Seasonal changes in the chloroplast ultrastructure of Diapensia lapponica

Leaf specimens of evergreen Diapensia lapponica were collected monthly in Northern Finland (ca 70°N) in order to study seasonal changes in the ultrastructure of the chloroplasts of the palisade mesophyll.
The volume fraction of chloroplasts per cell was lowest in summer and increased towards autumn and winter. However, the relative size seemed to be higher in summer than in other seasons. Length/width (L/W) ratio was calculated as an index of the chloroplast shape. The shape varied from elongated (usually concavo-convex in profile), with an L/W ratio from 1.9 to 2.5 in summer, to roundish or irregular (L/W ratio from 1.2 to 1.4) in midwinter. In autumn the chloroplasts were most elongated (LW ratio 2.6). The starch content was highest at the end of June when it constituted 38% of the volume of chloroplast. It decreased from then till November and was absent during the rest of the winter. Changes in the thylakoid system involved an increase in the number of partitions from an average of three in early summer to 11 in autumn and a decrease to M again towards winter. In spring it was up to 7 again. The large grana and high portion of stroma thylakoids observed in late August - September (the period of rhythmic light) are consistent with the high photosynthesis activity reported previously in D. lapponica in laboratory conditions.     

Food reserves of scots pine (Pinus sylvestris L.)

Summary Starch, soluble sugars, triacylglycerols, diacylglycerols and free fatty acids were measured in 30-year-old Scots pine (Pinus sylvestris L.) trees during an annual cycle in the sapwood (youngest ten xylem rings). The radial distribution of carbohydrates and lipids was studied in the trunkwood of 90 -to 150-year-old Scots pine trees collected at the end of the growing season. Determination of the compounds was performed using specific enzymatic assays, capillary gas chromatography and thin layer chromatography. The amounts of glucose, fructose, sucrose, and galactose/arabinose in the sapwood were slightly higher in winter than in summer. Raffinose/stachyose increased up to 5-fold during the cold period. At the beginning of the growing season starch amounts rose, and then decreased in summer and autumn. No concentration changes were observed in the total amounts of diacylglycerols and fatty acids throughout the year. Triacylglycerol levels were slightly higher in February than in summer and autumn. Relative frequencies of individual fatty acids were similar in all lipid fractions. Glucose, fructose, sucrose, starch and triacylglycerols disappeared almost entirely at the transition zone from sapwood to heartwood. In contrast, free fatty acids and galactose/arabinose rose in centripetal direction, and diacylglycerols remained constant across trunk cross-sections. The relative amounts of individual fatty acids changed markedly in the free fatty acid fraction and in the triacylglycerols when crossing the sapwood-heartwood boundary. Concentration changes of reserve materials are discussed in relation to season, mobilization and translocation processes, dormancy, frost resistance, and heartwood formation. The results are compared to those found in needles.     

Seasonal variation of storage substances in stem cells of Diapensia lapponica. A light microscopic study

Owerwintering strategy of the sub-arctic evergreen Diapensia lapponica has been studied by examining storage substances in the stem cells throughout different seasons. Stem segments were taken from 5 and 20 mm behind the shoot tip, fixed in glutaraldehyde/formaldehyde and embedded in Epon. Semithin sections were stained with Toluidine blue for general observation, Sudan black for lipids, Amido black for proteins and periodic acid-Schiff s reagent (PAS) for carbohydrates. Lipids occurred abundantly throughout the year and seem to be the main storage substances. They were particularly common in mid-winter in the lower part of the shoot. The highest lipid content was found in the pith cells and parenchyma cells of the conductive tissues. Large amyloplasts appeared in mid-summer in higher amounts in the cortex than in the pith of the upper shoot, but vice versa in the lower stem. Starch was almost entirely lacking from November to April. Amido black staining did not indicate presence of protein bodies at any season.
The occurrence of lipids and starch grains in the stem of Diapensia is in general similar to the occurrence of these substances in the leaves throughout the annual cycle.     

