The preparation and characterization of vitellogenin messenger RNA from rainbow trout (Salmo gairdneri).

Agarose-gel electrophoresis of polyadenylated RNA from livers of oestrogen-treated male rainbow trout revealed a major high-Mr species (7200 nucleotides), which is absent from the polyadenylated RNA isolated from hormonally unstimulated male trout liver. Translation in vitro of the RNA from oestrogen-treated males in a mRNA-dependent rabbit reticulocyte lysate produced a protein (Mr 200 000) that could be immunoprecipitated with antibodies against trout serum vitellogenin, but no immunoprecipitable protein was synthesized with RNA from control animals. DNA complementary to the RNA from oestrogen-stimulated and control male trout liver was synthesized and back-hybridized, with R0t1/2 of 3.8 X 10(-2) and 1 X 10(-1) mol X litre-1 X s for RNA from hormone-treated and control animals respectively. The 9% increase in the abundant mRNA after oestrogen stimulation is due to the induction of vitellogenin mRNA.     

Evidence for reverse cholesterol transport in vivo from liver endothelial cells to parenchymal cells and bile by high-density lipoprotein.

Acetylated low-density lipoprotein (acetyl-LDL), biologically labelled in the cholesterol moiety of cholesteryl oleate, was injected into control and oestrogen-treated rats. The serum clearance, the distribution among the various lipoproteins, the hepatic localization and the biliary secretion of the [3H]cholesterol moiety were determined at various times after injection. In order to monitor the intrahepatic metabolism of the cholesterol esters of acetyl-LDL in vivo, the liver was subdivided into parenchymal, endothelial and Kupffer cells by a low-temperature cell-isolation procedure. In both control and oestrogen-treated rats, acetyl-LDL is rapidly cleared from the circulation, mainly by the liver endothelial cells. Subsequently, the cholesterol esters are hydrolysed, and within 1 h after injection, about 60% of the cell- associated cholesterol is released. The [3H]cholesterol is mainly recovered in the high-density lipoprotein (HDL) range of the serum of control rats, while low levels of radioactivity are detected in serum of oestrogen-treated rats. In control rats cholesterol is transported from endothelial cells to parenchymal cells (reverse cholesterol transport), where it is converted into bile acids and secreted into bile. The data thus provide evidence that HDL can serve as acceptors for cholesterol from endothelial cells in vivo, whereby efficient delivery to the parenchymal cells and bile is assured. In oestrogen-treated rats the radioactivity from the endothelial cells is released with similar kinetics as in control rats. However, only a small percentage of radioactivity is found in the HDL fraction and an increased uptake of radioactivity in Kupffer cells is observed. The secretion of radioactivity into bile is greatly delayed in oestrogen-treated rats. It is concluded that, in the absence of extracellular lipoproteins, endothelial cells can still release cholesterol, although for efficient transport to liver parenchymal cells and bile, HDL is indispensable.     

Studies on the induction and biosynthesis of vitellogenin, an oestrogen-induced glycolipophosphoprotein

1. Oestrogen treatment induces the formation of a Ca(2+)-binding glycolipophosphoprotein, vitellogenin, in Xenopus laevis. 2. The incorporation of l-[4,5-(3)H]-leucine into vitellogenin in vivo and in vitro was observed 12-24h after hormone treatment and increased progressively up to 21 days after treatment. 3. Vitellogenin is shown to be the major protein component biosynthesized and released into the incubation medium in vitro by livers from oestrogen-treated animals. 4. The biosynthesis in vitro of vitellogenin was inhibited by cycloheximide and carbonyl cyanide m-chlorophenylhydrazone, stimulated by increased Ca(2+) concentrations and decreased by raising the incubation temperature from 22 to 37 degrees C. 5. Incorporation of labelled amino acids into vitellogenin began after approx. 2h. No lag phase was noted for the incorporation of labelled amino acids into total tissue proteins. 6. The incorporation of label from [(32)P]phosphate and [2-(14)C]acetate into the protein as well as into the lipid moiety of vitellogenin showed a lag phase similar to that noted for the incorporation of amino acids. 7. These results suggest that the release of vitellogenin into the incubation medium occurs about 2h after the initiation of its biosynthesis.     

