Phospholipid and fatty acid composition of frog (Rana esculenta) liver—a circannual study

Liver lipid composition of the frogRana esculenta was examined on a circannual basis. In particular, phospholipid and cholesterol content, relative phospholipid distribution, and fatty acid patterns have been studied. Seasonal acclimatization is associated with significant modifications of phospholipid content and of the relative proportion of phospholipid classes, while cholesterol level is unchanged throughout the year. In regard to the fatty acid composition of total phospholipids as well as of the four major phospholipid classes—phosphatidylcholine (PC); phosphatidylethanolamine (PE); sphingomyelin (SM); phosphatidylserine (PS)—it appears that the liver of “summer animals” is characterized by a higher unsaturation index due to a decrease of saturated fatty acids and to an increased content of n−3 and n−6 polyunsaturated fatty acids. The results suggest that relevant compositional changes occur mainly in spring and autumn: these changes could be interpreted as being the result of both a nutritionally- and thermally-induced seasonal adaptation directed toward the preservation of membrane-associated physiological activities that are linked to the transition from the active to the inactive state of the animal.     

Seasonal variation in the hepatoproteome of the dehydration and freeze-tolerant wood frog, Rana sylvatica

Winter’s advent invokes physiological adjustments that permit temperate ectotherms to cope with stresses such as food shortage, water deprivation, hypoxia, and hypothermia. We used liquid chromatography (LC) in combination with tandem mass spectrometry (MS/MS) quantitative isobaric (iTRAQ™) peptide mapping to assess variation in the abundance of hepatic proteins in summer- and winter-acclimatized wood frogs (Rana sylvatica), a northerly-distributed species that tolerates extreme dehydration and tissue freezing during hibernation. Thirty-three unique proteins exhibited strong seasonal lability. Livers of winter frogs had relatively high levels of proteins involved in cytoprotection, including heat-shock proteins and an antioxidant, and a reduced abundance of proteins involved in cell proliferation, protein synthesis, and mitochondrial function. They also exhibited altered levels of certain metabolic enzymes that participate in the biochemical reorganization associated with aphagia and reliance on energy reserves, as well as the freezing mobilization and post-thaw recovery of glucose, an important cryoprotective solute in freezing adaptation.     

Cholesterol metabolism in the liver and intestine of the chick: Effect of dietary cholesterol,taurocholic acid and cholestyramine

The effect of feeding cholesterol, taurocholic acid, or cholestyramine to chicks on cholesterolgenesis from [1-¹⁴C] acetate in liver and intestine was determined in vitro using tissue slices, and in vivo by i.v. injection of [¹⁴C] acetate. The conversion of cholesterol to bile acids in liver in vivo was measured in the same treatments after i.v. injection of [³H] cholesterol. Hepatic cholesterogenesis in vitro and in vivo was depressed by dietary cholesterol and taurocholate and enhanced by cholestyramine. Intestinal cholesterogenesis in vivo was depressed only by taurocholate whereas ileal cholesterogenesis in vitro was reduced by dietary cholesterol. Conversion of cholesterol to bile acids was enhanced by dietary cholesterol and cholestyramine and depressed by taurocholate. Hepatic cholesterol metabolism in the chick appears to be regulated by mechanisms similar to those reported for other species.     

ω- and (ω-1)-hydroxylation of 1-dodecanol by frog liver microsomes

Frog liver microsomes catalyzed the hydroxylation of 1-dodecanol into the corresponding ω- and (ω-1)-hydroxy derivatives. The hydroxylation rate for 1-dodecanol was much lower than that for lauric acid. Both NADPH and O₂ were required for hydroxylation activity. NADH had no effect on the hydroxylation. The hydroxylating system was inhibited 49% by CO at a CO∶O₂ ratio of 4.0. The formation of ω-hydroxydodecanol was more sharply inhibited by CO than was the formation of (ω-1)-hydroxydodecanol, implying that more than one cytochrome P-450 was involved in the hydroxylation of 1-dodecanol and that CO has a higher affinity for the P-450 catalyzing the ω-hydroxylation. The formation of laurate during the incubation of 1-dodecanol with frog liver microsomes suggests that a fatty alcohol oxidation system is also present in the microsomes. NAD⁺ was the most effective cofactor for the oxidation of 1-dodecanol and NADP⁺ had a little effect. Pyrazole (an inhibitor of alcohol dehydrogenase) had a slight inhibitory effect on the oxidation and sodium azide (an inhibitor of catalase) had no effect.     