Occurrence of esterified triterpenoid alcohols in the leaves of Pilosella officinarum

The mature winter leaves of Pilosella officinarum coll. Schultz and Schultz contained 29 mg esterified triterpenoid alcohols (g dry weight)⁻¹, of which over 80% was esterified with long-chain (C16-C18) fatty acids. The major fatty acids were 16:0, 18:2ω6 and 18:3ω3 and their amounts varied according to the season and stage of leaf development. In mature leaves the amount of triterpenoid alcohols esterified with long-chain fatty acids varied only slightly with the season. The changes in the fatty acid proportions in late winter-early spring, however, indicated a turnover in the esterified triterpenoid alcohol pool. In late winter after the snow had melted a 50% decrease occurred in the amount of triterpenoid alcohols esterified with short-chain fatty acids. The amount of esterified triterpenoid alcohols in immature leaves was relatively low [4 mg (g dry weight)⁻¹].
In the mature leaves esterified triterpenoid alcohols were found in globules whose appearance varied greatly according to the season. The globules were partly dissolved in late winter, and this together with the activation of respiration, suggests that the globules function as short-term energy reservoirs. Relationships between the appearance of lipid globules and the amount of esterified triterpenoid alcohols are discussed.     

The nectar of the Strelitzia reginae flower

The nectar of Strelitzia reginae Ait. was analysed using enzymatic methods and found to contain glucose, fructose and sucrose. Sugar composition changed considerably over the nectar producing period: there was an increase in the amount of glucose (41%) and fructose (32%) between the early and middle stage of secretion and thereafter a decrease of 13 and 24%, respectively, towards the end of secretion. Although the amount of sucrose secreted was initially as much as the glucose and fructose combined, it subsequently decreased, first by 14% and then by 70% at the end of the secretory period so that, whereas in the initial stages of secretion sucrose was quantitatively the dominant sugar, glucose and fructose made up the major part of the nectar as secretion reached its conclusion.
The amounts of potassium and sodium remained at the same low level (around 150 and 30 μg g^-1 [w/v) respectively) throughout secretion, while calcium (initially 18 μg g^-1) and magnesium (initially 8.0 μg g^-1) increased by 47 and 56% respectively, between the early and late stages of secretion. No free amino acids, inorganic phosphate or iron could be detected. Enzymatic analysis revealed only a trace amount of starch. Transmission electron micrographs from both immature and mature plants, however, showed starch grains among other cytoplasmic remnants in the nectary lumen. Mitochondria, vesicles, lipid droplets and ribosomes could also be identified among the luminal cytoplasmic remnants.     

Body composition and energy allocation in life-history stages of brown trout

Energy contents of immature parr and smolts, and mature resident and anadromous brown trout Salmo trutta sampled from a small stream in southern Norway were estimated from lipid, protein and carbohydrate concentrations. In immatures the lipid concentrations were highest in parr in the autumn. Mean lipid concentrations increased significantly with age in parr sampled in autumn (1·3% in age 0+ to 3·4% in age 3+), whereas they did not in smolts. The lipid concentrations of parr in spring were not significantly different from those of similarly aged smolts. By contrast, the relative water content (%) decreased with age in parr in the autumn and increased with age in smolts, mean values being slightly higher in smolts (78%) than in parr (77%). Protein and carbohydrate concentrations did not vary with age in the immature fish, mean protein concentrations being 18·0, 17·5 and 16·8% in parr in the autumn and spring, and in smolts, respectively. In residents, the concentrations of lipids were lower and of water higher, in age group 1 than in older fish, whereas there was no significant variation with age amongst anadromous trout. The energy concentration of 2+ smolts (349 kJ 100 g^-1) was similar to that of 0+ parr in the autumn. Mean somatic energy density in autumn was 1·1 times higher in freshwater residents than in parr at age 1+ (407 and 387 kJ 100 g^-1) and marginally different at age 2+ (462 and 426 kJ 100 g^-1, respectively). The energy contents per unit mass of residents were 1·3–1·6 times that of similar aged smolts. Mean somatic energy density of anadromous trout (504 kJ 100 g^-1) was higher than that of residents (455 kJ 100 g^-1). Somatic energy, lipid and protein concentrations were correlated highly with water contents of all life stages, age and sex groups.     

