| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Comparative effects of simvastatin and pravastatin on cholesterol synthesis in patients with primary hypercholesterolemia Feillet, C., M. Farnier, et al. (1995), Atherosclerosis 118(2): 251-8. Abstract: The effects of simvastatin and pravastatin on cholesterol biosynthesis were compared in 26 hypercholesterolemic patients who were randomly allocated to either simvastatin or pravastatin treatment (20 mg once daily) for 6 weeks in a crossover trial. Serum total cholesterol (TC), low density lipoprotein cholesterol (LDL-C) lathosterol (latho) concentrations and lathosterol/cholesterol (latho/chol) ratios (the latter two are considered as reliable indices of whole body cholesterol synthesis) were evaluated at the beginning and end of each therapeutic sequence. Reductions in TC and LDL-C were more pronounced (P < 0.001) with simvastatin (TC = -28.0%, LDL-C = -35.6%) than with pravastatin (TC = -19.6%, LDL-C = -25.2%). These results were associated with concomitant decreases in both latho concentrations (-59.0% with simvastatin and -37.0% with pravastatin) and latho/chol ratios (-43.0% with simvastatin and -20.3% with pravastatin). Simvastatin resulted in more marked diminutions of latho concentrations (P < 0.01) and latho/chol ratios (P < 0.05) than pravastatin. These results suggest that the better efficacy of simvastatin on serum cholesterol and LDL cholesterol might result in part from a greater inhibitory action of simvastatin on cholesterol synthesis compared with that of pravastatin. |
| Comparative effects on biliary concanavalin A-bound glycoproteins and calcium ion on cholesterol crystal nucleation and growth in model bile Teramen, K., S. Tazuma, et al. (1995), J Gastroenterol 30(4): 500-7. Abstract: The concanavalin A-bound glycoproteins in human gallbladder bile have recently been demonstrated to be strong promoters of cholesterol crystal nucleation. In the present study, we investigated the mechanism(s) whereby such promoters affect cholesterol crystal nucleation and/or growth, and compared these mechanisms with those of another promoter, calcium ion. Concanavalin A-bound glycoproteins were isolated from the Helix pomatia-unbound fraction of gallbladder bile from stone-free patients, and determined by electrohoresis to consist of six subclasses (MW 143, 98, 80, 58, 50, and 40 kDa). A cholesterol crystal growth assay showed that concanavalin A-bound glycoproteins both accelerated nucleation time and increased growth rate, whereas calcium ion affected nucleation time only. In the presence of both concanavalin A-bound glycoproteins and calcium ion, both cholesterol nucleation and growth were markedly enhanced. A gel permeation chromatographic study revealed that concanavalin A-bound glycoproteins shifted a considerable amount of cholesterol from micelles to vesicles, whereas calcium ion did not. These results suggest that concanavalin A-bound glycoproteins promote cholesterol crystal nucleation and growth, partly by shifting cholesterol from stable micelles to metastable nonmicellar fractions in bile. In contrast, calcium ion promotes these processes by other mechanisms and, therefore, enhances the effect of concanavalin A-bound glycoproteins. |
| Comparative gastrointestinal and plasma cholesterol responses of rats fed on cholesterol-free diets supplemented with guar gum and sodium alginate Seal, C. J. and J. C. Mathers (2001), Br J Nutr 85(3): 317-24. Abstract: The present study investigated the digestion and cholesterol-lowering effects of the water-soluble NSP guar gum (GG) and sodium alginate (SA) in laboratory animals. Groups of five male Wistar strain rats were fed semi-purified cholesterol-free diets containing 0, 50 or 100 g NSP source/kg for 21 d which comprised a 14-d adaptation period followed by a 7-d balance period. Weight gain over the balance period and food conversion ratio decreased linearly with increasing NSP intake (and respectively). DM digestibility decreased with increasing NSP intake and this effect was greater for SA-containing diets compared with GG-containing diets At the lower inclusion rate, 0.9-1.0 of the additional NSP was digested, but this value fell to 0.8 for both NSP sources at the 100 g/kg inclusion rate, implying that the capacity for near complete digestion of