Studies on the assembly and secretion of a multicomponent protein. The biosynthesis of vitellogenin, an oestrogen-induced glycolipophosphoprotein

1. Incorporation of [(32)P]P(i) and [(3)H]leucine into vitellogenin secreted in vitro by liver slices from oestrogen-treated Xenopus laevis is accompanied by a 2h lag; no lag is apparent for the incorporation into total tissue protein. 2. The addition of cycloheximide was found immediately to inhibit further incorporation of radioactive leucine into total tissue protein. The incorporation into secreted vitellogenin, however, continued for 2h after the addition of cycloheximide. 3. Pulse-labelling of liver slices with [(3)H]leucine for 30min, followed by a chase with a large excess of unlabelled leucine, resulted in the appearance of radioactivity in secreted vitellogenin from 90min after the end of the pulse period. 4. Evidence is presented which suggests that of the radioactivity from [(3)H]leucine incorporated into proteins by the liver of oestrogen-treated Xenopus some 70% is present in the single protein vitellogenin. 5. The incorporation of [(32)P]P(i) into vitellogenin followed a pattern identical with that found for [(3)H]leucine in the pulse-labelling experiments and this indicates that synthesis of the polypeptide chain and incorporation of P(i) are closely linked processes. 6. The cumulative evidence suggests that the 2h lag phase represents the time required for the assembly and secretion of this multicomponent protein.     

Purification and characterization of honey bee vitellogenin

A protocol has been developed for the purification of vitellogenin from the honey bee, Apis mellifera. Purification allows for the first characterization of a vitellogenin from the large order Hymenoptera. Hymenopteran vitellogenins are unusual among insect vitellogenins in that they contain only one type of apoprotein. The honey bee vitellogenin was isolated from hemolymph of honey bee queens by a combination of density gradient ultracentrifugation, ion-exchange chromatography, and affinity chromatography. The native vitellogenin particle is a very high density glycolipoprotein containing approximately 91% protein, 7% lipid, and 2% carbohydrate. Phospholipid and diacylglycerol are the major lipid components. The equilibrium density (1.28 g/ml) is the same as that for Manduca sexta vitellogenin, which contains a much higher proportion of lipid. The covalently bound carbohydrate moiety of the particle is high in mannose. The amino acid composition of vitellogenin is similar to those of vitellogenins from other insect species. The N-terminal amino acid sequence of the apoprotein was determined, the first such sequence for any insect vitellogenin. When analyzed by sodium dodecyl sulfate (SDS)-gel electrophoresis, A. mellifera vitellogenin resolved into a single band with an apparent Mr of 180,000. Gel filtration under reducing and native conditions yielded estimated Mr values of about 300,000.     

The formation of lipid-linked sugars as intermediates in glycoprotein synthesis in rabbit mammary gland

1. The incorporation of d-[1-(14)C]mannose, d-[2-(3)H]mannose and N-acetyl-d-[1-(14)C]-glucosamine into glycoproteins and lipid-linked intermediates of mammary explants obtained from lactating rabbits was studied. The amount of radioactivity incorporated into lipid-linked intermediates was very low compared with the incorporation into protein. Most of the radioactivity incorporated into the chloroform/methanol-soluble fraction was present as neutral lipid. Radioactivity from d-[2-(3)H]mannose was incorporated mainly into the fatty acid moiety, whereas radioactivity from d-[1-(14)C]mannose and N-acetyl-d-[1-(14)C]glucosamine was present in the glycerol moiety of triacylglycerol. 2. The labelled lipid-linked intermediate that was soluble in chloroform/methanol/water (10:10:3, by vol.) was partially characterized and was found to exhibit properties characteristic of an oligosaccharide linked to lipid via a pyrophosphate bridge. It migrated largely as a single zone of radioactivity on t.l.c. and was eluted from a column of DEAE-cellulose acetate as a single peak by 50mm-ammonium acetate. 3. The oligosaccharide moiety was released from the lipid by mild acid hydrolysis. The size of the oligosaccharide was estimated by paper chromatography to be 10 or 11 monosaccharide units. 4. d-[1-(14)C]Mannose was incorporated largely into glycopeptides with molecular weights in the range 40000-80000, as determined by polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. Label from N-acetyl-d-[1-(14)C]glucosamine was incorporated into a glycopeptide with an electrophoretic mobility identical with that of rabbit casein (mol.wt. 32000) as well as into glycopeptides of higher molecular weight. 5. Approx. 50% of the total radioactivity in the protein labelled from N-acetyl-d-[1-(14)C]glucosamine was present as galactosamine, a component of the carbohydrate portion of rabbit casein. No labelled galactosamine was present in the lipid-linked oligosaccharide labelled from N-acetyl-d-[1-(14)C]glucosamine. It thus appears that the lipid-linked oligosaccharide is not involved in the glycosylation of casein.     

