Influence of growth rate on pigment and lipid composition of the microalgaIsochrysis aff.galbana clone T.iso

A continuous culture ofIsochrysis aff.galbana clone T.iso, used to feedPecten maximus larvae at IFREMER (Brest, France), was carried out in a chemostat at its optimum temperature for growth (26 °C). Changes in pigments, lipid class (neutral, glyco- and phospholipids) and degree of fatty acid unsaturation were studied at three different growth rates (0.33, 0.5, 1 d^–1). As predicted by chemostat theory, a slow growth rate produced higher cell numbers and higher biomass per unit volume. These cells were low in chlorophylla and carotenoids, but rich in neutral lipids. In contrast, cultures with a fast growth rate yielded lower cell concentrations, buth higher chlorophylla, carotenoid and membrane lipid contents per cell. Changes in polyunsaturated fatty acid distribution were related to differences in algal growth rates. Neutral lipids contained mainly saturated and monounsaturated fatty acids (C18:19) at low growth rates whereas they were enriched in polyunsaturated fatty acids, especially C22:63, at high growth rates. Therefore, it is suggested that the growth rate in continuous cultures be controlled so as to adjust the relative proportions of polyunsaturated fatty acids in lipid classes of the diet meant for larval nutrition.Author for correspondence     

Reduction in omega-3 fatty acids by UV-B irradiation in microalgae

UV-B irradiation reduced the levels of omega-3 fatty acid, eicosapentaenoic acid (EPA, 20:53) and docosahexaenoic acid (DHA, 22:63), in microalgae; the degree of reduction varied with species.Chaetoceros calcitrans andSkeletonema costatum were high UV-B tolerant species, followed byPhaeodactylum tricornutum, Chroomonas salina, Pavlova lutheri, andThalassiosira pseudonana.Isochrysis galbana (T.ISO) andProrocentrum micans were UV- B sensitive. Cells in logarithmic phase were most sensitive to UV- B irradiation. Nitrate-, phosphate-, or sulphate-starved cells were more UV-B sensitive than non-starved cells grown in a complete basal medium. A relatively short exposure to high UV-B was more damaging than a longer exposure to lower irradiance. Visible light intensity levels had a profound impact on the sensitivity of microalgal cultures to UV-B, with high levels decreasing UV-B dependent damage. Addition of polyamines (putrescine, spermidine or spermine) or an amino acid (cysteine) to the culture medium minimized the reduction of omega-3 fatty acid content in microalgae caused by UV-B irradiation.Author for correspondence     

Developmental regulation of an acyl carrier protein gene promoter in vegetative and reproductive tissues

The expression of an Arabidopsis acyl carrier protein (ACP) gene promoter has been examined in transgenic tobacco plants by linking it to the reporter gene -glucuronidase (GUS). Fluorometric analysis showed that the ACP gene promoter was most active in developing seeds. Expression was also high in roots, but significantly lower in young leaves and downregulated upon their maturation. Etiolated and light-grown seedlings showed the same level of GUS activity, indicating that this promoter is not tightly regulated by light. Histochemical studies revealed that expression was usually highest in apical/ meristematic zones of vegetative tissues. Young flowers (ca. 1 cm in length) showed GUS staining in nearly all cell types, however, cell-specific patterns emerged in more mature flowers. The ACP gene promoter was active in the stigma and transmitting tissue of the style, as well as in the tapetum of the anther, developing pollen, and ovules. The results provide evidence that this ACP gene is regulated in a complex manner and is responsive to the array of signals which accompany cell differentiation, and a demand for fatty acids and lipids, during organogenesis.     

零下低温对杂交杨树皮层膜脂组成的影响

以不耐寒的美洲黑杨（Ｐｏｐｕｌｕｓｄｅｌｔｏｉｄｅｓｃｖ．“Ｌｕｘ”Ｉ－６９／５５,父本）和耐寒性较强的欧美杨（Ｐ．ｅｕｒａｍｅｒｉｃａｎａｃｌｃｖ．Ｉ－４５／５１,母本）的４个杂交Ｆ＿１代无性系（９５杨、５５９杨、６００杨和１３８１杨）为材料,分析了零下低温寒潮前后枝条皮层的脂质组成。结果表明,寒潮影响下,皮层中磷脂含量增加而组成基本不变,膜脂脂肪酸组成的变化规律是：寒潮前脂肪酸不饱和指数（ＩＵＦＡ）值大的无性系,寒潮前后的ＩＵＦＡ值变化量小;寒潮前ＩＵＦＡ值较小的无性系,寒潮前后ＩＵＦＡ值变化量较大。本文借用力学概念,提出相对抗性概念,给出杨树无性系的相对抗性序列。序列表明Ｆ＿１代无性系的耐寒性已较不耐寒的父本提高,这与田间观察基本一致。     