Seasonal variations in the seed oil ofThevetia peruviana (Pers.) K. Schum

The fixed oil ofThevetia peruviana (Pers.) K. Schum. (T. neriifolia Juss) was obtained by solvent extraction, and its yield and composition were studied to reflect the effect of seasonal variations. Ripe and unripe seeds collected in December and February (the dry season) gave average yields of 72 and 52%, v/w, respectively, and those of May and August (the rainy season) gave 56 and 41%, v/w, respectively. Sitosterol was isolated and identified from the unsaponifiable fraction. Oleic, linoleic, stearic and palmitic acids were shown to be present in all the oils, while myristic, lauric, capric and caprylic acids were identified only in the oil from unripe seeds collected in the rainy season. The physical and chemical constants of the oils are given also.     

Seasonal changes in the lipid classes and fatty acid compositions of hake (Merluccius hubbsi) liver oil

The lipid content, lipid class composition, and fatty acid composition of hake (Merluccius hubbsi) liver oil was studied for a whole year. The lipid content of the liver ranged from 41 to 60%. Triacylglycerols were the main lipid class present in the oil, with a mean value of 80%. Docosahexaenoic acid was the main polyunsaturated fatty acid during the year and was twice that of the eicosapentaenoic acid content. The composition of hake liver oil makes it useful as a raw material for encapsulated pharmaceutical products.     

Lipid classes of fresh cassava roots (Manihot esculenta Crantz): Identification and quantification

Fresh cassava roots (Manihot esculenta Crantz, c.v. Algodona) were processed for lipid analysis within five hr after harvest. The total lipid content was 0.25% fresh weight, and the lipid mixture obtained was complex. Polar lipids plus sterols and steryl esters made up the major part of the extracted lipids (77.9 mol%). Seven phospholipids were identified. Those in higher amount were: phosphatidylcholine, 265.4 nmol/g fresh weight; phosphatidylethanolamine, 151.8 nmol/g fresh weight, and phosphatidylinositol, 143.1 nmol/g fresh weight. Among the six glycolipids identified, digalactosyldiacylglycerol in a content of 333.2 nmol/g fresh weight and monogalactosyldiacylglycerol in a content of 217.1 nmol/g fresh weight were the most abundant. Free sterols were at 304.3 nmol/g fresh weight and triacylglycerol was measured at 444.4 nmol/g fresh weight. Results are discussed in view of recent knowledge of the kind of lipid classes expected in plant material. This work is intended to be the starting point of further research on cassava lipids upon subjecting the roots to conditions leading to its preservation.     

Cholesterol metabolism in relation to aging and dietary fat in rats and humans

A review of research in the authors' laboratories regarding effects of dietary fat polyunsaturation upon longevity in rats and some aspects of the regulation of cholesterol metabolism with regard to age of rats and humans is presented. The longevity of the rat was found to be enhanced by consumption of dietary fat providing a polyunsaturated to saturated fatty acid (P/S) ratio of 0.3 to 1, corresponding to about 5–12% of energy (en%) as linoleate, compared with less or more polyunsaturated fat, mechanisms of the effects of the fats upon cholesterol metabolism were studied. With advancing age, there seems to be a decline in the rate of catabolism of cholesterol, resulting in longer retention in the body of the rat. In the human, there seems to be a decline in regulation of uptake of cholesterol by leukocytes and, therefore, perhaps other tissues, resulting in increased synthesis of cholesterol by the peripheral tissues. Moderate rather than high dietary consumption of polyunsaturated fat seems to be favorable to metabolic processes contributing to longevity. Presented at the AOCS meeting in Chicago, May 1983.     

