Effect of conjugation on the incorporation of glycine into Tetrahymena

• 1.1. Conjugation of Tetrahymena enhanced the incorporation of glycine into the nuclear fraction by 500%.
• 2.2. Incorporation of glycine into the microsomal supernatant was augmented by almost 500% by conjugation.
• 3.3. Mitochondrial incorporation was stimulated nearly 3-fold in the conjugating strains while the incorporation of glycine into the microsomes was enhanced approximately 2.5 times.
• 4.4. In the whole cell, glycine incorporation was increased nearly 2-fold by conjugation.
• 5.5. Strong nuclear involvement was indicated by elevated metabolic activity and incorporation of glycine into RNA and DNA.
• 6.6. Stimulation of the metabolism of Tetrahymena by cell communication suggests that the contents of a cell can have a synergistic effect on another cell.
• 7.7. Augmentation of the biosynthetic capacities of cells by fusion is a demonstration of the dominant role of the cell membrane in the regulation and control of cells.
• 8.8. Enhancement of biosynthesis of nuclear proteins in conjugating strains of cells indicates that fusion gives rise to the synthesis of new protein from previously existing protein or protein procursors.
• 9.9. The specific activities of the subcellular fractions after the incorporation of glycine into 2 separated starved strains of Tetrahymena followed the usual pattern of nucleus less than whole cells, whole cells less than mitochondria, mitochondria less than microsomes, but with the microsomal supernatant being much greater than that of the microsomes.

     

Cotranslational fatty acylation of mucus glycoprotein. Addition of palmitic acid to peptidyl-tRNA occurs prior to peptide chain completion and its release

• 1.1. The fatty acylation of mucus glycoprotein nascent peptides was investigated using [³H]palmitic acid and [³⁵S]methionine-labeled peptidyl-tRNA of rat gastric mucous cells.
• 2.2. The mucus glycoprotein peptidyl-tRNA fraction was found to contain covalently bound palmitic acid in its complexes.
• 3.3. RNase digestion of the mucus glycoprotein peptidyl-tRNA released [³H]palmitic acid labeled peptides which, on SDS-polyacrylamide gel, separated into a multitude of bands ranging in size from 2000 to 60,000 Da.
• 4.4. The analyses of low molecular weight peptides revealed that palmitic acid was present in methionine-labeled peptides containing 30–43 amino acids and those of 18–25 amino acids or larger devoid of methionine, but was not identified in methionine-labeled peptides containing 10–15 amino acids.
• 5.5. The results indicate that the N-terminal fatty acylation of mucus glycoprotein nascent peptides is a cotranslational process which is occuring in an immediate vicinity of the signal peptide fragment.

     

Driving forces for the uphill transport of amino acids into epidermal brush border membrane vesicles of the sea anemone,Anemonia sulcata (Cnidaria,anthozoa)

• 1.1. The transport of amino acids into membrane vesicles prepared from epidermal tentacle tissue of the sea anemone, Anemonia sulcata, depends on an electrochemical potential difference caused, e.g. by sodium chloride gradients.
• 2.2. Potassium or choline chloride gradients energized the transport less effectively than sodium chloride gradients. Both Na⁺-ions and Cl⁻-ions were required for the amino acid transport.
• 3.3. The uphill transport of amino acids along the downhill movement of driver ions (sodium chloride gradient conditions) was characterized by an overshoot; under sodium chloride equilibrium conditions, however, an accumulation of amino acids within the vesicles could not be measured.
• 4.4. Potassium diffusion potentials in combination with valinomycin indicated that hyperpolarization (vesicle inside negative) and hypopolarization (vesicle inside positive) enhanced or depressed the accumulation of amino acids within the vesicles.
• 5.5. Being at the phylogenetic base of the Eumetazoa, cnidarians show characteristics for the transmembrane transport of amino acids comparable to those established for vertebrates.

