bluuebunny/crossref_metadata_2025 huggingface dataset:
Biosynthesis of geraniol and nerol and their β-d-glucosides in Perlargonium graveolens and Rosa dilecta
Authors: Banthorpe Derek V. , Le Patourel Geoffrey N. J. , Francis Martin J. O.
Published: August 2015

1. 3R-[2-14C]Mevalonate was incorporated into geranyl and neryl β-d-glucosides in petals of Rosa dilecta in up to 10.6% yield, and the terpenoid part was specifically and equivalently labelled in the moieties derived from isopentenyl pyrophosphate and 3,3-dimethylallyl pyrophosphate. A similar labelling pattern, with incorporations of 0.06–0.1% was found for geraniol or nerol formed in leaves of Pelargonium graveolens The former results provide the best available evidence for the mevalonoid route to regular monoterpenes in higher plants. 2. Incorporation studies with 3RS-[2-14C,(4R)-4-3H1]-mevalonate and its (4S)-isomer showed that the pro-4R hydrogen atom of the precursor was retained and the pro-4S hydrogen atom was eliminated in both alcohols and both glucosides. These results suggest that the correlation of retention of the pro-4S hydrogen atom of mevalonate with formation of a cis-substituted double bond, such as has been found in certain higher terpenoids, does not apply to the biosynthesis of monoterpenes. It is proposed that either nerol is derived from isomerization of geraniol or the two alcohols are directly formed by different prenyltransferases. Possible mechanisms for these processes are discussed. 3. The experiments with [14C,3H]mevalonate also show that in these higher plants, as has been previously found in animal tissue and yeast, the pro-4S hydrogen atom of mevalonate was lost in the conversion of isopentenyl pyrophosphate into 3,3-dimethylallyl pyrophosphate.
The sites of synthesis and transport of extracellular polysaccharides in the root tissues of maize
Authors: Bowles Dianna J. , Northcote D. H.
Published: August 2015

1. Subcellular fractionation of maize roots resulted in the isolation of the following enriched fractions: cell wall, dictyosome, smooth-membrane and rough-microsomal fractions. In addition, extracellular polysaccharide of the root slime was isolated. 2. Maizeseedling roots were incubated in vivo with d-[U-14C]glucose, and the pattern of incorporation of radioactivity into the polysaccharides of each fraction was investigated. 3. The differentiation of maize-root cells with respect to the synthesis of specific extracellular polysaccharide directly relates to the polysaccharide synthesized and transported within the membrane system of the cell. A fucose-containing polysaccharide, characteristic only of root slime, was present only in the membrane system of the root-tip region of the root. Regions of typical secondary wall development within the root were characterized by an increased incorporation of radioactivity into xylose of polysaccharide within the membrane system. 4. The incorporation of radioactivity into glucan polymers in the membrane fractions was very low in all regions of the root. Since in regions of secondary wall development greater than 60% of all radioactive incorporation was into a glucan polymer, it can be inferred that this polymer, most probably cellulose, is not synthesized or transported within the compartments of the membrane system. It is suggested that synthesis of cellulose occurs at the surface of the plasmalemma. 5. Maize-root cells contained 40 times more rough endoplasmic reticulum than dictyosome membrane. The relative specific radioactivities of each fraction indicated that polysaccharide was concentrated in the region of the Golgi apparatus, which showed a 100% increase in specific radioactivity compared with the rough endoplasmic reticulum. The Golgi apparatus can thus be regarded as a localized focal point on the synthetic and transport system of polysaccharide by the intracellular membrane compartments.
Kinetic properties of the partially purified pyruvate dehydrogenase complex of ox brain
Authors: Blass John P. , Lewis Carole A.
Published: August 2015

The properties of a purified preparation of the pyruvate dehydrogenase complex from ox brain have been compared with those of a similar preparation from ox kidney. A broad pH optimum around 7.8, similar dependence on ionic strength, and independence of the nature of the buffer anions or cations characterized preparations from both tissues. Michaelis constants for the binding of pyruvate, thiamin pyrophosphate, NAD+ and CoA were also similar. Enzyme from both tissues was inhibited by NADH, by copper and other heavy metals, by high concentrations of tricarboxylic acid-cycle intermediates, and by preincubation with ATP. Acetyl-CoA itself did not appear to inhibit these preparations, although some commercial preparations of acetyl-CoA did contain an inhibitor. Although oxaloacetate and α-oxobutyrate were weak inhibitors, a number of other α-oxo acids including phenylpyruvate did not inhibit. The properties of the pyruvate dehydrogenase complex from brain and kidney appeared similar.
The deoxyfluoro-d-glucopyranose 6-phosphates and their effect on yeast glucose phosphate isomerase
Authors: Bessell Eric M. , Thomas Peter
Published: August 2015

1. The deoxyfluoro-d-glucopyranose 6-phosphates were prepared from the corresponding deoxyfluoro-d-glucoses and ATP by using hexokinase. 2. 3-Deoxy-3-fluoro- and 4-deoxy-4-fluoro-d-glucose 6-phosphate were substrates for glucose phosphate isomerase, and in addition the products of this reaction, 3-deoxy-3-fluoro- and 4-deoxy-4-fluoro-d-fructose 6-phosphate respectively, were good substrates for phosphofructokinase. 3. Some C-2-substituted derivatives of d-glucose 6-phosphate were found to be competitive inhibitors of glucose phosphate isomerase. 4. The possible role of the hydroxyl groups in the binding of d-glucose 6-phopshate to glucose phosphate isomerase is discussed.
The amino acid sequence of cytochrome c from Spinacea oleracea L. (spinach)
Authors: Brown R. H. , Richardson M. , Scogin R. , Boulter D.
Published: August 2015

