Morphological and Chemical Differentiation between Tunisian Populations of Pinus halepensis,Pinus brutia,and Pinus pinaster

The lipid fraction of seeds from different pine species and populations was studied regarding total lipid content, fatty acid profile and vitamin E composition. The investigated seeds contained a high percentage of lipid (13.6 to 31.5 %). Lipid fractions were found to be rich in vitamin E, which varied significantly among species and populations. P. halepensis (Ph−Hn) showed the highest content of vitamin E (256.3 mg/kg of seeds) and the uppermost content of α-tocopherol (44 mg/kg). However, P. halepensis (Ph−Kas) was the richest in γ-tocopherol (204.9 mg/kg). Lipid fractions had a low content of δ-tocopherol (1.2 to 3.6 mg/kg. The highest content of γ-tocotrienol (∼18 %) was determined for P. halepensis (Ph−Dc and Ph−Hn). Thirteen fatty acids were identified by GC-FID with significant variation between the investigated species. The linoleic acid was the major fatty acid followed by oleic acid and palmitic acid. The chemical differentiation among species for the composition of fatty acids and vitamin E was confirmed by PCA. Significant correlations were observed between the content of vitamin E and fatty acids and ecological parameters of P. halepensis populations.     

Enhanced prostaglandin synthesis as a mechanism for inhibition of melanoma cell growth by ascorbic acid

Both ascorbic acid and the 1-series prostaglandins have been reported to be important regulators of cell growth and since ascorbic acid also increases the synthesis of the 1-series prostaglandins, it is possible that the effects of ascorbic acid on cell growth might be mediated by changes in 1-series prostaglandin synthesis induced by ascorbic acid. This study attempted to examine this possible relationship. The effects of ascorbic acid, prostaglandin E1 and the essential fatty acid precursors of the prostaglandins, linoleic acid and gamma-linolenic acid on the in vitro growth of transformed BL6 murine melanoma cells and untransformed monkey kidney (LLCMK) cells was determined. The effects of ascorbic acid addition on the growth inhibitory effect of the essential fatty acids and on the activity of delta-6-desaturase, a key enzyme in 1-series prostaglandin synthesis were also examined. Addition of ascorbic acid, prostaglandin E1 and both essential fatty acids was found to reduce BL6 growth while PGE1 and to a lesser extent the essential fatty acids reduced LLCMK cell growth. The growth inhibitory effect of the essential fatty acids was enhanced by ascorbic acid which was also found to stimulate delta-6-desaturase activity in BL6 cells. The growth inhibitory effect of ascorbic acid on BL6 cells may thus be mediated by changes in prostaglandin synthesis through an association with the metabolism of the essential fatty acid precursors of the prostaglandins.     

Effects of various non-esterified fatty acids on the particle size redistribution of high density lipoproteins induced by the human cholesteryl ester transfer protein

The effects of various non-esterified fatty acids on the CETP-mediated particle size redistribution of HDL were studied by incubating HDL3 and CETP for 24 h at 37 degrees C in the absence or in the presence of either saturated, monounsaturated or polyunsaturated non-esterified fatty acids. In the absence of non-esterified fatty acids, CETP induced a redistribution of the initial population of HDL3 (Stokes' radius 4.3 nm) by promoting the appearance of one larger (Stokes' radius 4.8 nm) and two smaller (Stokes' radii 3.9 and 3.7 nm) HDL subpopulations. Whereas the non-esterified fatty acids alone did not modify the HDL3 distribution profile, they were able to alter markedly the capacity of CETP to induce the particle size redistribution of HDL. All the saturated fatty acids with at least 10 carbons were able to increase the formation of the very small sized particles (Stokes' radius 3.7 nm) in a concentration dependent manner, the medium chain fatty acids (12 and 14 carbons) being the best activators. The potential effect of non-esterified fatty acids was also influenced by the presence of double bonds in their monomeric carbon chain. While at low concentrations of non-esterified fatty acids (0.1 mmol/l) the enhancement of the formation of very small HDL particles appeared to be greater with oleic and linoleic acids than with stearic acid, at higher concentrations (0.4 mmol/l), oleic, linoleic and arachidonic acids decreased the formation of the 3.7 nm radius particles. The inhibition of the process at high concentrations of unsaturated fatty acids was linked to the degree of unsaturation of their carbon chain, arachidonic acid being the strongest inhibitor. The present study has demonstrated that non-esterified fatty acids can modulate the particle size redistribution of HDL3 mediated by the cholesteryl ester transfer protein even in the absence of any other lipoprotein classes. The effect of non-esterified fatty acid is dependent on both the length and the degree of unsaturation of their monomeric carbon chain.     

