bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of the acetylation of proteins and nucleic acids
Authors: Paik Woon Ki , Kim Sangduk
Published: August 2015

The possibility of acetylation of nucleic acids was examined. Although protein is actively acetylated with [1-14C]acetic acid in rat liver systems in vivo and in vitro and in a frog liver system in vivo, nucleic acids are not acetylated under these conditions; nucleic acids purified from these sources are without radioactivity. Requirements for acetylation in vitro of protein in rat liver are different from those in frog liver; GSH has no effect in the rat liver system and is inhibitory in the frog liver system. Among various acetylated proteins, proteins insoluble in 0.1m-sulphuric acid have the highest radioactivity.
An analysis of the interaction of protein with lipid monolayers at the air/water interface
Authors: Quinn P. J. , Dawson R. M. C.
Published: August 2015

1. Measurements have been made of the interaction of cytochrome c, bovine serum albumin and synthetic oxytocin with low-pressure (2dyn/cm) monolayers of stearic acid, phosphatidylcholine and phosphatidylethanolamine. 2. [14C]Carboxymethylation of the cytochrome c and albumin followed by surface-radioactivity determinations have shown that only a proportion of the protein added to the subphase is bound to the monolayers and that initially the degree of binding is dependent on the protein concentration. The binding is irreversible in the sense that the adsorbed protein cannot be removed by transferring the film containing the interacted protein to a fresh subphase containing no protein. 3. Three successive types of interaction can usually be recognized. (a) Initially, whole molecules of protein penetrate the lipid film and occupy the same area as those of the protein spread at the air/water interface. (b) Above certain film pressures a part of each protein molecule, probably hydrophobic side chains, penetrates the film. The change in surface pressure per unit of bound protein is much smaller than in (a). (c) At higher film pressures, adsorption without penetration occurs. With cytochrome c this is initially dependent on a favourable electrostatic interaction.
Factors affecting formiminoglutamic acid excretion in vitamin B12 deficiency
Authors: Marston Hedley R. , Allen Shirley H.
Published: August 2015

1. Formiminoglutamic acid, a product of the catabolism of histidine, is excreted in abnormally large amounts in the urines of vitamin B12-deficient rats and of vitamin B12-deficient sheep; the excretion is reduced to negligible amounts after administration of vitamin B12. 2. After administration of certain methyl donors to vitamin B12-deficient rats or sheep urinary excretion of formiminoglutamic acid is temporarily decreased. 3. Irrespective of the pteroylglutamic acid status of the animals neither vitamin B12-deficient rats nor vitamin B12-deficient sheep have the ability to deal efficiently with histidine. 4. In sheep, urinary excretion of formiminoglutamic acid is increased after administration of aminopterin; treatment with pteroylglutamic acid restores the ability of the animal to deal with the catabolic products of histidine. 5. The possible functions of vitamin B12 and methionine in relieving a virtual deficiency of pteroylglutamic acid are discussed.
Membrane studies with polarity-dependant and excimer-forming fluorescent probes
Authors: Brocklehurst J. R. , Freedman R. B. , Hancock D. J. , Radda G. K.
Published: August 2015

1. The interaction of electron-transporting particles from heavy mitochondria of ox heart with several fluorescent probes was examined. 2. 1-Anilinonaphthalene-8-sulphonate and 2-(N-methylanilino)naphthalene-6-sulphonate both show an energy-dependent response. 3. Energy transfer between the electron-transporting particles and the dyes and the kinetics of the dye–particle interaction were studied in order to locate the binding regions in the membrane. 4. The energy-dependent probe responses were shown to be a result of changes in the quantum yield of fluorescence of the bound dyes together with increased binding of the dyes to the energized membrane. 5. Fluorescence lifetime measurements were also used to observe changes on energization. 6. A new type of probe was found in pyrene-3-sulphonate, which may be regarded as a ‘volume indicator’ for the internal membrane binding region, since it shows a concentration-dependent excimer fluorescence. 7. By comparing the responses of all these dyes when energized particles are uncoupled, a membrane transition with a time-constant of 2–3s is inferred.
Gluconeogenesis in the cow. The effects of a glucocorticoid on hepatic intermediary metabolism
Authors: Baird G. D. , Heitzman R. J.
Published: August 2015

1. The hepatic concentrations of the ketone bodies and of metabolites and activities of enzymes involved in gluconeogenesis were measured in healthy lactating and non-lactating cows 48h after administration of Voren, an ester of dexamethasone, and compared with those found in control animals given saline. Parallel measurements were also made of the blood concentrations of several of the metabolites. 2. Blood glucose concentrations were raised in the Voren-treated animals, whereas blood ketone body and free fatty acid concentrations were unaltered. Similarly there was no change in the hepatic concentrations of the ketone bodies. 3. Significant increases were found in the hepatic concentrations of citrate, 2-oxo-glutarate and malate in both groups of animals given Voren. 4. The hepatic concentrations of those glycolytic intermediates that were measured either decreased or did not change after Voren treatment. 5. The enzymes aspartate transaminase and fructose 1,6-diphosphatase were unchanged in activity after Voren administration, whereas phosphopyruvate carboxylase (EC 4.1.1.32) activity was depressed in the lactating group. However, glucose 6-phosphatase, tryptophan oxygenase and tyrosine aminotransferase increased in activity. 6. In several cases those hepatic metabolites that increased in concentration after Voren administration were present in lower concentration in normal lactating cows than in normal non-lactating cows. The same applied mutatis mutandis to those metabolites that were decreased by Voren. 7. These findings are discussed in relation to the use of glucocorticoids in the treatment of bovine ketosis.
Concentrations of putrescine and polyamines and their enzymic synthesis during androgen-induced prostatic growth
Authors: Pegg A. E. , Lockwood D. H. , Williams-Ashman H. G.
Published: August 2015