The amino acid sequence of spinach (Spinacea oleracea L., var. Monster Viroflay) cytochrome c was determined on 1μmol of protein. The molecule consists of 111 residues and is homologous with other mitochondrial cytochromes c. Experimental details are given in a supplementary paper that has been deposited as Supplementary Publication SUP 50013, at the National Lending Library for Science and Technology, Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1973), 131, 5.
Protein synthesis and the viability of rye grains. Loss of activity of protein-synthesizing systems in vitro associated with a loss of viability
Authors: Roberts B. E. , Payne P. I. , Osborne D. J.
Published: August 2015

A study was made of the integrity of some components of the protein-synthesizing system from viable and non-viable embryos of rye grains. In comparison with viable-embryo components both post-ribosomal supernatant and ribosomal fractions from non-viable embryos are impaired, for neither will fully support polyphenylalanine synthesis in poly(U)-directed cell-free systems. The lesion in the supernatant lies in components other than the tRNA or the aminoacyl-tRNA synthetase, for these are as functional as those present in the fully active cell-free systems from viable embryos. The ribosomes of embryos of lowered viability show considerable fragmentation and degradation of both 18S and 25S rRNA. This breakdown does not, however, account for the complete lack of polypeptide synthesis in the poly(U)-directed non-viable-embryo system, for if provided with viable-embryo supernatant, non-viable-embryo ribosomes will sustain 60% of the viable-embryo ribosome activity. A lesion in non-viable-embryo supernatant has been located in the binding of the aminoacyl-tRNA to the ribosome. The impaired components in both supernatant and ribosomes in systems in vitro may reflect the site of faults in protein synthesis in vivo in the early hours of germination. The development of these lesions during grain storage could contribute to senescence and loss of viability in the embryos of rye.
The quantitative determination of glycosaminoglycans in urine with Alcian Blue 8GX
Authors: Whiteman P.
Published: August 2015

1. The effect of MgCl2 concentration on the interaction of Alcian Blue 8GX and glycosaminoglycans in the urine of patients with mucopolysaccharidosis was studied by using a new quantitative micro method for the measurement of Alcian Blue–glycosaminoglycan complexes. This provided a means of measuring the critical electrolyte concentrations of urinary glycosaminoglycans. 2. Theoretical considerations based on the preceding paper (Whiteman, 1973) and experimental evidence provided here show that Alcian Blue 8GX may be used for the direct quantitative determination of total urinary glycosaminoglycans. The method is simple, requires sample volumes of 50μl or less, and gives results comparable with those obtained by other more complicated methods.
Hepatic redox state and gluconeogenesis from lactate in vivo in the rat
Authors: Hawkins Richard A. , Houghton C. Roger S. , Williamson Dermot H.
Published: August 2015

1. To examine the role of the hepatic redox state on the rate of gluconeogenesis the effects of sodium crotonate injection (6mmol/kg body wt.) on rat liver metabolite concentrations and gluconeogenesis from lactate were studied in vivo. 2. Crotonate caused a marked oxidation of cytoplasmic and mitochondrial redox couples; decreases were observed in the ratios of [lactate]/[pyruvate], [glycerol 3-phosphate]/[dihydroxyacetone phosphate], [hydroxybutyrate]/[acetoacetate] and measured [NAD+]/[NADH]. 3. Increases occurred in the liver concentrations of all gluconeogenic intermediates from pyruvate through to glucose 6-phosphate, but there was no change in lactate concentration. 4. To determine whether gluconeogenesis from lactate was altered by the more-oxidized hepatic redox state l-[2-14C]lactic acid was infused into the inferior vena cava (50μmol/min per kg body wt.) and the incorporation of radioactivity into blood glucose was measured. 5. Administration of crotonate transiently decreased the rate of lactate incorporation into glucose but within a few minutes the rate of incorporation returned to that of the controls. 6. The results indicate that in these experiments alteration of the NAD+–NADH systems of cytoplasm and mitochondria to a more-oxidized state did not change the rate of gluconeogenesis.
The intramitochondrial location of the glutaminase isoenzymes of pig kidney
Authors: Crompton M. , Mcgivan J. D. , Chappell J. B.
Published: August 2015

1. The glutaminase activity of pig kidney is located almost entirely in the cortex. 2. Pig renal cortex contains two glutaminases, one phosphate-dependent and one phosphate-independent. Both isoenzymes are localized exclusively in the mitochondria. 3. After sonication of the mitochondria, the phosphate-dependent isoenzyme is entirely soluble, whereas approximately half the phosphate-independent isoenzyme is associated with the membranes. 4. In intact mitochondria, the activities of both isoenzymes respond to changes in the pH of the intramitochondrial compartment. 5. It is concluded that both glutaminase isoenzymes are situated in the intramitochondrial compartment, and that the phosphate-independent glutaminase may be bound to the inside of the inner mitochondrial membrane.
Trimethylamine metabolism in obligate and facultative methylotrophs
Authors: Colby J. , Zatman L. J.
Published: August 2015