the test NSP had been exceeded. Intestinal tissue mass was increased in response to inclusion of both NSP sources. Caecal digesta pH decreased linearly with additional GG, but increased slightly with consumption of SA. Total caecal short-chain fatty acid concentrations (micromol/g caecal contents) increased markedly with 50 g GG/kg but did not increase further with 100 g GG/kg, and were slightly lower than control values in rats consuming SA. Plasma cholesterol concentration fell linearly with increasing NSP in the diet and the effect was similar for both GG and SA. Total output of faecal bile acids rose in rats fed 50 g GG/kg and 50 g SA/kg (59 micromol/7 d v. 24 micromol/7 d for control rats) with no further increase at the higher inclusion rate. These results show that SA has a strong hypocholesterolaemic effect in rats which is similar to that of GG, and that this effect is most likely to be mediated through an interruption in the entero-hepatic circulation of bile acids and not through increased hepatic supply of propionate from fermentation of the NSP in the large bowel. |
| Comparative hypocholesterolemic effects of capybara (Hydrochoerus hydrochaeris dabbenei) oil, horse oil, and sardine oil in cholesterol-fed rats Fukushima, M., Y. Takayama, et al. (1997), Lipids 32(4): 391-5. Abstract: The hypocholesterolemic efficacy of various polyunsaturated fatty acids was compared in rats given cholesterol-enriched diets. Capybara oil (CO, linoleic + alpha-linolenic acids), horse oil (HO, alpha-linolenic acid), and sardine oil (SO, eicosapentaenoic + docosahexaenoic acids) were added to diets at 50 g/kg. The weight gain, food intake, and liver weight in the CO-fed group were significantly higher than those in other groups during the 6-wk experimental period. The serum total and very low density lipoprotein (VLDL) + intermediate density lipoprotein (IDL) + low density lipoprotein (LDL) cholesterol concentrations of the CO-fed and SO-fed groups were significantly lower than in the HO-fed group after 6 wk. The serum high density lipoprotein cholesterol concentration in the SO-fed group was significantly higher than that in the CO-fed and HO-fed groups. The fecal neutral sterol concentration in the CO-fed group was reduced significantly compared with the other groups, and the fecal bile acid concentration in the HO-fed group was significantly higher than that in the SO-fed group. The results of this study demonstrate that CO lowers the serum total cholesterol and VLDL + IDL + LDL-cholesterol concentrations in the presence of excess cholesterol in the diet as well as SO. |
| Comparative hypocholesterolemic effects of five animal oils in cholesterol-fed rats Fukushima, M., T. Ohashi, et al. (1999), Biosci Biotechnol Biochem 63(1): 202-5. Abstract: The hypocholesterolemic efficacy of various animal oils was compared in rats given a cholesterol-enriched diet. After acclimatization for one week, male F344 DuCrj rats (8 weeks of age) that had been fed with a conventional diet were assigned to diets containing 5% of oil from emu (Dromaius), Japanese Sika deer (Cervus nippon yesoensis, Heude), sardine, beef tallow, or lard with 0.5% cholesterol for 6 weeks. After this feeding period, the concentrations of serum total cholesterol and of very-low-density lipoprotein + intermediate-density lipoprotein + low-density lipoprotein-cholesterol in the sardine oil group were significantly lower than those in the other groups. The serum high-density lipoprotein-cholesterol concentration in the Japanese Sika deer oil group was significantly higher than that in the other groups. The atherosclerotic index and liver cholesterol concentration in the sardine oil and Japanese Sika deer oil groups were significantly lower than those in the other groups. The fecal cholesterol excretion by the Japanese Sika deer oil group was significantly higher than that of the other groups, except for the sardine oil group, and the fecal bile acid excretion by the sardine oil group was significantly higher than that of the other groups, except for the lard group. These results suggest that Japanese Sika deer oil reduced the atherosclerotic index and liver cholesterol concentration in the presence of excess cholesterol in the diet as well as sardine oil did by increasing the excretion of cholesterol from the intestines of rats. |