Response ofBrassica napus L. Microspore-derived embryos to exogenous abscisic acid and desiccation

Summary Microspore-derived embryos fromBrassica napus cv. Topas (low erucic acid) and Reston (high erucic acid) were subjected to treatment with abscisic acid (ABA) during late-stage embryo development and then dried under controlled relative humidities to mature dry seed levels of moisture. Exogenously medium-supplied ABA arrested growth and development, reduced moisture content, increased total fatty acids on a dry weight basis, and stimulated systhesis of proteins in microspore-derived embryos. ABA also resulted in a higher proportion of 22∶1 in cv. Reston (high 22∶1) and increased the level of fatty acid unsaturation in cv. Topas (low 22∶1). The accumulation of two proteins that co-migrated with cruciferin and napin on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional gels were also promoted by exposure to ABA, and the degree of accumulation was dependent on the concentration and time of application of ABA. Controlled desiccation of microspore embryos, used to simulate normal maturation and dehydration of zygotic embryos during seed development, did not seem to cause an increase of either storage proteins, total fatty acids, or 22∶1 (in cv. Reston), suggesting that dehydration is not a prerequisite for these processes, at least in culturedBrassica embryos.     

Influence of fatty acids and bovine serum albumin on the growth of human hepatoma and immortalized human kidney epithelial cells

Summary The protective influence of bovine serum albumin against growth inhibition caused by fatty acids was studied in human hepatoma (HepG2) and immortalized human kidney epithelial (IHKE) cells. In general, growth inhibition by unsaturated fatty acids (0.15 mmol/liter) increased with increasing number of double bonds. For HepG2 cells crude albumin (1g/100 ml) did not greatly modify growth inhibition by arachidonic, eicosapentaenoic, and docosahexaenoic acid. With oleic, linoleic, and linolenic acids, crude and defatted albumin stimulated cell growth. In contrast, for IHKE cells both albumins counteracted growth inhibition by unsaturated fatty acids to approximately the same extent. When HepG2 cells were cultured in the presence of saturated fatty acids (0.3 mmol/liter), C2, C6, and C8 had no or little inhibitory effect. C10 and C12 inhibited cell growth appreciably, whereas C14, and especially C16, had poor inhibitory effects. Crude albumin counteracted growth inhibition by all these fatty acids. In contrast, defatted albumin had little or no effect (except against C10 and C12), and even increased the growth inhibition by C14 and C16. With unsaturated fatty acids there seemed to be an inverse relationship between cell growth and the concentration of thiobarbituric acid reactive substances (TBARS) in media. Vitamin E abolished growth inhibition (and the increase in TBARS concentration) by unsaturated fatty acids. The complex interaction between fatty acids and albumins calls for great caution when interpreting data on growth effects.     

4-Hydroxy-2-Nonenal Levels Increase in the Plasma of Patients with Adult Respiratory Distress Syndrome as Linoleic Acid Appears to Fall

Gas chromatography-mass spectrometry has been applied to the analysis of plasma linoleic acid and one of its oxidation products, 4-hydroxy-2-nonenal (HNE), in adult patients with the acute respiratory distress syndrome (ARDS). Peak areas of total ion chromatograms showed there to be negative correlations between loss of linoleic acid and formation of HNE (measured by selective ion monitoring) in 7 out 10 patients studied. When HNE was quantitated by selective ion monitoring, with reference to a pure standard of HNE and an internal standard of nonanoic acid, ARDS patients showed significantly increased levels of HNE (0.412 ± 0.023 nmol/ml) compared with normal healthy controls (0.205 ± 0.018 nmol/ml).     