The lipid composition and permeability to the triazole antifungal antibiotic ICI 153066 of serum-grown mycelial cultures of Candida albicans

The total lipid content of Candida albicans (serotype A: NCPF 3153) exponential-phase mycelial cultures grown in tissue-culture medium 199 (containing 10%, v/v, foetal calf serum) was 29.8 +/- 8 mg (g dry weight)-1 (mean +/- SD). The weight ratios of phospholipid to neutral lipid and phospholipid to non-esterified sterol were 2.6 +/- 0.4 and 24.9 +/- 0.5, respectively. The major phospholipid was phosphatidylcholine with smaller amounts of phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, phosphatidylglycerol and diphosphatidylglycerol; the most abundant fatty acids were palmitic, palmitoleic, oleic and linoleic acids. The major neutral lipids comprised esterified sterol, triacylglycerol and non-esterified fatty acid with a smaller amount of non-esterified sterol. The fatty acid compositions of the three fatty-acid-containing neutral lipids were distinct from each other and the phospholipids. Comparison with previous data on yeast cultures of C. albicans A grown in glucose broth shows that mycelial cultures have a larger lipid content, lower phospholipid to neutral lipid ratio and higher phospholipid to non-esterified sterol ratio. We now show that mycelial cultures were more permeable to a [14C]triazole antifungal antibiotic compared with exponentially growing yeast cultures of several azole-sensitive strains. Taken together these data are consistent with there being a relationship between the phospholipid/non-esterified sterol ratio of a culture and its ability to accumulate a triazole.     

Lipid peroxidation-related 1,N2-propanodeoxyguanosine-DNA adducts induced by endogenously formed 4-hydroxy-2-nonenal in organs of female rats fed diets supplemented with sunflower, rapeseed, olive or coconut oil

Animal and epidemiological studies confirm an impact of the fatty-acid composition in the diet on cancer development. We investigated the role of supplementation of the diet of female F344-rats with sunflower, rapeseed, olive or coconut oil on the formation of the promutagenic, exocyclic 1,N2-propanodeoxyguanosine adduct of the main lipid peroxidation product 4-hydroxy-2-nonenal in the mucosa of the glandular stomach, the small intestine, the colon, the whole kidney and the lung. This adduct is considered as the predominant DNA adduct arising from lipid peroxidation. The correlations between adduct levels and the different fatty acids were not uniform for all organs. No clear relationships between fatty acids and adduct levels were found in the colon. Significant positive correlations were observed between linoleic acid, total polyunsaturated fatty acids (PUFAs), vitamin E and DNA adduct levels in the small intestine and in the kidney. The results indicate an increasing effect on cancer risk in these organs as a result of high intake of linoleic acid. Inverse relationships between linoleic acid, PUFA and vitamin E intake and adduct levels were found in the glandular stomach and the lung. We could not confirm a chemopreventive effect of linolenic acid (C-18 omega-3 PUFA) on the formation of adducts in our animal study, as was shown in white blood cells of women in a previous study. A tendency towards a decrease in adduct levels was seen with monounsaturated fatty acids (MUFAs) in all organs except the lung. Saturated fatty acids showed a significant positive correlation with adduct levels in the mucosa of the glandular stomach and a significant inverse correlation in the small intestine. Saturated fatty acids are not considered to directly influence lipid peroxidation to a major extent.     