1. Castration of adult rats resulted in marked decreases in the amounts of putrescine, spermidine and spermine in the ventral prostate gland. Spermidine concentrations decline rapidly over the first 11 days after androgen withdrawal, reaching a value of only 12% of normal controls. Spermine concentrations diminish more slowly, reaching 24% of normal within 11 days. The spermidine/spermine molar ratio falls from 0.9 to 0.46 under these conditions. Putrescine concentrations decrease by 70% at 7 days after castration and then remain constant for some days. 2. After daily injections of testosterone propionate to rats castrated 7 days previously, prostatic spermidine and putrescine concentrations increase significantly within 24h; normal or even greater values are observed within 8 and 4 days respectively. In contrast, the spermine concentration does not increase until 5 days after commencement of androgen treatment. 3. The activities of two enzymes involved in polyamine biosynthesis (ornithine decarboxylase and a putrescine-activated S-adenosyl-l-methionine decarboxylase system) were greatly decreased soon after castration: after 7 days the respective values were 15% of normal for ornithine decarboxylase and 7% of normal for putrescine-dependent decarboxylation of S-adenosyl-l-methionine. Injection of testosterone propionate into animals castrated 7 days previously induced a rapid increase in both enzymic activities: ornithine decarboxylase was doubled in 6h, and increased three- to four-fold within 48h, whereas the putrescine-dependent decarboxylation of S-adenosyl-l-methionine doubled in 3h and increased tenfold within 48h of commencement of daily androgen treatments. 4. The activity of these enzyme systems was very low in the ventral prostates of hypophysectomized rats and was increased by administration of testosterone in a manner similar to that found in castrated rats. 5. Alterations in the activity of two ventral-prostate enzymes involved in ornithine production (arginase) and utilization (ornithine–2-oxoglutarate transaminase) that result from changes in the androgenic status of rats are described. 6. The findings presented suggest that the activities of ornithine decarboxylase and the putrescine-dependent S-adenosyl-l-methionine decarboxylase system, rather than ornithine concentrations, are rate-limiting for the formation of putrescine and polyamines in rat ventral prostate. 7. The relation of polyamines to androgen-induced prostatic growth is discussed with particular reference to the biosynthesis of proteins and nucleic acids.
Protein-hydrocarbon interactions. Interactions of various proteins with pure decane
Authors: Cecil R. , Louis C. F.
Published: August 2015

1. Solutions of a number of proteins were subjected to gentle agitation in the presence of small quantities of decane. 2. Some of the protein was lost from solution and adsorbed on the surface of the emulsion formed; at the same time some of the decane was bound to the protein remaining in solution. 3. The two processes were found to be related and a mechanism is proposed to explain the relationship. 4. With lysozyme and ribonuclease, the protein in the aqueous phase of an emulsion exhibited normal enzymic activity, whereas the fraction adsorbed on the interface was much less active but recovered activity on desorption.
The roles of pregn-5-ene-3β,20α-diol and 20α-hydroxy steroid dehydrogenase in the control of progesterone synthesis preceding parturition and lactogenesis in the rat
Authors: Kuhn N. J. , Briley M. S.
Published: August 2015

1. The activity of 20α-hydroxy steroid dehydrogenase in rat ovarian corpora lutea increased at least 50-fold between 2 days before and 2 days after parturition, and then fell gradually during lactation. The activity of 3β-hydroxy Δ5-steroid dehydrogenase decreased by 50% at parturition but remained constant at other times. 2. The 20α-hydroxypregn-4-en-3-one/progesterone concentration ratio in the ovary fell tenfold between 1 day before and 1 day after parturition, in contrast with the increase of the ratio for these steroids in plasma. 3. Pregnenolone was metabolized in intact cells or cell-free systems either to pregn-5-ene-3β,20α-diol and then to 20α-hydroxypregn-4-en-3-one by 20α-hydroxy steroid dehydrogenase and 3β-hydroxy Δ5-steroid dehydrogenase respectively, or directly to progesterone by the latter enzyme. The relative activities of these pathways appeared to reflect the relative amounts of the two enzymes and the concentrations of their respective coenzymes NADPH and NAD+. 4. From these and other observations it was concluded that the cessation of progesterone secretion, which precedes parturition and lactogenesis at the end of pregnancy, is partly due to the redirected metabolism of pregnenolone away from progesterone and towards 20α-hydroxypregn-4-en-3-one as the secreted end product. This is primarily the consequence of the sharp increase in the activity of 20α-hydroxy steroid dehydrogenase. This mechanism is super-imposed on the already declining rate of net Δ4-steroid release by the ovary. 5. A relationship of these pathways to subcellular compartments of luteal cells is proposed.
Adenine nucleotides and the adenylate kinase equilibrium in livers of foetal and newborn rats
Authors: Ballard F. J.
Published: August 2015

1. Measurements of ATP, ADP and AMP concentrations in livers of rats that had been delivered by Caesarian section indicate a rapid shift from a low to a high [ATP]/[AMP] ratio. This change is consistent with the cessation of glycolysis and the initiation of gluconeogenesis at birth. 2. When newborn animals are exposed to a 100% nitrogen atmosphere the hepatic ATP concentration falls and AMP increases. 3. Calculations of the [ATP][AMP]/[ADP]2 ratio give values that are close to the equilibrium constant of adenylate kinase except when the ATP concentration is high. 4. This difference cannot be accounted for by the preferential binding of available Mg2+ to ATP4− rather than ADP3−. It is concluded that the relative proportions of adenine nucleotides at any level of phosphorylation are only partly regulated by adenylate kinase.
Steroid metabolism in the rabbit. Biliary and urinary excretion of metabolites of [4-14C]cortisone
Authors: Taylor W.
Published: August 2015