| Comparative hypocholesterolemic effects of six dietary oils in cholesterol-fed rats after long-term feeding Fukushima, M., T. Matsuda, et al. (1997), Lipids 32(10): 1069-74. Abstract: Rats (8 wk of age) fed a conventional diet were shifted to diets containing 10% Oenothera biennis Linn oil (OBLO, linoleic acid + gamma-linolenic acid) from a wild plant, evening primrose oil (EPO, linoleic acid + gamma-linolenic acid) from a cultivated plant, bio-gamma-linolenic acid oil from mold (BIO, palmitic acid + oleic acid + linoleic acid + gamma-linolenic acid), safflower oil (linoleic acid), palm oil (PLO, palmitic acid + oleic acid + linoleic acid), or soybean oil (linoleic acid + alpha-linolenic acid) with 0.5% cholesterol for 13 wk. Though there were no significant differences in the food intake among the groups, the body weight gain of the OBLO group was significantly lower than that of the other groups except for the BIO and PLO groups, and that of the EPO and SBO groups were the highest among the groups. The liver weight of the OBLO group was significantly lower than that of other groups, and that of the PLO group was the highest among the groups. The serum total cholesterol and very low density lipoprotein (VLDL) + intermediate density lipoprotein (IDL) + low density lipoprotein (LDL) cholesterol concentrations of the OBLO and EPO groups were consistently lower than those in the other groups. However, those of the BIO group were higher than those in the OBLO and EPO groups. The liver cholesterol concentration of the PLO group was the highest among all groups except for the EPO group. The fecal neutral sterol and bile acid extraction of the BIO group tended to increase compared to the other groups. The results of this study demonstrate that OBLO and EPO inhibit the increasing of serum total cholesterol and VLDL + IDL + LDL-cholesterol concentrations in the presence of excess cholesterol in the diet compared with the other dietary oils. |
| Comparative hypocholesterolemic effects of six vegetable oils in cholesterol-fed rat Fukushima, M., S. Akiba, et al. (1996), Lipids 31(4): 415-9. Abstract: The hypocholesterolemic efficacies of various polyunsaturated fatty acids were compared in rats given cholesterol-enriched diets. Oenothera biennis Linn oil (OBLO, linoleic + gamma-linolenic), sunflower oil (linoleic), palm oil (PLO, oleic + linoleic), soybean oil (linoleic + alpha-linolenic), high-oleic safflower oil (oleic + linoleic), or mixed oil (linoleic + alpha-linolenic) was added to the diet at 200 g/kg (20% groups). OBLO was also added at 100 g/kg diet (10% group). The serum total and very low density lipoprotein + intermediate lipoprotein + low density lipoprotein cholesterol concentrations of the 10 and 20% OBLO groups were consistently lower than those in the other groups. The liver cholesterol concentration in the PLO group was lower in all groups. The liver cholesterol concentrations in the 10 and 20% OBLO groups were also lower than in the other groups. There were no significant differences in the fecal neutral sterol and bile acid extraction among groups. |
| Comparative molecular dynamics simulations of amphotericin B-cholesterol/ergosterol membrane channels Baginski, M., H. Resat, et al. (2002), Biochim Biophys Acta 1567(1-2): 63-78. Abstract: Amphotericin B (AmB) is a very effective anti-fungal polyene macrolide antibiotic whose usage is limited by its toxicity. Lack of a complete understanding of AmB's molecular mechanism has impeded attempts to design less toxic AmB derivatives. The antibiotic is known to interact with sterols present in the cell membrane to form ion channels that disrupt membrane function. The slightly higher affinity of AmB toward ergosterol (dominant sterol in fungal cells) than cholesterol (mammalian sterol) is regarded as the most essential factor on which antifungal chemotherapy is based. To study these differences at the molecular level, two realistic model membrane channels containing molecules of AmB, sterol (cholesterol or ergosterol), phospholipid, and water were studied by molecular dynamics (MD) simulations. Comparative analysis of the simulation data revealed that the sterol type has noticeable effect on the properties of AmB membrane channels. In addition to having a larger size, the AmB channel in the ergosterol-containing membrane has a more pronounced pattern of intermolecular hydrogen bonds. The interaction between the antibiotic and ergosterol is more specific than between the antibiotic and cholesterol. These observed differences suggest that the channel in the ergosterol-containing membrane is more stable and, due to its larger size, would have a higher ion conductance. These observations are in agreement with experiments. |