1. Twelve bacterial isolates that grow with trimethylamine as sole source of carbon and energy were obtained in pure culture. All the isolates grow on methylamine, dimethylamine and trimethylamine. One isolate, bacterium 4B6, grows only on these methylamines whereas another isolate, bacterium C2A1, also grows on methanol but neither grows on methane; these two organisms are obligate methylotrophs. The other ten isolates grow on a variety of Ci and other organic compounds and are therefore facultative methylotrophs. 2. Washed suspensions of the obligate methylotrophs bacteria 4B6 and C2A1, and of the facultative methylotrophs bacterium 5B1 and Pseudomonas 3A2, all grown on trimethylamine, oxidize trimethylamine, dimethylamine, formaldehyde and formate; only bacterium 5B1 and Ps. 3A2 oxidize trimethylamine N-oxide; only bacterium 4B6 does not oxidize methylamine. 3. Cell-free extracts of trimethylamine-grown bacteria 4B6 and C2A1 contain a trimethylamine dehydrogenase that requires phenazine methosulphate as primary hydrogen acceptor, and evidence is presented that this enzyme is important for the growth of bacterium 4B6 on trimethylamine. 4. Cell-free extracts of eight facultative methylotrophs, including bacterium 5B1 and Ps. 3A2, do not contain trimethylamine dehydrogenase but contain instead a trimethylamine monooxygenase and trimethylamine N-oxide demethylase. It is concluded that two different pathways for the oxidation of trimethylamine occur amongst the isolates.
Studies of mammalian glucoside conjugation
Authors: Gessner T. , Jacknowitz A. , Vollmer C. A.
Published: August 2015

The mammalian glucoside-conjugation pathway was studied by using p-nitrophenol as the model substrate and mouse liver microsomal preparations as the source of enzyme. The microsomal preparations supplemented with UDP-glucose glucosylated p-nitrophenol; p-nitrophenyl glucoside was identified by chromatography in six solvent systems. The unsolubilized glucosyltransferase of fresh microsomal preparations did not follow the usual Michaelis–Menten kinetics and was easily inhibited by many steroids. All the steroids tested inhibited glucosylation of p-nitrophenol to a greater degree than glucuronidation of p-nitrophenol when assayed in the same microsomal preparations. The steroids inhibited glucosylation with the following decreasing effectiveness: pregnan-3α-ol-20β-one (3α-hydroxypregnan-20-β-one)>oestradiol-17β 3-methyl ether>oestradiol-17β>oestriol>pregnane-3α,20β-diol>oestrone. Pregnan-3α-ol-20β-one, pregnane-3α,20β-diol and oestrone had negligible effect on glucuronidation.
Free amino acids of testes. Concentrations of free amino acids in the testes of several species and the precursors of glutamate and glutamine in rat testes in vivo
Authors: Mushahwar Isa K. , Koeppe Roger E.
Published: August 2015

Determination of the free amino acid and lactate content of testicular tissue in rat, guinea pig, rabbit, cat, gerbil, hamster, chicken and bullfrog indicates a substantial species variation. Insulin hypoglycaemia and ammonium acetate toxicity changes the concentration of several free amino acids of rat testes. 14C radioactivity from labelled acetate and ethanol is rapidly incorporated into some of the free amino acids of rat testes in vivo, whereas incorporation from [14C]glucose is relatively slow. These results have been compared with those obtained from similar studies with rat brain. In contrast to brain, there is no evidence for glutamate compartmentation in testes.
The role of membrane phospholipids in the interaction of ribosomes with endoplasmic-reticulum membrane (Short Communication)
Authors: Jothy S. , Tay S. , Simpkins H.
Published: August 2015

It is shown that the ionic head groups of the membrane phospholipids cannot be solely responsible for the attachment of the ribosome and that other membrane components must also be involved in the binding process.
The catalytic activity of horse spleen apoferritin. Preliminary kinetic studies and the effect of chemical modification
Authors: Bryce Charles F. A. , Crichton R. R.
Published: August 2015

1. Horse spleen apoferritin catalyses the oxidation of Fe2+ to Fe3+ with molecular O2 as electron acceptor under conditions where a number of other proteins have no such effect. The product is similar to ferritin by a number of criteria. 2. The progress curve is hyperbolic and the increase in initial velocity is linear with increasing apoferritin concentration. With respect to Fe2+ the reaction follows Michaelis–Menten kinetics. The pH-dependence of the reaction was determined between pH4.3 and 6.0. 3. Modification of both tryptophan residues/apoferritin subunit with 2-nitrophenylsulphenyl chloride does not affect either kcat. or Km for the oxidation. Neither does the guanidination of seven out of nine lysine residues/subunit, the modification of nine out of ten arginine residues/subunit with cyclohexanedione, or the nitration of one out of five tyrosine residues/subunit with tetranitromethane. 4. The carboxymethylation of two out of three cysteine residues/subunit and of one out of six histidine residues/subunit can be achieved with iodoacetic acid. This carboxymethylated apoferritin is completely inactive in Fe2+ oxidation. 5. Apoferritin does not take up Fe3+. It appears from these results that Fe2+ is the form in which iron is taken up by ferritin in a reaction where the protein acts as an enzyme which traps the product in the interior of the protein shell.
Adenosine diphosphate sulphurylase activity in leaf tissue
Authors: Burnell Jim N. , Anderson John W.
Published: August 2015

1. A new method is described for the assay of ADP sulphurylase. The method involves sulphate-dependent [32P]Pi–ADP exchange; the method is simpler, more sensitive and more direct than the method involving adenosine 5′-sulphatophosphate-dependent uptake of Pi. 2. ADP sulphurylase activity was demonstrated in crude extracts of leaf tissue from a range of plants. Crude spinach extract catalysed the sulphate-dependent synthesis of [32P]ADP from [32P]Pi; spinach extracts did not catalyse sulphate-dependent AMP–Pi, ADP–PPi or ATP–Pi exchange under standard assay conditions. ADP sulphurylase activity in spinach leaf tissue was associated with chloroplasts and was liberated by sonication. 3. Some elementary kinetics of crude spinach leaf and purified yeast ADP sulphurylases in the standard assay are described; addition of Ba2+ was necessary to minimize endogenous Pi–ADP exchange of the yeast enzyme and crude extracts of winter-grown spinach. 4. Spinach leaf ADP sulphurylase was activated by Ba2+ and Ca2+; Mg2+ was ineffective. The yeast enzyme was also activated by Ba2+. The activity of both enzymes decreased with increasing ionic strength. 5. Purified yeast and spinach leaf ADP sulphurylases were sensitive to thiol-group reagents and fluoride. The pH optimum was 8. ATP inhibited sulphate-dependent Pi–ADP exchange. Neither selenate nor molybdate inhibited sulphate-dependent Pi–ADP exchange and crude spinach extracts did not catalyse selenate-dependent Pi–ADP exchange. 6. The presence of ADP sulphurylase activity jeopardizes the enzymic synthesis of adenosine 5′-sulphatophosphate from ATP and sulphate with purified ATP sulphurylase and pyrophosphatase.
The N-acetylhexosaminidase components of the ram testis and epididymis
Authors: Bullock Sarah , Winchester Bryan
Published: August 2015

