Synaptic Vesicle Ultrastructural Changes in the Rat Hippocampus Induced by a Combination of α-Linolenate Deficiency and a Learning Task

Abstract: Rats fed either a safflower oil (α-linolenate-deficient) or a perilla oil (α-linolenate-sufficient) diet through two generations (F1) showed significant differences in the brightness-discrimination learning task. In this task, correct responses were lever-pressing responses, which were reinforced with dietary pellets, and incorrect responses were those with no reinforcement. The inferior learning performance in the safflower oil group was caused mainly by the inferior ability to rectify the incorrect responses through the learning sessions. In the safflower oil group after the learning task, the average densities of synaptic vesicles in the terminals of the hippocampus CA1 region were decreased by nearly 30% as compared with those in the perilla oil group, and it is notable that this difference was not detected without the learning task. These results suggest that dietary oil-induced morphological changes in synapses in the hippocampus of rats are related to the differential learning performance and that the turnover rate of synaptic vesicles in the hippocampus may be an important factor affecting learning performance.     

Effect of the dietary alpha-linolenate/linoleate balance on lipid compositions and learning ability of rats. II. Discrimination process, extinction process, and glycolipid compositions

Donryu strain rats through two generations were fed semi-purified diets supplemented with safflower seed oil (rich in linoleic acid) or with perilla seed oil (rich in alpha-linolenic acid), or a conventional laboratory chow (normal control diet). Brightness-discrimination learning ability was determined to be the highest in the perilla oil-fed group, followed by the normal group, and then by the safflower group, extending our earlier observation in a different strain of rat that alpha-linolenic acid is a factor in maintaining high learning ability (Yamamoto, N., M. Saitoh, A. Moriuchi, M. Nomura, and H. Okuyama. 1987. J. Lipid Res. 28: 144-151). After the brightness-discrimination learning test was administered, extinction of learning was measured. The time required for extinction was significantly longer in the safflower group than in either the perilla group or the normal diet group. Thus, the dietary alpha-linolenate/linoleate balance affected both the learning and the extinction of learning. The glycolipids of the cerebrum, cerebellum, and olfactory lobe were analyzed. Although the fatty acid compositions of the sulfatide and gangliosides were significantly different in the three parts of the brain, relatively little difference was observed in the fatty acids of glycolipids between the safflower group and the perilla group, suggesting that gross changes in brain glycolipids are not responsible for the differences in learning abilities between these dietary groups.     

Occurrence and Properties of Phospholipases A1 of Plasma Membranes Prepared from Neuronal- and Glial-Enriched Fractions of the Rabbit Cerebral Cortex

Abstract: Exogenously added glycerophosphatides, specifically radioactively labelled either in the 1 or in the 2 position, were used to investigate the occurrence and properties of phospholipase A₁ in plasma membranes prepared from neuronal- and glial-enriched fractions of rabbit brain. Phospholipase A₁ activity was maximal at pH values ranging between 8.0 and 9.0 for the plasma membranes of both cell types. The enzyme activity was most abundant in the microsomal fraction, with a neurondglial ratio of about 2. The plasma membranes displayed about half the enzymic activity of the microsomal fraction, whereas only small amounts of phospholipase A₁ were present in the neuronal and glial mitochondria. Investigations on the substrate specificity showed a different pattern for the enzyme of neuronal and glial origin. The release of labelled fatty acids from phosphatidylcholine by the neuronal plasma membrane phospholipase A₁ decreased with increasing degree of unsaturation of the fatty acids at the 1 position. The presence of plasmalogens and plasmalogen precursors in the incubation mixture appreciably inhibited the hydrolysis of the corresponding diacyl compounds.     

Effect of dietary alpha-linolenate/linoleate balance on brain lipid compositions and learning ability of rats

