bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sunlight, melanogenesis and radicals in the skin
Authors: Chedekel Miles R. , Zeise Lisa 
Published: November 2006

AbstractMelanocytes are cells of neural crest origin residing at the dermal‐epidermal juncture. They produce specialized organelles called melanosomes within which the biochemical processes of melanization occurs. UV radiation is capable of inducing melanogenesis and, during the biosynthesis of melanins, several of the putative precursors “leak out” of the melanosome and can be detected in the skin, serum and urine of individuals undergoing active melanogenesis. Most notable are the cysteinyldopas (formed by nucleophilic addition of cysteine to dopaquinone) and several dihydroxyindoles (formed by intramolecular cyclization of dopaquinone). These catechols often are methylated in the melanocyte to afford a mixture of the monomethoxy derivatives and, in some cases, the dimethoxy species.Recent investigations in our laboratories have demonstrated that the cysteinyldopas, dihydroxyindoles, and their various methylated derivatives are photochemically unstable. Irradiation with biologically relevant ultraviolet radiation (i.e. wavelengths >300 nm) results in the rapid destruction of the precursors/metabolites and the production of a variety of free radical species. The photochemistry and potential photobiological significance of melanogenic intermediates is discussed.
Reactive oxygen in the tumor promotion stage of skin carcinogenesis
Authors: Fischer Susan M. , Cameron Gregory S. , Baldwin James K. , Jasheway Daniel W. , Patrick Kelly E. 
Published: November 2006

AbstractExposure of isolated SENCAR mouse epidermal cells to the tumor promoter 12‐0‐tetradecanoylphorbol‐13‐acetate (TPA) in vitro resulted in the production of oxidant species detected as chemiluminescence. This oxidant response can be inhibited by superoxide dismutase and copper complexes but not catalase or scavengers of hydroxyl radical or singlet oxygen, suggesting that the oxidant is superoxide anion. Inhibitors of various parts of the arachidonate cascade affect the TPA‐induced oxidant response in a manner that corresponds to their effects on in vivo tumor promotion experiments. Agents that inhibit lipoxygenase activity, i.e. nordihydroguaiaretic acid, benoxaprofen, but not agents that are cyclooxygenase inhibitors, i.e. indomethacin, are effective in suppressing the oxidant response to TPA. Phospholipase C but not phospholipase A2 or D produced an oxidant response kinetically similar to that elicited by TPA. The inhibitors of TPA‐induced oxidants inhibited the phospholipase C response to the same extent, suggsting that TPA and phospholipase C may produce an oxidant species through a common mechanism, via phospholipid turnover‐protein kinase C activation. The relevance of oxidant production to the tumor promotion process is suggested by the ability of exogenous xanthine/xanthine oxidase, a superoxide anion‐generating system, to induce ornithine decarboxylase, a characteristic of TPA‐treated cells. In addition, oxidant production is significantly lower in cells from the TPA‐promotion resistant C57BL/6J mouse. These studies provide further support for a role for reactive oxygens in the tumor promotion process.
Biopsy method for human adipose with vitamin E and lipid measurements
Authors: Handelman Garry J. , Epstein William L. , Machlin Lawrence J. , van Kuijk Frederik J. G. M. , Dratz Edward A. 
Published: November 2006

AbstractAn adaptation of the needle biopsy procedure of Beynen and Katan for human adipose tissue, which yields 2–10 mg adipose samples, is described and evaluated. Micromethods are presented for the analysis of α‐tocopherol, cholesterol and fatty acids in each adipose specimen. The needle biopsy procedure, which uses a Vacutainer to create suction, is compared with a punch biopsy method. The needle biopsy is rapid (6 samples/hr), simple and unobjectionable to the subjects, and provides samples with reproducible ratios of cholesterol and α‐tocopherol. Unlike the punch biopsy, the needle biopsy reliably obtains specimens with a lipid composition typical of adipocytes. The needle biopsy method is adaptable to nutritional studies of tocopherol and fatty acid metabolism in adipose, and to studies of hazardous compounds stored in adipose. The linoleic acid content of adipose from residents of the West Coast was found to be considerably higher than values reported earlier. The adipose fatty acid data indicate an increase in human adipose linoleate when compared with earlier reports and suggest a trend toward increasing linoleic acid in the American diet.
A simplified approach to the analysis of subclasses of phospholipids: Application to human platelets
Authors: Vishnubhatla Indira , Kates Morris , Adams George A. 
Published: November 2006