Piperine modulation of carcinogen induced oxidative stress in intestinal mucosa

The plasma-borne long-chain free fatty acids (FFA) enter skeletal muscle cells. Upon entering they are oxidized or esterified and a fraction remains free (non-esterified). The data on free fatty acids in skeletal muscles remain highly controversial. Furthermore, the composition of individual fatty acids in various lipid fractions including free fatty acids, monoglyceride and diglyceride in muscles has not been characterized. Also data on the composition of fatty acids esterified into muscle triglycerides and phospholipids are incomplete. The present study was undertaken to examine a composition of fatty acids in lipid fractions of different skeletal muscle types. For this purpose, samples of the rat soleus, red and white portions of gastrocnemius were excised, trimmed of visible fat and fascias and immediately frozen in liquid nitrogen. Samples were then pulverized and, lipids were extracted and fractionated by thin-layer chromatography. Individual long-chain fatty acids in different fractions were identified, characterized and quantitated by gas-liquid chromatography. FFA composition in the plasma was also determined. The total FFA content in the soleus, red and white gastrocnemius was 69.1 ± 10.8, 49.0 ± 13.6 and 22.7 ± 8.6 nmol/g, respectively. Palmitic and oleic acids were the major fatty acids in the muscles FFA fraction. Monoglyceride fraction of each muscle contained palmitic, stearic and linoleic acid as the major fatty acids, Diglyceride fraction contained mostly palmitic and oleic acid whereas triglyceride fraction mostly palmitic and linoleic acid.. The fraction of phospholipids was composed mostly of palmitic and linoleic acid but contained also considerable percentage of archidonic acid. Total plasma FFA/muscle FFA ratio depended on a muscle type and was: 2.4 in the soleus, 3.5 in the red and 7.4 in the white gastrocnemius. This assured transport of FFA to the myocytes. However, there were great differences in the ratio between particular FFA within the same muscle as well between the muscles. It indicates that individual FFA are either selectively transported from the plasma to the muscles or selectively used within the myocytes or both.     

Effect of dietary oils containing different amounts of precursor and derivative fatty acids on prostaglandin E2 synthesis in liver, kidney and lung of rats.

The availability of the fatty acids which are precursors of prostaglandins is affected by dietary intake. We have studied, in particular, the effects of dietary intake of lipids with different amounts of precursor and derivative fatty acids on the synthesis of prostaglandin E2 (PGE2) in rat liver, kidney and lung. Fifteen-month-old rats were fed for 3 months diets containing different amounts of oleic, linoleic, alpha linolenic, gamma linolenic and stearidonic acids. The fatty acid compositions of total phospholipids and prostaglandin E2 levels of liver, kidney and lung were investigated. In the organs studied, the intake of lipids at different amount of precursor/derivative fatty acids caused variations in the fatty acid composition of phospholipids. PGE2 showed different values which did not seem directly affected by tissue availability of arachidonate but by the effect of dietary lipids on the metabolic pool of polyunsaturated fatty acids (PUFAs).     

Influence of an increased intake of linoleic acid on the incorporation of dietary (n-3) fatty acids in phospholipids and on prostanoid synthesis in rat tissues.

We investigated whether the amount of dietary linoleic acid (LA) (as corn oil) influences the incorporation of dietary eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) in tissue phospholipids and the prostanoid biosynthesis. Rats were fed four different levels of corn oil (at a total dietary fat level of either 2.5%, 5%, 10% or 20%); at each corn oil level, two groups of rats were supplemented with either EPA and DHA (200 mg/day) during 6 weeks, and compared with a group receiving oleic acid. The phospholipid fatty acid composition of liver, kidney and aorta showed, as expected, that the incorporation of EPA was highly suppressed by increasing the content of dietary linoleic acid in the diets. On the other hand, DHA was almost unaffected by the amounts of (n - 6) fatty acids in the diets. These results indicate that EPA levels but not DHA levels in tissue phospholipids were influenced by the competing dietary (n - 6) fatty acids. The tissue arachidonate content was similar under the various dietary linoleic acid conditions, but feeding EPA or DHA lowers the AA content. Moreover, the amount of dietary linoleic acid did not significantly influence the prostaglandin E2 (PGE2) production in stimulated aortic rings. However, PGE2 synthesis was significantly decreased in the groups treated with either EPA or DHA. Thromboxane B2 levels in serum followed a similar pattern. It is suggested that an increase of dietary (n - 3) PUFAs is more efficient to reduce (n - 6) eicosanoid formation than a decrease of dietary (n - 6) fatty acids.     