Effects of salinity and replacement of K+ by Na+ on lipid composition in two sugar beet inbred lines

The effects of NaCl and replacement of K⁺ by Na⁺ on the lipid composition of the two sugar beet inbred lines FIA and ADA were studied (a) with increasing additions of NaCl to the basal medium, and (b) with increasing replacement of K⁺ by Na⁺ at the same total concentration as in the basal medium. Direct relations were noted between NaCl concentration of the nutrient solution and the phospholipid concentration in the roots of FIA, the genotype characterized by a low K⁺/Na⁺ ratio, as well as between NaCl in the medium and the phospholipid concentration in the shoots of ADA, the genotype with a high K ⁺/Na ⁺ ratio. The sulfolipid level in the roots of FIA was maintained at higher NaCl concentrations, while it was decreased in ADA. The glycolipid concentration in the shoots of ADA and the degree of unsaturation of the fatty acids of the total lipid fraction were decreased by salinity, indicating reduced biosynthesis of chloroplast glycolipids and/or accelerated oxidation of these lipids in the presence of NaCl.
In the Na⁺ for K⁺ replacement experiment a low content of K⁺ in the medium resulted in decreased levels of total lipids, phospholipids and sulfolipid in the roots of both genotypes, which did not relate to root growth. K⁺-leakage from the roots at low K⁺-level in the medium may be reduced by the increase in saturation of the lipids. In the shoots of ADA increased levels of total lipids, phospholipids and Sulfolipid were noted at a low K⁺-concentration of the nutrient solution.     

Temperature-induced Changes in the Synthesis of Unsaturated Fatty Acids by Acanthamoeba castellanii

ABSTRACT. Major fatty acid components of Acanthamoeba castellanii lipids extracted after growth at 30°C include myristate, palmitate, stearate and the polyunsaturates linoleate, eicosadienoate, eicosatrienoate and arachidonate, with oleate as the sole major monounsaturated fatty acid. By comparison, growth at 15°C gave increased linoleate, eicosatrienoate and arachidonate, but decreased oleate and palmitate. When the growth temperature was shifted downwards from 30°C to 15°C, increased lipid unsaturation occurred over a period of 24 h; thus decreases of oleate and eicosadienoate were accompanied by increases in linoleate, eicosatrienoate, arachidonate and eicosapentaenoate. An upwards shift from 15°C to 30°C gave negligible alterations in fatty acid composition over a similar period. At 15°C organisms rapidly use [1-¹⁴C] acetate for de novo fatty acid synthesis; stearate is converted via oleate to further desaturation and chain elongation products. Similar short term experiments at 30°C indicate only de novo synthesis and Δ9-desaturation; synthesis of polyunsaturates was a much slower process. Rapid incorporation of [1-¹⁴C] oleate at 30°C was not accompanied by metabolic conversion over two hours, whereas at 15°C n-6 desaturation to linoleate was observed. Temperature shift of organisms from 15°C to 30°C in the presence of [1-¹⁴C] acetate revealed that over half of the fatty acids in newly-synthesised lipids were saturated, but the proportions of unsaturated fatty acids increased with time until the total polyenoate components reached 17% after 22 h. A shift of temperature in the reverse direction gave a corresponding figure of 60% for polyunsaturated fatty acids. These results emphasize the importance of n-6 desaturation in the low temperature adaptation of Acanthamoeba castellanii .     

Factors affecting the growth of Listeria monocytogenes on minimally processed fresh endive

The influence of various factors on the fate of Listeria monocytogenes on cut leaves of broad-leaved endive has been studied. Factors considered were temperature, characteristics of the leaves (age, quantity and quality of the epiphytic microflora) and characteristics of the L. monocytogenes inoculum (concentration, strain). The increases in numbers of L. monocytogenes were lower than those of the aerobic mesophilic microflora at 3°, 6°, 10° and 20°C. Doubling times of the populations of L. monocytogenes were in the same order of magnitude as those of aerobic bacteria at 10° and 20°C, but longer at 3° and 6°C. There were positive significant correlations between growth of L. monocytogenes and populations of aerobic bacteria, and between growth of L. monocytogenes and extent of spoilage on the leaves.
Of 225 bacteria isolated from the leaves, 84% were identified as fluorescent pseudomonads; there was no difference in the species isolated from leaves that showed a low growth of L. monocytogenes and leaves that showed a high growth of L. monocytogenes. Populations of L. monocytogenes increased faster during the first 2 and 4 d of storage at 10°C on leaves inoculated with 10–10³ cfu g^-1 than on leaves inoculated with about 10⁵ cfu g^-1, but the population reached after 7 d was lower. The behaviour of L. monocytogenes was similar among the three strains tested.     

