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61.
K. K. Carroll 《Journal of the American Oil Chemists' Society》1967,44(11):607-614
Effects of diet on acetate incorporation into cholesterol and fatty acids in liver slices, and on the level of plasma cholesterol,
were studied in rats and rabbits. Feeding fats and oils in a com-mercial diet stimulated acetate incorporation into rat-liver
cholesterol much more than feeding them in a semisynthetic diet. This effect seemed to be specific for cholesterol since incorporation
into fatty acids was not similarly affected. High levels of dietary casein inhibited acetate incorporation into both cholesterol
and fatty acids. Rat-liver slices generally incorporated more acetate into cholesterol than rabbit-liver slices, but incorpora-tion
into fatty acids was often higher in the latter. Rabbit plasma cholesterols were higher on butter diets than on corn oil diets.
Further eleva-tion of plasma cholesterol was observed when casein was added to the butter diet but not when it was added to
the corn oil diet. Plasma cho-lesterols were elevated, and acetate incorporation into liver cholesterol and fatty acids was
inhibited in suckling rats and rabbits whereas recently weaned animals gave results similar to those of adults. The inverse
relationship between plasma cholesterol level and acetate incorporation into cholesterol may be attributable to feedback con-trol
of liver cholesterol biosynthesis. Other mechanisms which may account for the observed effects of dietary fats and protein
on cholesterol metabolism, and the possible relevance of the findings to atherosclerosis, are discussed. 相似文献
62.
An explicit finite difference scheme is proposed for nonlinear convective problems. The procedure is applied to a nonlinear convective diffusion problem with a nonlinear boundary condition. It is shown that the nonlinear boundary condition may be treated directly without linearization which has to be carried out in the implicit method to avoid a nonlinear system of algebraic equations. The explicit procedure is more direct and less cumbersome than the implicit procedure and the answers are in excellent agreement with those of the implicit method. 相似文献
63.
High-Strength Zirconia Fibers 总被引:1,自引:0,他引:1
David B. Marshall F. F. Lange Peter D. Morgan 《Journal of the American Ceramic Society》1987,70(8):187-C
Fine-grained polycrystalline zirconia fibers have been formed from an acetate precursor. The fibers contained a Y2 O3 additive, which inhibited grain growth (grain size ≤0.5 μm) and allowed the tetragonal phase to be retained at room temperature. Fibers with diameters in the range 2 to 5 μm had strengths in the range 1.5 to 2.6 GPa. 相似文献
64.
Sowdhamini R; Mitchell TJ; Andrew PW; Morgan PJ 《Protein engineering, design & selection : PEDS》1997,10(3):207-215
Pneumolysin and proaerolysin are bacterial toxins that form pores in host
cells by oligomerization. We propose that they may have similar structures
despite a poor sequence identity. The crystal structure of proaerolysin
reveals a protein composed of four domains, arranged in the shape of an
elongated comma. Electron microscopy of the pneumolysin monomer shows a
similar arrangement of domains. The sequence of pneumolysin recognizes the
template of proaerolysin from a library of protein folds. A
three-dimensional model of pneumolysin has been constructed by the
comparative approach using the structure of proaerolysin. This model,
together with results on the activity of site- specific mutants and the
positions of antigenic sites, has been used to propose functional roles of
individual domains.
相似文献
65.
The inhibitory effect of plant sterols, fatty acids and lecithin on cholesterol intestnal absorption was studied in the unanesthetized
rat using a single pass perfusion technique. Bile was excluded from the perfused intestine. Cholesterol absorption did not
change following the additions of cholestanol, cholestanone, lanosterol, stigmasterol and β-sitosterol. A 3-fold increase
in the molarity of cholestanol and β-sitosterol or the separate additions of the saturated short and medium chain fatty acids,
butyric and octanoic, also did not change cholesterol absorption. The unsaturated long chain fatty acids, oleic, linoleic,
linolenic and arachidonic, inhibited cholesterol absorption. Lecithin additions at concentrations of 0.1–1.5 mM caused a progressive,
dose-related inhibition of cholesterol absorption. The inhibitory effect of these agents on cholesterol absorption is likely
to have been caused by changes in cholesterol solubility in the micelle and shifts in the partition coefficient of cholesterol
away from the cell membrane to the micelle. 相似文献
66.
