High Sterol Content Research Articles

Lipid Composition of Cells of Heterothallic Strains in the Developmental Cycle of Blakeslea trispora

Lipid compositions in mycelium and spores of Blakeslea trispora heterothallic strains were studied. Distinctions between the strains in the ability to synthesize linolenic acid and in optimal growth temperature were demonstrated. The (-) strain grew at a higher temperature and was unable to synthesize linolenic acid, whereas the (+) strain accumulated this acid up to 20% of total fatty acids. The distinctions between the strains remained at different developmental stages (mycelium and spores). A higher thermophilicity of the (-) strain correlated with a high sterol content, which is typical of thermophilic fungi. The lipid compositions of heterothallic strains studied differed in lipid content, their fractional composition, the degree of unsaturation, and carotenoid composition.

High-resolution detection of adulteration of maize oil using multi-component compound-specific delta13C values of major and minor components and discriminant analysis.

Maize oil commands a premium price and is thus a target for adulteration with cheaper vegetable oils. Detection of this activity presents a particular challenge to the analyst because of the natural variability in the fatty acid composition of maize oils and because of their high sterol and tocopherol contents. This paper describes a method that allows detection of adulteration at concentrations of just 5% (m/m), based on the Mahalanobis distances of the principal component scores of the delta(13)C values of major and minor vegetable oil components. The method makes use of a database consisting of delta(13)C values and relative abundances of the major fatty acyl components of over 150 vegetable oils. The sterols and tocopherols of 16 maize oils and 6 potential adulterant oils were found to be depleted in (13)C by a constant amount relative to the bulk oil. Moreover, since maize oil contains particularly high levels of sterols and tocopherols, their delta(13)C values were not significantly altered when groundnut oil was added up to 20% (m/m) and it is possible to use the values for the minor components to predict the values that would be expected in a pure oil; therefore, comparison of the predicted values with those obtained experimentally allows adulteration to be detected. A refinement involved performing a discriminant analysis on the delta(13)C values of the bulk oil and the major fatty acids (16:0, 18:1 and 18:2) and using the Mahalanobis distances to determine the percentage of adulterant oil present. This approach may be refined further by including the delta(13)C values of the minor components in the discriminant analysis thereby increasing the sensitivity of the approach to concentrations at which adulteration would not be attractive economically.

Lipid Composition and Fluidity of Plasma Membranes Isolated from Corn (Zea mays L.) Roots

Although the results of lipid analyses from several plant species have been available for many years a complete characterization of the corn root plasma membrane is still lacking. The present study provides a detailed analysis of individual lipids and a characterization of the membrane fluidity of corn (Zea mays L.) root plasma membranes isolated by phase-partitioning. Phospholipids (43.9 mol%), sterols (40.8 mol%), and sphingolipids in the form of glucocerebroside (6.8 mol%) constitute the major lipid classes. Stigmasterol (19.8 mol%), campesterol (13.0 mol%), phosphatidylcholine 15.8 mol%), and phosphatidylethanolamine (14.2 mol%) represent the most ubiquitous individual lipids. Hydroxy fatty acids make up 80.9 mol% and very long chain fatty acids are almost 78% of fatty acids in glucocerebroside. Hydroxy arachidic acid (20:0 h) and hydroxy lignoceric acid (24:0 h) are most prominent and glucocerebroside from corn root plasma membranes contains virtually no unsaturated fatty acids. Among the phospholipids only phosphatidylserine displayed a high proportion of very long chain fatty acids (e.g., behenic and lignoceric acid). Membrane fluidity was estimated by fluorescence anisotropy. Due to the high sterol content the plasma membrane of corn roots is relatively rigid.

Chemical Composition of Soybean Oil Extracted from Hypocotyle-Enriched Soybean Raw Material and Its Cholesterol Lowering Effects in Rats.

Soybean oil (termed Soybean-germ oil to distinguish it from normal soybean oil) was extracted from hypocotyle-enriched (37%) soybean raw material and its chemical composition was analyzed. The total sterol content in Soybean-germ oil was 1.7% which is higher than that in soybean oil (0.4%), corn oil (1.1%) and rice bran oil (1.0%). The ratio of Campesterol to the total sterols of Soybean-germ oil was 8.1% that was lower than those of soybean oil (20.2%), corn oil (20.5%) and rice bran oil (15.7%), respectively. The sum of Δ7-Stigmastenol, Δ7-Avenasterol and Citrostadienol in Soybean-germ oil was 517mg/100g which was higher than in corn oil (30mg) and rice bran oil (230mg), respectively. Its cholesterol lowering effects in rats were evaluated. Between the rats fed test feeds containing 0.5% cholesterol and 10% test oils, the increases in the serum and liver cholesterol levels were more suppressed in the rats fed Soybean-germ oil than in those fed soybean oil. The higher sterol content in Soybean-germ oil may be related to its enhanced cholesterol lowering effects.