     

Investigation of phycocyanin-membrane interaction: Promotion of membrane interactions

• 1.1. In a continuing investigation of phycocyanin-membrane surface interaction, fluorescence quenching experiments were performed with a mixture of two populations of fluorescence probe-encapsulated phospholipid bilayer vesicles in the presence and absence of phycocyanin.
• 2.2. These membrane vesicles were prepared with 1,2-dimyristoyl phosphatidylcholine (DMPC), cholesterol and a probe molecule.
• 3.3. A fluorophore was encapsulated in one population of membrane vesicles, while a quencher was encapsulated in another population of membrane vesicles.
• 4.4. The result was compared with those of experiments in the presence of other biomolecules, including albumin, cytochrome c, hemoglobin, myoglobin or RNA.
• 5.5. Interestingly, a one-third reduction of the fluorescence intensity was observed in the mixture of these two populations of membrane vesicles in phycocyanin's presence.
• 6.6. In contrast, the other biomolecules caused no significant reduction in the fluorescence intensity.
• 7.7. These findings were evidence of a phycocyanin-induced membrane perturbation.
• 8.8. This was further demonstrated by a phycocyanin-induced change in the thermotropic behavior of DMPC vesicles, as measured by differential scanning microcalorimetry.
• 9.9. Such a unique property of phycocyanin is believed to be associated with its known membrane surface-interacting character.
• 10.10. A possible phycocyanin-modulated membrane-membrane interaction was discussed.

     

Amino acid accumulation in kidney cortex of lambs and piglets as affected by insulin

• 1.1. Insulin stimulated intracellular accumulation of α-amino-isobutyric acid (AIB) in kidney cortex slices from young lambs and piglets.
• 2.2. The effect was similar in the absence or presence of glucose.
• 3.3. The induction of the stimulatory effect on renal AIB transport was blocked by cycloheximide. an inhibitor of protein synthesis.
• 4.4. The insulin stimulation of intracellular AIB accumulation is due to an increased influx and not to a reduced efflux of AIB.
• 5.5. Analysis of transport kinetics for AIB showed that insulin increased V_max but did not change K_m.
• 6.6. It is concluded that insulin stimulates uptake of certain neutral amino acids into kidney cortex cells in young animals.
• 7.7. The effect on renal amino acid transport appears to be mediated through increased synthesis of a membrane carrier.

     

Transintegumentary absorption of acidic amino acids in the oligochaete annelid Enchytraeus albidus

• 1.1. Transintegumentary absorption of acidic amino acids in Enchytraeus albidus amounts to only a few per cent of neutral amino acid uptake.
• 2.2. Influx of acidic amino acids is composed of a mediated route with high affinity and an apparent diffusional entry.
• 3.3. Glutamic acid influx is susceptible to metabolic inhibition, reduced salinity and Na⁺-levels and the presence of additional acidic amino acids.
• 4.4. Inhibition experiments suggest the presence of a distinct integumentary uptake system for acidic amino acids.

     

The influence of seasonal changes on energy metabolism in Mytilus edulise (L.).—III. Anaerobic energy metabolism

• 1.1. Seasonal changes in the accumulation of end products after 48 hr of exposure to air and in the composition of the free amino acid pool were studied in Mytilus edulis.
• 2.2. The accumulation levels of succinate and acetate showed only weak seasonal changes.
• 3.3. Conversion of succinate to propionate was high in summer and virtually zero in winter
• 4.4. Alanine and most other free amino acids were present in relatively high concentrations in summer and early autumn and reached minimal values in winter and early spring.
• 5.5. Exceptions were glutamate, aspartate and taurine, which showed hardly an season related changes and glycine, which changed inversely to the majority of the free amino acids.
• 6.6. The anaerobic formation of alanine was inversely proportional to the endogenous concentration.
• 7.7. The only other free amino acids affected by anaerobiosis were glutamate and aspartate, which respectively increased and decreased under these conditions.

     

Spingophosphonolipids in microsomes of Diplodon delodontus. Distribution and effect on the membrane microviscosity

• 1.1. The distribution of ceramide aminoethylphosphonate (CAEP) in microsomal membranes obtained from different tissues of the bivalve mollusc Diplodon delodontus was determined.
• 2.2. The concentration of CAEP reached from 9 to 19% of the total microsomal polar lipids, depending on the kind of tissue.
• 3.3. Palmitic acid was the main fatty acid in the ceramide moiety, followed by stearic and eicosamonoenoic acids.
• 4.4. Artificial membranes were prepared with microsomal phospholipids or phospholipids plus sterols, with and without the addition of CAEP.
• 5.5. It was shown that the phosphonate confers minor mobility to the membranes. This effect is more effective when the membrane contains the natural sterols and the phospholipids are unsaturated.