AbstractA procedure for the determination of the proportions of diacyl, alkenylacyl and alkylacyl subclasses of glycerolphospholipids was developed. The procedure involves: (1) acid methanolysis of the phospholipid followed by Bligh/Dyer extraction of fatty acid methyl esters (FAME) derived from acyl chain types, dimethylacetals (DMA) derived from alkenyl ether chain types, and lysoalkyl phosphatidic acids (lysoalkyl‐PA) derived from alkyl ether chain types; and (2) subsequent acetolysis to convert the lysoalkyl‐PA to monoalkyl glycerol diacetates (MAGD). GLC analysis and quantitation (using internal standard, 21∶0 FAME) of FAME, DMA and MAGD allowed calculation of the proportions of the three molecular subclasses. The methanolysis/acetolysis procedure gave an overall mean phospholipid recovery of 95±3%. Analysis of the major phospholipids in four separate preparations of fresh resting human platelets by this procedure showed the following range of molecular subclasses: phosphatidylcholine (PC), 86–92 mol % diacyl, 6–10 mol % alkylacyl and 2–3 mol % diacyl, 5–8 mol % alkylacyl and 34–55 mol % alkenylacyl. The results of these subclass analyses were in general agreement with those reported in the literature.
Modification of the fatty acid composition of L1210 leukemia subcellular organelles
Authors: Burns C. Patrick , North James A. , Mossman Craig J. , Ingraham Leah M. 
Published: November 2006

AbstractWe have examined the extent to which it is possible to modify the fatty acid composition of subcellular organelles of L1210 leukemia cells. A polyunsaturated fatty acid, docosahexaenoic acid, or a monounsaturated fatty acid, oleic acid, were added to the culture media. After 48 hr, the cells were ruptured and the subcellular fractions isolated. Fatty acid analysis revealed that nuclei, mitochondria, plasma membranes and microsomes of the cells grown in media supplemented with docosahexaenoic acid contained increased amounts of polyenoic fatty acids, mean number of double bonds and docosahexaenoic acid compared with cells grown in oleic acid. We conclude that it is possible to experimentally modify the lipids of multiple intracellular structures of L1210 cells by the addition of fatty acids to the growth media.
Identification of N‐ε‐(2‐propenal)lysine as a major urinary metabolite of malondialdehyde
Authors: Draper H. H. , Hadley M. , Lissemore L. , Laing N. M. , Cole P. D. 
Published: November 2006

AbstractN‐ε‐(2‐propenal)lysine (ε‐PL) was identified as one of two major metabolites of malondialdehyde (MDA) excreted in rat and human urine. This compound is derived mainly but not exclusively from the diet, where it arises from a reaction between free MDA generated in the oxidative decomposition of polyunsaturated fatty acids and the ε‐amino of the lysine residues of food proteins. It is released during protein digestion and represents the main form in which MDA is absorbed. It is excreted partially in unchanged form and partially as the acetylated derivative N‐α‐acetyl‐N‐ε‐(2‐propenal)lysine. Its administration to rats did not result in an increase in the excretion of free MDA in the urine. The findings that MDA in foods is absorbed mainly as ε‐PL, and that this compound is not metabolized to free MDA in vivo, mitigate concern over the possible mutagenicity and carcinogenicity of MDA in the diet.
Lipoprotein(a): Nonhuman primate models
Authors: Makino Kazuhiko , Scanu Angelo M. 
Published: November 2006