Three and four N-acetylhexosaminidase components, from ram testis and epididymis respectively, have been separated by ion-exchange chromatography on DEAE-cellulose. Although they all have the same molecular weight (approx. 140000) and very similar catalytic properties towards the synthetic substrates, 4-methylumbelliferyl N-acetyl-β-glucosaminide and N-acetyl-β-galactosaminide, isoelectric focusing of the individual components showed that each had a distinct pI value. Isoelectric focusing has also been used to demonstrate the occurrence of multiple forms in ejaculated ram semen.
X-ray diffraction patterns from chondroitin 4-sulphate, dermatan sulphate and heparan sulphate (Short Communication)
Authors: Atkins E. D. T. , Laurent T. C.
Published: August 2015

Ordered conformations from the sodium salts of chondroitin 4-sulphate, dermatan sulphate and heparan sulphate were observed by X-ray diffraction. Chondroitin 4-sulphate shows similar threefold helical character to that previously reported for chondroitin 6-sulphate and hyaluronates. Dermatan sulphate forms an eightfold helix with an axial rise per disaccharide of 0.93nm, which favours the l-iduronic acid moiety in the normal C1 chair form. The layer-line spacing and axial projection in heparan sulphate of 1.86nm favours a tetrasaccharide repeat with glycosidic linkages alternating β-d-(1→4) and α-d-(1→4).
Regulation of renal gluconeogenesis by calcium ions, hormones and adenosine 3′:5′-cyclic monophosphate
Authors: Roobol Anne , Alleyne George A. O.
Published: August 2015

1. The effect of Ca2+, glucagon, adrenaline and adenosine 3′:5′-cyclic monophosphate on gluconeogenesis by rat kidney-cortex slices was studied. 2. Glucose formation from a range of substrates, with the exception of glycerol, was increased by an increase in extracellular Ca2+ concentration. 3. Hormones and adenosine 3′:5′-cyclic monophosphate, at low Ca2+ concentrations, stimulated glucose production from several substrates, but not from glycerol, fructose, malate or fumarate. 4. Hormonal stimulation was not detected in the absence of Ca2+ or at 2.5mm-Ca2+. 5. Ca2+, hormones and adenosine 3′:5′-cyclic monophosphate had no effect on phosphoenolpyruvate carboxylase activity. 6. It is proposed that Ca2+ and adenosine 3′:5′-cyclic monophosphate-mediated hormone action activate the same rate-limiting step in gluconeogenesis: this step is tentatively identified as the rate of transfer of substrates across the mitochondrial membrane.
Synthesis and degradation of phosphoenolpyruvate carboxylase in rat liver and adipose tissue. Changes during a starvation–re-feeding cycle
Authors: Hopgood M. F. , Ballard F. J. , Reshef Lea , Hanson R. W.
Published: August 2015

A specific antibody against liver cytosol phosphoenolpyruvate carboxylase (EC 4.1.1.32) was used to isolate the enzyme from liver and adipose tissue. With this technique we have shown that phosphoenolpyruvate carboxylase synthesis in starved rats accounts for 3% of the total synthesis of cytosol protein in each tissue. Re-feeding starved animals decreases this relative rate of phosphoenolpyruvate carboxylase synthesis to 0.2% and 1% respectively in liver and adipose tissue, and the activity of the enzyme in each tissue is decreased to 25% of the starvation value. An additional starvation period is accompanied by an increased rate of enzyme synthesis, but the response to starvation is considerably slower than that caused by re-feeding. The degradation rate of phosphoenolpyruvate carboxylase is also subject to regulation. Thus re-feeding starved animals decreases the half-life of the enzyme in liver from 13h to 5.2h, but the rapid rate of degradation is maintained at least during the first 20h of subsequent starvation. Only slight changes in the degradation rate of phosphoenolpyruvate carboxylase are found in adipose tissue. We conclude that the large alterations in the rate of enzyme synthesis during a starvation–re-feeding cycle are the major cause of fluctuations in activity.
Regulation of vitamin D metabolism: factors influencing the rate of formation of 1,25-dihydroxycholecalciferol by kidney homogenates (Short Communication)
Authors: Colston Kay W. , Evans Imogen M. A. , Galante Lee , MacIntyre Iain , Moss D. W.
Published: August 2015

The formation of 1,25-dihydroxycholecalciferol from 25-hydroxycholecalciferol by chick kidney homogenates is inhibited by increasing concentrations of Ca2+. The apparent Km for the hydroxylation reaction is 1×10-7m, significantly lower than that reported for isolated mitochondria. Separated cytoplasmic and particulate fractions are inactive, but on recombination activity is restored, possibly because of the presence in the soluble fraction of a factor with a high affinity for 25-hydroxycholecalciferol.
Histone acetylation and hormone action. Early effects of aldosterone on histone acetylation in rat kidney
Authors: Libby Paul R.
Published: August 2015

