Lipid biosynthesis in warm- and cold-acclimatized sea anemones, Metridium senile (L.)

Sea anemones, Metridium senile (L.), naturally acclimatized to warm (18°C) and cold (0°C) conditions, were exposed to either [2-¹⁴C]acetate, [16-¹⁴C]palmitate, or [4-¹⁴C]cholesterol for periods up to 24 h. Isotope incorporation into triglyceride (TG), wax esters (WE), and polar lipid (PL) was recorded. Compared to warm-acclimatized groups, incorporation of [2-¹⁴C]acetate into WE of cold anemones was dramatically reduced, while TG incorporation remained at about the same levels. Highest values were recorded for PL in both groups. Using radiolabeled palmitate, incorporation values for WE were very low in both acclimatization groups though TG uptake remained comparatively high. Also noteworthy was a significant decrease in PL activity in cold anemones. Fatty acid analysis of total lipid, wax ester, triglyceride and phospholipid fractions showed a general shift towards increased chain length and unsaturation in cold-acclimatized anemones.     

Further investigations of the incorporation of [1-14C]acetate into the lipids of the silkworm Bombyx mori L

1. After the injection of sodium [1-¹⁴C]acetate, the highest incorporation of ¹⁴C into the lipids of the silkworm was observed after 24hr. 2. The specific radioactivity of the palmitic acid fraction was greater and increased more rapidly than that of the stearic acid fraction, which was consistent with the precursor–product relationship to be expected on the basis of current concepts of fatty acid synthesis in vivo. 3. The results indicate the probability of synthesis of lipid components in tissues other than the fat body. 4. Fractionation studies indicate considerable differences in the rate of incorporation of [1-¹⁴C]acetate into neutral lipids and phospholipids between larvae and pupae as well as among tissues of larvae. 5. The rate of incorporation of [1-¹⁴C]acetate remains constant throughout pupal development.     

Stimulation of ion release from liposomes by the polyene antibiotic, filipin.

The effect of the polyene antibiotic, filipin, upon release of the ions Ca²⁺, Sr²⁺, SO₄^2? and phosphate out of phospholipid and phospholipid-cholesterol liposomal vesicles was studied. The addition of filipin at concentrations stoichiometrically comparable to the cholesterol concentration in the liposomes, resulted in 2–10 × stimulation of the rate of release of all of these ions. The filipin mediated stimulation of release of ions from liposomes was dependent upon the presence of cholesterol. The relative effectiveness of filipin increased when the mole percent of cholesterol incorporated into the liposomes increased from 10 to 50% and when the molar filipin:cholesterol ratio increased from 0.2 to 1.0. It has been previously shown that there is a 1:1 stoichiometry of interaction between filipin and cholesterol [Biochem. Biophys. Acta339, 57 (1974)]. The present studies suggest that this 1:1 stoichiometric interaction may also be responsible for the increased release of entrapped ions.A possible mechanism of action of polyene antibiotics is discussed which suggests that the rearrangement of membrane constituents occurring upon interaction of filipin with cholesterol is the basis for the enhancement of ion release. This would imply that the ion specificity observed upon interaction of polyene antibiotics with membranes would not only be determined by the polyene antibiotic itself, but also by the intrinsic properties of the membrane.     

Effects of Filipin and Cholesterol on K Movement in Etiolated Stem Cells of Pisum sativum L

Filipin, a polyene antibiotic known to induce leakage of materials from various cells, depresses K⁺ and NO₃⁻ uptake in etiolated pea epicotyl segments. Filipin concentrations which strongly reduce K⁺ influx have little effect on efflux; however, high concentrations enhance K⁺ efflux. Filipin has no effect on respiration rates or cell electropotentials; its action is presumed to be on the cell membranes. Cholesterol, but not a thiol-protecting agent (dithiothreitol), enhances K⁺ influx and counteracts the inhibition by filipin. Although this effect of cholesterol may be due to an interaction with filipin in the outer solution, there is reason to believe that its major effect is to impart stability to the membrane; filipin is believed to act by interfering with sterol stabilization of phospholipid layers. The predominant native sterols of etiolated pea stem (Pisum sativum L. var. Alaska), which cholesterol probably mimics, are β-sitosterol, campesterol, and stigmasterol.     