AbstractLipoprotein(a) [Lp(a)] is a low density lipoprotein which has apo(a) disulfide‐linked to apoB100. Apo(a) has recently been shown to have a striking homology with plasminogen, a knowledge that has stimulated a lot of interest in the mechanism of atherogenicity and thrombogenicity of this lipoprotein particle. Several studies have documented the presence of Lp(a) in nonhuman primates with particular reference to the rhesus monkeys and baboons. The Lp(a) of rhesus monkey is structurally very similar to that of humans, except for the absence of kringle V and the amino acid composition of the catalytic region. The Lp(a) of nonhuman primates, like their human counterparts, exhibit a wide range of interindividual plasma levels and also a wide size polymorphism of apo(a). Nonhuman primates appear to represent a good model for the study of the structure and biology of Lp(a).
ApoA‐I secretion by rabbit intestinal mucosa cell cultures
Authors: Carlson Ting L. , Kottke Bruce A. 
Published: November 2006

AbstractLipid and apolipoprotein (apo) A‐I concentrations in different density fractions of New Zealand White (NZW) and Watanabe (WHHL) rabbit plasma were studied. Aside from the low plasma apoA‐I and high density lipoprotein (HDL) cholesterol levels in WHHL rabbits, the distribution of apoA‐I was also different between the two rabbits. ApoA‐I was concentrated in both the HDL2 and HDL3 fractions of NZW rabbits but was found primarily in the HDL3 fraction of WHHL rabbits. ApoA‐I secretion in these two rabbits was further studiedin vitro by using intestinal and hepatocyte cell cultures. ApoA‐I secretion was highest from cultures of the duodenum and the proximal end of the jejunum; whereas, cell cultures of the distal end of the small intestine secreted very little apoA‐I into the medium. Intestinal cell cultures from WHHL rabbits secreted less, but significant amounts of, apoA‐I compared to that of NZW rabbits. ApoA‐I was most concentrated in the density range of 1.12–1.21 (HDL3) fraction in medium containing 10% fetal calf serum (FCS). Serum‐free medium promoted apoA‐I secretion by intestinal cell cultures that was mostly found in the d>1.21 (lipoprotein‐deficient) fraction. Hepatocytes isolated from the same rabbits by collagenase perfusion secreted little apoA‐I, and it was found only in the d>1.21 fraction. The addition of oleic acid into the culture medium with 10% FCS decreased the secretion of total apoA‐I and HDL by intestinal cell cultures and increased the secretion of very low density lipoprotein (VLDL) and intermediate density lipoproteins (IDL). The results indicate that intestinal cells, not hepatocytes, are responsible for the secretion of apoA‐I and HDL3 in rabbits, and that the secretion may be regulated under different nutritional conditions.
Characterization of the coronary vascular responses to platelet‐activating factor in the isolated perfused heart
Authors: Hu Weimin , Choy Patrick C. , Man Ricky Y. K. 
Published: November 2006

AbstractPlatelet‐activating factor (PAF) is a potent phospholipid mediator with diversein vivo andin vitro coronary vascular effects. In the present study, the coronary vascular responses to bolus injections of PAF were compared in rat hearts perfused under constant flow and under constant pressure. Low levels of PAF (1 pmol) produced vasodilatation only, while higher PAF concentrations (100 pmol) produced initial vasodilatation which was followed by a vasoconstriction under both experimental conditions. To determine species differences in PAF action, the effect of PAF was tested on perfused guinea pig hearts. Unlike in perfused rat hearts, only a dosedependent vasoconstrictor response was observed in perfused guinea pig hearts following a bolus injection of 1 fmol to 10 pmol of PAF. The results from repeated injections of PAf indicated that depletion of vasoactive mediators induced by PAF or receptor desensitization may explain a failure of a second injection of PAF to initiate a vasoconstrictor response. After PAF injection, the coronary vascular response to leukotriene was not altered, indicating that the reduced vasoconstrictor effect of a second injection of PAF cannot be due to a reduced ability of the smooth muscle to constrict. The study demon‐strates that similar coronary vascular responses to PAF are observed in perfused rat hearts under either constant flow rate or constant pressure and that some of the variable coronary vascular responses reported may be due to the difference between animal species.
Dietary fat composition influences fatty acid composition of milk fat globule membrane in lactating cows
Authors: Palmquist D. L. , Schanbacher F. L. 
Published: November 2006