Histone acetylation in the kidney of the adrenalectomized rat was increased 5 min after a physiological dose of aldosterone. The increase was exclusively in the histone F2a1. The increase in histone acetylation was given by 9α-fluorocortisol, deoxycorticosterone and cortisol, but not by progesterone. The increase in histone acetylation was abolished by prior treatment of the animals with the anti-mineralocorticoid agent, SC14266 [potassium 3-(3-oxo-17β-hydroxy-4,6-androstadien-17-yl) propionate]; the basal degree of histone acetylation was unaffected. Pretreatment of the animals with actinomycin D or cyclo-heximide did not affect the stimulation, showing the stimulation was not due to increased synthesis of enzyme.
Biogenesis of mitochondria. The effects of altered membrane lipid composition on cation transport by mitochondria of Saccharomyces cerevisiae
Authors: Haslam J. M. , Spithill T. W. , Linnane Anthony W. , Chappell J. B.
Published: August 2015

1. The fatty acid composition of the membrane lipids of a fatty acid desaturase mutant of Saccharomyces cerevisiae was manipulated by growing the organism in a medium containing defined fatty acid supplements. 2. Mitochondria were obtained whose fatty acids contain between 20% and 80% unsaturated fatty acids. 3. Mitochondria with high proportions of unsaturated fatty acids in their lipids have coupled oxidative phosphorylation with normal P/O ratios, accumulate K+ ions in the presence of valinomycin and an energy source, and eject protons in an energy-dependent fashion. 4. If the unsaturated fatty acid content of the mitochondrial fatty acids is lowered to 20%, the mitochondria simultaneously lose active cation transport and the ability to couple phosphorylation to respiration. 5. The loss of energy-linked reactions is accompanied by an increased passive permeability of the mitochondria to protons. 6. Free fatty acids uncouple oxidative phosphorylation in yeast mitochondria and the effect is reversed by bovine serum albumin. 7. The free fatty acid contents of yeast mitochondria are unaffected by depletion of unsaturated fatty acids, and free fatty acids are not responsible for the uncoupling of oxidative phosphorylation in organelles depleted in unsaturated fatty acids. 8. It is suggested that the loss of energy-linked reactions in yeast mitochondria that are depleted in unsaturated fatty acids is a consequence of the increased passive permeability to protons, and is caused by a change in the physical properties of the lipid phase of the inner mitochondrial membrane.
[2-(3-Nitrotyrosine)]oxytocin, a weakly active analogue of the hormone bound by neurophysin (Short Communication)
Authors: Hope Derek B. , Wälti Manfred
Published: August 2015

An analogue of oxytocin containing a nitro group ortho to the phenolic hydroxyl group of the tyrosyl residue was prepared by nitration of the hormone with tetranitromethane. [2-(3-Nitro-l-tyrosine)]oxytocin was bound by neurophysin although its pharmacological activity was virtually abolished. The oxytocic activity of the analogue on the isolated rat uterus was 1.1i.u./mg.
Incorporation of radioactive mevalonate into C50 and C55 prenols by Streptococcus mutans
Authors: Thorne Kareen J. I.
Published: August 2015

Growing cells of Streptococcus mutans Ingbritt incorporate radioactive mevalonate into unsaponifiable lipid. Of the radioactive lipid 40% was shown by chromatography and mass spectrometry to be C50 and C55 prenol.
Plasma lipoproteins and the synthesis and turnover of plasma triglyceride in normal and genetically obese mice
Authors: Salmon D. Michael W. , Hems Douglas A.
Published: August 2015

1. Lipoproteins in the plasma of mice were characterized by agarose-gel chromatography and polyacrylamide-gel electrophoresis: genetically obese (ob/ob) mice exhibited hyperlipoproteinaemia (compared with lean mice), largely owing to an increase in the concentration of cholesterol in high-density lipoprotein. Plasma concentrations of triglyceride and phospholipid were not markedly increased in genetically obese mice. 2. The formation of glycerolipids in liver and plasma was investigated with14C-labelled precursors. The synthesis of hepatic triglyceride and phospholipid from glucose or palmitate was enhanced in ob/ob mice, compared with lean mice. The rate of entry of triglyceride into plasma, calculated from the time-course of incorporation of14C from [14C]palmitate into plasma triglyceride, was increased in ob/ob mice (0.5μmol of fatty acid/min, compared with 0.2 in lean mice). 3. The removal from plasma of murine lipoprotein triglyceride-[14C]fatty acid was increased in ob/ob mice (half-time 2.2min, compared with 7.2min in lean mice). Similar results were obtained with an injected lipid emulsion (Intralipid). 4. From these measurements, estimates of the rates of turnover of plasma triglyceride in mice (fed on a mixed diet, female, 3 months old) are about 1.0μmol of fatty acid/min in ob/ob mice, and 0.25 in lean mice. 5. The major precursor of hepatic and plasma triglyceride in lean and ob/ob mice was calculated to be plasma free fatty acid. 6. These results are discussed, in connexion with the role of the liver in triglyceride metabolism in mice, especially in relation to genetic obesity.
Involvement of the superoxide anion in sulphoxidation (Short Communication)
Authors: Prema K. , Gopinathan K. P.
Published: August 2015

Sulphoxidation of compounds capable of undergoing biological sulphoxidation has been demonstrated in a model system (NADH–phenazine methosulphate–O2), known to generate superoxide anions (O2-). Addition of superoxide dismutase to this system results in complete inhibition, suggesting the involvement of O2- in sulphoxidation.
Physicochemical properties of low-density lipoproteins of normal human plasma. Evidence for the occurrence of lipoprotein B in associated and free forms
Authors: Lee Diana M. , Alaupovic P.
Published: August 2015