Spontaneously hypertensive rats (SHR) and normotensive control, Wistar/Kyoto (WKY) rats through two generations were fed a semipurified diet supplemented either with safflower oil (rich in linoleate) or with perilla oil (rich in alpha-linolenate). The cerebral lipid contents and phospholipid compositions did not differ between the two dietary groups of SHR rats. There were also no differences in the unsaturated/saturated ratios of individual phospholipids or the proportions of plasma-logens. However, the proportions of (n-3) and (n-6) fatty acids were significantly different. Decreases in the proportions of docosahexaenoate [22:6 (n-3)] in phosphatidylethanolamine and phosphatidylserine in the safflower oil group were compensated for with increases in the proportions of docosatetraenoic [22:4 (n-6)] and docosapentaenoic [22:5 (n-6)] acids as compared with the perilla oil group. These differences in phospholipid acyl chains were much smaller than the difference in the proportions of linoleate and alpha-linolenate of the diets. In a brightness-discrimination learning test, the total number of responses to the positive and negative stimuli were less in the groups fed perilla oil. However, the alpha-linolenate-deficient group took longer to decrease the frequency of R- responses and therefore longer to learn the discrimination. Consequently, the correct response ratios were higher in the perilla oil groups than in the safflower oil groups. Thus, the dietary alpha-linolenate/linoleate balance influenced the (n-3)/(n-6) balance of polyenoic fatty acids differently among brain phospholipids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative effects of perilla and fish oils on the activity and gene expression of fatty acid oxidation enzymes in rat liver

The activity and mRNA level of hepatic enzymes in fatty acid oxidation and synthesis were compared in rats fed diets containing either 15% saturated fat (palm oil), safflower oil rich in linoleic acid, perilla oil rich in α-linolenic acid or fish oil rich in eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) for 15 days. The mitochondrial fatty acid oxidation rate was 50% higher in rats fed perilla and fish oils than in the other groups. Perilla and fish oils compared to palm and safflower oils approximately doubled and more than tripled, respectively, peroxisomal fatty acid oxidation rate. Compared to palm and safflower oil, both perilla and fish oils caused a 50% increase in carnitine palmitoyltransferase I activity. Dietary fats rich in n-3 fatty acids also increased the activity of other fatty acid oxidation enzymes except for 3-hydroxyacyl-CoA dehydrogenase. The extent of the increase was greater with fish oil than with perilla oil. Interestingly, both perilla and fish oils decreased the activity of 3-hydroxyacyl-CoA dehydrogenase measured using short- and medium-chain substrates. Compared to palm and safflower oils, perilla and fish oils increased the mRNA level of many mitochondrial and peroxisomal enzymes. Increases were generally greater with fish oil than with perilla oil. Fatty acid synthase, glucose-6-phosphate dehydrogenase, and pyruvate kinase activity and mRNA level were higher in rats fed palm oil than in the other groups. Among rats fed polyunsaturated fats, activities and mRNA levels of these enzymes were lower in rats fed fish oil than in the animals fed perilla and safflower oils. The values were comparable between the latter two groups. Safflower and fish oils but not perilla oil, compared to palm oil, also decreased malic enzyme activity and mRNA level. Examination of the fatty acid composition of hepatic phospholipid indicated that dietary α-linolenic acid is effectively desaturated and elongated to form EPA and DHA. Dietary perilla oil and fish oil therefore exert similar physiological activity in modulating hepatic fatty acid oxidation, but these dietary fats considerably differ in affecting fatty acid synthesis.     

Activation of Ethanolamine Phospholipase A2 in Brain During Ischemia

Abstract: Extracts of acetone-dried powders from ischemic gerbil brain were examined for phospholipase A₁ and A₂ activities with phosphatidylethanolamine at pH 7.2. Ischemia was induced by bilateral ligation, and the animals were killed by immersion into liquid nitrogen. Bilateral ligation with ketamine as general anesthetic resulted in a rapid, transient increase in phospholipase A₂ activity. The activity increased from 0.46 nmolihimg protein at 0 time to 0.82 nmol/h/mg protein at 1 min of ligation. Phospholipase A₁ activity also increased from 0.7 to 1.3 nmol/h/mg protein within the 1st min. When Nembutal was used as anesthetic, the phospholipase activation was earlier, within the first 30 s. Similar results were found for ischemia induced by decapitation of Wistar rats without anesthesia. Bilateral ligation of the carotid arteries of the gerbil is known to increase the concentration of free fatty acids, particularly arachidonate. This increase is, at least in part, due to phospholipase A activation. As ethanolamine phospholipase A₂ in brain does not require Ca²⁺ for activity, these results suggest that phospholipase A₂ activation in ischemic brain results from a covalent modification of the enzyme.     

