| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Constantly low HDL-cholesterol concentration relates to endothelial dysfunction and increased in vivo LDL-oxidation in healthy young men Toikka, J. O., M. Ahotupa, et al. (1999), Atherosclerosis 147(1): 133-8. Abstract: To test the hypothesis that low HDL-C concentration interferes with vascular endothelial function and lipoprotein oxidation, we measured endothelium-dependent flow mediated dilatation (FMD, %) of the brachial artery in young men (n=20) classified prospectively into two groups on basis of having either low or high HDL-C concentration over the past 2 years. As an estimate of in vivo low-density lipoprotein oxidation (ox-LDL), we measured LDL diene conjugation. FMD was present in the group with high HDL-C concentration, but impaired in the group with low HDL-C (5.5+/-3.2 vs 0.2+/-1.2%, P<0. 001). The group with high HDL-C level had significantly lower levels of ox-LDL compared to low HDL-C group (18.0+/-1.8 vs 22.9+/-4.4, P |
| Constant-pressure molecular dynamics investigation of cholesterol effects in a dipalmitoylphosphatidylcholine bilayer Tu, K., M. L. Klein, et al. (1998), Biophys J 75(5): 2147-56. Abstract: We report a 1.4-ns constant-pressure molecular dynamics simulation of cholesterol at 12.5 mol% in a dipalmitoylphosphatidylcholine (DPPC) bilayer at 50 degrees C and compare the results to our previous simulation of a pure DPPC bilayer. The interlamellar spacing was increased by 2.5 A in the cholesterol-containing bilayer, consistent with x-ray diffraction results, whereas the bilayer thickness was increased by only 1 A. The bilayer/water interface was more abrupt because the lipid headgroups lie flatter to fill spaces left by the cholesterol molecules. This leads to less compensation by the lipid headgroups of the oriented water contribution to the membrane dipole potential and could explain the experimentally observed increase in the magnitude of the dipole potential by cholesterol. Our calculations suggested that 12.5 mol% cholesterol does not significantly affect the conformations and packing of the hydrocarbon chains and produces only a slight reduction in the empty free volume. However, cholesterol has a significant influence on the subnanosecond time scale lipid dynamics: the diffusion constant for the center-of-mass "rattling" motion was reduced by a factor of 3, and the reorientational motion of the methylene groups was slowed along the entire length of the hydrocarbon chains. |
| Constipation: is it a risk factor for cholesterol gallstones? Watkins, J. L., T. E. Wiley, et al. (1993), Hepatology 18(2): 457-8. |
| Constitutive steroidogenesis does not require the actions of cAMP on cholesteryl ester hydrolysis or internalization of plasma membrane cholesterol Freeman, D. A. (1996), Endocr Res 22(4): 557-62. Abstract: The R2C Leydig tumor cells demonstrate constitutive steroidogenesis as well as the constitutive production of the steroidogenic acute regulatory peptide (StAR). Since the introduction of StAR into cells does not by itself reproduce the steroidogenic response of cAMP, the present studies were designed to determine whether processes normally stimulated by cAMP in responsive cells were maximally, constitutively expressed in the R2C cells. Measurements of cholesteryl ester hydrolytic rate and plasma membrane cholesterol internalization revealed that both processes are stimulated by dibutyryl-cAMP in R2C cells. The effect of cAMP on these processes was of the same magnitude as that detected in hormonally responsive cells. Thus, in R2C cells the unstimulated basal rate of either process was sufficient to maintain maximal stimulation of steroidogenesis. |
| Consumer understanding and use of fat and cholesterol information on food labels Reid, D. J. and S. M. Hendricks (1994), Can J Public Health 85(5): 334-7. Abstract: As part of a comprehensive study looking at consumer awareness of nutrition labelling, this descriptive market research evaluated the understanding and use of label information about fat and cholesterol. Mall intercept interviews of 149 food shoppers (80% women, 20% men) revealed that 60% believed it is extremely or very important to reduce their dietary fat. However, the claims "low in saturated fat" and "no cholesterol" and the term "non-hydrogenated" were often misunderstood. Fifty to 66% of respondents correctly interpreted "% B.F./M.F." "low fat" versus "reduced in fat" claims, and the fat content of margarines. Only 18% used % B.F. information to choose cheese and yoghurt. Depending on the claim, 34-56% of respondents reported consulting other label information along with the claim; with the lowest rate of "additional consultation", (34%) reported for the "no cholesterol" claim. Consumer education is needed to enhance understanding and use of fat and cholesterol label information. |