AbstractMilk fat globule membranes are derived directly from the apical plasma membrane of mammary epithelial cells. To evaluate the effect of dietary fat on mammary membranes, we determined the fatty acid composition of the milk fat globule membrane in lactating dairy cows fed diets supplemented with fats of different fatty acid composition, or infused intravenously with soy oil emulsion. A preliminary survey, using an abbreviated preparation procedure (membranes isolated at 48,000×g‐max for 15 min), yielded about 45% of the total membrane fatty acids that could be recovered by centrifuging at the same speed for 120 min, and showed that changes in fatty acid composition of membranes reflected dietary fatty acids to some extent. Dietary palmitic acid increased the content of 16∶0 in the membranes. A high corn diet increased ruminal formation oft18∶1, and its level increased to 12% of membrane fatty acids. Infusion of soy oil emulsion increased 18∶2 membrane content, and decreased the levels of 18∶1 and 20∶4. All treatments decreased the ratio of unsaturated/saturated fatty acids as compared to controls, whereas the ratio of polyunsaturated/saturated fatty acids was increased by feeding a high corn diet or by infusing soy oil. The ratio of 18∶2/c18∶1 increased from 0.31 to 1.0 after infusing soy oil for 4 days. The fatty acids of membranes isolated upon 120‐min centrifugation were slightly more saturated. The differences were not sufficiently large, however, to affect overall results significantly.
Tocopherol contents of lipoproteins from frozen plasma separated by affinity chromatography
Authors: Clevidence Beverly A. , Ballard‐Barbash Rachel 
Published: November 2006

AbstractWe investigated whether freezing and storage of plasma altered α‐tocopherol levels of whole plasma or the lipoprotein fractions derived from such plasma. Plasma from 24 men, at each of two collection periods, was frozen at −20°C for six weeks, then high‐density lipoproteins (HDL) were separated from low‐ plus very low‐density lipoproteins (LDL‐VLDL) by heparin affinity chromatography. Whole plasma and the lipoprotein fractions were analyzed for α‐tocopherol content and compared to counterparts from fresh plasma. Freezing and storage did not reduce α‐tocopherol levels of plasma or the lipoprotein fractions. α‐Tocopherol values from fresh and frozen plasma were highly correlated for both plasma (period 1, r=0.94; period 2, r=0.93) and the LDL‐VLDL fractions (periods 1 and 2, r=0.97). Percent distribution of α‐tocopherol between the two lipoprotein fractions was comparable for lipoproteins derived from fresh and frozen plasma. Under the storage conditions used in this study, plasma can be frozen for at least six weeks prior to lipoprotein fractionation with no detectable detrimental effects on α‐tocopherol content of either plasma or lipoproteins.
Metabolism of meadowfoam oil fatty acids in mice
Authors: Emken E. A. , Adlof R. O. , Abraham S. 
Published: November 2006