| Comparative regulation of hepatic sterol 27-hydroxylase and cholesterol 7alpha-hydroxylase activities in the rat, guinea pig, and rabbit: effects of cholesterol and bile acids Nguyen, L. B., G. Xu, et al. (1999), Metabolism 48(12): 1542-8. Abstract: The regulation of the classic and alternative bile acid synthetic pathways by key hepatic enzyme activities (microsomal cholesterol 7alpha-hydroxylase and mitochondrial sterol 27-hydroxylase, respectively) was examined in bile acid depletion and replacement and cholesterol-feeding experiments with rats, guinea pigs, and rabbits. The bile acid pool was depleted by creating a bile fistula (BF) and collecting bile for 2 to 5 days, and it was replaced by intraduodenal infusion of the major biliary bile acids (taurocholic acid TCA, glycochenodeoxycholic acid GCDCA, and glycocholic acid GCA in the rat, guinea pig, and rabbit, respectively) at rates equivalent to the measured hepatic flux of the bile acids. To study the effects of cholesterol, the animals were fed for 7 days on a basal diet with and without 2% cholesterol. Cholesterol 7alpha-hydroxylase and sterol 27-hydroxylase activities, measured by isotope incorporation assays, were related to bile acid output and composition and hepatic cholesterol concentrations. Intraduodenal infusion of bile acids increased the output of the tested bile acids, but did not significantly change hepatic cholesterol concentrations and had no effect on sterol 27-hydroxylase activity. Neither bile acid depletion nor replacement affected sterol 27-hydroxylase activity when three different substrates (cholesterol, 5beta-cholestane-3alpha,7alpha-diol, and 5beta-cholestane-3alpha,7alpha,12alpha-triol) were tested. In contrast, feeding 2% cholesterol increased hepatic cholesterol concentrations in rats, guinea pigs, and rabbits threefold, twofold, and eightfold, respectively, and increased hepatic mitochondrial sterol 27-hydroxylase activity (conversion of cholesterol to 27-hydroxycholesterol) in all three animal models. The stimulation and feedback inhibition of cholesterol 7alpha-hydroxylase activity by bile acid depletion and replacement were observed in all three animal models, whereas the effect of cholesterol feeding was species-dependent (cholesterol 7alpha-hydroxylase activity increased in the rat, did not change in the guinea pig, and was inhibited in the rabbit). Thus, in contrast to sterol 27-hydroxylase, which was upregulated by cholesterol but not affected by bile acid depletion and replacement in all three animal models, cholesterol 7alpha-hydroxylase activity was controlled consistently and inversely by the hepatic flux of bile acids, but was species-dependent in its response to a 1-week feeding with 2% cholesterol. |
| Comparative regulation of major enzymes in the bile acid biosynthesis pathway by cholesterol, cholate and taurine in mice and rats Chen, W., K. Suruga, et al. (2005), Life Sci 77(7): 746-57. Abstract: These enzymes play important roles in the biosynthesis of bile acids. They are cholesterol 7alpha-hydroxylase (CYP7A1), the rate limiting enzyme in the classic pathway, sterol 12alpha-hydroxylase (CYP8B1), the key enzyme for synthesis of cholic acid (CA), and sterol 27-hydroxylase (CYP27), the initial enzyme in the alternative pathway. In the present study, the susceptibility of these three enzymes to dietary cholesterol and cholate, and the cholesterol lowering effect of taurine were determined in male C57BL/6 mice and Wistar rats. Both mice and rats were divided into 6 groups: control group (N), high cholesterol diet group (C), high cholesterol and cholate diet group (CB), and their 1% taurine-supplemented groups (NT, CT, CBT, respectively). After animals were fed with the respective diets for one week, the mRNA levels of CYP7A1 increased in the C-group compared with those of the N-group, and decreased in the CB-group