Nutrient reserves of Salicornia europaea seeds

Seeds of Salicornia europaea L. were analyzed for their nutrient reserves. The content of potassium and sodium was 216 and 39 mmol (kg dry seeds)^-1, respectively. Calcium and magnesium accounted for 30 and 138 mmol (kg dry seeds)^-1, respectively. Whereas most of the alkali metals were water soluble, the alkaline earth metals were mostly acid soluble. The acid-soluble calcium plus magnesium corresponded well with the acid-soluble phosphate. Chloride was accumulated to a level equivalent to that of sodium. Carbonate was present at a concentration of 9 mmol (kg dry seeds)^-1. Carbohydrates accounted for 93 g (kg dry seeds)^-1, nearly half of which was derived from sucrose. Fructose and glucose were present only in traces. Total nitrogen was determined to be 55 g (kg dry seeds)^-1, 16% of which was diethylether soluble. The remaining nitrogen was separated into 39 g (kg dry seeds)^-1 ethanol-insoluble and 8 g (kg dry seeds)^-1 ethanol-soluble nitrogen. About 10% of the ethanol-soluble nitrogen were derived from amino acids. Total lipid content was about 280 g (kg dry seeds)^-1. The alcoholic component of the storage lipids was glycerol and the glycerides were calculated from gas chromatography to be 66% of the total lipids. About 90% of the fatty acids consisted of unsaturated acids, linoleic and oleic acid, the majority (77%) of which was linoleic acid.     

Transmission of pea bacterial blight (Pseudomonas syringae pv. pisi) from seed to seedling: effects of inoculum dose, inoculation method, temperature and soil moisture

Quantitative analyses of the utilization of amino acids by Lactococcus lactis subsp. cremoris FD1 in yeast extract medium (YE) and in casein peptone medium (CP) have been performed. Both free and peptide-bound amino acids were measured. In the CP most amino acids are peptide-bound and some amino acids are virtually only present in peptides. Thirty-six per cent of all peptide bonds in CP are hydrolysed during fermentation (6·3 mmol peptide bonds per gram biomass formed) and there is a transition of the growth rate related ATP consumption Y _xATP (mmol ATP g biomass^-1) from 25 mmol g^-1 to 71 mmol g^-1 coincident with a decrease of the peptide consumption. In YE most of the amino acids are on the free form and only 26% of the peptide bonds are hydrolysed during fermentation (1·5 mmol peptide bonds per gram biomass formed). A constant Y _xATP= 38 mmol g^-1 prevails throughout the fermentation in YE.     

Effects of moderately enhanced levels of ozone on the acyl lipid composition and dynamical properties of plasma membranes isolated from garden pea (Pisum sativum)

Plasma membranes were isolated from leaves of 16-day-old garden pea, Pisum sativum L., that had been grown in the absence or presence of 65 nl l⁻¹ ozone for 4 days prior to membrane isolation. Plasma membranes from ozone-fumigated plants contained significantly more acyl lipids per protein than those from leaves of plants grown in filtered air on a molar/weight ratio. The ratio between the major acyl lipids, phosphatidylethanolamine (PE) and phosphatidylcholine (PC), also increased due to the ozone fumigation, while the fatty acid unsaturation level was unaltered in total plasma membrane acyl lipids, as well as in PC and PE. The amount of free sterols per protein was unaltered, but the percentage of campesterol increased, concomitant with a decrease in stigmasterol. The dynamical properties of the isolated plasma membranes were assessed using Laurdan fluorescence spectroscopy, which monitors water penetration and mobility at the hydrophilic-hydrophobic interface of the membrane. At 0°C, the molecular mobility was slightly lower in plasma membranes from ozone-fumigated plants than in plasma membranes from control plants, possibly reflecting the increased PE/PC, campesterol/stigmasterol and lipid/protein ratios, and suggesting that ozone-fumigated pea plants may be more susceptible to freezing injuries.     