| Consumption of boiled coffee is correlated with serum cholesterol in Finland Pietinen, P., A. Aro, et al. (1990), Int J Epidemiol 19(3): 586-90. Abstract: The association between coffee consumption and serum cholesterol concentration was studied in a cross-sectional epidemiological study among 5704 men and women in Finland. The mean serum cholesterol values of those consuming boiled coffee (24% of the subjects) was significantly higher than that of drinkers of filtered coffee (69% of the subjects) in both sexes after adjusting for age, body mass index, smoking, serum gamma-glutamyltransferase, index of saturated fat intake, and physical activity: in men 6.37 versus 6.02 mmol/l, in women 6.22 versus 5.84 mmol/l, both significant at p less than 0.001. A significant dose-dependent effect was observed between the consumption of boiled coffee both in men and in women. For filter coffee drinkers a weak coffee dose-cholesterol association was found only for women. The magnitude of the effect of boiled coffee, 0.3-0.4 mmol/l in serum cholesterol values, is in accordance with the results from controlled trials carried out among both hyper- and normocholesterolaemic subjects. |
| Consumption of buckwheat protein lowers plasma cholesterol and raises fecal neutral sterols in cholesterol-Fed rats because of its low digestibility Kayashita, J., I. Shimaoka, et al. (1997), J Nutr 127(7): 1395-400. Abstract: Buckwheat protein product (BWP) has a strong hypocholesterolemic activity in rats fed a cholesterol-enriched diet. In this study, we examined the influence of BWP on fecal excretion of sterols and nitrogen in rats fed a diet containing 5 g/kg cholesterol and 1.25 g/kg sodium cholate, and we examined whether the cholesterol-lowering activity of BWP is due to its low digestibility. In Experiment 1, rats fed BWP for 3 wk had significantly lower concentrations of plasma cholesterol and enhanced excretion of fecal total neutral sterols and nitrogen compared with rats fed casein. There was a significant correlation between fecal total neutral sterols and nitrogen (r = 0.89, P < 0.01). Fecal excretion of acidic sterols was unaffected by BWP. In Experiment 2, plasma cholesterol in rats fed trypsin-digested BWP for 2 wk was significantly higher than that in rats fed intact BWP. In Experiment 3, rats were fed BWP, low-molecular-weight fraction of the digest of BWP (LMF) or high-molecular-weight fraction of the digest of BWP (HMF) for 3 wk. Plasma cholesterol was lower in the BWP group than in the LMF group (P < 0.05), whereas that in the HMF group was intermediate. The in vitro digestibility of BWP with pepsin and pancreatin was significantly lower than that of casein. The results suggest that the cholesterol-lowering effect of BWP is mediated by higher fecal excretion of neutral sterols and that lower digestibility of BWP is at least partially responsible for the effect. |
| Consumption of fermented and nonfermented dairy products: effects on cholesterol concentrations and metabolism St-Onge, M. P., E. R. Farnworth, et al. (2000), Am J Clin Nutr 71(3): 674-81. Abstract: The objective of this article was to review existing literature concerning the effects and mechanisms of action of fermented dairy products on serum cholesterol concentrations. Although not without exception, existing evidence from animal and human studies suggests a moderate cholesterol-lowering action of fermented dairy products. Mechanistically, fermented milk has been shown to cause an increase in human gut bacterial content. These bacteria, once resident in the large intestine, are believed to ferment food-derived indigestible carbohydrates. Such fermentation causes increased production of short-chain fatty acids, which decreases circulatory cholesterol concentrations either by inhibiting hepatic cholesterol synthesis or by redistributing cholesterol from plasma to the liver. Furthermore, increased bacterial activity in the large intestine results in enhanced bile acid deconjugation. Deconjugated bile acids are not well absorbed by the gut mucosa and are excreted. Consequently, cholesterol, being a precursor of bile acids, is utilized to a greater extent for de novo bile acid synthesis. These actions combined are proposed as contributing mechanisms to the association of fermented milk consumption with decreased circulating cholesterol concentrations. |