Catabolism of N-Acylethanolamine Phospholipids by Dog Brain Preparations

Abstract: N -Acylphosphatidylethanolamine, incubated with dog brain homogenate or microsomes, was hydroyzed to phosphatidic acid and N -acylethanolamine by a phosphodiesterase of the phospholipase D type. In the absence of F⁻, phosphatidic acid was further hydrolyzed to diacylglycerol and P_i while N -acylethanolamine was hydrolyzed by an amidase to fatty acid and ethanolamine. The phosphodiesterase showed an alkaline pH optimum and was also active towards N -acetylphosphatidyletha-nolamine, N -acyl-lysophosphatidylethanolamine, and glycerophospho( N -acyl)ethanolamine but showed little activity toward phosphatidylethanolamine and phosphati-dylcholine. Ca²⁺ stimulated slightly at low concentrations but inhibited at higher concentrations. Triton X-100 stim ulated the hydrolysis of N -acylphosphatidylethanol-amine, inhibited that of N -acyl-lysophosphatidyletha-nolamine and glycerophospho( N -acyl)ethanolamine, and had no effect on phosphatidylethanolamine or phospha-tidylcholine hydrolysis. The N -acylethanolamine hydrolase (amidase) was also present in the microsomal fraction and exhibited a pH optimum of 10.0. In addition to hydrolysis by the phosphodiesterase, N -acylphosphati-dylethanolamine was also catabolized by microsomal phospholipases A₁ and/or A₂ to N -acyl-lysophosphati-dylethanolamine, some of which was further hydrolyzed to glycerophospho( N -acyl)ethanolamine.     

Modulation of plasma membrane H+-ATPase from oat roots by lysophosphatidylcholine, free fatty acids and phospholipase A2

Plasma membrane vesicles were purified from 8-day-old oat ( Avena sativa L. cv. Brighton) roots in an aqueous polymer two-phase system. The plasma membranes possessed high specific ATPase activity [ca 4 μmol P₁ (mg protein)⁻¹ min⁻¹ at 37°C]. Addition of lysophosphatidylcholine (lyso-PC) produced a 2–3 fold activation of the plasma membrane ATPase, an effect due both to exposure of latent ATP binding sites and to a true activation of the enzyme. Lipid activation increased the affinity for ATP and caused a shift of the pH optimum of the H⁺ -ATPase activity to 6.75 as compared to pH 6.45 for the negative H⁺-ATPase. Activation was dependent on the chain length of the acyl group of the lyso-PC, with maximal activition obtained by palmitoyl lyso-PC. Free fatty acids also activated the membrane-bound H⁺-ATPase. This activation was also dependent on chain length and to the degree of unsaturation, with linolenic and arachidonic acid as the most efficient fatty acids. Exogenously added PC was hydrolyzed to lyso-PC and free fatty acids by an enzyme in the plasma membrane preparation, presumably of the phospholipase A type. Both lyso-PC and free fatty acids are products of phospholipase A₂ (EC 3.1.1.4) action, and addition of phospholipase A₂ from animal sources increased the H⁺-ATPase activity within seconds. Interaction with lipids and fatty acids could thus be part of the regulatory system for H⁺-ATPase activity in vivo, and the endogenous phospholipase may be involved in the regulation of the H⁺-ATPase activity in the plasma membranne.     

Effect of dietary alpha-linolenate on platelet-activating factor production in rat peritoneal polymorphonuclear leukocytes.

The effects of dietary alpha-linolenate (18:3, n-3) and linoleate (18:2, n-6) on platelet-activating factor (PAF) production were examined. Rats were fed an alpha-linolenic acid-rich (perilla oil) diet or a linoleic acid-rich (safflower oil) diet for 6 wk, and polymorphonuclear leukocytes (PMN) were elicited by peritoneal injection of casein. The overall phospholipid content and composition as well as the subclass distribution of choline and ethanolamine glycerophospholipids in PMN were not altered by these diets. However, with the perilla oil diet their content of a putative precursor of PAF, 1-alkyl-2-arachidonoyl-sn-glycero-3-phosphocholine was approximately 50% of that with safflower oil diet. On exposure to various concentrations of FMLP, PAF formation by PMN in the perilla oil group was less than 50% of that by PMN in the safflower oil group. A larger difference in PAF productions by PMN in the two dietary groups was observed on their stimulation with calcium ionophore A23187. These results demonstrate that PAF production is modulated in some as yet unknown way by changing the alpha-linolenate/linoleate balance of the diet.     