Oestrogen-induced cholesterol and fatty acid biosynthesis in Xenopus laevis liver during vitellogenic response

1. Oestradiol-17β induces livers of Xenopus laevis (South African clawed toad) to synthesize and secrete into the serum large quantities of the egg-yolk-protein precursor, vitellogenin. The peak of this response occurs 9–16 days after hormone treatment [Dolphin, Ansari, Lazier, Munday & Akhtar (1971) Biochem. J. 124, 751–758]. It is now shown that 6 days after hormone treatment a 120–160-fold stimulation of the synthesis of cholesterol and fatty acid compared with control values occurred. 2. A cell-free system, derived from Xenopus liver, which synthesizes squalene and fatty acid is described. By using this system, several hundredfold stimulation of incorporation of [¹⁴C]acetate into squalene was recorded 6 days after the administration of oestradiol-17β, compared with a 3–4-fold stimulation of incorporation of [³H]mevalonate compared with control values. It is argued that oestradiol-17β must affect enzyme(s) catalysing step(s) between acetate and mevalonate in the biosynthetic pathway to cholesterol. 3. In incubation of liver slices in vitro, most of the lipid and cholesterol synthesized in response to the steroid hormone was associated with those subcellular fractions that contained membranes. Moreover, pulse-labelling experiments in vivo showed that 70% of this lipid and cholesterol was retained in the liver. The remainder appeared in the serum, where it was equally distributed between vitellogenin and vitellogenin-free serum. 4. G.l.c. analyses of the cholesterol content of liver microsomal fractions of Xenopus laevis indicated that the cholesterol content was at least 50% higher in microsomal fractions obtained from livers that had been exposed to oestradiol-17β. Meanwhile, g.l.c. analysis of the lipid moiety of secreted vitellogenin showed that up to 35% of its lipid was cholesterol.     

Influences of Nano-TiO2 on the chloroplast aging of spinach under light

The aim of this study was to investigate the biochemical effects of niacin and chromium(III)-chloride on serum lipid peroxidation, uric and sialic acids, and the extent of lipid peroxidation and glutathione levels in skin and lung tissues of hyperlipidemic rats. In this study, female Swiss albino rats, 12 mo old, were used. They were randomly divided into four groups. Group I animals were fed with a standard pellet diet and water ad libitium. Group II rats were fed with a standard pellet diet and were treated with a dose of 250 μg/kg body weight CrCI₃·6H₂O and 100 mg/kg body weight niacin, for 45 d, by the gavage technique. Group III rats were fed a lipogenic diet in which 2% cholesterol, 0.5% cholic acid, and 20% sunflower oil were added to the pellet chow. In addition, the animals in this group drank water containing 3% ethanol. This regime was maintained for 60 d. The rats in group IV were maintained in the same food and drink regime as the animals in group III. After 2 wk, the animals showed symptoms of hyperlipemia and they were treated with 250 μg/kg body weight CrCI₃·6H₂O and 100 mg/kg body weight niacin, by gavage, for 45 d. On d 60, the blood and the skin and lungs samples were taken from animals. In the hyperlipemic groups, a reduction of the lung glutathione level and an increase in serum, lung, and skin lipid peroxidation levels and in serum sialic and uric acid were observed. In rats treated with a combination of niacin and Cr(III), the skin and serum lipid peroxidation and the sialic and uric acid levels decreased while showing an increase of lung glutathione activity. These results suggest that niacin and Cr(III), when administered in combination, have a protective effect against skin and lung tissues damage as a result of hyperlipidemia.     