Madia sativa,a potential oil crop of central Chile

Madia sativa seeds were studied for their oil content and fatty acid composition. Oil content in wild seeds was 26% w/w. The samples analyzed showed comparable fatty acid composition, with palmitic (12.9–14.0), stearic (3.8–3.9), oleic (7.9-10.2) and linoleic acid (71.4–72.4) as the major acids. The mean molecular weight of the oil ranges from 876.1 to 894.6 with saponification values of 190–194 mg and unsaturation values of 126–131. The seed meal showed a high crude protein content (28–31%). The oil composition of Madia sativa and its adaptability to poor soils, suggest considerable potential as a future oil crop.     

Effect of different combinations of exogenous higher fatty acids on cardiac function during coronary ischemia and reperfusion

Experiments on 77 white random-bred male rats weighing 200 +/- 10 g have shown that combinations of high unsaturated fatty acids (HUFA) containing the precursors of prostaglandin synthesis, arachidonic and linoleic acids, produce a powerful antiarrhythmic action during transitory coronary insufficiency. The effect was seen not only during ischemia but also during subsequent myocardial reperfusion. The combination of HUFA containing arachidonic and linoleic acids as precursors of prostaglandin synthesis exerted a more demonstrable antiarrhythmic action than that without arachidonic acid. The degree of the ischemia-induced depression of contractile process was less versus control, provided HUFA combinations contained arachidonic acid.     

Lipids and lipid metabolism in the brown alga, Fucus serratus

The lipids of the brown alga Fucus serratus were isolated, identified and quantified. The major acyl lipids were the three glycosylglycerides, diacylgalactosylglycerol, diacyldigalactosylglycerol and diacylsulphoquinovosylglycerol. These represent over 70% of the total acyl lipids. The fatty acid compositions of the major lipids were examined and most showed rather distinctive fatty acid contents. For example, diacylgalactosylglycerol was enriched in n-3 polyunsaturated fatty acids while phosphatidylcholine and phosphatidylethanolamine had very high levels of arachidonate. Phosphatidylglycerol contained the unusual trans-Δ3-hexadecenoic acid. The labelling of lipids and fatty acids from [¹⁴C]acetate was examined and the distribution of label between individual components as a function of the incubation period and in algae collected at different times of the year is reported. Algae collected in the winter incorporated much more radioactivity into non-esterified fatty acids when compared to algae collected in the summer. All algae could label myristate, palmitate, stearate and oleate at high rates. Longer incubation times allowed the labelling of polyunsaturated fatty acids such as linoleic acid.     

Brush border membrane non-esterified fatty acids. Physiological levels and significance for mucosal iron uptake in mouse proximal intestine

Brush border membrane vesicles prepared using divalent cation precipitation methods can contain unphysiological levels of non-esterified fatty acids. Fatty acid production from endogenous lipid during brush border membrane vesicle preparation is effectively prevented by the lipase inhibitor diethyl 4-nitrophenylphosphate plus cooling. Vesicles prepared using this procedure have variable levels of non-esterified fatty acids (range 22-193 nmol mg-1 protein). Changes in non-esterified fatty acid levels in brush border membrane vesicles parallel Fe uptake by vesicles from Fe/ascorbate solutions. Brush border membrane vesicle fatty acids appear to be derived from the diet but hypoxic mice are able to maintain high brush border membrane non-esterified fatty acid levels despite reduced dietary intake. Non-esterified fatty acids in brush border membrane may thus provide a physiological mechanism of mucosal Fe uptake.     