AbstractMeadowfoam oil is unusual because over 95% of the fatty acids are 20‐ and 22‐carbon aliphatic acids withcisdouble bonds located principally at the 5‐ and/or 13‐position. Since little information is available on the metabolism of the 5c−20∶1 and 5c,13c−22∶2 fatty acids, an exploratory study in mice was conducted to investigate the metabolism of purified samples of the free fatty acids isolated from meadowfoam oil, and to determine the effect of meadowfoam oil on weight gain and tissue lipid composition. Mice fed diets containing 5% by wt of the purified 5c−20∶1 or 5c,13c−22∶2 for 6 days exhibited no apparent physiological problems. Total liver lipids from mice fed the purified fatty acid diets contained mean values of 2.0% 5c−20∶1 and 2.1% 5c,13c−22∶2; total heart lipids contained 1.7% 5c−20∶1 and 10.7% 5c,13c−22∶2. Liver total phospholipids from mice fed a 5% meadowfoam oil diet for 19 wk contained 1.4% 5c−20∶1 and 1.9% 5c,13c−22∶2. There was no evidence of desaturation, elongation or retroconversion. Weight gain for mice fed the meadowfoam oil diet for 19 wk was similar to mice fed corn oil, and was higher than for mice fed hydrogenated cottonseed oil. Considering the high 5c−20∶1 and 5c,13c−22∶2 content of the diets, the percentages of these fatty acids in mouse tissue lipids from both the short‐ and long‐term studies were low. Weight gain was surprisingly good since the meadowfoam oil diet was essential fatty acid‐deficient. Results of this initial investigation suggest that the 5c−20∶1 and 5c,13c−22∶2 fatty acids were utilized primarily for energy. In the short‐term study, these fatty acids did not produce toxic effects or cause metabolic problems.
Prostaglandin synthesis and fatty acid composition of phospholipids and triglycerides in skeletal muscle of chicks fed combinations of flaxseed oil and animal tallow
Authors: Olomu J. M. , Baracos V. E. 
Published: November 2006

AbstractChicks were fed isocaloric and isonitrogenous diets containing 6% (w/w) added fat consisting of various proportions of animal tallow and flaxseed oil (FSO). No differences among treatments were seen in growth rate, muscular deposition of protein and lipids nor in the muscle phospholipid (PL) and triglyceride (TG) contents. Prostaglandin (PG)E2 synthesis in isolated skeletal muscle was depressed significantly by feeding FSO or by treatment with naproxen (6‐methoxy‐α‐methyl‐2‐napthaleneacetic acid), an inhibitor of PG synthesis. The changes associated with diet may be related to differences in the fatty acid composition of muscle lipids. Levels of saturated fatty acids in muscle PL and TG were relatively insensitive to dietary treatments. Monounsaturated fatty acid levels were significantly lower in the FSO‐fed groups. FSO diets caused significant depression in muscle PL 20∶4ω6 and almost completely inhibited 22∶5ω6 incorporation. FSO diets decreased ratios of ω6/ω3 fatty acids and increased the unsaturation index of muscle PL. Muscles of chicks fed FSO showed increased levels of 18∶3ω3, and of its derivatives 20∶4ω3 and 22∶5ω3. These results suggest that FSO inhibits PG synthesis and modifies the fatty acids of PL and TG of chick muscle. These changes may have implications for PG‐dependent and/or membrane‐dependent processes in muscle metabolism.
High‐performance liquid chromatographic separation of enantiomeric alkyl glycerol ethers
Authors: Foglia Thomas A. , Maeda Kazuhito 
Published: November 2006

AbstractThe resolution of a series of racemic 1‐alkyl‐3‐trityl‐rac‐glycerols and 1‐alkyl‐2‐benzyl‐rac‐glycerols into their enantiomers by high‐performance liquid chromatography (HPLC) was investigated. Of the racemic glycerol derivatives studied, only three (1,2‐0‐isopropylidene‐rac‐glycerol, 1,2‐0‐isopropylidene‐3‐benzyl‐rac‐glycerol and 1‐hexadecyl‐2‐benzyl‐rac‐glycerol) could be resolved into their enantiomers. The compounds were resolved on a silica (10 μm) column coated with cellulose tribenzoate and eluted isocratically with hexane/isopropanol as mobile phase. The effects of mobile phase composition, column temperature and flow rate on the resolution of enantiomeric pairs were investigated. Also, the effect of substituents,i.e., trityl, benzyl, hydroxyl or alkyl, on the resolution of the alkyl glycerol ethers by HPLC was evaluated.
A high cholesterol/cholate diet induced fatty liver in spontaneously hypertensive rats
Authors: Ueno Kohji , Okuyama Harumi 
Published: November 2006