Effects of CaCl2 on viscosity of culture broth, and on activities of enzymes around the 2-oxoglutarate branch, in Bacillus subtilis CGMCC 2108 producing poly-(γ-glutamic acid)

CaCl(2) was used as a novel additive to enhance poly-(γ-glutamic acid) (γ-PGA) production by Bacillus subtilis strain CGMCC 2108. Addition of CaCl(2) to medium effectively reduced viscosity of culture broth, and increased consumption of extracellular glutamate by 11.4%, leading to γ-PGA yield of 9.07 g/l, compared to 7.88 g/l in control. CaCl(2) also increased activities of three key enzymes around the crucial 2-oxoglutarate branch of the γ-PGA biosynthesis pathway: isocitrate dehydrogenase (ICDH), glutamate dehydrogenase (GDH), and 2-oxoglutarate dehydrogenase complex (ODHC). In particular, GDH activity was increased more than 8-fold, indicating that more 2-oxoglutarate was directed to synthesis of glutamate, the substrate of γ-PGA. Interestingly, the molecular weight of γ-PGA remained constant regardless of CaCl(2) addition.     

Role of Acetyl-l-Carnitine in Rat Brain Lipogenesis: Implications for Polyunsaturated Fatty Acid Biosynthesis

Abstract: This study was undertaken to explore the metabolic fate of acetyl- l -carnitine in rat brain. To measure the flux of carbon atoms into anabolic processes occurring at regional levels, we have injected [1-¹⁴C]acetyl- l -carnitine into the lateral brain ventricle of conscious rats. After injection of [1-¹⁴C]acetyl- l -carnitine, the majority of radioactivity was recovered as ¹⁴CO₂ expired (60% of that injected). The percentage of radioactivity recovered in brain was 1.95, 1.60, 1.30, and 0.93% at 1, 3, 6, and 22 h, respectively. Radioactivity distribution in various lipid components indicated that the fatty acid moiety of phospholipid contained the majority of radioactivity. The radioactive profile of these fatty acids showed that the acetyl moiety of acetyl- l -carnitine was incorporated into saturated (60%), monounsaturated (15%), and polyunsaturated (25%) fatty acids [mainly present in 20:4 (5.2%) and 22:6 (7.8%)]. Injection in the brain ventricle of radioactive glucose, the major source of acetyl-CoA in the CNS, revealed that glucose was a precursor of saturated (85%) and monounsaturated (15%) but not of polyunsaturated fatty acids. Thus, this study demonstrated distinct fates of glucose and acetyl- l -carnitine following intracerebroventricular injection. In summary, these data implicate acetyl- l -carnitine as an important member of a complex acetate trafficking system in brain lipid metabolism.     

Serum lipoproteins in the spiny lobster, Panulirus interruptus.

1. Most of the lipids in the hemolymph of the spiny lobster, Panulirus interruptus, were associated with a high density lipoprotein (HDL3). The lipid of this lipoprotein was composed of phospholipid (88%), sterol (4%) and triglyceride (3%). 2. In animals fed 14C-labeled triglyceride radioactivity was not seen in the serum until 12 hr after feeding. Most of this serum radioactivity was associated with phosphatidyl choline. 3. Electron micrographs showed that negatively stained high density lipoproteins of the lobster had a polymorphic appearance.     