Effect of fatty acid modification on prostaglandin production by cultured 3T3 cells

We have investigated the extent to which modifications in the essential fatty acid content of mammalian cells can affect prostaglandin production. Swiss mouse 3T3 cells stimulated with the calcium ionophore A23187 produced 1.7 to 7 times more prostaglandin E(2) (PGE(2)) when the cultures were supplemented with linoleic acid. Increases in PGE(2) production as a result of linoleic acid supplementation occurred under all culture conditions except during the first 24 hr after attachment, when prostaglandin production was very high. Arachidonic acid supplementation produced a similar enhancement in the capacity of the cells to produce PGE(2), but no appreciable increase occurred when the cultures were supplemented with oleic acid. The phospholipids of the cells exposed to the linoleate-enriched medium contained 4 times more arachidonic acid and twice as much linoleic acid as compared with the corresponding controls. The choline phosphoglycerides were most highly enriched in arachidonic acid, but 2- to 3-fold increases also occurred in the inositol and ethanolamine phosphoglycerides. When cultures initially enriched with linoleic acid were transferred to an unsupplemented medium, the fatty acid composition as well as the capacity of the cells to produce PGE(2) reverted almost to control values. The amount of exogenous arachidonic acid converted to PGE(2) as measured by radioimmunoassay also was greater when the cells were enriched with linoleic acid. Studies with radioactive arachidonic acid indicated that the distribution of prostaglandin metabolites was not affected appreciably by linoleic acid enrichment. These findings suggest that at least two factors contribute to the increased capacity of the cultures supplemented with linoleate to produce PGE(2). One is enrichment of the phospholipid substrate pools with arachidonic acid. The other is an increased ability of the cells to synthesize PGE(2) from unesterified arachidonic acid, perhaps because the prostaglandin-forming enzymes are more active.-Denning, G. M., P. H. Figard, and A. A. Spector. Effect of fatty acid modification on prostaglandin production by cultured 3T3 cells.     

Modification of upper gastrointestinal prostaglandin synthesis by dietary fatty acids

The effects of dietary iols on gastric, duodenal mucosa and liver were investigated ina rat model. Unsaturated fatty acid profles and in vitro prostaglandin (PG) synthesis (PGE₂, PGF_2α, 6-oxo-PGF_1α and thromboxane B₂). were measured after 14 days of dietary oil supplements.There were no significant differences in prostanoid synthesis between rats fed coconut oil (high saturated fat content) and standard diet. After fish oil supplement, tissue eicosapentaenoic acid and docosahexaenoic acid levels were higher, arachidonic acid levels were lower, and prostanoid synthesis was reduced in both stomach and duodenum. After corn oil and evening primrose oil, linoleic acid levels were variaby increased, bt there were no significant differences in arachidonic acid or prostanoid synthesis. Dihomogamma-linolenic acid levels were slightly increased after evening primrose oil.Dietary incorporation of fatty acids into gastroduodenal tissue is not uniform. When incorporated, fatty acids can modify prostaglandin synthesis.     

Dose-dependent effects of dietary gamma-linolenic acid on rat spleen lymphocyte functions.