1. [4-14C]Cortisone was administered to anaesthetized male and female New Zealand White rabbits as a single injection or as a 45–60min infusion. 2. The method of administration of the steroid did not significantly affect the total excretion of radioactivity in bile and urine [83.8±10.8%(s.d.)]. 3. The mean ratio of metabolites in urine to those in bile was 0.97±0.23% (range 0.64–1.3). 4. When bile and urine samples were hydrolysed successively by β-glucuronidase, cold acid and hot acid, neutral metabolites extracted by ethyl acetate–ether were found mainly after hydrolysis by β-glucuronidase. 5. An approximately equal proportion of the dose was converted into substances not extractable from alkaline aqueous solution after hydrolysis.
The sensitivity of acetyl-coenzyme A carboxylase to citrate stimulation in a homogenate of rat liver containing subcellular particles
Authors: Iliffe Jill , Myant N. B.
Published: August 2015

1. Although citrate is known to activate purified preparations of acetyl-CoA carboxylase, it had no stimulatory effect on the incorporation of [14C]acetate into long-chain fatty acids in a whole homogenate of rat liver (S0.7) under conditions in which the activity of acetyl-CoA carboxylase was rate-limiting for fatty acid synthesis. 2. The rate of incorporation of acetyl carbon into fatty acids was estimated in S0.7 preparations incubated with [14C]acetate, by measuring the specific radioactivity of the acetyl carbon of acetyl-CoA and the incorporation of 14C into fatty acids. These estimates were compared with estimates of acetyl-CoA carboxylase activity in the S0.7 preparation obtained by direct assay in conditions in which the enzyme was in the fully activated state. 3. In the absence of citrate, incorporation of acetyl carbon into fatty acids was about 75% of the value expected if the acetyl-CoA carboxylase in the S0.7 preparation were in the fully activated state. 4. Incorporation of acetyl carbon into fatty acids in the S0.7 preparation was stimulated by citrate, but the effect was many times less than the stimulation of [14C]acetate incorporation by citrate in particle-free preparations. 5. When the mitochondria and microsomes were removed from the S0.7 preparation, [14C]acetate incorporation into fatty acids fell to a negligible value and the preparation became highly sensitive to stimulation by citrate. 6. It is suggested that in the presence of mitochondria and microsomes, and in the intact liver cell, the degree of activation of acetyl-CoA carboxylase is such that citrate activation may not be of physiological significance.
Partial characterization of a biologically active steroid glycoside isolated from the starfish Marthasterias glacialis
Authors: Mackie A. M. , Turner A. B.
Published: August 2015

1. A steroid glycoside (M2), which induces avoidance and other reactions in the mollusc Buccinum undatum, has been isolated from extracts of the starfish Marthasterias glacialis by ion-exchange chromatography. 2. The steroid glycoside was homogeneous by t.l.c. and contained glucose, quinovose, fucose and sulphate in the molar proportions 1:2:1:1, in addition to a water-insoluble aglycone. 3. The aglycone was identified as a cholestane derivative containing an unusual Δ24-23-ketone system, two secondary hydroxyl groups and an olefinic double bond, and had the molecular formula C27H42O3. 4. The rates of release of sugars and sulphate suggested that fucose was at the non-reducing end of the oligosaccharide, with glucose glycosidically linked to the steroid. The sulphate group appeared to be linked to the other hydroxyl group of the steroid.
Measurement of oxidized glutathione and total glutathione in the perfused rat heart
Authors: Wendell P. L.
Published: August 2015

1. A method was developed for the assay of GSSG in heart tissue. 2. GSSG and total glutathione were measured in rat hearts perfused under a variety of conditions. About 2% of the total glutathione is present as GSSG. The concentrations of GSSG and GSH remained constant under all the conditions tested. 3. These results are discussed with reference to the equilibrium and rate of the glutathione reductase reaction in the cell. It is concluded that the enzyme reaction does not lie near equilibrium.
Aggregation of ferrihaems. Dimerization and protolytic equilibria of protoferrihaem and deuteroferrihaem in aqueous solution
Authors: Brown S. B. , Dean T. C. , Jones Peter
Published: August 2015

1. The absorption spectra of deutero- and proto-ferrihaem in aqueous solution at 25°C show marked changes with concentration and pH in the Soret band region. Quantitative studies of these phenomena imply that they are associated with ferrihaem dimerization and with protolytic equilibria involving monomeric (M) and dimeric (D) ferrihaem species according to the scheme: [Formula: see text] 2. For deuteroferrihaem we obtain K=1.9×10−2, pKa(M)=7.1, pKa(D)=7.4. Protoferrihaem has a much higher dimerization constant, K=4.5 and pKa(D)=7.5 (pKa(M) is not accessible). 3. Possible structural relationships between monomeric and dimeric ferrihaem species in solution are discussed in relation to recent work on the oxo-bridged nature of crystalline ferrihaem dimers.
The binding in vitro of colchicine to axoplasmic proteins from chicken sciatic nerve
Authors: James K. A. C. , Austin L.
Published: August 2015

1. Axoplasmic proteins were fractionated by means of Sephadex G-200 chromatography followed by isoelectric focusing. Nine groups of proteins were separated. 2. The binding of colchicine to these groups of proteins was examined and it appeared to associate most strongly with one protein group, of pI value 4.9–5.0, which is the major 14C-labelled component of slow-transport protein. 3. Other fractions also bind colchicine. It is not clear whether these are separate proteins or subunits of the major colchicine-binding fraction.
Microbial growth on oxalate by a route not involving glyoxylate carboligase
Authors: Blackmore Maureen A. , Quayle J. R.
Published: August 2015