| Consumption of French-press coffee raises cholesteryl ester transfer protein activity levels before LDL cholesterol in normolipidaemic subjects De Roos, B., A. Van Tol, et al. (2000), J Intern Med 248(3): 211-6. Abstract: OBJECTIVES: To determine the long-term effects of unfiltered coffee consumption on the activity levels of cholesteryl ester transfer protein (CETP), phospholipid transfer protein (PLTP) and lecithin:cholesterol acyltransferase (LCAT) and to assess a possible role of CETP activity levels in the rise in serum LDL cholesterol. SUBJECTS AND DESIGN: Forty-six healthy normolipidaemic subjects consumed 0.9 L of either French-press or filtered coffee for 24 weeks. Fasting blood samples were obtained after 0, 2, 12 and 24 weeks of intervention and after and 12 weeks of follow-up. MAIN OUTCOME MEASURES: Serum activity levels of CETP, PLTP and LCAT. RESULTS: Relative to baseline, French-press coffee significantly increased average CETP activity by 12% after 2 weeks, by 18% after 12 weeks, and by 9% after 24 weeks. PLTP activity was significantly increased by 10% after 12 and 24 weeks. LCAT activity was significantly decreased by 6% after 12 weeks and by 7% after 24 weeks. The increase in CETP clearly preceded the increase in LDL cholesterol, but not the increase in total triglycerides. However, consumption of French-press coffee caused a persistent rise in CETP activity, whereas the rise in serum triglycerides was transient. CONCLUSIONS: Consumption of cafestol and kahweol cause a long-term increase in CETP as well as PLTP activity; the increase in CETP activity may contribute to the rise in LDL cholesterol. |
| Consumption of lipids in the university population of Spain, evaluation of the hepatic profile and of serum cholesterol Gonzalez, M., B. Caride, et al. (1999), Nutr Hosp 14(3): 133-4. Abstract: In the present study we tried to characterise the diet of university students in Northwest Spain, paying particular attention to lipids and fibre intake. We administered a 24 hour recall dietary-habits questionnaire. Saturated and monounsaturated fats predominated, with the intake of polyunsaturated fatty acids being considerably lower. Mean daily cholesterol intake was in most cases in excess of the recommended maximum and mean fibre intake showed a considerable variation among individuals. The obtained hepatic profile is found within normal range. The calories provided by the diet result adapted in half of the studied population approximately, while the fourth part does not cover the recommended quantity. These results could be considered a risk in the future. |
| Consumption of oat milk for 5 weeks lowers serum cholesterol and LDL cholesterol in free-living men with moderate hypercholesterolemia Onning, G., A. Wallmark, et al. (1999), Ann Nutr Metab 43(5): 301-9. Abstract: The aim of this study was to investigate whether consumption of a newly developed oat milk deprived of insoluble fiber would result in lower serum cholesterol and low-density lipoprotein (LDL) cholesterol levels in men with moderate hypercholesterolemia. The study had a randomized, controlled double-blind design, and oat milk was compared with an identically flavored control drink. Sixty-six men were recruited from a screening program and were randomly assigned to two groups. Each group took either oat milk or a control drink (rice milk) for 5 weeks (0.75 liters/day) and then switched to the other drink regimen for another 5-week period with a 5-week washout period between the test periods. The oat milk contained more dietary fiber, especially beta-glucan (0.5 g/100 g), than the control drink (<0.02 g/100 g). Both drinks were well appreciated and got similar sensory evaluation, indicating that the double-blind design had been attained. In the final analysis 52 subjects remained. Compared with the control drink, intake of oat milk resulted in significantly lower serum total cholesterol (6%, p = 0.005) and LDL cholesterol (6%, p = 0.036) levels. The decrease in LDL cholesterol was more pronounced if the starting value was higher (r = -0.55, p < 0.001). The concentration of high-density lipoprotein cholesterol was not significantly different after consumption of the two drinks. Serum triglycerides did not change significantly after intake of oat milk, but a significant increase was observed after intake of the control drink (p = 0.003). It is concluded that also oat milk deprived of insoluble fiber has cholesterol-reducing properties. |