1. Low-density (d 1.006–1.063g/ml) lipoproteins from normal human plasma were separated by differential preparative ultracentrifugation into six subfractions. Each low-density (LD) lipoprotein subfraction contained lipoprotein B as the major and lipoproteins A and C as the minor lipoprotein families. 2. Three lipoprotein B subfractions (LP-B), LP-B-III (d 1.019–1.030g/ml), LP-B-IV (d 1.030–1.040g/ml) and LP-B-V (d 1.040–1.053g/ml) were prepared from the corresponding LD lipoprotein subfractions by immunoprecipitating small amounts of lipoproteins A and C. 3. Determination of hydrodynamic properties indicated that LD lipoproteins consisted of three molecular segments characterized by a stepwise change in the molecular weight: LDL-I and LDL-II subfractions (d 1.006–1.019g/ml) with an average mol.wt. of 4.75X106, LDL-III (d 1.019–1.030g/ml) with a mol.wt. of 3.99X106, and LDL-IV, LDL-V and LDL-VI (d 1.030–1.063g/ml) with a mol.wt. of 2.85X106. 4. All three lipoprotein B subfractions had an average mol.wt. of 3.16X106. 5. The LDL-I and LDL-II subfractions consisted of lipoprotein B and lipoprotein C families which were present in the form of an association complex. This was isolated from serum by immunoprecipitation with antibodies to lipoprotein B. The complex had a mol.wt. of 4.35X106. 6. The results indicate a fundamental difference between the LD lipoprotein subfractions with d 1.006–1.019g/ml and those subfractions with d 1.030–1.063g/ml. In the former, lipoprotein B occurs as a part of an association complex, whereas in the latter it occurs as a separate entity.
Sites of methylation of purified transfer ribonucleic acid preparations by enzymes from normal tissues and from tumours induced by dimethylnitrosamine and 1,2-dimethylhydrazine
Authors: Pegg Anthony E.
Published: August 2015

1. The sites within the tRNA sequence of nucleosides methylated by the action of enzymes from mouse colon, rat kidney and tumours of these tissues acting on tRNAAsp from yeast and on tRNAGlu2, tRNAfMet and tRNAVal1 from Escherichia coli were determined. 2. The same sites in a particular tRNA were methylated by all of these extracts. Thus tRNAGlu2 was methylated at the cytidine residue at position 48 and the adenosine residue at position 58 from the 5′-end of the molecule; tRNAAsp was methylated at the guanosine residue at position 26 from the 5′-end of the molecule; tRNAfMet was methylated at the guanosine residues 9 and 27, the cytidine residue 49 and the adenosine residue 59 from the 5′-end; tRNAVal1 was methylated at the guanosine residue 10, the cytidine residue 48 and the adenosine residue 58 from the 5′-end. 3. All of these sites within the clover leaf structure of the tRNA sequence are occupied by a methylated nucleoside in some tRNA species of known sequence. It is concluded that methylation of tRNA from micro-organisms by enzymes from mammalian tissues in vitro probably does accurately represent the specificity of these enzymes in vivo. However, there was no evidence that the tumour extracts, which had considerably greater tRNA methylase activity than the normal tissues, had methylases with altered specificity capable of methylating sites not methylated in the normal tissues.
The reaction of diethyl pyrocarbonate with pyruvate kinase
Authors: Dann Leighton G. , Britton Hubert G.
Published: August 2015

Diethyl pyrocarbonate inactivates muscle pyruvate kinase with the substitution of 3–4 histidine residues per subunit. Phosphoenolpyruvate, ATP and ADP to a lesser extent, and Mg2+ and pyruvate to a small extent, protect against inactivation.
The enzymology of short-chain fatty acyl-coenzyme A synthetase from seeds of Pinus radiata. Kinetic studies and a proposed reaction mechanism
Authors: Young Owen A. , Anderson John W.
Published: August 2015

1. Short-chain fatty acyl-CoA synthetase from seeds of Pinus radiata was examined by acetate- and propionate-dependent PPi–ATP exchange. Reaction mixtures came to equilibrium almost instantly as judged by rates of exchange and analysis of an incubation mixture. 2. The activity of the enzyme was correlated with the concentration of MgP2O72- but not with the concentration of Mg2+, as judged by PPi–ATP exchange and fatty acyl AMP-dependent synthesis of ATP in the presence of PPi. In PPi–ATP exchange assays, no clear relationship between activity and any single species of ATP was apparent. 3. High concentrations of fatty acid inhibited PPi–ATP exchange. PPi–dATP exchange was less than PPi–ATP exchange at low concentrations of fatty acid, but at higher concentrations PPi–dATP exchange exceeded PPi–ATP exchange. The rate of synthesis of fatty acyl-CoA in the presence of dATP was less than with ATP. 4. ATP and propionate inhibited the synthesis of ATP from propionyl-AMP and PPi. The inhibition by ATP was competitive with respect to propionyl-AMP and non-competitive with respect to PPi. The inhibition by propionate was non-competitive with respect to propionyl-AMP and PPi. 5. AMP was a competitive inhibitor of propionyl-AMP-dependent synthesis of ATP and competitively inhibited propionate-dependent PPi–ATP exchange when ATP was the variable substrate. 6. It was concluded that the first partial reaction catalysed by the enzyme is ordered; ATP is the first substrate to react with the enzyme and PPi is probably the only product released.
myo-Inositol dehydrogenase(s) from Acetomonas oxydans. Optimization of conditions for solubilization of membrane-bound enzyme
Authors: Criddle W. J. , Fry J. C. , Keaney Maureen M.
Published: August 2015