1. The metabolism of oxalate by the pink-pigmented organisms, Pseudomonas AM1, Pseudomonas AM2, Protaminobacter ruber and Pseudomonas extorquens has been compared with that of the non-pigmented Pseudomonas oxalaticus. 2. During growth on oxalate, all the organisms contain oxalyl-CoA decarboxylase, formate dehydrogenase and oxalyl-CoA reductase. This is consistent with oxidation of oxalate to carbon dioxide taking place via oxalyl-CoA, formyl-CoA and formate as intermediates, and also reduction of oxalate to glyoxylate taking place via oxalyl-CoA. 3. The pink-pigmented organisms, when grown on oxalate, contain l-serine–glyoxylate aminotransferase and hydroxypyruvate reductase but do not contain glyoxylate carboligase. The converse of this obtains in oxalate-grown Ps. oxalaticus. This indicates that, in contrast with Ps. oxalaticus, synthesis of C3 compounds from oxalate by the pink-pigmented organisms occurs by a variant of the `serine pathway' used by Pseudomonas AM1 during growth on C1 compounds. 4. Evidence in favour of this scheme is provided by the finding that a mutant of Pseudomonas AM1 that lacks hydroxypyruvate reductase is not able to grow on oxalate.
Anaerobic rat heart. Effects of glucose and tricarboxylic acid-cycle metabolites on metabolism and physiological performance
Authors: Penney D. G. , Cascarano J.
Published: August 2015

1. The ability of tricarboxylic acid-cycle metabolites to influence the physiological performance of the perfused anaerobic rat heart was investigated. Energy expenditure/h [(beats/min)×60×systolic pressure/g of protein] for various anoxic conditions compared with oxygenated control hearts were: 5mm-glucose, 4.5%; 20mm- or 40mm-glucose, 10%; 20mm-glucose plus fumerate+malate+glutamate, 29%; 20mm-glucose plus oxaloacetate and α-oxoglutarate, 31%. 2. The energy expenditure/lactate production ratio was increased by the tricarboxylic acid-cycle metabolites, indicating that alterations in anaerobic physiological performance did not result from changes in glycolysis. 3. Analysis of tissue constituents provided further indication of an enhanced energy status for fumarate+malate+glutamate- and oxaloacetate+α-oxoglutarate-perfused hearts; tissue concentrations of both glycogen and ATP were higher than in the 20mm-glucose-perfused groups. 4. A marked increase in the accumulation of succinate in tissues perfused with oxaloacetate+α-oxoglutarate or fumarate+malate+glutamate provided further evidence that these metabolites were stimulating mitochondrial energy production under anoxia. 5. These studies indicate that mitochondrial ATP production can be stimulated in an isolated mammalian tissue perfused under anaerobiosis with a resulting enhancement of cell function.
Adenosine 3′:5′-cyclic monophosphate and catabolite repression in Escherichia coli
Authors: Moses V. , Sharp Pamela B.
Published: August 2015

1. Both permanent and transient catabolite repression of β-galactosidase synthesis in Escherichia coli are abolished by 5mm-3′:5′-cyclic-AMP when elicited by glucose, but not when caused by a mixture of glucose, glucose 6-phosphate, gluconate and casein hydrolysate (casamino acids). 2. Glucose uptake is slightly increased by 3′:5′-cyclic-AMP. 3. No significant effects of the nucleotide were found on the synthesis of protein and RNA, either in exponential growth on one substrate, or during a growth shift from glycerol to glycerol plus glucose. 4. Marked changes in the soluble-protein profiles of cells growing in glycerol and glucose were caused by the presence of 3′:5′-cyclic-AMP. 5. Measurements of 14CO2 release from specifically-labelled glucose showed that 3′:5′-cyclic-AMP greatly stimulated glycolytic activity while having a minor depressing effect on the metabolic flow through the pentose phosphate cycle. 6. The concentrations of several metabolic intermediates, particularly fructose 1,6-diphosphate, were greatly affected by the presence of 3′:5′-cyclic-AMP. 7. Several metabolites partially relieved glucose repression of β-galactosidase synthesis in EDTA-treated cells; three out of five of these metabolites reversed the effect more effectively than did 3′:5′-cyclic-AMP. 8. The evidence for and against a direct role for 3′:5′-cyclic-AMP is discussed. It is concluded that the evidence for indirect action is at least as strong as that for direct action.
The effect of electrical stimulation on the incorporation of l-[U-14C]valine into the protein of chopped tissue from guinea-pig cerebral cortex
Authors: Jones C. T. , Banks P.
Published: August 2015

1. Chopped tissue from guinea-pig cerebral cortex carried out an energy-dependent incorporation of [14C]valine into protein. 2. At all times studied the nuclear fraction of the homogenized tissue accounted for about 25% of the total labelled protein. 3. Electrical stimulation at first increased, but subsequently decreased, the rate of incorporation of [14C]valine into protein of the chopped tissue. 4. The initial increase in the incorporation of [14C]valine into protein occurred in the nuclear fraction. At later times electrical stimulation decreased the incorporation into all the subcellular fractions, but the relative contribution of the nuclear fraction to the total labelled protein increased. 5. These changes are discussed in relation to the changes in the rates of respiration, glycolysis, high-energy phosphate content and intracellular Na+ and K+ concentrations, which were measured under the same experimental conditions as those used to study protein synthesis.
The binding of kinetin to plant ribosomes
Authors: Berridge M. V. , Ralph R. K. , Letham D. S.
Published: August 2015