| Consumption of olive oil has opposite effects on plasma total cholesterol and sphingomyelin concentrations in rats Geelen, M. J. and A. C. Beynen (2000), Br J Nutr 83(5): 541-7. Abstract: The hypothesis that olive-oil consumption alters plasma sphingomyelin concentrations and hepatic sphingomyelin metabolism was tested. Rats were fed on purified, high-cholesterol diets with either coconut fat or olive-oil (180 g/kg). In accordance with previous work, olive-oil v. coconut-fat consumption significantly elevated hepatic and total plasma cholesterol concentrations. During the course of the experiment, the concentration of plasma sphingomyelin rose in the coconut-fat group and remained constant in the olive-oil group. When compared with the coconut-fat-fed group, the plasma sphingomyelin levels were significantly lower in the olive-oil-fed group after 14 and 21 d of treatment. Dietary olive oil raised the amounts of cholesterol and sphingomyelin in the VLDL density region, and this change was associated with a reduction in the cholesterol and sphingomyelin contents of the LDL and HDL density ranges. Olive-oil consumption reduced the activity of serine palmitoyltransferase, while the activities of phosphatidylcholine:ceramide cholinephosphotransferase and phosphatidylethanolamine:ceramide ethanolaminephosphotransferase were left unchanged. Dietary olive oil also enhanced the activity of acidic sphingomyelinase, but not that of neutral sphingomyelinase. The present data indicate that dietary olive oil v. coconut fat has opposite effects on total plasma cholesterol and sphingomyelin concentrations. The lower plasma sphingomyelin levels observed in olive-oil-fed, as compared with coconut-fat-fed rats, may be explained by a simultaneous elevation and reduction in sphingomyelin catabolism and synthesis respectively, as based on the measured enzyme activities. |
| Consumption of soy protein reduces cholesterol absorption compared to casein protein alone or supplemented with an isoflavone extract or conjugated equine estrogen in ovariectomized cynomolgus monkeys Greaves, K. A., M. D. Wilson, et al. (2000), J Nutr 130(4): 820-6. Abstract: Dietary intake of soy protein is associated with reductions in plasma cholesterol. Isoflavones are thought to be active components of soy and responsible for the beneficial effects because of their structural similarities to estrogen. The purposes of this study were to determine if i) soy protein or a semipurified soy extract, rich in isoflavones, is responsible for improving the lipid profile and ii) altered intestinal cholesterol metabolism is one mechanism for hypocholesterolemic effects. Ovariectomized adult female cynomolgus monkeys (40) were assigned to groups fed diets containing i) casein-lactalbumin (CAS) ii) intact soy protein (SOY), iii) CAS plus an isoflavone-rich semipurified soy extract similar in isoflavone content as SOY (ISO) or iv) CAS plus conjugated equine estrogen (CEE) for 20 wk. Cholesterol absorption was determined using the fecal isotope ratio method. Bile acid excretion was measured using the 3alpha-hydroxysteroid dehydrogenase assay. The SOY group had significantly lower total- and VLDL + LDL-cholesterol compared to the other three groups and significantly higher HDL-cholesterol compared to the CAS and CEE groups. Cholesterol absorption was significantly lower in the SOY group compared to the other groups, but bile acid excretion was not significantly affected. The hypocholesterolemic effect of soy protein appears to be mediated in part by decreased cholesterol absorption. The semipurified soy extract, rich in isoflavones, added to casein protein did not have lipid-lowering effects. Other components of soy such as saponins, phytic acid or the amino acid composition may be involved in the hypocholesterolemic effects seen in this study. |
| Consumption of tall oil-derived phytosterols in a chocolate matrix significantly decreases plasma total and low-density lipoprotein-cholesterol levels De Graaf, J., P. R. De Sauvage Nolting, et al. (2002), Br J Nutr 88(5): 479-88. Abstract: In a randomized, double-blind, placebo-controlled trial we evaluated the effect of dietary chocolates enriched with a wood-based phytosterol-phytostanol mixture, containing 18 % (w/w) sitostanol, compared with placebo dietary chocolates in seventy subjects with primary hypercholesterolaemia (total cholesterol levels below 8 mmol/l). For 4 weeks, participants consumed three servings of the phytosterol-enriched chocolate/d that provided 1.8 g unesterified phytosterols/d or a placebo chocolate in conjunction with a low-fat, low-cholesterol diet. Plasma total and LDL-cholesterol levels were statistically significantly reduced by 6.4 % (-0.44 mmol/l) and 10.3 % (-0.49 mmol/l), respectively, after 4 weeks of phytosterol-enriched-chocolate treatment. Plasma HDL-cholesterol and triacylglycerol levels were not affected. Consumption of phytosterol-enriched chocolates significantly increased plasma lathosterol concentration (+20.7 %), reflecting an increased endogenous cholesterol synthesis in response to phytosterol-induced decreased intestinal cholesterol absorption. Furthermore, the chocolates enriched with phytosterols significantly increased both plasma sitosterol (+95.8 %) and campesterol (+64.1 %) levels, compared with the placebo chocolate group. However, the absolute values of plasma sitosterol and campesterol remained within the normal range, that is, below 10 mg/l. The chocolates with phytosterols were palatable and induced no clinical or biochemical side effects. These findings indicate that dietary chocolate enriched with tall oil-derived phytosterols (1.8 g/d) is effective in lowering blood total and LDL-cholesterol levels in subjects with mild hypercholesterolaemia and thus may be helpful in reducing the risk of CHD in these individuals. |