     

Proteins of the kidney microvillar membrane: Topological considerations

• 1.1. A method for the asymmetric labelling of pig kidney microvillar membrane proteins is described.
• 2.2. The photo-activated reagent, 3,5-di[¹²⁵I]iodo-4-azido-benzene sulphonate, enabled four of the membrane peptidases to be characterized as transmembrane proteins.

     

Locust vitellogenin receptor: an acidic glycoprotein with N- and O-linked oligosaccharides

• 1.1. The locust vitellogenin (VTG) receptor which is embedded in oocyte plasma membranes is a glycoprotein.
• 2.2. With various lectins oligosaccharide units have been identified, among them neuraminic acid linked to Gal or GalNAc, mannose chains, Gal linked to GalNAc or GlcNAc and fucose linked to GlcNAc.
• 3.3. With specific enzymes it could be shown that mannose and most other oligosaccharides are O-linked while others like fucose are N-linked.
• 4.4. Enzymatic removal of all O-linked carbohydrates resulted in a drop of the molecular mass of the receptor protein from 200,000 to 110,000.
• 5.5. A total of N- and O-linked oligosaccharides of 54% was calculated.
• 6.6. The isoelectric point of the receptor was found to be at pH 3.4 increasing slightly after removal of neuraminic acid.
• 7.7. Removal of neuraminic acids destroyed the binding ability for VTG.

     

Acetylcholinesterase in Apis mellifera head during post-embryonic development. Existence of a glycoinositol-anchored membrane form at eary pupal stages

• 1.1. Properties of acetylcholinesterase (AChE, EC 3.1.1.7) from Apis mellifera head were studied during pupal development and at the adult stage.
• 2.2. During post-embryonic development, tissue and specific activities were closely related and increased to reach a maximum value at emergence and at last pupal stage, respectively.
• 3.3. In adults, AChE activity was weaker in foragers than in emerging bees.
• 4.4. The membrane form occurred in adult bees as well as in pupae whereas the soluble enzyme only appeared from Pd pupal stage.
• 5.5. The proportion of soluble and membrane forms fluctuated during late development but, in all cases, the percentage of the soluble form remained less than 10% of total AChE activity.
• 6.6. At all post-embryonic stages, the membrane form was sensitive to the action of phosphatidylinositol-specific phospholipase C (PI-PLC) and was converted into a hydrophilic enzyme.
• 7.7. In adult bees, the sensitivity to PI-PLC depended on the season. In summer, about 60% of the membrane activity could be solubilized by PI-PLC vs only 5% in winter.
• 8.8. The sensitivity of AChE to pirimicarb varied with the developmental stage.
• 9.9. In foraging bees, AChE was more susceptible to pirimicarb than in emerging bees. This difference of sensitivity to carbamate was abolished after removal of the membrane anchor either by mild trypsin digestion of PI-PLC treatment.

     

Modulation of mitochondrial ATPase sensitivity to inhibitors and stimulators by diet-induced changes in membrane lipid

• 1.1. Weanling rats were fed diets differing in fatty acid composition to determine if changes induced in cardiac mitochondrial membrane structural components alter the sensitivity of mitochondrial ATPase to inhibition by oligomycin and stimulation by 2,4-dinitrophenol.
• 2.2. Mitochondrial ATPase assayed in situ within the mitochondrial membrane isolated from animals fed diets higher in fatty acids of longer chain length, exhibited greater oligomycin sensitivity and lower 2,4-dinitrophenol-induced stimulation.
• 3.3. Concomitant diet-induced changes occur in the fatty acid, composition of phosphatidylcholine, phosphatidylethanolamine and cardiolipin, increasing overall length of fatty-acyl tails in the membrane phospholipids.
• 4.4. Diet fat mediated alterations in oligomycin sensitivity of mitochondrial ATPase and membrane fatty acid chain length suggest that _vivo changes in thickness of the lipid bilayer may alter mitochindrial ATPase functions.
• 5.5. The present study extends the concept that dietary fat affects mitochondrial membrane structure and function by demonstrating that the membrane-dependent sensitivity of mitochondrial ATPase to inhibitors and stimulators may be modulated by dietary fat.