The synthetic cytokinins kinetin and 6-benzylaminopurine exhibit equilibrium-type binding to purified chinese-cabbage leaf ribosomes. At 23μm and 4°C one molecule of kinetin and 1.34 molecules of 6-benzylaminopurine are bound per ribosome. Adenine and adenine derivatives that are inactive as cytokinins showed much less affinity for ribosomes. Pretreatment of ribosomes with 0.5m-ammonium chloride or Triton X-100 did not decrease the extent of cytokinin binding. Binding appeared to be to the 83S ribosome species. A positive correlation between the extent of binding and the biological effect of various cytokinin analogues was demonstrated. These results are discussed in terms of cytokinin control of growth processes at the ribosomal level.
The regulation of triglyceride synthesis and fatty acid synthesis in rat epididymal adipose tissue. Effects of insulin, adrenaline and some metabolites in vitro
Authors: Saggerson E. D. , Greenbaum A. L.
Published: August 2015

1. Adipose tissues from rats fed a balanced diet were incubated in the presence of glucose (20mm) with the following additions: insulin, anti-insulin serum, insulin+acetate, insulin+pyruvate, insulin+lactate, insulin+phenazine methosulphate, insulin+oleate+albumin, insulin+adrenaline+albumin, insulin+6-N-2′-O-dibutyryl 3′:5′-cyclic AMP+albumin. 2. Measurements were made of the whole tissue concentrations of adenine nucleotides, hexose phosphates, triose phosphates, glycerol 1-phosphate, 3 phosphoglycerate, 6-phosphogluconate, long-chain fatty acyl-CoA, acid-soluble CoA, citrate, isocitrate, malate and 2-oxoglutarate, and of the release into the incubation medium of lactate, pyruvate and glycerol after 1h of incubation. 3. Fluxes of [14C]glucose carbon through the major pathways of glucose metabolism were calculated from the yields of 14C in various products after 2h of incubation. Fluxes of [14C]acetate, [14C]pyruvate or [14C]lactate carbon in the presence of glucose were also determined. 4. Measurements were also made of the whole-tissue concentrations of metabolites in tissues taken directly from Nembutal-anaesthetized rats. 5. Whole tissue mass-action ratios for phosphofructokinase, phosphoglucose isomerase and the combined (aldolase×triose phosphate isomerase) reaction were similar in vivo and in vitro. The reactants of phosphofructokinase appeared to be far from mass-action equilibrium. In vitro, the reactants of hexokinase also appeared to be far from mass-action equilibrium. 6. Correlation of observed changes in glycolytic flux with changes in fructose 6-phosphate concentration suggested that phosphofructokinase may show regulatory behaviour. The enzyme appeared to be activated in the presence of oleate or adrenaline and to be inhibited in the presence of lactate or pyruvate. 7. Evidence is presented that the reactants of lactate dehydrogenase and glycerol 1-phosphate dehydrogenase may be near to mass-action equilibrium in the cytoplasm. 8. No satisfactory correlations could be drawn between the whole-tissue concentrations of long-chain fatty acyl-CoA, citrate and glycerol 1-phosphate and the observed rates of triglyceride and fatty acid synthesis. Under the conditions employed, the concentration of glycerol 1-phosphate appeared to depend mainly on the cytoplasmic [NAD+]/[NADH] ratios. 9. Calculated hexose monophosphate pathway flux rates roughly correlated with fatty acid synthesis rates and with whole tissue [6-phosphogluconate]/[glucose 6-phosphate] ratios. The relative rates of production of NADPH for fatty acid synthesis by the hexose monophosphate pathway and by the `malic enzyme' are discussed. It is suggested that all NADH produced in the cytoplasm may be used in that compartment for reductive synthesis of fatty acids, lactate or glycerol 1-phosphate.
Stimulation by Erwinia carotovora of the synthesis of ethylene in cauliflower tissue
Authors: Lund Barbara M. , Mapson L. W.
Published: August 2015

The synthesis of ethylene by cauliflower floret tissue was increased when the tissue was inoculated with the soft-rot bacterium Erwinia carotovora. This effect was clearly associated with the production of pectic enzymes by the micro-organism. These enzymes, acting together with the plant enzymes, stimulated the production of ethylene from methionine. The increased synthetic activity was due to the release and increased activity of a glucose oxidase enzyme apparently attached to plant cell-wall material and liberated by the action of pectic enzymes of the bacterium.
The effect of steroids and nucleotides on solubilized bilirubin uridine diphosphate glucuronyltransferase
Authors: Adlard B. P. F. , Lathe G. H.
Published: August 2015

1. It was confirmed that bilirubin glucuronyltransferase can be obtained in solubilized form from rat liver microsomes. 2. Michaelis–Menten kinetics were not followed by the enzyme with bilirubin as substrate when the bilirubin/albumin ratio was varied. High concentrations of bilirubin were inhibitory. 3. The Km for UDP-glucuronic acid at the optimum bilirubin concentration was 0.46mm. 4. Low concentrations of Ca2+ were inhibitory in the absence of Mg2+ but stimulatory in its presence; the converse applied for EDTA. 5. UDP-N-acetylglucosamine and UDP-glucose enhanced conjugation by untreated, but not by solubilized microsomes. 6. The apparent 9.5-fold increase in activity after solubilization was probably due to the absence of UDP-glucuronic acid pyrophosphatase activity in the solubilized preparation. 7. The activation of solubilized enzyme activity by ATP was considered to be a result of chelation of inhibitory metal ions. 8. The solubilized enzyme activity was inhibited by UMP and UDP. The effect of UMP was not competitive with respect to UDP-glucuronic acid. 9. A number of steroids inhibited the solubilized enzyme activity. The competitive effects of stilboestrol, oestrone sulphate and 3β-hydroxyandrost-5-en-17-one, with respect to UDP-glucuronic acid, may be explained on an allosteric basis.
Studies in vivo on the biosynthesis of collagen and elastin in ascorbic acid-deficient guinea pigs. Evidence for the formation and degradation of a partially hydroxylated collagen
Authors: Barnes M. J. , Constable B. J. , Morton L. F. , Kodicek E.
Published: August 2015