Transport, utilization and biliary secretion of lysophosphatidylcholine in the rat liver

The hepatic uptake, transport and utilization of plasma lysophosphatidylcholine (lysoPC) and its contribution to biliary lipid secretion have been investigated in bile-fistula rats. The animals were given a single intravenous dose of sn-1-[1-14C]palmitoyl-lysoPC, under constant intravenous sodium taurocholate infusion (1 mumol/min), and the fate of the label was followed in blood, bile and liver for up to 3 h. The livers were excised at given time points, extracted and/or homogenized to determine the lipid distribution and subcellular location of radioactivity. LysoPC was rapidly cleared from plasma, though a consistent fraction of the label persisted in plasma over the experimental time-period in the form of either lysoPC or PC. Recovery of radioactivity in the liver varied from 15.6% after 5 min to 19.5% after 3 h. Hepatic lysoPC underwent rapid microsomal acylation to form specific PC molecular species (mainly 16:0-20:4 and, to a lesser extent, 16:0-18:2 and 16:0-16:1). Ultrafiltration, dialysis and gel-chromatographic analyses of cytosolic fractions (post 105,000 X g supernatants) indicated that lysoPC is transported to the site of acylation mostly as a macromolecular aggregate with an approx. Mr of 14,400. Small amounts of radioactivity were secreted into bile over 3 h (20% in the form of lysoPC and the remainder as 16:0-18:2 and 16:0-20:4 PC species). Plasma lysoPC, taken up by the liver, is mostly transported by a cytosolic carrier with a molecular weight close to fatty-acid-binding proteins; it then enters a distinct acylation pathway, selective for some polyunsaturated-PC species and does not contribute significantly to biliary secretion, either directly, or through its products.     

Retention of 45Ca in rats and lambs associated with the onset of nutritional muscular dystrophy.

Nutritional myopathy has been induced in both rats and lambs by feeding diets low in selenium. The distribution of 45Ca, administered as 45CaCl2, has been examined firstly by autoradiography, and secondly by measuring the excretion of 45Ca in urine and faeces. Autoradiographs of skeletal muscle from unsupplemented animals showed radioactivity over discrete muscle fibres at a stage when no abnormalities were apparent using conventional staining techniques. Similar retention of 45Ca was found in some of the tubules in the kidneys of selenium-deficient rats. Total excretion in urine and faeces of lambs, examined for 48 h after intravenous administration of 45CaCl2, showed that in normal animals 18-6% of the dose was excreted, whereas in dystrophic lambs 12-0% was lost. The difference was significant at the 2% level. The respiratory rates of isolated skeletal muscle mitochondria, measured polarographically in the presence of glutamate and pyruvate as substrates, were low for dystrophic rats. Respiratory control indices were 1-0 for the same preparations but for supplemented rats they were all above 1-0. The differences in respiratory rates were significant at the 1% level. The major conclusion drawn from the results of these experiments is that one of the first effects of sleenium deficiency which can be visualized is the abnormal retention of calcium by individual muscle fibres.     

Isolation and Characterization of a Proteolipid in Defatted Soybean Meals

A proteolipid was isolated from the chloroform–methanol (2:1, by vol.) extract of defatted soybean meals by a modified Folch method. The proteolipid gave a yield of 0.05% of the defatted meals, and the ratio of protein and lipid was neary 3:4. The complex gave a single band containing both protein and lipid on polyacrylamide gel electrophoresis. TLC analysis of the lipid moiety showed that the major components were glycolipids and phospholipids. The protein moiety contained more hydrophobic amino acids and less acidic amino acids in comparison with the amino acid composition of soybean globulin. The protein moiety contained two kinds of protein component (I and II) which have molecular weights of 13,000 (I) and 15,000 (II) on SDS-urea polyacrylamide gel electrophoresis, and N-terminal amino acids of alanine (I) and glutamic acid (II). The apoprotein is a new protein and different from the whey proteins or globulins of soybean.     

Biosynthesis of murein lipoprotein in Escherichia coli: effects of 3,4-dihydroxybutyl-1-phosphonate.

The effects of 3,4-dihydroxybutyl-1-phosphonate, a four-carbon analog of sn-glycerol 3-phosphate, on the biosynthesis of the glyceryl moiety in murein lipoprotein of Escherichia coli were studied. The compound at a concentration of 55 microM strong inhibits in the incorporation of [2-3H]glycerol radioactivity into lipoprotein by virtue of its inhibition of the synthesis of phosphatidylglycerol. On the other hand, the incorporation of prelabeled [2-3H]glycerol radioactivity into lipoprotein was only partially inhbited by 3,4-dihydroxybutyl-1-phosphonate even at a much higher concentration (1 mM). These data were consistent with the postulated pathway for the biosynthesis of the lipid moiety in lipoportein: cysteine-lipoprotein + phosphatidylglycerol leads to glycerylcystein-lipoprotein + phosphatidic acid.     