Binding of sulfosuccinimidyl fatty acids to adipocyte membrane proteins: Isolation and ammo-terminal sequence of an 88-kD protein implicated in transport of long-chain fatty acids

Summary We recently reported (Harmon et al., J. Membrane Biol. 124:261–268, 1991) that sulfo-N-succinimidyl derivatives of long-chain fatty acids (SS-FA) specifically inhibited transport of oleate by rat adipocytes. These compounds bound to an 85–90 kD membrane protein which was also labeled by another inhibitor of FA transport [³H]DIDS (4,4-diisothiocyanostilbene-2-2-sulfonate). These results indicated that the protein was a strong candidate as the transporter for long-chain fatty acids. In this report we determined that the apparent size of the protein is 88 kD and its isoelectric point is 6.9. We used [³H]SS-oleate (SSO), which specifically labels the 88-kD protein, to isolate it from rat adipocyte plasma membranes. Identification of 15 amino acids at the N-terminus region revealed strong sequence homology with two previously described membrane glycoproteins: CD36, a ubiquitous protein originally identified in platelets and PAS IV, a protein that is enriched in the apical membranes of lipidsecreting mammary cells during lactation. Antibody against PAS IV cross-reacted with the adipocyte protein. This, together with the N-terminal sequence homology, suggested that the adipocyte protein belongs to a family of related intrinsic membrane proteins which include CD36 and PAS IV.     

Segmental differences in short-chain fatty acid transport in rabbit colon: Effect of pH and Na

Short-chain fatty acids (SCFAs) are the predominant luminal anion in the mammalian colon. Although they are rapidly absorbed in vivo, little is known about the mechanisms of transepithelial transport in vitro. Previous studies have suggested that SCFA transport may be linked to Na absorption or an anion exchange mechanism. We compared the transport of propionate under short-circuit conditions in rabbit proximal and distal colon to determine whether there were segmental differences, how SCFAs may be linked to either Na absorption or anion transport, and whether SCFAs, as weak electrolytes, may be affected by transepithelial pH gradients. In distal colon, propionate transport was not significantly altered by stimulation of electrogenic Na absorption, epinephrine or Cl removal. However, a modest transepithelial pH gradient (luminal 6.8/serosal 7.4) stimulated propionate absorption. In proximal colon, propionate transport was significantly altered by manuevers that either stimulated (lowered [Na] in the bathing media) or inhibited (theophylline) apical Na−H exchange. Neither Cl removal, nor the anion exchange inhibitor DIDS, nor a transepithelial bicarbonate gradient, altered propionate transport. A transepithelial pH gradient inhibited propionate secretion, but not in a manner entirely consistent with the effect of pH on the distribution of a weak electrolyte. These results suggest that there is significant segmental heterogeneity in colonic SCFA transport; that transepithelial propionate fluxes are altered by changes in pH or electroneutral Na absorption (Na−H exchange), but not by chloride removal, bicarbonate gradients or electrogenic Na absorption. Regulation of SCFA transport may be an important factor in the physiology of colonic fluid balance.     

Decreased Electroconvulsive Shock-Induced Diacylglycerols and Free Fatty Acid Accumulation in the Rat Brain by Ginkgo biloba Extract (EGb 761): Selective Effect in Hippocampus as Compared with Cerebral Cortex

Abstract: The effect of Ginkgo biloba extract (EGb 761) treatment (100 mg/kg/day, per os, for 14 days) on electroconvulsive shock (ECS)-induced accumulation of free fatty acids (FFA) and diacylglycerols (DAG) was analyzed in rat cerebral cortex and hippocampus. EGb 761 reduced the FFA pool size by 33% and increased the DAG pool by 36% in the hippocampus. These endogenous lipids were unaffected in cerebral cortex. During the tonic seizure (10 s after ECS) the fast accumulation of FFA, mainly 20:4, was similar in sham- and EGb 761 -treated rats, in both the cerebral cortex and hippocampus. However, further accumulation of free 18:0 and 20:4, observed in the hippocampus of sham-treated rats during clonic seizures (30 s to 2 min after ECS), did not occur in EGb 761-treated animals. The rise in DAG content triggered in the cortex and hippocampus by ECS was delayed by EGb 761 treatment from 10 s to 1 min, when values similar to those in sham animals were attained. Moreover, in the hippocampus the size of the total DAG pool was decreased by 19% during the tonic seizure. At later times, DAG content showed a faster decrease in EGb 761-treated rats. By 2 min levels of all DAG acyl groups decreased to values significantly lower than in sham animals in both cortex and hippocampus. This study shows that EGb 761 treatment affects, with high selectivity, lipid metabolism and lipid-derived second messenger release and removal in the hippocampus, while affecting to a lesser extent the cerebral cortex.