Effect of glutamate intake during gestation on adenosine A(1) receptor/adenylyl cyclase pathway in both maternal and fetal rat brain

Pregnant Wistar rats were orally treated with 1 g/L l -glutamate during the entire gestational period and the status of adenosine A₁ receptor (A₁R)/adenylyl cyclase transduction pathway from maternal and fetal brain was analyzed. Glutamate consumption, estimated from the loss of water from the drinking bottles, was 110 ± 4.6 mg/kg/day. In mother brains glutamate intake did not significantly alter the B _max value, although the K _d value was significantly decreased. However in fetus brain, a significant decrease in B _max was observed, without an alteration of K _d value. Similar results were observed by western blot assays using specific A₁R antibody, suggesting a down-regulation of A₁R in fetal brain. Concerning α subunits of inhibitory G proteins (Gi), αGi₃ protein was slightly but significantly decreased in maternal brain without alterations of either Gi₁ or Gi₂. In contrast, αGi₁ and αGi₂ isoforms were increased in fetal brain. On the other hand, basal, forskolin, and forskolin plus GTPγS-stimulated adenylyl cyclase activity was significantly decreased in both maternal and fetal brain, and this was more prominent in fetal than in maternal brain. Finally, A₁R functionality was significantly decreased in mother brain whereas no significant differences were detected in fetus brain. These results suggest that glutamate administered to pregnant rats modulates A₁R signaling pathways in both tissues, showing an A₁R down-regulation in fetal brain, and desensitization in maternal brain.     

Coupling Among Energy Failure, Loss of Ion Homeostasis, and Phospholipase A2 and C Activation During Ischemia

Abstract— The objective of the present experiments was to correlate changes in cellular energy metabolism, dissipative ion fluxes, and lipolysis during the first 90 s of ischemia and, hence, to establish whether phospholipase A₂or phospholipase C is responsible for the early accumulation of phospholipid hydrolysis products. Ischemia was induced for 15–90 s in rats, extracellular K⁺ (K⁺_e) was recorded, and neocortex was frozen in situ for measurements of labile tissue metabolites, free fatty acids, and diacylglycerides. Ischemia of 15-and 30-s duration gave rise to a decrease in phosphocreatine concentration and a decline in the ATP/free ADP ratio. Although these changes were accompanied by an activation of K⁺ conductances, there were no changes in free fatty acids until after 60s, when free arachidonic acid accumulated. An increase in other free fatty acids and in total diacylglyceride content did not occur until after anoxic depolarization. The results demonstrate that the early functional changes, such as activation of K⁺ conductances, are unrelated to changes in lipids or lipid mediators. They furthermore suggest that the initial lipolysis occurs via both phospholipase A₂ and phospholipase C, which are activated when membrane depolarization leads to influx of calcium into cells.     

Reversibility of n-3 fatty acid deficiency-induced alterations of learning behavior in the rat: level of n-6 fatty acids as another critical factor

Rats fed a semipurified diet supplemented with 3% (w/w) safflower oil [Saf, n-3 fatty acid deficient, high linoleic acid (18:2n-6)] through two generations exhibit decreased correct response ratios in a brightness-discrimination learning test compared with rats fed 3% perilla oil [Per, high alpha-linolenic acid (18:3n-3)]. This is associated with a decreased DHA (22:6n-3)-to-arachidonic acid (20:4n-6) ratio in brain lipids. In the first set of experiments, dietary oil was shifted from Saf to a mixture of 2.4% safflower oil plus 0.6% DHA after weaning (Saf-DHA), but all parameters measured in the learning test were essentially unchanged. Brain 22:6n-3 content of the Saf-DHA group reached that of the Per group but the levels of 20:4n-6 and docosatetraenoic acid (22:4n-6) did not decrease to those of the Per group at the start of the test. In the second set of experiments, dietary oil was shifted to a mixture of 0.6% safflower oil plus 1.2% oleic acid (OA) plus 1.2% DHA (Saf-OA-DHA group) with 18:2n-6 content comparable to that of the Per group. The Saf-OA-DHA group exhibited a learning performance similar to that of the Per group; brain 22:6n-3, 20:4n-6, and 22:4n-6 contents were also comparable to those of the Per group. These results indicate that the altered learning behavior associated with a long-term n-3 fatty acid deficiency is reversed by supplementing 22:6n-3 after weaning, when the levels of competing n-6 fatty acids in the diet and brain lipids are limited.     