Preferential In Vivo Incorporation of [3H]Arachidonic Acid from Blood into Rat Brain Synaptosomal Fractions Before and After Cholinergic Stimulation

Abstract: Awake adult male rats were infused intravenously with [³H]arachidonic acid for 5 min, with or without prior administration of an M1 cholinergic agonist, arecoline (15 mg/kg i.p.). Methylatropine was also administered (4 mg/kg s.c.) to control and arecoline-treated animals. At 15 min postinfusion, the animals were killed, brains were removed and frozen, and subcellular fractions were obtained from homogenates of whole brain. Total radioactivity and radioactivity in various lipid classes were determined for each fraction following normalization for exposure by use of a unidirectional incorporation coefficient, k ^⋆_brain. In control animals, incorporation was greatest in synaptosomal and microsomal fractions, accounting for 50 and 30% of total label incorporated into membrane lipids, respectively. Arecoline increased incorporation in these two fractions by up to 400% but did not increase incorporation into the myelin, mitochondrial, or cytosolic fractions. Of the incorporated radioactivity, 50–80% was in phospholipid in microsomal and synaptosomal fractions, indicating that phospholipid is the major lipid affected by cholinergic stimulation. These results demonstrate that plasma [³H]arachidonic acid is preferentially incorporated into phospholipids of synaptosomal and microsomal fractions of rat brain. Cholinergic stimulation increases incorporation into these fractions, likely by activation of phospholipase A₂ and/or C in association with acyltransferase activity. Thus, intravenously infused radiolabeled arachidonic acid can be used to examine synapse-mediated changes in brain phospholipid metabolism in vivo.     

响应面法优化酿酒酵母产油脂条件

运用响应面法对酿酒酵母(Saccharomyces cerevisiae)产油脂以及发酵条件优化进行了研究。首先根据单因素实验结果,利用Plackett-Burman设计对影响其产油脂相关因素进行评估并筛选出具有显著效应的3个因素:柠檬酸,CaCl2和初始pH值。接着用最陡爬坡试验逼近以上3个因子的最大响应区域后,采用Box-Behnken设计以及响应面分析法,确定其优化后发酵条件为(w/v):葡萄糖15%,蛋白胨0.2%,酵母浸粉0.4%,柠檬酸0.471%,MgSO4·7H2O0.1%,ZnSO4·7H2O0.2%,CaCl20.025%,FeSO4·7H2O0.005%,初始pH值为6.74,180r/min,30°C培养96h。优化后的油脂产率(干重)达到14.55%,比在种子培养基中油脂产率4.76%提高了2倍左右。     

Effects of ethynyloestradiol on the metabolism of [1-14C]-oleate by perfused livers and hepatocytes from female rats