Methods are described for the first reported successful isolation of the soluble form of the membrane-bound myo-inositol dehydrogenase(s) from Acetomonas oxydans. Conditions for optimum yields of active enzyme in a crude membrane-free protein extract were established. The relevant conditions are (a) cell rupture by solid-shearing, (b) solubilization of the complete 60000g pellet with sodium deoxycholate at pH7.2, (c) rapid separation of the released protein from sodium deoxycholate by gel chromatography.
Studies on the form and synthesis of messenger ribonucleic acid in the rat ventral prostate gland, including its tissue-specific stimulation by androgens
Authors: Mainwaring W. Ian P. , Wilce Peter A. , Smith Allan E.
Published: August 2015

1. When prostate polyribosomes are labelled with radioactive precursors in vivo and subsequently dissociated with sodium dodecyl sulphate, a heterogeneous 6–15S RNA species may be identified that possesses all of the distinctive properties of mRNA. 2. Apart from the selective incorporation of 5′-fluoro-orotic acid into this 6–15S RNA component, it is bound by nitrocellulose filters under experimental conditions where only poly(A)-rich species of RNA are specifically retained. Most importantly, however, only the 6–15S RNA fraction is capable of promoting the incorporation of amino acids into peptide linkage in an mRNA-depleted cell-free system derived from ascites-tumour cells. 3. With the development of a simpler method for labelling the total RNA fraction of the prostate gland in vitro, the poly(A)-enriched RNA fraction may be readily isolated by adsorption and elution from oligo(dT)-cellulose. The synthesis of the poly(A)-enriched 6–15S RNA fraction is stringently controlled by androgens in a highly tissue- and steroid-specific manner. 4. From an analysis of the proteins synthesized in the ascites cell-free system in the presence of the poly(A)-rich RNA fraction, it appears that protein synthesis in the prostate gland is stimulated in a rather general way, even during the earliest phases of the androgenic response. This conclusion may require modification when more specific means of analysis are available than those used in the present investigation. 5. The implications of these findings to the mechanism of action of androgens are discussed.
The pancreatic β-cell recognition of insulin secretagogues. Effects of calcium and sodium on glucose metabolism and insulin release
Authors: Hellman Bo , Idahl Lars-Åke , Lernmark Åke , Sehlin Janove , Täljedal Inge-Bert
Published: August 2015

The transport and oxidation of glucose, the content of fructose 1,6-diphosphate, and the release of insulin were studied in microdissected pancreatic islets of ob/ob mice incubated in Krebs–Ringer bicarbonate medium. Under control conditions glucose oxidation and insulin release showed a similar dependence on glucose concentration with the steepest slope in the range 5–12mm. The omission of Ca2+, or the substitution of choline ions for Na+, or the addition of diazoxide had little if any effect on glucose transport. However, Ca2+ or Na+ deficiency as well as diazoxide (7-chloro-3-methyl-1,2,4-benzothiadiazine 1,1-dioxide) or ouabain partially inhibited glucose oxidation. These alterations of medium composition also increased the islet content of fructose 1,6-diphosphate, as did the addition of adrenaline. Phentolamine [2-N-(3-hydroxyphenyl)-p-toluidinomethyl-2-imidazoline] counteracted the effects of adrenaline and Ca2+ deficiency on islet fructose 1,6-diphosphate. After equilibration in Na+-deficient medium, the islets exhibited an increase in basal insulin release whereas the secretory response to glucose was inhibited. The inhibitory effects of Na+ deficiency on the secretory responses to different concentrations of glucose correlated with those on 14CO2 production. When islets were incubated with 17mm-glucose, the sudden replacement of Na+ by choline ions resulted in a marked but transient stimulation of insulin release that was not accompanied by a demonstrable increase of glucose oxidation. Galactose and 3-O-methylglucose had no effect on glucose oxidation or on insulin release. The results are consistent with a metabolic model of the β-cell recognition of glucose as insulin secretagogue and with the assumption that Ca2+ or Na+ deficiency, or the addition of adrenaline or diazoxide, inhibit insulin release at some step distal to stimulus recognition. In addition the results suggest that these conditions create a partial metabolic block of glycolysis in the β-cells. Hence the interrelationship between the processes of stimulus recognition and insulin discharge may involve a positive feedback of secretion on glucose metabolism.
Metabolism of two adrenocorticotrophin analogues in the intestine of the rat
Authors: Lowry P. J. , McMartin C.
Published: August 2015

1. At 30min after oral administration unchanged Synacthen [corticotrophin-(1–24)-tetracosapeptide] was found in the stomach but could not be detected in the lumen of the small intestine of the rat. 2. Synacthen and 41795-Ba {[d-Ser1, Lys17, Lys18]corticotrophin-(1–18)-octadecapeptide amide} were rapidly metabolized in vitro by both intestinal juice and everted pieces of small intestine. Peptide products were not found either in the intestinal tissue or in the fluid bathing the serosal tissue. 3. Glucose but not O2 was necessary for the breakdown of the two adrenocorticotrophin analogues by everted tissue. 4. When the products obtained after partial digestion were chromatographically separated and identified, a pattern of breakdown emerged. The N-terminus of Synacthen and the Phe(7)–Arg(8) bond in both analogues were particularly labile. The d-serine N-terminal residue of 41795-Ba conferred a marked protection to aminopeptidase action. 5. The relative susceptibilities of peptide bonds would have been difficult to predict on the basis of existing knowledge of the properties of enzymes of the small intestine.
Calcium transport in the early conceptus and associated maternal tissues in the rabbit
Authors: McIntosh J. E. A. , Lutwak-Mann C.
Published: August 2015