compared with those of the C-group in both mice and rats. But the extent of decrease is different between the two species. CYP8B1 was also markedly repressed by cholate in mice, but not in rats. These results are consistent with the changes in serum and liver cholesterol concentrations. Taurine significantly increased CYP7A1 mRNA levels in the CBT-group compared with the CB-group in both animal models, with a subsequent decrease in serum and liver cholesterol levels and increase in fecal bile acid excretion. Up-regulated CYP8B1 was also observed after taurine supplementation in the CBT-group in mice. No increase in CYP7A1 was produced by taurine in the CT-group compared with that of the C-group in mice, although the changes of serum and liver cholesterol and fecal bile acids indicated taurine showed an efficient cholesterol lowering effect. In addition, CYP27 was induced in both C- and CB-groups of rats but not of mice, and no changes were produced by taurine. The overall results suggest that there are differences between mice and rats in susceptibility of the three enzymes to dietary cholesterol and cholate, and taurine induced CYP7A1 to produce its cholesterol-lowering effect only in the presence of cholate in the cholesterol diet. |
| Comparative specificity of plasma lecithin:cholesterol acyltransferase from ten animal species Grove, D. and H. J. Pownall (1991), Lipids 26(6): 416-20. Abstract: The molecular specificities of plasma lecithin:cholesterol acyltransferase (LCAT) from ten animal species have been compared. Using a reassembled high density lipoprotein containing a mixture of phosphatidylcholines, the relative rates of liberation of different species of cholesteryl ester were measured. All but two species of LCAT clustered according to one of three patterns of substrate specificity. The LCAT from six species, including human, did not transfer highly polyunsaturated fatty acyl chains. In addition, human LCAT transesterified saturated fatty acyl chains more effectively than unsaturated fatty acyl chains. We conclude that the structures of the active sites of the enzymes differ, and that this may be related to size constraints that prevent efficient binding of large bulky phosphatidylcholines. |
| Comparative studies on acid cholesterol esterase in renal blood vessels and aorta of control and hypercholesterolemic rabbits Kamanna, V. S., S. Vora, et al. (1992), Atherosclerosis 94(1): 27-33. Abstract: Decreased acid cholesterol esterase has been linked to cholesteryl ester accumulation and may be fundamental in the development of atherosclerosis. The present study compared cholesterol esterase activity with the accumulation of cholesterol and its esters in aorta, renal artery and renal preglomerular microvessels. Tissue was obtained from white New Zealand rabbits fed either a control or 2%-cholesterol diet for 1 month. Cholesterol esterase was increased in microvessels from cholesterol-fed animals when compared to aorta and renal artery. Cholesterol feeding generally produced an increase in cholesterol and cholesteryl ester accumulation in all vascular tissues. The percent distribution of esterified/total cholesterol in renal microvessels was decreased consistent with the concomitant increase in cholesterol esterase. In contrast, aorta and renal artery exhibited an increase in cholesterol and cholesteryl ester accumulation and an increase in the percent of esterified cholesterol consistent with a decrease in acid cholesterol esterase after cholesterol feeding. The data suggest that renal microvessels, when compared to aorta and renal artery, may be relatively protected from developing atherosclerotic microvascular lesions through an organ-specific increase in acid cholesterol esterase activity. |
| Comparative studies on soy protein and rice protein for cholesterol metabolism in rats Yoshida, A., H. Fukui, et al. (1990), J Nutr Sci Vitaminol (Tokyo) 36 Suppl 2: S137-9. Abstract: The serum level of cholesterol in rats fed a diet containing soy protein isolate was lower than that in rats fed either casein or rice protein at the level of 15% even after one day feeding, although fecal excretion of bile acids of rats fed soy protein isolate was almost equal with that of rats fed rice protein. Similar effect was also observed in the secretion rate of lipoproteins from the liver. Dietary proteins may affect the synthesis of apolipoproteins directly or through the hormonal system. |