Effect of paclobutrazol and chilling on leaf membrane lipids in cucumber seedlings

The effects of paclobutrazol on the leaf membrane lipid composition of seedlings of cucumber ( Cucumis sativus L. cv. Victory) subjected to chilling temperatures were assessed. At a non-injurious temperature (12.5°C), there was no difference in the polar lipid fatty acid composition or in the glycolipid, phospholipid or free sterol content of leaves from treated vs untreated seedlings, regardless of whether paclobutrazol was administered 1 or 7 days prior to analysis. In the latter case (7 days pretreatment), there were clear effects of the bioregulator on plant growth and morphology as well as on leaf chlorophyll content. At an injurious chilling temperature (5°C), desaturation of leaf polar lipid fatty acids was markedly reduced in both treated and untreated seedlings. Chilling at 5°C resulted in losses of fresh weight and membrane lipids in leaves of both groups of plants. These losses were either reversible or irreversible, depending upon the duration of chilling and of pretreatment with paclobutrazol. Seedlings pretreated with 10 μg ml⁻¹ paclobutrazol generally sustained less chilling injury than untreated controls, as judged by the extent of wilting, necrosis and desiccation. This correlated with reduced losses of leaf fresh Weight and membrane lipids.     

Spawning and season affect lipid content and fatty acid composition of ovary and liver in Japanese catfish (Silurus asotus)

The influences of spawning and season on lipid content, lipid classes, and fatty acid composition were assessed in ovary and liver of wild and cultured Japanese catfish (Silurus asotus). The lipid content (7.3+/-1.6 g/100 g wet wt.) of ovary from wild catfish at spawning was higher than that at post-spawn. However, no influence of spawning on the lipid content of liver was observed. Docosahexaenoic acid [DHA, C22:6(n-3)] in ovary lipids was 12.3+/-0.5% of total fatty acids. The percentage of n-7 monounsaturated fatty acids in triacylglycerol from the ovary and liver in the spawning season was high. Percentages of C22:6(n-3) in phosphatidylcholine and phosphatidylethanolamine from ovary were higher during spawning than after spawning. No significant differences were observed in the lipid content of ovary and liver from cultured catfish between seasons (summer vs. winter). Content of arachidonic acid (C20:4n-6) in ovary and liver from cultured catfish was higher in summer than in winter. There were differences in lipid classes of ovary and liver by spawning and season. These results suggest that the lipid metabolism in Japanese catfish is greatly influenced by spawning and season.     

Chemical and carbon isotopic composition of fatty acids in adipose tissue as indicators of dietary history in wild arctic foxes (A lopex lagopus) on Svalbard

The chemical and carbon isotope compositions of triacylglycerol fatty acids were analysed in samples from two or more adipose depots dissected from adult and subadult arctic foxes collected between November 1991 and March 1992 in four different areas of Spitsbergen in the Svalbard archipelago (latitude 78° 5' to 79° 50' N). Site-specific differences were minor but there were large and consistent differences in the fatty acid composition of the storage lipids of foxes caught in the same areas, suggesting that residents of contiguous territories may have had quite different diets. The adipose tissue of adult foxes caught in Austfjordneset, an area where reindeer are rare, contained a much greater proportion of unsaturated fatty acids, suggesting that these animals were feeding mainly in the marine ecosystem, probably on seabirds and/or fish in summer and the remains of polar bear kills in winter. Measurements of the relative abundance of the carbon isotopes ¹²C and ¹³C in individual fatty acids show that palmitoleic acid (C16:1) in storage triacylglycerols originates from the marine food chain, probably together with most other unsaturated lipids, but that the foxes obtain oleic acid (C18:1), and probably most saturated fatty acids, from either terrestrial or marine sources.     

Temperature-dependent changes in phospholipid and fatty acid composition and membrane lipid fluidity of Yersinia enterocolitica

Temperature-dependent compositional changes of phospholipids and their fatty acids were analysed in Yersinia enterocolitica grown at 5°, 25° and 37°C. The relative amounts of the four phospholipids, phosphatidylethanolamine (75–78%), phosphatidylglycerol (10–11%), cardiolipin (<7%) and lysophosphatidylethanolamine (<5%), were essentially the same at all growth temperatures. The degree of fatty acid unsaturation of the four phospholipids increased with decrease in growth temperature, mainly due to an increase of C_16:1 and C_18:1 and a corresponding decrease of C_16;0, C_18:0 and cyclo C_17:0. An electron spin resonance spectroscopic study of the membrane lipids showed that membrane lipid fluidity was enhanced by decreasing the growth temperatures. The changes in fatty acid composition of phospholipids in response to varied temperatures were consistent with the temperature-dependent changes in the membrane lipid fluidity of Y. enterocolitica , and were similar to those reported for other bacteria.     