1. After the administration of l-[G-3H]proline to guinea pigs deprived of ascorbic acid for increasing periods of time, the specific radioactivities of proline and hydroxyproline in skin collagen and aortic elastin were determined at various time-intervals after administration of the labelled compound with a view to studying the formation and degradation of collagen and elastin both deficient in hydroxyproline. 2. As judged from the incorporation of radioactivity into elastin proline, elastin synthesis was not decreased in the ascorbic acid-deficient animals. There was however, a rapid decline in the specific radioactivity of elastin hydroxyproline. The proline/hydroxyproline specific-radioactivity ratio was approx. 1.5:1 after 6 days and 20:1 after 12 days of ascorbic acid deprivation, in contrast with the ratio of 1:1 in controls. The results suggested that the effect of ascorbic acid deficiency on elastin biosynthesis could be regarded as simply an elimination of hydroxylation of elastin proline with the formation and retention of a polymer increasingly deficient in hydroxyproline. 3. Collagen proline and hydroxyproline specific radioactivities were derived from material that was soluble in hot trichloroacetic acid, non-diffusible and collagenase-degradable. In contrast with elastin, there was a rapid decline in the specific radioactivity of proline as well as hydroxyproline in collagen from the ascorbic acid-deficient animals. However, the proline/hydroxyproline specific-radioactivity ratio in all samples from scorbutic animals was consistently slightly above 1:1. The results suggest the appearance in place of collagen, but in rapidly diminishing amounts, of a partially hydroxylated collagen in which the degree of hydroxylation may be decreased only by approx. 10%. 4. Incorporation of radioactivity into the diffusible hydroxyproline in skin remained relatively high despite the rapid decline in the incorporation of radioactivity into collagen. This observation is interpreted as indicative of an increasing degree of degradation of partially hydroxylated collagen to diffusible peptides. An alternative explanation might be that partially hydroxylated peptides are released to an increasing extent from ribosomes before they attain a length at least sufficient to render them non-diffusible. In either case it implies the accumulation in scurvy of low-molecular-weight peptides enriched in proline and deficient in hydroxyproline and could explain the failure to accumulate a high-molecular-weight collagen deficient in hydroxyproline. 5. It is thought, however, that, in addition, an inhibition of ribosomal amino acid incorporation leading to decreased synthesis of partially hydroxylated collagen may also occur, perhaps secondarily to impaired hydroxylation.
Creatine regulation in the embryo and growing chick
Authors: Ramírez Oscar , Calva Edmundo , Trejo Augusto
Published: August 2015

1. The absence of creatine was demonstrated enzymically in the hen's-egg yolk and in the albumin contrary to former reports. 2. A comparison of the results obtained by enzymic and colorimetric methods to measure creatine is presented. 3. Creatine phosphate was not detected in the yolk extracts. 4. The content of free arginine enzymically assayed was 15.7μmol in the yolk and 3.38μmol in the albumin. Arginine amounts to practically all of the guanidine compounds in the yolk and one-half of those in the albumin. 5. No glycine amidinotransferase activity was found in the egg-yolk homogenates. 6. The heart of the chick embryo does not receive creatine from the egg and the creatine kinase activity present in this organ starting from the 27th hour of incubation suggests that the enzyme is a constitutive one working probably as an adenosine triphosphatase in a way similar to the kinase isolated from rabbit skeletal muscle. 7. Liver glycine amidinotransferase activity appeared clearly after day 5 of incubation. The specific activity reached a maximum at day 12 and then declined; however, the activity per total mass of liver increased steadily during all the prenatal period. Concomitantly with this steady increase a rise in the creatine content of the whole embryo was observed. An analogous increasing relationship between total liver amidinotransferase activity and liver creatine content was also detected during the postnatal period. 8. Repression of amidinotransferase by creatine cannot be accepted as occurring under physiological conditions since an inverse relationship between the two parameters was not observed. 9. Repression of liver amidinotransferase is observed only when pharmacological concentrations of the exogenous creatine are present in the chick liver.
Metabolism of phenylalanine in mice homozygous for the gene ‘dilute lethal’
Authors: Woolf L. I. , Jakubovic A. , Woolf F. , Bory P.
Published: August 2015

Mice homozygous for dl have been suggested as models for phenylketonuria. We found: (1) the concentration of phenylalanine in the blood was normal at all ages examined; (2) phenylalanine hydroxylase activity in the liver in vitro equalled that in unaffected littermates; (3) the apparent Km values for phenylalanine and cofactor respectively in dl/dl mice were the same as in their normal littermates; (4) inhibition of the overall reaction by the particulate fraction, excess of substrate, excess of cofactor or phenylpyruvic acid showed no difference between dl/dl mice and their unaffected littermates; (5) phenylalanine injected in vivo had equal, small, effects on phenylalanine hydroxylase activity of the liver measured in vitro in the two groups of mice. An explanation of the findings of other workers, based on the natural history of the disease process, is tentatively put forward.
An effect of insulin on adipose-tissue adenosine 3′:5′-cyclic monophosphate phosphodiesterase
Authors: Loten E. G. , Sneyd J. G. T.
Published: August 2015