AbstractA high cholesterol diet was found to induce fatty liver in spontaneously hypertensive rats. Although cholesterol ester and triacylglycerol accumulated in large amounts in liver, the increases of these lipids in plasma were relatively small and no increase in cholesterol and cholesterol ester was observed in aorta. In rats fed normal diet, plasma cholesterol ester mainly consisted of arachidonate species; however, oleate and linoleate esters became the most prominent species in rats fed a high‐cholesterol diet. The amounts of oleate and linoleat at the 2‐position of phosphatidylcholine in both plasma and liver were increased slightly, but the fatty acids of aorta lipids changed little by feeding a high cholesterol diet. These results indicate that the livers of rats fed the high cholesterol diet do not secrete cholesterol ester and triacylglycerol with altered fatty acids as rapidly as they are synthesized and that the increased levels of cholesterol oleate in liver and plasma are not directly correlated with atherogenic lesions under these conditions.
Substrate specificity of lysosomal cholesteryl ester hydrolase isolated from rat liver
Authors: Klemets Rabbe , Lundberg Bo 
Published: November 2006

AbstractThe effect of various physicochemical forms of substrate on the activity of acid cholesteryl ester hydrolase isolated from rat liver lysosomes was studied. The amount of sodium taurocholate was varied in the substrate mixture which contained constant amounts of egg phosphatidylcholine (PC) and cholesteryl oleate. The resulting substrate forms produced were PC vesicles, PC vesicles with incorporated sodium taurocholate, mixed micelles, and mixed micelles together with free bile salt micelles. Gradually increasing amounts of sodium taurocholate activated cholesteryl oleate hydrolysis until the molar sodium taurocholate/PC ratio of ca. 0.6; thereafter hydrolytic activity decreased rapidly. The presence of sodium taurocholate micelles clearly inhibits cholesteryl oleate hydrolysis. We therefore propose that the activation observed at low bile salt concentrations depends on bile salt interaction with the substrate vehicle, whereas the inhibition observed at high bile salt concentrations depends on sodium taurocholate interacting with the enzyme. When comparing different phospholipid components in the supersubstrate, the enzyme activity was highest in the presence of dioleyl PC and decreased when present with dipalmitoyl PC and egg PC. Egg lysoPC completely inhibited the enzyme activity. A net negative charge on the surface of the vesicle substrate increased cholesteryl ester hydrolase activity while a net positive charge on the surface inhibited the enzyme activity. Only part of the product inhibition of cholesteryl oleate hydrolase caused by Na‐oleate was reversible when tested with bovine serum albumin present in the incubation mixture.
(24S)‐14α,24‐dimethyl‐9β,19‐cyclo‐5α‐cholest‐25‐en‐3β‐ol: A new sterol and other sterols inMusa sapientum
Authors: Akihisa Toshihiro , Shimizu Naoto , Tamura Toshitake , Matsumoto Taro 
Published: November 2006

AbstractThe structure of a new sterol isolated fromMusa sapientum has been shown by chemical and spectroscopic methods to be (24S)‐14α,24‐dimethyl‐9α,19‐cyclo‐5α‐cholest‐25‐en‐3β‐ol. In addition, several known (24S)‐24‐methyl‐Δ25‐sterols, their 24‐methylene isomers and other sterols (4,4‐dimethyl‐, 4α‐methyl‐ and 4‐demethyl‐sterols) together with 3‐oxo‐4α‐methylsteroids were isolated from the plant and identified. The biogenetic implication of these sterols and 3‐oxosteroids is discussed.