Brugia pahangi: uptake and incorporation of adenosine and thymidine.

The uptake and incorporation of adenosine and thymidine by infective larvae, 10-day-old juvenile, and adult stages of Brugia pahangi were investigated using scintillation counting and autoradiographic techniques. No evidence of thymidine incorporation by the worm was obtained in this study. Scintillation counting methods demonstrated that ¹⁴C-labeled adenosine was incorporated by all three stages of this filarial worm. Autoradiography, performed on worms incubated in [³H] adenosine from 5 min through 2 hr, revealed that following 5–15 min incubation the greatest degree of adenosine incorporation occurred in the hypodermis and somatic cords. Adenosine incorporation into the deeper body tissues, including the gut, increased significantly with longer periods of incubation. The results obtained further support the concept that nutrient uptake in B. pahangi occurs by a transcuticular route.     

The effect of Habrobracon hebetor venom on the activity of the prophenoloxidase system, the generation of reactive oxygen species and encapsulation in the haemolymph of Galleria mellonella larvae

The cellular and humoral immune reactions in haemolymph of the wax moth Galleria mellonella larvae naturally injected by venom of ectoparasitic wasp Habrobracon hebetor were analyzed. A strong decline of phenoloxidase (PO) activity in the haemolymph and the number of haemocytes with PO activity of envenomated wax moth was observed. In addition, it has been shown that the rate of capsule melanization in the envenomated larvae was half that of the control. Also production of reactive oxygen species (ROS) in the haemolymph of envenomated larvae decreased. The obtained data casts light on the suppression of the main immune reactions in G. mellonella larvae during natural envenomation by H. hebetor.     

Pathology of Spiroplasma floricola in Galleria mellonella larvae

Spiroplasma floricola strain 23-6, originally isolated from tulip tree flowers, was injected into larvae of the greater wax moth. Histopathology and cytopathology of disease larvae were studied by histochemical, fluorescent antibody, and electron microscopical methods. The gut was empty, polysaccharides in fat and muscle tissue were reduced, the fat body was broken down, and phospholipids were depleted in larvae 4 days after injection. Fluorescein conjugated S. floricola antibody was adsorbed onto hemocytes, sarcolemma, gut epithelial membrane, and the cortex of the ventral ganglia. By electron microscopy, spiroplasmas were found in hemocoel, hemocytes, pericardial cells, connective tissues, basement membranes, epidermal cells of the cuticle, the neural lamella, and the peripheral glial cells of the ventral nerve cord, and on midgut and epidermal membranes. It is postulated that the cytopathological effects induced in the body of the insect released nutritional elements that allow extensive reproduction of S. floricola.     

Relationships between the parasitoid Hyposoter exiguae and Trichoplusia ni: Prevention of host pupation at the endocrine level

RNA synthesis in normal Trichoplusia ni fifth instars and hosts parasitized at ca. 12 hr post-ecdysis was followed by measuring ³H-uridine incorporation with an autoradiographic technique.Uptake of ³H-uridine was high in control prothoracic glands at 6 and 30 hr and their cytology indicated an active secretory phase which was most pronounced at 30 hr. At the same time, glands of parasitized larvae decreased incorporation and appeared less active than controls. At > 75 hr, control fat body cells incorporated almost no label but were filled with RNA-protein granules apparently sequestered from the haemolymph preparatory to pupation. With respect to incorporation and cytology, fat body of parasitized larvae was unchanged from earlier in the instar, which indicates that the changeover to pupal preparations had not taken place. Imaginal wing disks incorporated label and grew appreciably in control larvae but abruptly decreased uptake and showed no size increase in parasitized larvae. Incorporation of Malpighian tubule, midgut epithelium, and certain muscles at > 75 hr showed little change in parasitized larvae, but in controls activity was reduced and histolysis occasionally was evident in muscles.The parasitoid, Hyposoter exiguae, apparently prevented host larvae from pupating by preventing activation of host prothoracic glands in the fifth instar. Other tissues which are normally activated for metamorphosis by the prothoracic glands continued normal larval activities until the end of the association.     