1. 3′:5′-Cyclic nucleotide phosphodiesterase activity was measured in homogenates prepared from epididymal fat-pads and isolated fat-cells incubated in the absence and presence of insulin. 2. Homogenates of insulin-treated tissues showed an increase in phosphodiesterase activity compared with controls. No effect of insulin was observed when the hormone was added directly to homogenates. 3. There was kinetic evidence for the presence of two 3′:5′-cyclic nucleotide phosphodiesterases in adipose tissue. Insulin raised the maximal velocity of the low-Km enzyme and lowered the Km of the higher-Km enzyme. 4. It is suggested that the effect of insulin on adipose tissue phosphodiesterase accounts for the ability of this hormone to lower cyclic-AMP concentration in the tissue.
Decreased ribonucleic acid synthesis in isolated rat liver nuclei during starvation
Authors: Rickwood D. , Klemperer H. G.
Published: August 2015

1. Isolated nuclei from starved rats showed a lowered incorporation of [14C]UMP into RNA. 2. The Mg2+-dependent incorporation was decreased by 30% after 1 day of starvation, but incorporation in the presence of Mn2+ and ammonium sulphate decreased only after longer periods of starvation. 3. RNA synthesis by nuclei in the presence of excess of added RNA polymerase was unchanged after 1 day of starvation and was inhibited by 20% after 4 days. 4. The capacity of nuclei to bind actinomycin D was unchanged after 1 day and was decreased by 20% after 4 days of starvation.
The purification and properties of carbonic anhydrases from guinea-pig erythrocytes and the mucosae of the gastrointestinal tract
Authors: Carter M. J. , Parsons D. S.
Published: August 2015

Procedures for isolating carbonic anhydrase (EC 4.2.1.1) enzymes from the erythrocytes and the mucosae of the gastrointestinal tract of guinea pigs are described. From a haemolysate, haemoglobin was removed by the addition of ammonium sulphate, and also by two other methods, namely by gel filtration or by adsorption on DEAE-Sephadex. The crude enzyme thus obtained was resolved into the different isoenzymes by chromatography with DEAE-cellulose. From particle-free supernatants of homogenates of some gastrointestinal tissues, carbonic anhydrases were purified by ammonium sulphate fractionation, gel filtration, and ion-exchange chromatography with DEAE-cellulose. The major isoenzymes from blood, stomach, proximal colonic mucosa and caecal mucosa were homogeneous during ion-exchange chromatography, acrylamide-gel electrophoresis, and centrifugal examination. From these tissues, carbonic anhydrase was isolated as two major isoenzymes. They resemble the pairs of isoenzymes discovered in the bloods of other species. The carbon dioxide hydratase activity of one isoenzyme (`high activity' carbonic anhydrase) was 40 times that of the other isoenzyme (`low activity' carbonic anhydrase), as measured at a single substrate concentration. Two other minor components of the enzyme are also found in guinea-pig erythrocytes. All of the enzymes isolated had molecular weights of nearly 30000 (sedimentation equilibrium). `High activity' carbonic anhydrases from blood and gastrointestinal tissues were indistinguishable according to some chemical, physical and kinetic measurements; similarly `low activity' carbonic anhydrases from those tissues were indistinguishable. `High activity' carbonic anhydrase was markedly different from the `low activity' carbonic anhydrase with respect to its amino acid composition, chromatographic behaviour and isoelectric pH value. Marked differences were also found in the tissue concentrations of the major isoenzymes. It is suggested that the characteristic and selective distribution of the different forms of carbonic anhydrase in the guinea-pig tissues is related to the specific and different physiological functions of the enzymes.
The concentration of amino acids by yeast cells depleted of adenosine triphosphate
Authors: Eddy A. A. , Backen K. , Watson G.
Published: August 2015

1. The ATP content of preparations of a strain of Saccharomyces carlsbergensis was lowered below 0.3nmol/mg of yeast by starving the yeast cells in the presence of both antimycin and 5mm-deoxyglucose. 2. When the depleted cells were put at pH4.5 with glycine up to about 20nmol of the amino acid/mg of yeast was absorbed without being chemically modified. The mechanism did not depend on an exchange with endogenous amino acids. 3. The concentration of the absorbed glycine could apparently reach 100–200 times that outside the cells. 4. Replacement of the cellular K+ by Na+ almost stopped amino acid absorption in the presence of antimycin and deoxyglucose, but not in their absence. 5. It is suggested that, when energy metabolism itself had stopped, a purely physical process, namely the movements of H+ and K+ into and out of the yeast respectively, served to concentrate the amino acids in the cells. Both ionic species appear to be co-substrates of the system transporting amino acids.
Mass-spectrometric study of the azopigments obtained from bile pigments with diazotized ethyl anthranilate
Authors: Compernolle F. , Jansen F. H. , Heirwegh K. P. M.
Published: August 2015

The structures of some azopigments obtained by diazotization of conjugated and unconjugated bile pigments with diazotized ethyl anthranilate were studied by mass spectrometry. The α0-azopigments derived from rat bile and human bile were shown to be identical (t.l.c. and mass spectra) with azobilirubin derived from unconjugated bilirubin. The presence of two methyl vinyl isomers (Ia) and (Ib) in equal amounts was shown by t.l.c. and mass spectrometry. The structure of the δ-azopigment derived from rat bile was studied by two methods: (a) ammonolysis gave rise to an amide having a CH2·CH2·CO·NH2 side chain as shown by its mass spectrum; (b) the mass spectrum of a trimethylsilyl derivative of the δ-azopigment methyl ester confirmed the ester to be a β-d-monoglucuronide ester of azobilirubin I.
Regulation of gluconeogenesis during exposure of young rats to hypoxic conditions
Authors: Ballard F. J.
Published: August 2015

