming of crude oils with water, do not hydrate, swell, form gel, or precipitate and hence are not removed by centrifugation. 

The idea of a lipid bilayer was first proposed by E. Gorter and F. Grendel, who showed in 1925 that the phospholipid content of the erythrocyte plasma membrane is approximately the amount needed to enclose the cell with a bilayer. Subsequent x-ray diffraction measurements confirmed this picture (fig. 17.8). 

Intermediate-sized unilamellarvesicles (lUVs) have diameters of the order of magnitude of 100 nm, and are called large unilamellarvesicles (LUVs) if the size is more than 100 nm and they consist of a single bilayer. For unilamellarvesicles, the phospholipid content is related to the surface area of the vesicles, which is proportional to the square of the radius, while the entrapped volume varies with the cube of the radius. In addition, because of the Lnite thickness of the membrane (ca. 4 nm), as thf vesicles become smaller, their aqueous volume is further reduced since the phospholipids occupy more of the internal space. Consequently, for a given quantity of lipid, large unilamellar liposomes... 

Many changes in the lipid composition of the plasma membrane have been associated with hardening (Lynch Steponkus, 1987). In rye (cv. Puma) an increase of the total lipid content has been measured during hardening (Cloutier, 1987). Free sterols increased while steryl-glycoside and acylated steryl-glycoside decreased. In addition the phospholipid contents of the plasma membrane increased. 

Wanasundara et al. (1999) reported that neutral lipids (acylglycerols and fatty acids) constitute 96% of the total lipid in flaxseed, whereas polar lipids (glycolipids and phospholipids) account for 1.4%. Stenberg et al. (2005) observed similar findings except that less phospholipid was detected. Froment et al. (1999) discussed the effects of cultivar, location, and late harvest on phospholipid content. Neutral lipid fraction of flaxseed meal was 95-98% triacylglycerols (TAG) and thus accounts for the predominant lipid in flaxseed (Oomah et al., 1996). 

Adaptations to change in temperature involve not only the fatty acids in the phospholipids but may affect the proportions of different lipid fractions in the total lipids as well. Some workers (Shatunovsky, 1980 Lapin and Shatunovsky, 1981 van den Thillart and de Bruin, 1981 Sidorov, 1983) claim that a drop in temperature results in an increased proportion of phospholipids in the total lipids. There is a larger concentration of polyunsaturated fatty acids in the phospholipid fraction than in other lipid fractions. However, other workers (Anderson, 1970 Caldwell and Vembeig, 1970 Selivonchick and Roots, 1976 Wodtke, 1978 Hazel, 1979) have not found this effect, and Knipprath and Mead (1966) found that the phospholipid content of goldfish actually decreased during adaptation to cold. 

Within each of two Black Sea species, anchovy (warm water) and sprat (cold water), both the concentrations and absolute amounts of phospholipids fluctuate within similar limits, but do not change during the annual cycles in the same tissues. This contrasts with, for example, the considerable differences between the phospholipid contents of red and white muscle or between that of either of them and liver (Shchepkina, 1980a Shchepkin and Minyuk, 1987). The content of polyenoic acids in the phospholipids of anchovy is higher than that in the sprat (Yuneva, 1990) possible explanations will be given in Chapter 3. 

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