Normal female rats were given 15mug of ethynyloestradiol/kg body wt. for 14 days and were killed on day 15 after starvation for 12-14h. The livers were isolated and were perfused with a medium containing washed bovine erythrocytes, bovine serum albumin, glucose and [1-(14)C]oleic acid; 414mumol of oleate were infused/h during a 3h experimental period. The output of bile and the flow of perfusate/g of liver were decreased in livers from animals pretreated with ethynyloestradiol, whereas the liver weight was increased slightly. The rates of uptake and of utilization of [1-(14)C]oleate were measured when the concentration of unesterified fatty acid in the perfusate plasma was constant. The uptake of unesterified fatty acid was unaffected by pretreatment of the animal with oestrogen; however, the rate of incorporation of [1-(14)C]oleate into hepatic and perfusate triacylglycerol was stimulated, whereas the rate of conversion into ketone bodies was impaired by treatment of the rat with ethynyloestradiol. Pretreatment of the rat with ethynyloestradiol increased the output of very-low-density lipoprotein triacylglycerol, cholesterol, phospholipid and protein. The production of (14)CO(2) and the incorporation of radioactivity into phospholipid, cholesteryl ester and diacylglycerol was unaffected by treatment with the steroid. The net output of glucose by livers from oestrogen-treated rats was impaired despite the apparent increased quantities of glycogen in the liver. The overall effect of pretreatment with oestrogen on hepatic metabolism of fatty acids is the channeling of [1-(14)C]oleate into synthesis and increased output of triacylglycerol as a moiety of the very-low-density lipoprotein, whereas ketogenesis is decreased. The effect of ethynyloestradiol on the liver is apparently independent of the nutritional state of the animal from which the liver was obtained. It is pertinent that hepatocytes prepared from livers of fed rats that had been treated with ethynyloestradiol produced fewer ketone bodies and secreted more triacylglycerol than did hepatocytes prepared from control animals. In these respects, the effects of the steroid were similar in livers from fed or starved (12-14h) rats. Oestrogens may possibly inhibit hepatic oxidation of fatty acid, making more fatty acid available for the synthesis of triacylglycerol, or may stimulate the biosynthesis of triacylglycerol, or may be active on both metabolic pathways.     

THE INCORPORATION OF [1-14C]LINOLENATE INTO LIPIDS OF DEVELOPING RAT BRAIN DURING ESSENTIAL FATTY ACID DEPRIVATION

Abstract— Twenty-one-day old essential fatty acid (EFA) deprived rats incorporated about twice the radioactivity from [1-¹⁴C]linolenate into brain lipid fractions as did controls. At 5 min after injection, 2/3 of the radioactivity was associated with the less polar lipid fraction of both control and EFA deprived animals. By 30 min after injection, 70% of the radioactivity was in the phospholipid fraction. This value increased to 90% at later time points.
The specific activity of brain phospholipids from EFA deprived rats was always greater than that of controls. This held true for the individual phosphatide fractions also. In general, phosphatidylcholine (PC) was labeled most rapidly. With increasing time intervals, radioactivity was transferred to phospha-tidylethanolamine (PE) and phosphatidylserine + phosphatidylinositol (PS + PI).
The transfer of fatty acid radioactivity into phospholipid and the distribution of radioactivity among individual phosphatides did not appear to be affected by the dietary state. However, the total amount of radioactivity incorporated was related to the amount initially retained by brain after injection. Our data suggest that one or more components of the less polar lipid fraction may act as a 'trap' or reservoir for fatty acids which are required for phospholipid synthesis.     

Flight-oogenesis syndrome in a blood-sucking bug: biochemical aspects of lipid metabolism

Lipophorin (Lp), either labeled in diacylglycerol moiety with [(3)H]-Palmitic acid or in phospholipid moiety with (32)Pi, was injected into Rhodnius prolixus females. Insects were induced to flight for different times. In just a few minutes of flight, the transfer of radioactivity to ovaries decreased, accompanied by its increase to flight muscles. After one hour of flight, Lp density was higher (1.132 g/mL) than before flight (1.116 g/mL). Lp purified from insects after flight was analyzed by gel filtration chromatography and a polyacrylamide gel pore limit electrophoresis. Both analyses demonstrated a decrease in Lp molecular mass after flight but no changes in apoLp-III amounts were observed. Time-course experiments showed that only 30 min of flight are required for the detection of changes in Lp density and molecular mass. About the same time of rest is necessary for Lp density and molecular mass to return to the baseline value. The lipid content from Lp particles, determined by high-performance thin-layer chromatography (HPTLC), showed a decrease in total lipids after flight. At the same time, an increase of many classes of lipids was observed in flight muscles except for triacylglycerol, which was reduced. The increase of flight muscle lipids was accompanied by a decrease of the ovaries lipid content. The insects subjected to daily exhaustive flight showed a significant decrease in total number of eggs produced. But insects subjected to a single exhaustive flight showed only a small reduction in total number of eggs. Lp density variation during the flight activity of Rhodnius prolixus females is discussed in association with physiological events such as oogenesis.