     

Chemical feeding stimulants for the herbivorous fish,Tilapia zillii

• 1.1. Chemical feeding stimulants for an herbivorous fish, Tilapia zillii have been determined by fractionation and bioassay of substances derived from a model food plant.
• 2.2. Stimulation was produced by amino acids; glutamic acid, aspartic acid, serine, lysine and alanine produced the bulk of stimulatory activity.
• 3.3. These amino acids are among the most abundant in the test plant, and are markedly different from the amino acids found to stimulate feeding in carnivorous fish.
• 4.4. On the basis of these results, a chemically-mediated mechanism of feeding niche separation is postulated.

     

Specific dynamic action (SDA) in the supralittoral isopod,Ligia pallasii: Effect of ration and body size on SDA

• 1.1. Ration and body size effects on specific dynamic action (SDA) were investigated in the supralittoral isopod Ligia pallasii using seaweed and chemical diets.
• 2.2. SDA increased asymptotically with ingested meal size for all diets.
• 3.3. Body weight had a significant positive effect on SDA for only one of the six diets tested, but weak tendencies were present in the data for the other diets.
• 4.4. SDA appeared to increase geometrically with increasing concentration of amino acids at high ration levels.

     

Purification and some properties of isocitrate dehydrogenase of a blowfly Aldrichina grahami

• 1.1. NADH-dependent isocitrate dehydrogenase has been purified 110-fold from the crude extract of the flight muscle mitochondria of Aldrichina grahami.
• 2.2. The purification procedure involved Triton X-100 treatment of isolated mitochondria, column chromatography on DEAE-cellulose, Affi-gel blue, and P-cellulose.
• 3.3. The purified enzyme was homogeneous by criteria of the polyacrylamide gel electrophoresis.
• 4.4. The enzyme of the blowfly contains more acidic amino acids and less hydrophobic amino acids than that of pig heart.
• 5.5. The molecular weight was determined to be 330,000 daltons. The subunit construction differs from ghat of mammalian isocitrate dehydrogenase.

     

Reabsorption and accumulation of α-amino-iso-butyric acid in the nephridia of Sabella pavonina Sa vigny (Annelida polychaeta)

• 1.l. High amino acid concentrations were found in the anterior coelomic fluid of a Polychaeta (Sabella pavonina Savigny).
• 2.2. The concentrations being much higher in the fluid which penetrates the nephrostomia into the nephridia lumen than in the final urine indicates that the nephridia reabsorbs large amounts of amino acids.
• 3.3. Nephridial perfusion experiments showed that an amino acid analogue (α-amino-iso-butyric acid, AIB) is transported by the nephidia.
• 4.4. The transport took place across the nephridial wall owing to the presence of a carrier-mediated transport system and a diffusion system.
• 5.5. For the carrier-mediated transport, the V_max was 0.234 ± 0.025 nmol·min⁻ and the K_m 3.715 ± 0.315mmol·l⁻.
• 6.6. AIB accumulated in the nephridial cells up to a maximum rate of 01.17 nmol·min⁻.
• 7.7. Intracellular accumulation stopped increasing when the V_max for reabsorption was reached.
• 8.8. These results indicate that the carrier-mediated transport of AIB is located at the apical membrane of the nephridial cell, and that AIB transport by simple diffusion takes place through the paracellular pathway.

     

Changes in free amino acid composition in haemolymph of larvae of the wax moth,Galleria mellon ella L., during cold acclimation

• 1.1. Free amino acids were analysed in the haemolymph of Galleria mellonella larvae by HPLC chromatography with o-phthaldialdehyde (OPA)-l-thio-β-d-glucose as derivatization agent.
• 2.2. Fourteen primary amino acids were detected among which glutamine, alanine, γ-aminobutyric acid (GABA) and glycine predominated and constituted 67.7% of the amino acids found.
• 3.3. The concentration of GABA increased significantly with the age of larvae entering the wandering phase and reached a maximum during metamorphosis.
• 4.4. Analysis of cold-acclimated larvae revealed a net increase of free primary amino acids from 96 to 151.8 μmol/ml during consecutive acclimation to 0°C within 20 days and to 205.4μmol/ml during cold shock injury at 0°C (3 hr).
• 5.5. The bulk of this increase was accounted for by alanine, glycine, phenylalanine and lysine.