Cassava (Manihot esculenta Crantz) stump biochar: Physical/chemical characteristics and dye affinity

Aiming investigated the pyrolysis of the agricultural waste known as cassava stump, the portion of the plant to which the tuberous roots and aerial parts of the plant are attached, this study had as objective to produce biochars from cassava stump by conducting vacuum pyrolysis at 400, 500, or 600?°C. The biochars were characterized by proximate analysis, thermogravimetric analysis, Fourier-transform infrared absorption spectroscopy, X-ray diffraction, scanning electron microscopy, and nitrogen adsorption. Adsorption affinity tests were performed with four different dyes: methylene blue, basic fuchsin, acid fuchsin, and alizarin. Biochar obtained at 500?°C, heating rate of 20?°C.min^?1, and 90?min of residence at the final temperature, had 22% higher fixed carbon content as compared to the other biochars and 3.16 times greater fixed carbon content than the original cassava stump. This biochar showed the best adsorption capacity (0.0679?mmol/g) and percentage of removal (87.6%) of methylene blue dye from aqueous solution. The material characterization reveals that biochars from Manihot esculenta Crantz stump may have potential application in carbon sequestering. Besides that, these biochars could be applied with efficiency as adsorbent of dyes.     

Seasonal and clonal variations in technological and thermal properties of raw Hevea natural rubber

This study was undertaken over a 10‐month period under environmental conditions within the state of Mato Grosso, Brazil, to evaluate the causes of variation in the technological and thermal properties of raw natural rubber (NR) from different clones of Hevea brasiliensis (GT 1, PR 255, FX 3864, and RRIM 600). These clones were chosen to represent good clones available in Brazil. The technological properties of raw NR were evaluated in terms of their dry rubber content (DRC), Wallace plasticity, plasticity retention index (PRI), and Mooney viscosity. The thermal performance was evaluated with the thermogravimetry (TG)/differential thermogravimetry (DTG) technique. There were significant variations (p < 0.01 and p < 0.05) between clones and tappings for all technological properties, except for the percentage DRC among the clones. Of the clones studied, clone PR 255 presented the highest sensitivity to thermooxidation, as measured by its PRI value. The clone type and period of the year did not significantly influence the thermal behavior (TG/DTG under a nitrogen atmosphere) among the four clones evaluated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Cholesterol metabolism in the rat lactating mammary gland: The role of cholesteryl ester hydrolase

An acid cholesteryl ester hydrolase activity associated with a fraction containing mitochondria and lysosomes from rat lactating mammary glands was found to have a pH optimum of 5.0. Its sedimentation pattern was closely related to that of the lysosomal enzyme markers acid phosphatase and β-glucuronidase, suggesting that the activity is associated with the lysosomes. The enzyme was strongly inhibited by Cu²⁺, but was inhibited little by other divalent metal ions. Acid cholesteryl ester hydrolase activity was almost completely abolished byp-hydroxymercuribenzoate, but this effect was reversed in the presence of an equimolar concentration of reduced glutathione (GSH), indicating that the enzyme requires free sulfhydryl groups for activity. These properties are similar to those of acid, lysosomal cholesteryl ester hydrolases found in other tissues. Acid cholesteryl ester hydrolase activity was 8–14 fold higher in mammary tissue from lactating as compared to virgin rats. Neutral cholesteryl ester hydrolase activities associated with the microsomal and cytosolic subcellular fractions were also increased in lactating glands, but to a lesser extent. In addition, a 2-fold increase in the activities of both the acid and microsomal neutral enzymes was seen during the first few days of lactation, while the cytosolic neutral activity remained constant. These results suggest that mammary gland cholesteryl ester hydrolases have a role in the regulation of cholesterol metabolism in mammary cells, and in the provision of cholesterol for secretion into milk.     