| Comparative studies on the substrate specificity of lecithin:cholesterol acyltransferase towards the molecular species of phosphatidylcholine in the plasma of 14 vertebrates Subbaiah, P. V. and M. Liu (1996), J Lipid Res 37(1): 113-22. Abstract: Comparative studies indicate that plasma cholesteryl ester (CE) composition is correlated with susceptibility to atherosclerosis. We previously showed that the lecithin:cholesterol acyltransferases (LCATs) of susceptible species such as rabbit, pig, and chicken (group I) differ in their substrate and positional specificities from the LCATs of resistant species such as rat and mouse (group II). However, the relative importance of enzyme specificity and substrate phosphatidylcholine (PC) composition in determining the CE composition is not known. To address this, we analyzed the molecular species composition of plasma PC in the same 14 vertebrates in which we previously studied the CE composition and LCAT specificity. The utilization of native PC species by LCAT was studied by determining the loss of each PC after incubation of plasma at 37 degrees C. The major contributor for LCAT reaction was either 16:0-18:2 PC or 18:0-18:2 PC in all species except dog, in which it was 18:0-20:4 PC. The formation of 20:4 CE correlated more with the consumption of 18:0-20:4 PC in group I, and with the consumption of 16:0-20:4 PC in group II. The group II enzymes exhibited higher selectivity for sn-2-20:4 PCs, whereas the group I enzymes showed preference for sn-2-18:2 PCs. The synthesis of high percentage of 20:4 CE in dog plasma was found to be due to the presence of unusually high concentration of 18:0-20:4 PC, rather than due to enzyme selectivity. These results show that the PC molecular species composition, especially the concentrations of sn-2-20:4 phosphatidylcholines has profound influence on plasma CE composition, and possibly on atherogenic risk. |
| Comparative study of gemfibrozil versus pravastatin in the treatment of patients with coronary artery disease and low HDL cholesterol levels Santos, R. D., A. P. Mansur, et al. (1995), Arq Bras Cardiol 65(2): 181-3. Abstract: PURPOSE--To evaluate the effects of gemfibrozil and pravastatin in coronary artery disease patients with HDL-cholesterol (HDL-C) < 35 mg/dl). METHODS--Twenty-nine patients (20 males, 60 +/- 9) were divided in a gemfibrozil group (G) (1200 mg/day n = 15) and a pravastatin group (P) (10 or 20 mg n = 10 and 4, respectively). The plasma lipid profile (LP) e.g. total cholesterol (TC), fractions and triglycerides (TG) was determined at 4 and 12 weeks of treatment. RESULTS--HDL-C was not affected in P, TC and LDL-cholesterol (LDL-C) reductions were superior to those in G (31.3% vs 13.4% and 38.7 and 11.5%, p < 0.05 and < 0.01 respectively). In G HDL-C raised by 50% (12th week p < 0.01). Gemfibrozil reduced TG levels in 44.7% while in P it varied -32.2% (12th week p < 0.01 and < 0.05 respectively). CONCLUSION--Gemfibrozil is more effective in reducing TG and raising HDL-C than pravastatin. On the other hand, pravastatin was more potent in reducing LDL-C levels. |
| Comparative study of LpAI lipoparticles, HDL cholesterol and apolipoprotein AI in a control population, in a group of subjects with coronary diseases, and in a group of subjects with angiographically normal coronary vessels Ardissone, J. P., A. Cohen-Billiemaz, et al. (1992), Ann Biol Clin (Paris) 50(3): 149-53. Abstract: A new method for directly measuring LpAI lipoparticles containing apolipoprotein AI, but not apolipoprotein AII, is now disponible for laboratories. Concentrations of LpAI were measured in serum from 158 presumably healthy normolipidemic subjects (72 male, 86 female), for the age group 30-60 years. Concentrations of LpAI were also measured in subjects with angiographically defined coronary artery disease (coro+) and without angiographically defined coronary artery disease (coro-). After comparison of the groups, lipoprotein particle LpAI did not appear to be a better discriminative marker than HDL cholesterol or apolipoprotein AI for atherogen risk. |
| Comparative study of serum cholesterol levels in the Chinese population Cheng, T. O. (1997), J Cardiovasc Nurs 12(1): vii. |