| Contact dissolution of cholesterol gallstones with organic solvents Hofmann, A. F., C. D. Schteingart, et al. (1991), Gastroenterol Clin North Am 20(1): 183-99. Abstract: Contact dissolution of cholesterol gallstones with organic solvents is emerging as a rapid, safe, alternative treatment for symptomatic cholesterol gallbladder stones. Placement of a percutaneous transhepatic catheter into the gallbladder is a rapid and safe technique. The availability of safe, effective cholesterol solvents and solvent transfer devices means that cholesterol gallbladder stones can be eliminated rapidly and safely by CDOS, without the risk of general anesthesia or surgical dissection of the gallbladder bed. Patients with single gallstones are better candidates for CDOS than are patients with multiple gallstones because recurrence after dissolution is less common. Contact dissolution may well be judged the treatment of choice by the medical-surgical gallstone management team in some patients. |
| Content of antioxidants, preformed lipid hydroperoxides, and cholesterol as predictors of the susceptibility of human LDL to metal ion-dependent and -independent oxidation Frei, B. and J. M. Gaziano (1993), J Lipid Res 34(12): 2135-45. Abstract: Oxidative modification of low density lipoprotein (LDL) has been suggested to play a casual role in human atherosclerosis, and prevention of LDL oxidation may be an effective strategy to prevent or slow the progression of this disease. It is important, therefore, to identify the factors that determine LDL's susceptibility to oxidation. We have analyzed 62 human LDL samples for content of antioxidants, preformed lipid hydroperoxides, and cholesterol. To investigate their oxidative susceptibility, the LDL samples were exposed to either a metal ion-dependent (Cu2+) or -independent (aqueous peroxyl radicals) oxidizing system; the length of the lag phase of inhibited lipid peroxidation was measured, as well as the rate of lipid peroxidation during the lag and ensuing propagation phases. The susceptibility of LDL to metal ion-dependent oxidation was not related to its susceptibility to metal ion-independent oxidation. A strong predictor of an increased susceptibility of LDL to metal ion-dependent oxidation was a decreased vitamin E-to-cholesterol ratio, in contrast to the vitamin E-to-protein ratio. Elevated levels of performed lipid hydroperoxides in LDL and an increased cholesterol content were also associated with an increased susceptibility of the lipoprotein to Cu(2+)-induced oxidation. Remarkably, a strong predictor of an increased susceptibility of LDL to metal ion-independent oxidation was an increased, rather than decreased, vitamin E content relative to protein. An increased cholesterol content also was associated with an increased oxidative susceptibility of LDL to aqueous peroxyl radicals, while preformed lipid hydroperoxides showed no significant correlation. Ubiquinol-10, beta-carotene, and lycopene, whether quantitated relative to cholesterol or protein, did not show significant protective effects against both metal ion-dependent and -independent oxidation of LDL. Our data suggest that a high lipid content of LDL, relative to its protein content, renders the lipoprotein more susceptible to oxidative modification, while vitamin E may have either a protective or promoting effect on LDL oxidation, depending on the oxidative stress conditions. Other known antioxidants in LDL do not appear to play a significant role in protecting LDL against oxidative modification. |
| Content of cholesterol extracted from human skin surface--a possible discriminant of atherosclerosis? Torkhovskaia, T. I., E. S. Fortinskaia, et al. (1992), Biull Eksp Biol Med 113(5): 481-3. Abstract: Basing on the data of Bouissou et al. on an increase of cholesterol content in the skin biopsies in atherosclerosis patients, the cholesterol amount was evaluated after superficial atraumatic rapid treatment of patients palm skin. The optimization of the extraction conditions was performed: the surface skin cholesterol value was constant for individual subjects (variability factor 5%). The range of this value was 1.5-6 Mg/cm2 and it was higher for atherosclerotic patients. No correlations with any conventional plasma lipoprotein parameters were observed. At the same time positive correlation (r = 0.54. p < 0.01) was observed with dyslipoprotein coefficient--(Ch+TG/alpha-Ch). Possible diagnostic significance of this skin cholesterol parameter is discussed. |