1. Two-day-old rats were exposed at constant temperature to atmospheres containing air and nitrogen with the air content varied in steps from 100 to 0%. By using this system of graded hypoxia a comparison was made between rates of gluconeogenesis from lactate, serine and aspartate in the whole animal and the concentrations of several liver metabolites. 2. Gluconeogenesis, expressed as the percentage incorporation of labelled isotope into glucose plus glycogen, proceeds linearly for 30min when the animals are incubated in a normal air atmosphere, but is completely suppressed if the atmosphere is 100% nitrogen. 3. Preincubation of animals for between 5 and 30min under an atmosphere containing 19% air results in the attainment of a new steady state with respect to gluconeogenesis and hepatic concentrations of ATP, ADP, AMP, lactate, pyruvate, β-hydroxybutyrate and acetoacetate. 4. When lactate (100μmol), aspartate (20μmol) or serine (20μmol) was injected, it was shown that the more severe the hypoxia the greater the depression of gluconeogenesis. Under conditions when gluconeogenesis was markedly inhibited there were no changes in the degree of phosphorylation of hepatic adenine nucleotides, but free [NAD+]/[NADH] ratios fell in both cytosol and mitochondrial compartments of the liver cell. 5. Measurements of total liver NAD+ and NADH showed that the concentrations of these nucleotide coenzymes changed less with anoxia, in comparison with the concentration ratio of free coenzymes. 6. Calculations showed that the difference in NAD+–NADH redox potentials between mitochondrial and cytosol compartments increased with the severity of hypoxia. 7. From the constancy of the concentrations of adenine nucleotides it is concluded that liver of hypoxic rats can conserve ATP by lowering the rate of ATP utilization for gluconeogenesis. Gluconeogenesis may be regulated in turn by the changes in mitochondrial and cytosol redox state.
Mitochondrial development in liver of foetal and newborn rats
Authors: Jakovcic S. , Haddock J. , Getz G. S. , Rabinowitz M. , Swift H.
Published: August 2015

The development of the inner mitochondrial membrane in foetal and neonatal rat liver was studied by following three parameters: (1) the activity of several respiratory enzymes in homogenates and purified mitochondria, (2) the spectrophotometric determination of cytochrome content in the mitochondria and (3) the cardiolipin content in both homogenates and purified mitochondria. Respiratory-enzyme activities of homogenates of foetal liver were one-quarter to one-twentieth of those of homogenates of adult liver, and the enzyme specific activities in purified mitochondria from foetal liver were one-half to one-eighth of those in mitochondria from adult liver. The cardiolipin content of liver homogenates increased approximately twofold during the development period, but there was no significant change in the cardiolipin content of purified mitochondria. It is concluded that cell mitochondrial content approximately doubles in the immediate postnatal period. There was no evidence for an increase in the relative amount of cristae protein in mitochondria during this period to account for increases in mitochondrial enzyme specific activity, since cardiolipin and cytochrome concentrations remained unchanged and electron micrographs revealed no differences. The cause of the lower respiratory-enzyme specific activity in foetal liver mitochondria is unclear. Qualitative differences in respiratory units in foetal and mature animals are suggested.
Homoserine and diaminobutyric acid in the mucopeptide-precursor-nucleotides and cell walls of some plant-pathogenic corynebacteria
Authors: Perkins H. R.
Published: August 2015

The nucleotide precursors of cell-wall mucopeptide were prepared by vancomycin inhibition of Corynebacterium insidiosum and Corynebacterium poinsettiae. The amino acid in the third position in the former peptide was shown by optical rotatory dispersion of the bisdinitrophenyl derivative to be l-diaminobutyric acid. Homoserine in the nucleotide from C. poinsettiae was catalytically oxidized to aspartic acid, which was then shown to be the l-isomer by optical rotatory dispersion of the trinitrophenyl compound. The sequence for C. insidiosum was UDP-N-acetylmuramyl-glycyl-isoglutamyl- (γ-acetyl)-diaminobutyryl-alanyl-alanine. The cell walls of C. insidiosum and Corynebacterium sepedonicum contained diaminobutyric acid that was optically inactive. It is proposed, therefore, that the primary peptide chain contains the l-isomer with its γ-amino group blocked by acetylation and that cross-linking is achieved by means of the d-isomer, analogous to d-ornithine in C. poinsettiae.
The biosynthesis of gangliosides. The incorporation of galactose, N-acetylgalactosamine and N-acetylneuraminic acid into endogenous acceptors of subcellular particles from rat brain in vitro
Authors: Arce A. , Maccioni H. J. , Caputto R.
Published: August 2015

Gangliosides bound to subcellular particles from rat brain were labelled by incubation of the particles (i) with CMP-N[3H]-acetylneuraminic acid and (ii) simultaneously, with CMP-N[3H]-acetylneuraminic acid and UDP-N-acetyl-[14C1]galactosamine or with CMP-N[3H]-acetylneuraminic acid and UDP-[U-14C]-galactose. Analysis of the labelled gangliosides showed that in (i), (a) the labelling was mostly in the neuraminidase-labile sialyl groups, (b) rigid relationships exist between the enzymes and the sialyl acceptors; the enzymes are not free to interact with all the specific substrates present in the preparation and (c) the precursor of the trisialoganglioside was the major disialoganglioside with a sialyl 2→8 sialyl group. In (ii), (a) precursor–product relationships between the main pools of each ganglioside apparently do not exist, (b) for the labelling of Tay–Sachs ganglioside the amount formed from hematoside was at least 2.5 times that from aminoglycolipid and (c) the major monosialoganglioside was the precursor for the major disialoganglioside with a sialyl 2→8 sialyl group.