Sterols and polyamines in ipt-transformed tobacco plants

Free sterol and free polyamine contents were determined in the apex and the leaves of control and Pssu-ipt transformed tobacco ( Nicotiana tabacum L. cv. Petit Havana SR1). The older leaves of ipt-transformed plants contained a much higher putrescine (put) content than those of control SR1 plants, whereas no significant differences for spermidine (spd) or spermine (spm) were found between control and ipt plants. Putrescine content corresponded well with endogenous cytokinin (free-bases) content and with ornithine- and ornithine-decarboxylose (ODC and ADC) activities. Plants transformed with ipt were characterized by a higher sterol content in the leaves and by a delay in the increase in the stigmasterol/sitosterol ratio that occurs from the upper to the lower leaves.

Cold shock damage is due to lipid phase transitions in cell membranes: a demonstration using sperm as a model.

When cells are cooled to temperatures above the freezing point of water at rates greater than a few degrees per minute, they sustain irreversible injury. Reduction of this "cold shock" damage could increase the survival of animals and plants at low environmental temperatures and improve the cryopreservation of plant and animal cells. Leakage of solutes across membranes, associated with thermotropic phase transitions in membrane lipids, is thought to be responsible, but this hypothesis has not been tested directly. Using Fourier transform infrared spectroscopy (FTIR), we measured the lipid phase transitions in intact, living sperm, the animal cell in which cold shock has been studied most extensively. A shift in the CH2 absorbance peaks indicates the transition from liquid-crystalline to gel phase. The phase transition in sperm membranes occurred at a lower temperature for a marine shrimp than for the pig. In each case, potassium leakage, which is a hallmark of cold shock damage, increased abruptly near the end of the phase transition. Human sperm are quite resistant to cold shock, and an abrupt lipid phase transition was not detected. This phase behavior is typical of membranes containing a high proportion of cholesterol, and human sperm have an unusually high sterol content. High cholesterol levels are known to stabilize membranes during cooling. Overall, the lipid phase behavior was consistent with the temperature range over which cooling was damaging for pig and shrimp sperm, and the with the extent of damage produced in pig and human sperm. This is the first direct evidence that cold shock results from lipid phase transitions in cell membranes.

Flow‐cytometric investigation of sterol content and profliferation activity of yeast

AbstractTo understand and control the dynamics of microbial growth and metabolism, a theoretical background based on segregated models is necessary, and therefore flow cytometry is the suitable measuring method.It is shown that additional information to the usual mean‐value information, and to the well‐known cytometric methods for determining DNA content and size/shape measurement by scattered light, like the distribution of membrane sterol content of baker's yeast, leads to a more detailed knowledge of growth dynamics.We have found, that a low content of membrane sterols is a characteristic of cells with suppressed proliferation activity, but necessary for high fermentation activity. Also, a high content of membrane sterols seems to enhance the viability and survival capability of harvested and dryed baker's yeast cells. Therefore, we recommend harvesting cells at a point of medium content of membrane sterols.

Lipid composition of an obligate osmophilic mutant in Zygosaccharomyces rouxii

A Zygosaccharomyces rouxii mutant which required a high osmotic pressure for cell growth at a temperature higher than 30°C contained higher amounts of free sterol and linoleic acid but a lower amount of oleic acid than the wild type strain. The low ratio of oleic acid to linoleic acid and high sterol content cosegregated with the osmophilic trait in meiotic segregants.

Orthogonal arrays of particles in non-pigmented cells of rat ciliary epithelium: relation to distribution of filipin- and digitonin-induced alterations of the basolateral membrane.