| Continuous infusion of adrenocorticotropin elevates circulating lipoprotein cholesterol and corticosterone concentrations in chickens Latour, M. A., S. A. Laiche, et al. (1996), Poult Sci 75(11): 1428-32. Abstract: The purpose of the present study was to investigate the effects of elevated corticosterone (CORT) on circulating lipoprotein cholesterol during a 1-wk period. For this study, 15 commercial broilers were randomly assigned to one of three treatment groups. Group 1 served as the control (CON) and received no treatment, whereas Groups 2 and 3 received subcutaneous mini-osmotic pumps containing either physiological saline (PS) or adrenocorticotropin (ACTH), respectively. The ACTH was delivered at a rate of 8 IU/kg of BW/d. Blood samples were taken at Time 0 (before implants) and on Days 2, 4, and 7 postimplantation. Continuous infusion of ACTH increased plasma glucose, cholesterol, triglycerides, very low density lipoprotein cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and CORT during the postimplantation period. The group treated with ACTH also exhibited a decrease in BW during the last 2 sampling d. There were no differences in any of the serum constituents measured between CON and PS birds, which suggest that CON birds can serve as useful controls. These data suggest that birds given a continuous infusion of ACTH at 8 IU/kg of BW/d can experience changes in plasma lipoprotein cholesterol concentrations along with changes in other blood parameters and may serve as a useful model in accelerated lipoprotein production. |
| Continuous infusion of interleukin-1 beta in rats induces a profound fall in plasma levels of cholesterol and triglycerides Hermus, A. R., C. G. Sweep, et al. (1992), Arterioscler Thromb 12(9): 1036-43. Abstract: During infectious diseases, striking alterations in plasma concentrations of cholesterol (hypocholesterolemia) and triglycerides (hypertriglyceridemia) may occur. It has been suggested that interleukin-1 is a mediator of these alterations. We studied the effects of continuous administration of recombinant human interleukin-1 beta (rhIL-1 beta) on plasma levels of cholesterol and triglycerides. A total of 42 rats were equipped with minipumps loaded with either rhIL-1 beta (delivery rate of 0.5, 2.0, or 4.0 micrograms/day i.p. for 1 week) or saline. After 1 day of treatment with rhIL-1 beta, plasma cholesterol levels had not changed. On day 2 a remarkable decrease of plasma cholesterol levels was observed in rats treated with 2.0 micrograms rhIL-1 beta/day (1.49 +/- 0.13 versus 2.23 +/- 0.08 mmol/l, p less than 0.005; rhIL-1 beta versus saline) or 4.0 micrograms rhIL-1 beta/day (1.46 +/- 0.04 versus 2.18 +/- 0.04 mmol/l,p less than 0.0005). This decrease persisted until the end of the experiment and occurred in all major lipoprotein fractions. Triglycerides in plasma (and in very low density lipoprotein) decreased almost concomitantly with plasma cholesterol, although to a lesser degree. Infusion of 2.0 micrograms rhIL-1 beta/day did not affect either cholesterol esterification or total postheparin lipolytic activity in plasma. Long-term infusion with 4.0 micrograms rhIL-1 beta/day induced prolonged fever, whereas at the lower doses temperatures were elevated only the first 2 days. rhIL-1 beta at a dose of 2.0 and 4.0 micrograms/day induced a transient decrease of food intake and a suppression of body weight gain.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Contrast inversion in the epifluorescence of cholesterol-phospholipid monolayers Okonogi, T. M. and H. M. McConnell (2004), Biophys J 86(2): 880-90. Abstract: A number of dihydrocholesterol-phospholipid mixtures have been examined using the epifluorescence microscopy of monolayers at the air-water interface. These mixtures form two coexisting liquids. Fluorescence contrast was provided using a variety of different lipid probes. With increasing monolayer pressure, all of the charged probes show contrast inversion at higher dihydrocholesterol concentrations. That is, with increasing pressure the charged probes transfer from one liquid to the other, reversing the fluorescence contrast. A wide variety of phospholipids were studied, and the inversion was seen in all cases. In the inverted state and at the higher dihydrocholesterol concentrations, the immiscibility persists to the highest pressures employed, 30-40 mN/m. The data show that binary dihydrocholesterol-phospholipid mixtures can form three distinct liquids, one of which is interpreted as a phase rich in condensed complex. |