Effects of Abscisic Acid on Senescence, Permeability and Ribosomal Patterns in Mimosa Hypocotyl Callus Tissue

Abscisie acid effects on ³²P uptake, polysomal patterns and senescence in mimosa (Albizzia julibrissin Durazzini) hypocotyl callus tissues were compared. Incubation of hypocotyl callus tissue with, abscisic acid for 4.5 h significantly decreased tissue uptake of ³²P, and quantitatively, but not significantly, decreased incorporation of ³²P into ribosomal fractions after adjusting for uptake. Abscisic acid accelerated senescence in the callus tissues. Abscisic acid inhibition of ³²P uptake is presented as a possible source of misinterpretation of ribosomal ³²P incorporation data.     

The calcium-stimulated incorporation of ethanolamine and serine into the phospholipids of the housefly Musca domestica

1. The calcium-stimulated incorporation of [2-¹⁴C]ethanolamine and l-[3-¹⁴C]-serine into the phospholipids of homogenates of the fat bodies from larval houseflies (Musca domestica) was studied. 2. Ethanolamine and serine acted as competitive inhibitors with one another. N-Methylethanolamine was not distinguished from ethanolamine by the system. Tris buffer was also a competitor with these compounds, and a number of other amino alcohols were inhibitory, probably competitively. 3. The incorporation of [³²P]phosphorylethanolamine into phospholipids was observed in suspensions of whole fat bodies. This incorporation was stimulated by magnesium. 4. During the incubation of the homogenates, a calcium-stimulated breakdown of phospholipids by a phospholipase A occurred. 5. These results are compared with results published for similar mammalian systems, and their possible physiological significance is discussed.     

A basic model for the association of ligands with membrane cholesterol: application to cytolysin binding

Almost all the cholesterol in cellular membranes is associated with phospholipids in simple stoichiometric complexes. This limits the binding of sterol ligands such as filipin and perfringolysin O (PFO) to a small fraction of the total. We offer a simple mathematical model that characterizes this complexity. It posits that the cholesterol accessible to ligands has two forms: active cholesterol, which is that not complexed with phospholipids; and extractable cholesterol, that which ligands can capture competitively from the phospholipid complexes. Simulations based on the model match published data for the association of PFO oligomers with liposomes, plasma membranes, and the isolated endoplasmic reticulum. The model shows how the binding of a probe greatly underestimates cholesterol abundance when its affinity for the sterol is so weak that it competes poorly with the membrane phospholipids. Two examples are the understaining of plasma membranes by filipin and the failure of domain D4 of PFO to label their cytoplasmic leaflets. Conversely, the exaggerated staining of endolysosomes suggests that their cholesterol, being uncomplexed, is readily available. The model is also applicable to the association of cholesterol with intrinsic membrane proteins. For example, it supports the hypothesis that the sharp threshold in the regulation of homeostatic endoplasmic reticulum proteins by cholesterol derives from the cooperativity of their binding to the sterol weakly held by the phospholipids. Thus, the model explicates the complexity inherent in the binding of ligands like PFO and filipin to the small accessible fraction of membrane cholesterol.     

大蜡螟防控技术研究进展

大蜡螟Galleria mellonella L.是蜂群中普遍存在的害虫,其幼虫蛀毁巢脾,造成封盖蛹不能孵化出房,使蜂群群势下降甚至飞逃.当前,大蜡螟作为试验昆虫受到越来越多的关注,而其防控技术的研究相对薄弱,蜡螟危害仍是限制养蜂发展的因素之一.本文对国内外大蜡螟的防控技术进行了梳理总结,为我国制定蜡螟综合防控措施提供...     