It has been suggested that orthogonal arrays of particles may increase the rigidity of plasma membrane, as does cholesterol. Therefore, using freeze-fractured non-pigmented ciliary epithelium, the distribution of such arrays was compared to the distribution of membrane deformations induced by the sterol-probes filipin and digitonin in different domains of the basolateral plasma membrane. The distribution of orthogonal arrays of particles was homogeneous between different regions of the basolateral membrane of the non-pigmented ciliary epithelium, while the number of filipin-induced alterations was nearly 4 times higher in the membrane domains not in contact with the basal lamina than in domains in contact with it. Contrary to the homogeneous distribution of arrays, digitonin-induced deformations also differed markedly in these two basolateral membrane domains. Considering that a marked positive response to sterol probes implies a high sterol content, we conclude that orthogonal arrays of particles can occur in plasma membrane regions well-provided with cholesterol and not in direct contact with the basal lamina. Other possible roles of these arrays are discussed.

Transmembrane calcium movement in 20,25-diazacholesterol myotonia

An abnormality in myoplasmic Ca 2+ regulation has frequently been proposed in 20,25-diazacholesterol (20,25-D) myotonia. We report here the results of several studies of transmembrane Ca 2+ movement in this animal model. (i) Physiologic Ca 2+ release by intact sarcoplasmic reticulum (SR) was examined in chemically skinned single muscle fibers preloaded in EGTA-buffered Ca 2+ solutions ( pCa 2+ 7.0 to 6.4). Isometric tension development and Ca 2+ release thresholds in response to Cl − or caffeine showed no differences between control and 20,25-D fibers at any pCa 2+. (ii) The kinetics of energy-dependent Ca 2+ accumulation in purified SR vesicles were followed spectrophotometrically using Ca 2+-sensitive dyes. The apparent rate for ATP-dependent Ca 2+ uptake and Ca 2+ sequestering capacity were unchanged in SR from 20,25-D animals vs. controls. (iii) Surface membrane Ca 2+ ATPase activity was measured in red blood cell ghosts and sarcolemma. Enzyme V max was decreased by 25 to 50% in both membranes in the 20,25-D-treated animals with a compensatory increase in the number of Ca 2+ ATPase molecules. In general, the SR handling of Ca 2+ appears normal in 20,25-D myotonia, although the activity of Ca 2+ ATPase in membranes with high sterol content may be altered in response to changes in the lipid environment in this model.

The photosensitizing activity of haematoporphyrin on mollicutes.

The photosensitizing activity of haematoporphyrin (HP) on Mycoplasma hominis and Acholeplasma laidlawii was studied as a function of the phase of growth and the amount of sterols in the cell membrane. Less HP was bound to cells when the membrane had a high sterol content. Both strains in the exponential but not in the stationary phase of growth were sensitive to HP treatment (above 1 microgram ml-1) in the dark. Visible light irradiation of HP-loaded cells caused in all cases a decrease of cell survival, with concomitant changes in the pattern of membrane proteins that suggested protein-protein cross-linking, and the appearance of ultrastructural alterations (rounded and lysed cells); the photosensitivity was indirectly related to the sterol content of the cell membrane. On the whole, our findings suggest that the cell membrane is a major target for HP photosensitization of mycoplasma cells.

Genetic analysis of tomatine insensitivity, sterol content and pathogenicity for green tomato fruits in mutants of Fusarium solani

Two Fusarium solani mutants of mating type (+), insensitive to tomatine and digitonin, pathogenic for green tomato fruits (containing tomatine) and with low sterol content, were crossed with a mating type (−) strain of Nectria haematococca (the perfect state of F. solani), sensitive to tomatine and digitonin, non-pathogenic for green tomato fruits and with high sterol content. Most asci produced had a reduced spore number. Tomatine insensitivity and mating type were inherited independently in 421 randomly selected F1 ascospores (P = 0·80). Linkage analysis showed that the mutations for tomatine insensitivity, induced in one mutant after N-methyl-N′-nitro-N-nitrosoguanidine and in the other after u.v. treatment, belonged to the same locus or were closely linked (n = 400, P = 0·096). Pathogenicity for green tomatoes, low sterol content and insensitivity to digitonin were always inherited together with tomatine insensitivity. We suggest that tomatine is a resistance factor of green tomatoes against F. solani and that low sterol content is a mechanism of insensitivity to tomatine and digitonin.

Freeze-fracture study of phagocytosis in Dictyostelium discoideum.