     

The free amino acids of muscle in the cephalochordate Branchiostoma,the cyclostome Myxine and some fishes

• 1.1. Branchiostoma and Myxine have the highest concentrations of amino acids (207 and 234 mM) of the five species investigated.
• 2.2. The predominant amino acids are glycine, proline, alanine, taurine, serine and valine, which form 83–98% of the total, except in Latimeria (60%).
• 3.3. Total amino acids are considered from the point of view of osmotic concentration in relation to other nitrogenous compounds of muscle.

     

Chemical composition of North Atlantic krill

• 1.1. The main chemical components of Meganyctiphanes norvegica (M. Sars), Thysanoessa inermis (Krøyer) and T. raschii (M. Sars) have been examined.
• 2.2. Protein accounted for 42–47% of the dry weight of M. norvegica and 32–50% of the dry weight of the Thysanoessa species. On a wet weight basis, the protein content was relatively constant and independent of season.
• 3.3. The dominating amino acids in the bulk protein of the krill were glutamic acid/glutamine, aspartic acid/asparagine, glycine, alanine, lysine and leucine.
• 4.4. Lipids were present in amounts of 13–29% of the dry weight in M. norvegica, 15–50% in T. inermis and 12–44% in T. raschii, and the lipid content varied with season.
• 5.5. The main nitrogen extractives in krill, expressed on a dry weight basis, were free amino acids (5–10%), trimethylamine oxide (about 4%), peptides (about 1%) and nucleotides (0.4–1.3%). Trimethylamine and ammonia were present in very low concentrations in living krill.
• 6.6. The amino acids taurine, glycine, proline, arginine, sarcosine and alanine made up 89–93 mol% of the free amino acid pool.
• 7.7. The ash content of krill was in the order of 10–13% of the dry weight, and fluoride represented 1040 and 3200 ppm in the Thysanoessa species and M. norvegioca, respectively.

     

The influence of calcium and magnesium on sea bass (Dicentrarchus labrax) intestinal brush border membrane purification and activity

• 1.1. The activity of brush border enzymes (alkaline phosphatase, maltase, sucrase, trehalase, leucine amino peptidase) was higher in purified membranes prepared with calcium. The contamination of these membranes with basolateral membranes was also lower (1.27 for Na-K-ATPase activity ratio).
• 2.2. The extraction of brush border lipids was carried out according to Folch adapted method. Two dimensional thin layer chromatography was used to separate the phospholipidic fractions. Fatty acids of phospholipids were analysed using gas chromatography after acid transmethylation (column SP 2330).
• 3.3. Phospholipids are composed of phosphatidylcholine (PC: 33%), phosphatidylethanolamine (PE: 30%), sphingomyeline (SM: 21%), phosphatidylserine (PS: 14%) and phosphatidylinositol (PI: 2%). 4. PC, PE and PS are characterized by high levels of unsaturated fatty acids (monounsaturated MUFA: 21.5% and polyunsaturated PUFA: 34.9%). The most abundant PUFA belong to the (n-3) family [18:3 (n-3), 20:5 (n-3) and 22:6 (n-3)].
• 4.5. Fatty acids from sphingomyelin of purified membranes have low proportions of PUFA (13.5%) but higher proportions of MUFA (39.5%).
• 5.6. No specific differences were found between calcium and magnesium prepared membranes.
• 6.7. The low content in LPC and the absence of LPE confirmed the absence of major structural lipids transformation during the membrane purification with calcium or magnesium.
• 7.8. Glycine transport was measured during 10 sec at different temperatures using the rapid filtration technique. Glycine transport was higher with Na⁺ than with K⁺. In the presence of Na⁺, this transport increases with temperature.
• 8.9. Arrhenius curves were mono phasic without obvious breakpoint and indicated no phase transition in the lipid bilayer.
• 9.10. A significant Na⁺ dependent glycine transport has been characterized at low temperatures (0°C) which suggests a possible role of membrane polyunsaturated fatty acids in the control of glycine transport.