THE SYNTHESIS OF PHOSPHOLIPIDS IN THE NUCLEUS AND NUCLEAR MEMBRANE OF SYNCHRONIZED HeLa CELLS

HeLa cells were synchronized by a double thymidine block and pulse labeled at different stages of the cell cycle with ³H-choline. The specific activity of phospholipids extracted from the cell, the nucleus and the nuclear membrane showed a progressive increase from S to G₁; the incorporation of choline into phospholipids of asynchronous cells showed a specific activity intermediate between the values of S and G₁ cells. Similar results were obtained when ³²phosphorus was used as a precursor instead of choline. Thin layer chromatographic analysis of phospholipids extracted from cells in S and from cells in G₁ failed to show any difference in the distribution of radioactivity among the various phospholipid classes. Choline uptake by HeLa cells in different phases of the cell cycle did not show significant variations. However, during the synchronization process, shortly after the addition of excess thymidine, an increased uptake of choline by cells and an increased incorporation of choline into phospholipids were found. The results indicate that some of the changes occurring in phospholipids synthesis may not be cell cycle dependent, but may be the effect of the synchronizing process.     

Effect of garlic oil on incorporation of amino acids into proteins of Culex pipiens quinquefasciatus Say larvae

Incorporation of [¹⁴C]leucine into proteins of 3rd instar Culex pipiens quinquefasciatus Say larvae increases linearly with time between 1 and 4 h. Garlic oil as well as the active larvacidal principle from it, viz. diallyl disulphide, inhibits significantly synthesis of the larval proteins. The maximum reduction in incorporation is observed during the first hour of treatment. The incorporation of [¹⁴C]phenylalanine is also inhibited by garlic oil and the effect is irreversible. Garlic oil does not seem to have any effect on proteins already labelled and it does not suppress substantially oxygen uptake by the larvae.     

EVIDENCE FOR INVOLVEMENT OF Ca2+ IN THE INCORPORATION OF 32Pi INTO THE PHOSPHATIDYLINOSITOL OF RAT DIAPHRAGM

Abstract— Ethyleneglycol-bis (β-aminoethyl ether)-N-N'-tetraacetic acid (EGTA) inhibited the incorporation of ³²P_i into phosphatidylinositol (PI) in rat diaphragm incubated in Ca²⁺-free Krebs-Ringer medium. Only the labelling of the PI was altered, and no effects on the pool size of PI or on the incorporation of ³²P_i into other phospholipids were observed. The effect of EGTA was concentration-dependent and appeared to be related to its Ca^a+-chelating properties; the inhibition of the incorporation of ³²P_i could be completely reversed by the addition of excess Ca²⁺ but not Mg²⁺. The inhibitory effect of the EGTA was progressively enhanced by lengthening the preincubation of the tissue with EGTA, an observation suggesting that chelation of intracellular or membrane-bound Ca²⁺, rather than extracellular Ca²⁺, was involved in the effect. In contrast to its inhibition of the incorporation of ³²P_i EGTA enhanced the incorporation of [³H]inositol into PI, but this effect was accompanied by an appreciable increase in total uptake of [³Hlinositol by the tissue. Our results suggest that the level of intracellular Ca²⁺ plays a role in the regulation of the incorporation of ³²P_i into PI. Addition of unlabelled α-glycerophosphate to the incubation medium of tissues which had been preincubated with 2-deoxy-d -glucose failed to cause a significant diminution in the inhibition by EGTA of the incorporation of ³²P_i into PI. This experiment suggests, but does not prove, that the effect of EGTA was not at the level of incorporation of ³²P_i into α-glycerophosphate.     

LIPIDS OF ACANTHAMOEBA CASTELLANII : Composition and Effects of Phagocytosis on Incorporation of Radioactive Precursors

The lipids of Acanthamoeba castellanii (Neff) consist of 52% neutral lipids and 48% polar lipids. Triglycerides account for 75% and free sterols for 17% of the neutral lipids. The major phospholipids are phosphatidylcholine (45%), phosphatidylethanolamine (33%), phosphatidylserine (10%), a phosphoinositide (6%), and diphosphatidylglycerol (4%). The phosphoinositide is unique in that it contains fatty acids, aldehyde, inositol, and phosphate in the ratio of 1.4:0.5:1.1, but it contains no glycerol. Sphingomyelin, cerebrosides, psychosine, and glycoglycerides were not detected, but small amounts of unidentified long chain bases and sugars are present. The rates of uptake of palmitate-1-¹⁴C and of its incorporation into glycerides and phospholipids were not affected by the phagocytosis of polystyrene latex beads. Although phagocytosis usually decreased the uptake by amebas of phosphate-³²P, serine-U-¹⁴C, and inositol-2-³H, their subsequent incroporation into phospholipids was not demonstrably stimulated or inhibited by phagocytosis. Phagocytosis did seem to increase the incorporation into ameba phospholipids of phosphatidylcholine-1 ,2-¹⁴C but not that of phosphatidylethanolamine-1 ,2-¹⁴C. These experiments, in which the incorporation of radioactive precursors into total cell lipids was measured, do not, of course, eliminate the possibility that localized effects may occur.     