Feeding rodents a diet rich in evening primrose oil (EPO), which contains 5-10 g gamma-linolenic acid (GLA)/100 g total fatty acids, has been shown to decrease lymphocyte proliferation and natural killer cell activity. However, EPO contains a very high level of linoleic acid which itself can affect lymphocyte functions and it is not clear to what extent the effects of EPO can be attributed to GLA. The current study investigated the effect of two levels of GLA in the rat diet upon immune cell functions; the level of linoleic acid was maintained below 30 g/100 g total fatty acids. Weanling rats were fed on high fat (178 g/kg) diets which contained 4.4 g or 10 g GLA/100 g total fatty acids in place of a proportion of linoleic acid. The total polyunsaturated fatty acid content and the n-6 to n-3 polyunsaturated fatty acid ratio of the diet were maintained at 35 g/100 g total fatty acids and 7, respectively. The fatty acid compositions of the serum and of spleen leukocytes were markedly influenced by that of the diet, with an increase in the proportions of GLA and dihomo-gamma-linolenic acid when the diets containing GLA were fed; these diets also increased the proportion of arachidonic acid in spleen leukocytes. Spleen lymphocyte proliferation in response to concanavalin A was significantly reduced (by 60%) by feeding the diet containing the higher level of GLA, but not by the diet containing the lower level of GLA. Spleen natural killer cell activity and prostaglandin E (PGE) production by spleen leukocytes were not significantly affected by inclusion of GLA in the diet, although there was a tendency towards decreased natural killer cell activity by cells from rats fed the high GLA diet. Thus, this study shows that dietary GLA is capable of altering the fatty acid composition of cells of the immune system and of exerting some immunomodulatory effects, but that the level of GLA in the diet must exceed 4.4 g/100 g total fatty acids for these effects to become apparent.     

黄粉虫蛹的营养成分分析

采用现代分析技术手段对黄粉虫Tenebrio molitor（L．）蛹的营养成分进行分析,结果表明：其蛋白质、粗脂肪、碳水化合物及灰分含量分别为鲜重的16．8％、7．6％、1．2％、1．4％,其氨基酸和胆固醇含量分别为18.7mg／g和0．4mg／g;含有7种人体必需氨基酸,其必需氨基酸占总氨基酸含量的44．40％,必需氨基酸与非必需氨基酸含量的比值为79.8％,第一限制性氨基酸为含硫氨基酸,即蛋氨酸和胱氨酸;同时,其不饱和脂肪酸与必需脂肪酸分别占总脂肪的73．9％和24．1％,特别是油酸和亚油酸含量较高,分别达49．8％和23．4％：另外,该昆虫还含有K、Ca、Mg、Fe、Zn、Cu、Mn等多种矿物质和微量元素。     

Influence of S-ethyl Dipropylthiocarbamate (EPTC) on the Fatty Acid Composition of Wheat Leaf Galactolipids

Winter wheat (Triticum sativum L. cv. Nisu) was grown in sand which contained 0, 0.25, 0.5 and 1.0 mg S-ethyl dipropylthiocarbamate (EPTC) per kg air dry sand. The galactolipids of leaves of 21-day-old seedlings were isolated by preparative thin layer chromatography. The fatty acids of the mono- and digalactosyl diglycerides were analysed by gas liquid capillary chromatography. The major fatty acids of the wheat leaf galactolipids were palmitic, palmitoleic, stearic, oleic, vaccenic, linoleic and linolenic acids (in the monogalactosyl diglyceride fraction of untreated plants 22.5, 2.4, 3.1, 5.2, 2.5, 51.1 and 1526.6 μg and in the digalactosyl diglyceride fraction 108.8, 2.3, 10.4, 9.9, 8.2, 42.3 and 1120.7 μg/g leaf fresh weight, respectively). Total fatty acid content of the mono- and digalactosyl diglyceride fractions was decreased by 85 and 87%, respectively, at 1 mg EPTC/kg sand, while decrease in the fresh weight of the leaves was 79%. The content of linoleic and linolenic acids/g fresh weight of the leaves was decreased in the monogalactosyl diglyceride fraction by 27 and 43%, respectively, while the content of all other fatty acids was increased. In the digalactosyl diglyceride fraction the content of both linoleic and linolenic acids/g leaf fresh weight was decreased by 55%. The content of palmitic and vaccenic acids was also decreased, whereas the content of other fatty acids remained at the level of the untreated samples. The general quality of the fatty acids in the mono- and digalactosyl diglyceride fractions was altered slightly by EPTC.     

Use of structured triacylglycerols containing predominantly stearic and oleic acids to probe early events in metabolic processing of dietary fat.