Yoshikazu Suzuki Naoki Kondo Tatsuki Ohji Peter E. D. Morgan 《International Journal of Applied Ceramic Technology》2004,1(1):76-85
Uniformly porous composites with 3-D network structure (UPC-3D) have been recently developed via a pyrolytic reactive sintering process, which takes advantage of the evolved CO2 gas from a decomposing carbonate source (e.g., dolomite, CaMg(CO3 )2 ) and does not require any additional pore-forming agent nor long-time burning-out process. Through liquid formation via LiF doping, strong necks are formed between constituent particles before completion of the pyrolysis of carbonate, resulting in the formation of a strong 3-D network structure. The pore size distribution is very narrow (with typical pore size: ∼1 μm), and the porosity was controllable (∼30–60%) by changing the sintering temperature. This article presents the development details of UPC-3D, and reports the recent findings in CaZrO3 /MgAl2 O4 system, which will be one of the more promising systems for practical applications. 相似文献
67.
Nikolaos Dimitratos Jose Antonio Lopez-Sanchez David Morgan Albert Carley Laura Prati Graham J. Hutchings 《Catalysis Today》2007,122(3-4):317-324
Solvent free oxidation of benzyl alcohol was investigated in the absence of a base using Au catalysts prepared by sol immobilization on titania and carbon supports. Comparison between the Au supported catalysts revealed that activity and distribution of products was dependent on the nature of support and heat treatment. Specifically, heat pre-treatment of the Au catalysts has a beneficial effect in terms of activity, but is detrimental in terms of selectivity to the benzaldehyde. We conclude that sol immobilization is a suitable technique for preparing gold catalysts with small particle size and narrow particle size distributions and very high activity and selectivity for benzyl alcohol oxidation. 相似文献
68.
Rabbits fed semipurified diets containing casein have elevated plasma cholesterol levels compared to those fed soy protein.
As part of continuing studies on the mechanism of casein-induced hypercholesterolemia, two groups of six rabbits were fed
these diets for 14 to 16 weeks. Animals fed the casein diet were found to have significantly higher plasma concentrations
of protein, cholesterol, triacylglycerol, phospholipid and apolipoprotein B (apo B) associated with low density lipoprotein
(LDL) than those fed the soy protein diet. Kinetic studies showed that the fractional catabolic rate of LDL-apo B was significantly
lower in animals fed casein than in those fed soy protein regardless of whether the tracer LDL was obtained from donors fed
casein or soy protein. The production rate of LDL-apo B was higher in casein-fed animals but this was not statistically significant.
These results show that the efficiency of removal of LDL is significantly reduced in animals fed casein compared to those
fed soy protein, and that the source of LDL did not affect the efficiency of its subsequent removal. The acumulation of LDL
in casein-fed animals is consistent with down-regulation of the LDL receptor. 相似文献
69.
Several polymer‐layered silicate (clay) nanocomposites (PLSNs) were analyzed by transmission electron microscopy (TEM) and wide‐angle X‐ray diffraction (XRD) in an effort to characterize the nanoscale dispersion of the layered silicate. The PLSNs investigated included thermoset (cyanate esters) and thermoplastic polymers (polystyrene, nylon 6, and polypropylene‐g‐maleic anhydride). The results of this study reveal that the overall nanoscale dispersion of the clay in the polymer is best described by TEM, especially when mixed morphologies are present. XRD is useful for the measurement of d‐spacings in intercalated systems but cannot always observe low clay loadings (<5%) or be used as a method to identify an exfoliated nanocomposite where no XRD peaks are present (constituting a negative result). Most importantly, the study showed that XRD is not a stand‐alone technique, and it should be used in conjunction with TEM. Our studies suggest that new definitions, or a clarification of existing definitions, are needed to properly describe the diversity of PLSN nanostructures seen in various materials. Published 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1329–1338, 2003 相似文献
70.