| Comparative values of CSF-cholesterol and CSF-triglycerides along with other biochemical parameters in neurological disorders Kamat, D. V. and B. P. Chakravorty (1996), Indian J Med Sci 50(8): 280-4. Abstract: Different parameters in CSF which are routinely investigated for the diagnosis and prognosis of neurological disorders do not provide confirmation to the type of neurological disorder. The rise in protein level in CSF was found to be nonspecific and estimation of glucose and chloride in CSF has lost its significance. Therefore, determination of concentration of CSF cholesterol and triglycerides may aid in the diagnosis of tuberculous meningitis, pyogenic meningitis, viral encephalitis and hydrocephalus. The mechanism by which the levels of CSF cholesterol end triglycerides are altered in neurological disorders is not known. The rise cholesterol and triglycerides levels in CSF may be due to increased activity of brain cells or by altered function of blood brain barrier. |
| Comparative yolk cholesterol content in four Spanish breeds of hens, an F2 cross, and a White Leghorn population Campo, J. L. (1995), Poult Sci 74(7): 1061-6. Abstract: Yolk cholesterol content (milligrams per gram of yolk and milligrams per egg) was studied in eggs of four Spanish breeds of hens (Castellana, Buff Prat, Vasca, and Villafranquina), an F2 from a cross between Castellana and Buff Prat (C x BP-F2), and a White Leghorn population. Birds were tested at 30 wk of age. There were differences among breeds (P <.001), cholesterol concentration being significantly lower in the C x BP-F2 (13.14 +/-.26 mg/g yolk) than in the other breeds. Villafranquina and Buff Prat showed significantly lower cholesterol (14.54 +/-.26 and 14.56 +/-.26 mg/g yolk, respectively) than the White Leghorn (16.30 +/-.26 mg/g yolk). Eggs from the Vasca breed contained significantly more cholesterol (19.09 +/-.26 mg/g yolk) than did eggs laid by the other breeds, whereas no differences were found between Leghorn and Castellana. A negative heterosis percentage of -13% was found in the C x BP-F2 when compared with the parental breed means. The reduction in cholesterol concentration per egg observed in the C x BP-F2 (220.49 mg per egg) was not related to breed differences in egg weight or to the proportion of yolk per egg. Eggs from the Vasca breed, with the lightest yolk and smallest yolk: albumen ratio (P <.05), contained the highest amount of cholesterol (304.29 mg per egg). Eggs from the White Leghorn containing the second highest amount of cholesterol (275.63 mg per egg). Thus, the variation in cholesterol content per egg was not attributable to differences in the proportion of yolk. |
| Compared effects of cholesterol and 7-dehydrocholesterol on sphingomyelin-glycerophospholipid bilayers studied by ESR Wolf, C. and C. Chachaty (2000), Biophys Chem 84(3): 269-79. Abstract: The ESR of 7- and 16-doxylstearic spin-labeled fatty acids (7NS and 16NS, respectively) reveal the distinct influence of cholesterol or cholesterol precursor analogue, delta7-dehydrocholesterol, on the molecular ordering and the fluidity of lipid mixtures containing sphingomyelin (SM). The phase-separation of sphingomyelin domains mixed within fluid glycerophospholipids (phosphatidylethanolamine and phosphatidylserine) can be followed by ESR as a function of the temperature and in the presence of sterols cholesterol (CHOL) or 7-dehydrocholesterol (DHCHOL). The time scale of spin-label exchange among phases is appropriate to follow the occurrence of the specific sphingomyelin/sterol association forming liquid ordered (Lo) microdomains which separate from the fluid surrounding phase Lalpha. Sphingomyelin embedded within the fluid bilayer associates with both sterols below 36 degrees C to give a phase Lo traceable by ESR in the form of a highly anisotropic component. Above 36 degrees C, the contribution in the ESR spectrum, of the Lo phase formed by 7-dehydrocholesterol with sphingomyelin is reduced by contrast with cholesterol forming a temperature-stable liquid ordered phase up to 42 degrees C. The consequences of this destabilization of the SM/sterol microdomains are envisioned in the biosynthesis defect where the precursor 7-dehydrocholesterol substitutes, for a significant part, the embryonic cell cholesterol. |