The insecticidal activity of foliage from New Zealand conifers

When incorporated into artificial diets, the milled foliages of many New Zealand conifers are toxic to larvae of housefly (Musca domestica), codling moth (Laspeyresia pomonella) and light-brown apple moth (Epiphyas postvittana). The most toxic foliages are those of Podocarpus nivalis which contains diterpene lactones, and Dacrydium laxifolium, which has a high concentration (1%) of phytoecdysones. The insecticidal activities of the plants are discussed in relation to their insect associations, chemistry and taxonomy.     

Molar proportions and relative rates of synthesis of histones in rat testis

The molar proportions and relative rates of synthesis of histones in normal and hypophysectomized rat testis seminiferous epithelial cells were determined. After hypophysectomy the molar proportions of histones H1, H2B and (H2A + protein A24) in seminiferous epithelial cells of rat testis increased while their corresponding variants TH1-x, TH2B-x and X₂ decreased, but the molar proportions of major-class histones (i.e., sum of subfractions) remained relatively constant and similar to the proportions in somatic cells. The apparent molar proportions of the labeled histones, determined immediately after 2-h periods of [³H]leucine incorporation, were much higher relative to H4 than the proportions of total histones determined by dye binding. The values, however, approached the molar proportions of total histones when rats were killed 11 days after the [³H]leucine injection. Two-dimensional gel electrophoresis confirmed that the high initial molar proportions relative to H4 by [³H]leucine incorporation were not due to the possible contamination by highly-labeled non-histone proteins. The specific activity of histone H4 relative to the specific activity of DNA, determined immediately after 3-h periods of [³H]leucine and [¹⁴C]thymidine incorporations was similar to the value when rats were killed 13 days after the injections. It is proposed that histones of seminiferous epithelial cells are synthesized disproportionally relative to H4 and in excess of the quantities required for polynucleosome assembly. The excess histones are subsequently displaced or degraded slowly.     

Separation and Characterization of Inositol Phospholipids from the Pulvini of Samanea saman

To supplement current thin-layer chromatographic methods for separation and quantitation of plant phospholipids, an alternative method, high-performance liquid chromatography was developed. The major inositol-containing lipids from the pulvini of Samanea saman Merr. were identified as phosphatidylinositol, phosphatidylinositol phosphate, and phosphatidylinositol bisphosphate based on comigration with authentic standards on high-performance liquid chromatography and on thin-layer chromatography. The patterns of incorporation of radioactivity into the putative phosphatidylinositol and phosphatidylinositol phosphate were consistent with these identifications when pulvini were labeled with [³H]glycerol, [³H]inositol, or [³²P]orthophosphate. Analysis of the products of enzymic hydrolysis, of chemical deacylation, and of `fingerprint' methanolysis of these phospholipids confirmed the identifications.     

Phosphoinositides in barley aleurone layers and gibberellic Acid-induced changes in metabolism

Phospholipids of barley (Hordeum vulgare L. cv Himalaya) aleurone layers were labeled with myo-[2-³H]inositol or [³²Pi], extracted, and analyzed by physical (chromatography) and chemical (deacylation) techniques. Three phospholipids were found to incorporate both myo-[2-³H]inositol and [³²Pi]—phosphatidylinositol, phosphatidylinositol-monophosphate, and phosphatidylinositol-bisphosphate. Stimulation of [³H]inositol prelabeled aleurone layers with GA₃ showed enhanced incorporation of label into phosphatidylinositol within 30 seconds and subsequent rapid breakdown. Stimulation of phosphatidylinositol labeling observed in these studies is the earliest response of aleurone cells to gibberellic acid reported.