Early events in the metabolic processing of dietary triacylglycerol may have an important impact on subsequent development of risk factors for coronary heart disease. We have used structured triacylglycerols containing predominantly stearic or oleic acids at the sn -2 position to probe aspects of the processing of dietary fatty acids presented to adipose tissue in chylomicron-triacylglycerol. Studies were conducted on 14 healthy women who were given meals containing 85 g carbohydrate and 60 g of either of the two structured triacylglycerols in random order. Systemic concentrations and arterio-venous differences across adipose tissue for plasma triacylglycerol and non-esterified fatty acids were measured, together with analysis of the fatty acid composition of the relevant fractions. The stereo-specific structure of the ingested triacylglycerol was largely preserved in chylomicron-triacylglycerol. Systemic concentrations of total and individual non-esterified fatty acids were not significantly different after ingestion of the two fats, nor were their rates of release across adipose tissue. The composition of non-esterified fatty acids released from adipose tissue changed after the meal to reflect more closely the composition of the triacylglycerol ingested, but again no significant differences were observed between the two test meals. There was no detectable release of monoacylglycerol from adipose tissue after either test meal.We conclude that the environment for lipoprotein lipase action in adipose tissue in vivo is likely to be highly organized, such that there is no release of monoacylglycerol, nor preferential uptake or release of fatty acids from chylomicron-triacylglycerol according to the nature or the position within triacylglycerol of the fatty acid.     

羚牛肉、脂、蹄腺分泌物的生化分析

人类对于大型偶蹄类动物的利用已有较多先例,北美麝牛(Ovibous muschtus)近年在加拿大、美国等已经驯养,并以其毛绒作为一种特殊的毛丝工业原料。美洲野牛(Bison Americasus)已与家牛杂交生产肉用牛。我国青藏高原的牦牛(Bos grinus)与黄牛杂交而成的犏牛,已成为藏民的主要肉乳兼用牛。羚牛(Budorcas taxicolor)系稀有动物,为亚洲特产,分布于中国、印度、缅甸及不丹。中国的羚牛分布于川、陕、甘、滇、藏5省区,为分布区最广、数量最多、资源量丰富的国家(Wu,1985)。     

Inhibition of brain prostaglandin D synthetase and prostaglandin D2 dehydrogenase by some saturated and unsaturated fatty acids

The activities of rat brain prostaglandin D synthetase and swine brain prostaglandin D2 dehydrogenase were inhibited by some saturated and unsaturated fatty acids. Myristic acid was most potent among saturated straight-chain fatty acids so far tested. The IC50 values of this acid were 80 microM for prostaglandin D synthetase and 7 microM for prostaglandin D2 dehydrogenase, respectively. Little inhibition was found with methyl myristate and myristyl alcohol. The IC50 values of these derivatives were more than 200 microM for both enzymes, suggesting that the free carboxyl group was essential for the inhibition. The effects of cis double bond structure of fatty acids on the inhibition potency were examined by the use of the carbon 18 and 20 fatty acids. The inhibition potencies for both enzymes increased with the number of cis double bonds; the IC50 values of stearic, oleic, linoleic and linolenic acid were, respectively, more than 200, 60, 30 and 30 microM for prostaglandin D synthetase, and 20, 10, 8.5 and 7 microM for prostaglandin D2 dehydrogenase. Arachidonic acid also inhibited the activities of both enzymes with respective IC50 values of 40 microM for prostaglandin D synthetase and 3.9 microM for prostaglandin D2 dehydrogenase, while arachidic acid showed little inhibition. The kinetic studies with myristic acid and arachidonic acid demonstrated that the inhibition by these fatty acids was competitive and reversible for both enzymes. Myristic acid and other fatty acids also inhibited the activities of several enzymes in prostaglandin metabolism, although to a lesser extent. The IC50 values of myristic acid for prostaglandin E isomerase, thromboxane synthetase and NAD-linked prostaglandin dehydrogenase (type I) were 200, 700 and 100 microM, respectively. However, this fatty acid showed little inhibition on fatty acid cyclooxygenase (20% at 800 microM), glutathione-requiring prostaglandin D synthetase from rat spleen (20% at 800 microM), and NADP-linked prostaglandin dehydrogenase (type II) (no inhibition at 200 microM).