Cholesterol metabolism and vitamin B6: II. Intestinal cholesterogenesis in vitamin B6 deficient rats

The in vitro incorporation of 1-¹⁴C-acetate into cholesterol by vitamin B₆ deficient and pair-fed rat intestinal tissue was assayed. It was found that vitamin B₆ deficiency increases, by a twofold factor, the incorporation of 1-¹⁴C-acetate into the cholesterol biosynthetic chain, when using a segment of the ileum, and on the other hand no increase was observed when using a segment from the jejunum. The production of¹⁴CO₂ from 1-¹⁴C-acetate was not found altered by a vitamin B₆ deficiency when using segments from the jejunum or the ileum. The effect of sodium cholate and sodium chenodeoxycholate on the incorporation of radioactivity into cholesterol and on the production of radioactive CO₂, with 1-¹⁴C-acetate as a substrate, was assayed with the two groups of animals. The significance of these findings and the posible relationships between these factors are discussed.     

Fatty acids,carbohydrates and crude protein in twenty cassava cultivars(Manihot esculenta Crantz)

Twenty cassava cultivars (Manihot esculenta Crantz) were analyzed for fatty acids, nonstructural carbohydrates and crude protein contents. The main constituent fatty acids were myristic, palmitic, stearic, oleic, linoleic and linolenic. Trace amounts of lauric, myristoleic and palmitoleic acids were detected. Saturated acids ranged from 26.58 to 58.05%. Acid-digestible carbohydrates ranged from 11.82 to 40.70% of the green matter. Reducing and non-reducing soluble oligosaccharides also were determined. Crude protein ranged from 1.39 to 4.70% of the dry matter. Linear regression analyses were made, but no significant correlations were found. Some possible genetic relationships are proposed for certain cultivars.     

Fabrication of cassava (Manihot esculenta Crantz) starch-based ultrafine fibers: Investigation of fundamental and antimicrobial properties

Micro/nano-based fibrous membranes loaded with antibacterial agents have been widely studied in the medical field. In this research, we describe the development of a new environmentally friendly medical dressing based on centrifugally spun cassava starch-based ultrafine fibers loaded with nanosilver (Ag). For this purpose, the spinnability of amylopectin-rich native cassava starch in a centrifugal spinning system was investigated. Polyvinyl alcohol (PVA) was applied to improve the water stability and mechanical properties of the starch-based fibers, and the water stability of the fibers was further improved by posttreatment with formic acid. The morphology, structure, thermal, and tensile properties were studied. The results indicated that the native cassava starch showed excellent spinnability in the centrifugal spinning system. The tensile strength and water stability of the obtained fibrous membranes were improved by adding PVA and further improved after the posttreatment. The antibacterial properties of fibers loaded with Ag were evaluated through a bacteriostatic zone test, and the results showed that the fibers presented good antibacterial properties against Escherichia coli. Therefore, the obtained fibers have great potential for application in the medical dressing field.     

Effect of inhibitors on ω-and (ω-1)-hydroxylation of lauric acid by frog liver microsomes