Effect of fatty acid supplementation on the lipid composition of Mycobacterium smegmatis ATCC 607, grown at 27° and 37°C

Mycobacterium smegmatis ATCC 607 was grown at 27 and 37°C, with and without exogenous unsaturated fatty acids, viz. elaidic, oleic and palmitoleic acids, added to the growth medium. The total lipid content of M. smegmatis ATCC 607 was lower at 27°C, and with added oleic acid, when compared with the controls, but higher in presence of palmitoleic acid. At 37°C no significant differences were noted in the total lipid content. In general, the total lipid content was lower with all of the fatty acid supplementations at both 27 and 37°C. The phosphatidylethanolamine content was slightly higher at 27°C in the presence of elaidic or palmitoleic acid, but was markedly lower with oleic acid supplementation at 37°C. The cardiolipin content was lower in the presence of any of the fatty acids at 27°C, and higher in the medium supplemented with elaidic or oleic acid at 37°C. The unsaturated to saturated fatty acids ratio was higher with palmitoleic acid supplementation at 27°C, but remained unchanged in cells grown at 37°C. The modifications in mycobacterial lipids are a reflection of the organism's ability to adapt to changing growth conditions.     

Occurrence of aflatoxin in some liver curative herbal medicines

Fifty herbal medicine samples of seven different taxa known to cure liver disorders were analysed for aflatoxin contamination. Twenty-three samples, out of 50, were contaminated with various levels of aflatoxins. Amongst the 23 contaminated samples the maximum level of aflatoxin B¹ recorded was 2.23 μg g^-1 in Asparagus racemosus and the minimum 0.28 μg g^-1 in Emblica officinalis . Aflatoxin G¹ was only found in one species, Terminalia belarica . Aflatoxin production of the isolates of Aspergillus flavus was also examined and the highest levels were produced by isolates from A. racemosus (1.07-2.47 μg ml^-1). Aflatoxin contamination of herbal drugs may be a risk for patients because the level of aflatoxins is much higher than the tolerance level fixed by the WHO for foods.     

Seasonal patterns in water, sodium and energy turnover in free-living echidnas, Tachyglossus aculeatus (Mammalia: Monotremata)

The energetics of an egg-laying mammal, the echidna ( Tachyglossus aculeatus ), were studied in the wild by means of isotope turnover techniques. Water and sodium influx rates were highest in summer (47.7±15.3 ml kg^-1 day^-1 and 1.20±0.52 mmol kg^-1 day^-1, respectively) and associated with high metabolic rates (0.509±0.048 ml CO₂ g^-1 h^-1). Water and sodium influxes and metabolic rates were lowest in May and June (7.8±6.4 ml H₂O kg^-1 day^-1, 0.21±0.12 mmol Na kg^-1 day^-1 and 0.205±0.129 ml CO₂ g^-1 h^-1, respectively). These low rates in late autumn/early winter are associated with reduced activity, the animals spending substantial periods of time in torpor. The comparatively low isotope turnover rates of echidnas are a consequence of their diet; ants and termites which have low mass-specific energy contents.     

Free fatty acids, neutral and polar lipids in Hordeum vulgare exposed to long-term fumigation with SO2

Three 9-day-old cultivars of Hordeum vulgare L. (Barberousse, Gerbel and Panda) were exposed to low levels of SO₂ fumigation (40 ± 5 and 117 ± 20 ppb). After 48 days of treatment the seedlings were harvested for lipid analysis. In comparison to the control (plants exposed to charcoal-filtered air), the total lipid content of fumigated seedlings declined at 40 ppb SO₂ and even more so at 117 ppb in all three cultivars. A large reduction in diacylglycerols. polar lipids and free sterols was also observed after fumigations at both SO₂ concentrations, whereas the treatments resulted in an increase in triacylglycerols and free fatty acids. The percentage composition of total fatty acids and that of each lipid class were changed by the fumigations. resulting in an increase in the degree of unsaturation. No changes in the percentage composition of sterols occurred in the fumigated leaves. These results suggest that even if SO₂ may not directly oxidize unsaturated fatty acids at the low concentrations used here (which do not cause visible injury). it may alter lipid metabolism. This alteration. which was particularly evident in the polar lipids and sterols, could affect the functions associated with membrane stabilization, in which lipids plus sterols play a key part.