1. The kinetics of calcium transport were studied in unmated (oestrous) and pregnant rabbits in the first half of gestation, with the aim of establishing evidence of hormonal (ovarian) influence on the pattern of transport. 2. The following tissues were examined at short- (45min and 2h) and long-duration (4, 16 and 48h) intervals after parenteral administration of 45Ca or 47Ca: maternal blood plasma, endometrium, uterine fluid, placental tissues, two developmentally disparate stages of rabbit conceptus, namely the unattached blastocyst and the early post-implantation foetus, and bone (femur). 3. Marked variability in calcium content characterized rabbit tissues and body fluids. 4. Compartmental analysis was applied to measurements of specific radioactivity. Oestrous endometrium had the largest rapidly exchanging calcium fraction (turnover time of 12min) and the highest value for calcium flux (500μg of Ca exchanged/h per g fresh wt. of tissue). A marked downward gradient in values of flux existed between the progestational endometrium, uterine fluid and blastocyst; there was a similar gradient between placental tissues and foetus. 5. An hormonal influence on calcium transport was evident in (i) the decrease in specific radioactivity of rabbit blood plasma with advancing pregnancy, (ii) the extraordinarily rapid calcium transport between blood plasma and endometrium, especially in the oestrous stage, and (iii) the effectiveness of ovarian hormone substitution in ovariectomized rabbits. 6. The very low specific radioactivity recorded for bone indicated that only a minute fraction of its calcium was exchanging with that of blood plasma under the experimental conditions examined. 7. The rate of uptake of 45Ca by rabbit blastocysts growing in vitro was one-tenth of that of 22Na, or that recorded for calcium in vivo. 8. Inhibition of carbonic anhydrase activity with acetazolamide in vivo, in maternal erythrocytes, endometrium and placental tissues, produced no appreciable changes in calcium uptake in these tissues or other systems examined as a routine on either day 6 or days 12–14 of gestation.
Studies with a reconstituted muscle glycolytic system. The anaerobic glycolytic response to simulated tetanic contraction
Authors: Scopes Robert K.
Published: August 2015

By using a reconstituted glycolytic system and a highly active adenosine triphosphatase (ATPase), the metabolism during muscular tetanic contraction was simulated and observed. With an ATPase activity somewhat greater than can be maintained in muscle tissue, phosphocreatine was rapidly and completely utilized, lactate production commenced about 5s after the ATPase was added and after 15s adenine nucleotides were lost through deamination to IMP. By 40s, all metabolism ceased because of complete loss of adenine mononucleotides. With a lower ATPase activity, glycolytic regeneration of ATP was capable of maintaining the ATP concentration at its initial value and even by 80s, only one-half of the phosphocreatine had been utilized. No deamination occurred in this time. It is suggested that the metabolic events observed in the simulated system are basically the same as occur in muscle doing heavy work.
Induction of guanine deaminase and its inhibitor in rodent liver and brain
Authors: Sitaramayya A. , Ali Shahid , Kumar K. Sree , Krishnan P. S.
Published: August 2015

1. Guanine deaminase activities in homogenates and supernatant fractions of liver and brain of rat and mouse were elevated by administration of guanine to the animals. The maximum induction in mouse tissues occurred within 24h and in rat tissues within 48h. 2. Mitochondria of rat (but not mouse) liver and brain contain an inhibitor of supernatant guanine deaminase, and this was also increased by guanine treatment. 3. Administration of ethionine, cycloheximide or actinomycin D prevented the guanine-dependent increase in deaminase activity and also the increase in mitochondrial inhibitory activity; chloramphenicol suppressed only the latter.
Changes in free and membrane-bound ribosomes during the development of chick liver
Authors: O'Toole K. , Pollak J. K.
Published: August 2015

A major difficulty in studying quantitative changes in free and membrane-bound ribosomes in a tissue under different physiological conditions is that membrane-bound ribosomes are not usually recovered quantitatively in a conventional microsomal fraction. This problem was resolved for developing chick liver by determining the conditions for the isolation of a microsomal fraction containing the highest practicable yield of rough vesicles, and then separating it into free-ribosome- and rough-vesicle-containing fractions. With the aid of a marker enzyme for the microsomal membranes and the RNA content of the recovered membrane-bound ribosomes, it was possible to correct for the recovery of rough vesicles and hence to determine the concentration of membrane-bound ribosomes in the homogenate. Despite the fact that morphological studies have suggested that most of the cellular ribosomes are not bound to membrane in chick liver cells at the earliest developmental age studied (6 days of egg incubation), 49% of the total ribosomes were found to be membrane-bound by using the new fractionation technique. This fraction increased (to 66%) during development. The discrepancy between the cell-fractionation and morphological approaches could not be attributed to artifacts of the separation method but rather to difficulties inherent in the morphological approach.
3-Mercaptopicolinic acid, an inhibitor of gluconeogenesis
Authors: DiTullio N. W. , Berkoff C. E. , Blank B. , Kostos V. , Stack E. J. , Saunders H. L.
Published: August 2015

1. 3-Mercaptopicolinic acid (SK&F 34288) inhibited gluconeogenesis in vitro, with lactate as substrate, in rat kidney-cortex and liver slices. 2. In perfused rat livers, gluconeogenesis was inhibited when lactate, pyruvate or alanine served as substrate, but not with fructose, suggesting pyruvate carboxylase or phosphoenolpyruvate carboxylase as the site of inhibition. No significant effects were evident in O2 consumption, hepatic glycogen, urea production, or [lactate]/[pyruvate] ratios. 3. A hypoglycaemic effect was evident in vivo in starved and alloxan-diabetic rats, starved guinea pigs and starved mice, but not in 4h-post-absorptive rats. 4. In the starved rat the hypoglycaemia was accompanied by an increase in blood lactate. 5. A trace dose of [14C]lactate in vivo was initially oxidized to a lesser extent in inhibitor-treated rats, but during 90min the total CO2 evolved was slightly greater. The total amount of the tracer oxidized was not significantly different from that in the controls.