To investigate the involvement of different cytochrome P-450 monooxygenases in fatty acid hydroxylation in frog liver microsomes, the effect of various inhibitors of cytochrome P-450 monooxygenases on the ω- and (ω-1)-hydroxylation of laurate was examined. The ω/ω-1-hydroxylation ratios were changed significantly by various levels of carbon monooxide (CO) inhibition; the formation of ω-hydroxylaurate was more sharply inhibited by various levels of CO than was the formation of (ω-1)-hydroxylaurate. On the contrary, metyrapone inhibited only the formation of (ω-1)-hydroxylaurate and stimulated the formation of ω-hydroxylaurate. 7,8-Benzoflavone as well as CO was more inhibitory to the ω-hydroxylation of laurate. At low concentrations of KCN (0.2 and 0.1 mM), the (ω-1)-hydroxylase activity was stimulated, but both the ω- and (ω-1)-hydroxylase activities were inhibited at the higher concentrations (5–10 mM). The effect of drugs and hydroxylaurate isomers on the ω- and (ω-1)-hydroxylation was also examined. Aminopyrine showed a stimulative effect on ω-hydroxylase activity and no effect on the (ω-1)-hydroxylase activity, whilep-nitroanisole inhibited the (ω-1)-hydroxylase activity and showed almost no effect on the ω-hydroxylase activity. 12-Hydroxylaurate inhibited both the ω- and (ω-1)-hydroxylase activities, but the ω-hydroxylase activity was inhibited to a much greater extent. 11-Hydroxylaurate had no effect on either hydroxylation. These findings strongly support the hypothesis that different cytochrome P-450 species are involved in the hepatic microsomal hydroxylation of laurate at ω- and (ω-1)-positions in the frog.     

Seasonal and spatial variations of alkaloids in Merendera montana in relation to chemical defense and phenology

Merendera montana (Liliaceae) is an endemic plant broadly, but exclusively, occurring in the Iberian Peninsula where it is one of the most abundant species in rangelands grazed by sheep and on the routes used by migrating sheep herds. In spite of showing a peculiar phenology adapted to Mediterranean regions (leaves remain green from fall to spring and are absent in summer), this species has also successfully colonized high altitude environments (up to 2300 m), and abundant populations can be found in montane and subalpine pastures. Chemical analysis has shown a high forage quality as well as the pre- sence of tropolone alkaloids (similar to other species of the genus Merendera), mainly colchicine, 3-demethylcolchicine, and colchicoside. In general terms, the alkaloid content was significantly lower in the subterranean corms than in the leaves. No remarkable seasonal variations in total alkaloids was found, although an increase of colchicoside in the corms and a decrease of colchicine was noted in summer. Both chemical deterrents and phenology could be the cause of the widespread ecological adaptation of Merendera montana. The alkaloid content would prevent intake by wild herbivores during winter, while the absence of aerial organs in summer, coinciding exactly with the highest domestic herbivore pressure, would permit this species to colonize rich soil habitats where there is low plant competition.     

Cholesterol metabolism in human monocyte-derived macrophages: Stimulation of cholesteryl ester formation and cholesterol excretion by serum lipoproteins

The role of lipoproteins and serum in the formation and accumulation of cholesteryl esters in human monocyte-derived macrophages (HMD macrophages) was investigated; studies were also carried out with IC21 cells (a cell line derived from mouse peritoneal macrophages). Following preincubation of HMD macrophages with lipoprotein-depleted serum (LPDS), both native and acetylated low density lipoprotein (LDL and AcLDL, respectively) stimulated the formation of cholesteryl esters with a resultant increase in cellular cholesteryl ester content. Cholesteryl ester formation and accumulation was also stimulated in macrophages exposed continuously to 25-hydroxycholesterol. However, the stimulation of cholesterol esterification by either lipoproteins or 25-hydroxycholesterol was not inhibited by progesterone in HMD macrophages, but was in the IC21 cells. Cholesterol efflux and the hydrolysis of cellular cholesterol ester, promoted by serum components, were studied in HMD macrophages preloaded with cholesteryl ester by incubation with 25-hydroxy cholesterol. Replacement of the medium with one devoid of 25-hydroxycholesterol resulted within 24 hr in at least a 30% decrease in the cholesteryl ester content of the HMD macrophages; replacement with a medium high in cholesterol acceptor content (LPDS or high density lipoprotein) and incubation for three days led to the most marked decreases in cellular cholesterol content. Thus, hydrolysis of the cholesteryl esters by HMD macrophages was not dependent on the presence of cholesterol acceptors in the medium, but cellular cholesterol content was.