The plasma membrane and its derivative, the phagosome membrane, were studied during and after ingestion of yeast of latex beads in Dictyostelium discoideum. Freeze-fracture electron microscopy, which provides information on the internal architecture of the membranes, and observation of thin sections of cells treated by cytochemical methods were used in parallel. For visualization of membrane sterols in the replicas, the cells were fixed in the presence of digitonin or the antibiotic filipin. No lateral phase separation occurred during yeast engulfment: the intramembranous particles (IMPs), phospholipids and sterols remained distributed at random in the forming phagosome membrane. In contrast architectural modifications of the membrane were observed upon phagosome internalization. Compared to the plasma membrane, the phagosome membrane displayed 2-3 times more IMPs a shift in the IMP size distribution and a higher sterol content. These changes were completed soon after phagosome closure; they were not related either to the nature of the ingested particles (yeast, latex beads) or to the pH in the membrane environment. The membrane changes too place when the phagosomes began to fuse with pre-existing digestive or autophagic vacuoles and lysosomes. Some of the experimental evidence suggests that the restructuring of the membrane may be related to the presence of hydrolases.

Ultrastructural localisation of sterols in ethylnitrosourea-induced Schwannomas.

Malignant schwannomas of the trigeminal nerves were induced transplacentally by a single intravenous injection of 30 mg of N-ethyl-N-nitrosourea per kg of body weight into pregnant BD-IX rats on the 15th day of gestation. These neoplasms consisted of a pleomorphic population of Schwann cells and occasional fibroblasts. In order to preserve sterols the tumours were fixed in a digitonin-containing aldehyde solution. The electron microscope investigation of the tissues so treated revealed various structures: lamellar, tubular and complex formations were all observed. In addition, the unit membranes, including those of various cytoplasmic organelles, showed areas of increased contrast. The abundance of these fine structural configurations indicated the high sterol content of ethyl-nitrosourea-induced schwannomas.

On the sterols of some ascidians.

The lipid content of sea squirts is low, namely less than a half percent of the fresh weight. Lipids consist of about seventy percent of saponifiable lipids and of about twenty percent of non-saponifiable lipids. Both types of these lipids, including sterols, can be synthesized from acetate by these animals. Small amounts of C30 sterols were observed only in Microcosmus sulcatus and Halocynthia papillosa, the species with a low content of C27 sterols and a high content of C28 sterols. In addition these species contained considerable higher amounts of sterols with a double bond at the C22 position than Ciona intestinalis and Styela plicata did.

Wirkung von Polyen-Makrolidantibiotica auf normale und zellwandlose Zellen vonEscherichia coli W1655F+

The polyene macrolide antibiotics are active against yeast, fungi, and other eukaryotic cells, but are with a few exceptions inactive against bacteria. The resistance of bacteria against these compounds is usually explained by the absence of sterols in their cells, the target sites of polyene antibiotics. However, in our experiments with mycotrienin, nystatin, tetramycin, lucenosmycin, rimocidin, filipin, lagosin, flavofungin, flavomycoin, antibiotic 2814P, antibiotic 5001P, and candicidin it was demonstrated that bacteria may be susceptible to polyene antibiotics, too, if the wall-less stable protoplast type L-form of E. coli W1655F+ is used. The measured growth inhibition concentrations were comparable with those of typical antibacterial antibiotics. Our experiments have shown that the normal rod form and the wall-less L-form of E. coli W1655F+ contain traces of sterols in nearly the same concentration range. This means that the selective sensitivity of the L-form cannot be explained by higher sterol content of these cells in comparison to the resistant normal rod form cells. We assume that the bacterial cell wall is responsible for the resistance of the normal rod form by masking internal target sites.

Wirkung von Polyen-Makrolidantibiotica auf normale und zellwandlose Zellen vonEscherichia coliW1655F+

The polyene macrolide antibiotics are active against yeasts, fungi, and other eukaryotic cells, but are with a few exceptions inactive against bacteria. The resistance of bacteria against these compounds is usually explained by the absence of sterols in their cells, the target sites of polyene antibiotics. However, in our experiments with mycotrienin, nystatin, tetramycin, lucensomycin, rimocidin, filipin, lagosin, flavofungin, flavomycoin, antibiotic 2814 P, antibiotic 5001 P, and candicidin it was demonstrated that bacteria may be susceptible to polyene antibiotics, too, if the wall-less stable protoplast type L-form of E. coli W1655F+ is used. The measured growth inhibition concentrations were comparable with those of typical antibacterial antibiotics. Our experiments have shown that the normal rod form and the wall-less L-form of E. coli W1655F+ contain traces of sterols in nearly the same concentration range. This means that the selective sensitivity of the L-form cannot be explained by higher sterol content of these cells in comparison to the resistant normal rod form cells. We assume that the bacterial cell wall is responsible for the resistance of the normal rod form by masking internal target sites.