Effect of dietary alpha-linolenate/linoleate balance on mean survival time, incidence of stroke and blood pressure of spontaneously hypertensive rats

Following the suckling period, stroke-prone spontaneously hypertensive rats (SHR-SP) were fed semi-purified diets supplemented either with safflower seed oil (rich in linoleic acid) or with perilla seed oil (rich in alpha-linolenic acid). The mean survival time of male SHR-SP fed the perilla diet was longer than that fed the safflower diet by 17% (p less than 0.001) while the difference was 15% in female SHR-SP (p less than 0.05). The mean survival times of female SHR-SP were more than 40% longer than those of male SHR-SP in both dietary groups. Post-mortem examinations of brains revealed apoplexy-related symptoms as the major cause of the death in both dietary groups. The systolic blood pressure was lower by ca. 10% (21 mmHg) in the perilla group than in both the safflower group and conventional diet group. The eicosapentaenoate (20:5 n-3)/arachidonate (20:4 n-6) ratio of platelet phospholipids in spontaneously hypertensive rat (SHR), a measure of platelet aggregability, was much higher in the perilla group than in the safflower group. Thus, increasing the dietary alpha-linolenate/linoleate ratio resulted in an increased mean survival time of SHR-SP rats, possibly by lowering blood pressure and platelet aggregability.     

Effect of the dietary alpha-linolenate/linoleate balance on leukotriene production and histamine release in rats

Rats were fed semi-purified diets supplemented either with safflower seed oil rich in linoleate (18:2n-6) or with perilla seed oil rich in alpha-linolenate (18:3n-3) through two generations. In the major phospholipids of polymorphonuclear leukocytes (PMNs), the proportions of n-6 polyunsaturated fatty acids (18:2, 20:4, 22:4 and 22:5) were higher but those of n-3 acids (20:5, 22:5 and 22:6) were lower in the safflower group than in the perilla group. When stimulated with a calcium ionophore, the PMNs from the safflower group produced 27% more leukotriene (LT)B4 than those from the perilla group. The formation of LTB5 which has biological activities less than 1/10 those of LTB4, was negligible in the safflower group but was 40 ng/10(7) PMN cells in the perilla group. The amount of the total LTB formed in the perilla group tended to be more than in the safflower group. The formation of SRS-A (slow-reacting substances of anaphylaxis) by PMNs was determined by measuring the spasmogenic activities of LTs on guinea pig ileum. SRS-A activity was 59% higher in the safflower group than in the perilla group. In contrast, histamine release from rat peritoneal mast cells was not significantly different between the two groups. Thus, the increasing the alpha-linolenate/linoleate ratio of diets results in the decreased formation of LTs derived from 20:4n-6 in PMNs. This may be beneficial in lowering the severity of allergic and inflammatory responses caused by LTs, and thereby shifting the pathological symptoms to normal self-defense mechanism.     

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.     

Influence of dietary fat on the activities of subcellular membrane-bound enzymes from different regions of rat brain

The effect of different dietary fats with varying degrees of unsaturation and essential fatty acid composition, which are commonly consumed in India, on the activity of some important membrane-bound enzymes was assessed in different brain regions of rat. Four groups of male CFY weanling rats were fed nutritionally adequate diets containing groundnut, coconut, safflower or mustard oil as fat source at 20% level for 16 weeks. The synaptosomal, microsomal and myelin membranes were prepared from three brain regions, viz., cerebrum, cerebellum and brain stem from each group. The activities of Na⁺, K⁺-ATPase, Mg²⁺-ATPase and acetylcholinesterase were assayed and the fatty acid composition was determined in these subcellular membrane fractions. The safflower oil-fed group showed higher Na⁺, K⁺-ATPase activity in most membrane fractions.than the coconut or mustard oil-fed groups. The Mg²⁺-ATPase activity was found to be similar amongst all groups in all the brain regions. The synaptosomal acetylcholinesterase activity was distinctly higher in coconut and groundnut oil-fed groups when compared to safflower or mustard oil consuming groups. Alterations in the activities of these subcellular membrane-bound enzymes are expected to exert a significant impact on the electrophysiological and metabolic functions of brain. Results of the present study show that depending on the nature of dietary fat the fatty acid composition of subcellular membranes is altered, which in turn could regulate the activity of membrane-bound enzymes that are vital for brain function.     

Mice Deficient in Group IV Cytosolic Phospholipase A2 Are Resistant to MPTP Neurotoxicity

Abstract: Phospholipase A₂ (PLA₂) enzymes are critical regulators of prostaglandin and leukotriene synthesis, and they may also play an important role in the generation of intracellular free radicals. The group IV cytosolic form of phospholipase A₂ (cPLA₂) is regulated by changes in intracellular calcium concentration, and the enzyme preferentially acts to release arachidonic acid esterified at the sn -2 position of phospholipids. We examined the susceptibility of mice carrying a targeted mutation of the cPLA₂ gene to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity. Mutant mice have no functional cPLA₂ activity. Mice that were homozygous for the mutation (cPLA₂^−/−) were significantly resistant to MPTP-induced dopamine depletion as compared with littermate control (cPLA₂^+/+) and heterozygous mice (cPLA₂^+/−). These findings provide evidence that cPLA₂ plays a role in MPTP neurotoxicity and suggest that cPLA₂ may play a role in the development of Parkinson's disease in humans.     