Biosynthesis of lipids in perfused dog aorta and coronary artery: III. Incorporation of [2- 14C]acetate into sterols and uptake of [ 3H]cholesterol in three aortic layers and in coronary artery of normal and hyperlipemic dogs and under the influence of nicotine

In dog aortas and coronary arteries perfused with the animal's own serum which contained [ 14H]acetate and [ 3H]cholesterol the controls showed an amount of exogeneous [ 3H]cholesterol which was nearly the same in the three aortic layers, but it was significantly higher in the coronary arteries. The intimal sterols incorporated the highest amount of 14C, whereas the highest sterol content was found in the media. The ratio per cent [ 3H]cholesterol: percent [ 14C]sterols, as related to the total sterol content, was approximately the same—10—in the aortic layers; it was 60 in the coronary arteries. Influence of nicotine reduced 14C-incorporation into sterols in the aortic layers. The difference in the [ 3H]cholesterol uptake by the intima and media was more pronounced while the coronary arteries remained unaffected. Animals exposed to an atherogenic diet showed no morphological changes despite a severe hyperlipemia. The sterol content was slightly increased in the aortic intima and the corresponding 14C-incorporation was significantly elevated. The [ 3H]cholesterol content was only increased in the adventitia. In the coronary arteries, the 14C-incorporation into sterols was diminished and the [ 3H]cholesterol uptake was increased. In the case of dog number 21, severe morphological changes were observed. As compared to the other animals exposed to the same diet, the 14C-incorporation was increased in the total lipids of the aortic intima and of the coronary artery. The content of sterolesters and their radioactivity were elevated in both vessels; the sterol content was also augmented but the corresponding 14C-activity was markedly diminished, mainly in the aorta. The amount of [ 3H]cholesterol was in the same range as the other hyperlipemic animals.

Isotonic contraction of induced myotonic muscle of rat: After contraction and prolonged relaxation time

An abnormality in myoplasmic Ca2+ regulation has frequently been proposed in 20,25-diazacholesterol (20,25-D) myotonia. We report here the results of several studies of transmembrane Ca2+ movement in this animal model. (i) Physiologic Ca2+ release by intact sarcoplasmic reticulum (SR) was examined in chemically skinned single muscle fibers preloaded in EGTA-buffered Ca2+ solutions (pCa2+ 7.0 to 6.4). Isometric tension development and Ca2+ release thresholds in response to Cl− or caffeine showed no differences between control and 20,25-D fibers at any pCa2+. (ii) The kinetics of energy-dependent Ca2+ accumulation in purified SR vesicles were followed spectrophotometrically using Ca2+-sensitive dyes. The apparent rate for ATP-dependent Ca2+ uptake and Ca2+ sequestering capacity were unchanged in SR from 20,25-D animals vs. controls. (iii) Surface membrane Ca2+ ATPase activity was measured in red blood cell ghosts and sarcolemma. Enzyme Vmax was decreased by 25 to 50% in both membranes in the 20,25-D-treated animals with a compensatory increase in the number of Ca2+ ATPase molecules. In general, the SR handling of Ca2+ appears normal in 20,25-D myotonia, although the activity of Ca2+ ATPase in membranes with high sterol content may be altered in response to changes in the lipid environment in this model.

Sterol content and distribution in two Nicotiana species and their spontaneous-tumoring hybrid

Sterol contents of Nicotiana suaveolens (Lehm), N. langsdorffii (Weinm.) and their spontaneous-tumoring hybrid were compared when plants of both species and the hybrid began flowering, and again after numerous tumours had developed spontaneously on the hybrid plants. In general, the upper plant parts (younger tissues) had higher sterol contents than did the lower plant parts (older tissues) at both sampling dates. β-Sitosterol was the most abundant sterol in the above ground portions while stigmasterol was most abundant in roots. Low cholesterol and high campesterol levels were found in N. suaveolens in contrast with high cholesterol and low campesterol in N. langsdorffii. Levels of cholesterol and campesterol in the hybrid were intermediate between the parental species. Low cholesterol and high campesterol contents were found in tumours of the hybrid, and in roots of both of the parental species and the hybrid.