Probable participation of phospholipase A2 reaction in the process of fertilization-induced activation of sea urchin eggs

In sea urchin eggs activated by sperm, A23187 or melittin, BPB (4-bromophenacyl bromide, a phospholipase A₂ inhibitor) blocked fertilization envelope formation and transient CN⁻-insensitive respiration in a concentration-dependent manner. BPB had virtually no effect on the increase in [Ca²⁺]_i, (cytosolic Ca²⁺ level), the activity of phosphorylase a and the rate of protein synthesis, as well as acid production and augmentation of CN⁻-sensitive respiration. BPB also inhibited fertilization envelope formation and augmentation of CN⁻-insensitive respiration induced by melittin. Melittin, known to be an activator of phospholipase A₂, induced the envelope formation, acid production, augmentation of CN⁻-insensitive and sensitive respiration, but did not cause any increase in [Ca²⁺]_i, the phosphorylase a activity and the rate of protein synthesis. An activation of phospholipase A₂ induced by Ca²⁺ or melittin seems to result in cortical vesicle discharge and production of fatty acids, which are to be utilized in CN⁻-insensitive lipid peroxidase reactions. Activation of other examined cell functions in eggs activated by sperm or A23187, probably results from Ca²⁺-triggered sequential reactions other than Ca²⁺-caused activation of phospholipase A₂.     

Chromatography of acid phytohormones on columns of Sephadex LH-20 and insoluble poly-N-vinylpyrrolidone, and application to the analysis of conifer extracts

The chromatographic behaviour of abscisic acid (ABA), indole-3-acetic acid (IAA), phenylacetic acid (PAA), and gibberellins A₁, A₄, A₈, A₉, A₁₃ and A₂₀ on columns of Sephadex LH-20 and insoluble poly- N -vinylpyrrolidone (PVP) eluted with buffers of different pH values is described. PVP shows considerable batch differences that must be carefully checked. Chromatography of acidic ethyl acetate-soluble fractions of Scots pine ( Pinus sylvestris L.) extracts at pH 4.5 resulted in great losses of phytohormones, due to poor solubility of the extracts. If the extracts were applied to the column dissolved in buffer of pH 7.5, subsequent elution at pH 4.5 was possible with only small losses. The performance of the chromatographic column was strongly affected by the application volume. A combined PVP/Sephadex LH-20 column eluted at pH 4.5 allows remarkable purification of pine and spruce ( Picea abies (L.) Karst.) extracts, collection of IAA in a fraction that can be directly analyzed by e.g. the indolo-α-pyrone method, and collection of another fraction containing ABA, PAA and probably most of the known C₁₉-gibberellins; whereas the C₂₀-gibberellin A₁₃ is eluted later (with IAA).     

Maternal Dietary Fat and Polyunsaturated Fatty Acids in the Developing Foetal Rat Brain

Abstract: Female rats were fed pursed diets containing 10% safflower oil, which is high in linoleic acid, from approximately 2 weeks prior to mating until the 14th day of gestation. They were then fed purified diets containing safflower oil, soybean oil (containing linoleic and linolenic acids), or hydrogenated coconut oil (essential fatty acid deficient). On days 16, 18, and 21 of gestation, foetuses were removed by caesarean section and the brains were subjected to fatty acid analysis. By day 16 of gestation, the ethanolamine glycerophospholipids and combined serine-inositol glycerophospholipids were rich in polyunsaturated fatty acids, particularly arachidonic acid. Between days 16 and 21 of gestation, there was a marked increase in the C₂₂-polyunsaturated acids in these glycerophospholipids, with 225n-6 deposited in foetuses from dams fed safflower or coconut oils and 22:6n-3 deposition occurring in the soybean oil group; the effects of essential fatty acid deficiency in this period were minimal. A similar pattern was evident in the choline glycerophospholipids but this fraction contained less of the polyunsaturated acids. The data are consistent with increased placental transfer of highly unsaturated fatty acids or increased foetal synthesis of these compounds during the last week of gestation, with the actual fatty acid pattern reflecting the dietary fat available to the dam.