bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of gluconeogenesis in neonatal rat liver. Effect of triamcinolone
Authors: Yeung D. , Stanley R. S. , Oliver I. T.
Published: August 2015

1. The normal development of the key enzymes of gluconeogenesis in rat liver, glucose 6-phosphatase, hexose diphosphatase, phosphopyruvate carboxylase and pyruvate carboxylase, was measured during the neonatal period. 2. Glucose 6-phosphatase, hexose diphosphatase and pyruvate carboxylase are all present in the late foetal liver, but all the enzymes show an increase in activity after birth. 3. Phosphopyruvate carboxylase is not present in liver extracts from foetal rats, but activity appears immediately after birth and increases rapidly over the first day and then more slowly to reach its maximum at the fourth postnatal day. 4. The fluorinated synthetic glucocorticoid, triamcinolone, was administered to foetal rats at various gestation times by intraperitoneal injection in utero and the animals were killed at intervals between 4 and 48hr. later. 5. The administration of triamcinolone results in slight depression of glucose 6-phosphatase, and a more significant depression of hexose diphosphatase to about one-half its normal activity in foetal rat liver. 6. Triamcinolone injection is without effect on pyruvate carboxylase activity and does not result in premature appearance of phosphopyruvate carboxylase in foetal rat liver. 7. Pyruvate kinase and aspartate amino-transferase activities in foetal rat liver are both depressed by triamcinolone treatment, whereas phosphofructokinase activity is elevated. 8. Tyrosine amino-transferase activity in foetal rat liver is markedly elevated in animals exposed to triamcinolone for 10hr. or more, but the effect is only observed in animals close to term. 9. The results are discussed in relation to mechanisms involved in the initial synthesis of tissue-specific enzymes in developing tissues, and it is concluded that glucocorticoids do not initiate the synthesis of the gluconeogenic enzymes.
The fate of ethyltin and diethyltin derivatives in the rat
Authors: Bridges J W , Davies D S , Williams R T
Published: August 2015

1. Ethyltin trichloride does not appear to be metabolized by the rat. When given orally excretion occurs almost entirely in the faeces, and when given intraperitoneally it occurs exclusively in the urine. Biliary excretion is almost negligible. 2. Di[1−14C]ethyltin dichloride has been synthesized. When given intraperitoneally it is excreted in the urine and faeces in the ratio about 1:2. Both the urine and faeces contain ethyltin3+ and diethyltin2+. Diethyltin is also excreted extensively in the bile. Di[14C]ethyltin is not converted into 14CO2 in the rat. 3. About 50% of the injected diethyltin dichloride is de-ethylated to ethyltin3+. Since ethyltin and diethyltin are found in the urine and faeces after intraperitoneal injection of diethyltin dichloride and since only diethyltin is excreted in the bile, then the de-ethylation of diethyltin occurs in the body tissues and the gut. 4. The conversion of diethyltin into ethyltin has been demonstrated in a preparation of rat caecal contents, but not in liver homogenates. 5. The dealkylation of diethyltin2+ to ethyltin3+ in the rat is discussed and it is suggested that the ethyl group is lost as ethane.
The presence of ribonucleic acid in the cell walls of higher plants
Authors: Phethean P. D. , Jervis L. , Hallaway Mary
Published: August 2015

A method for isolating extensively purified cell walls from higher plants is described; the preparations contain no detectable chloroplast or nuclear material and the protein content (2–5% of the dry wt. of walls) indicates that there is little contamination with cytoplasm. Incubation of purified cell walls with 0·3n-potassium hydroxide for 17hr. at 37° liberates ribonucleotides, which can be purified by adsorption on charcoal and by ion-exchange chromatography. Ribonucleotides are also liberated by incubating the walls with ribonuclease, but not with deoxyribonuclease. The RNA content varies from 0·5 to 6mg./g. dry wt. of walls, depending on the nature and age of the tissue, and at 3mg./g. dry wt. of walls accounts for about 7% of the total RNA of the tissue. Less than 0·2% of the RNA of the walls is due to the presence of bacteria in the preparation. The base composition of the cell-wall RNA is identical with that of ribosomal RNA.
A comparison of glycopeptides from the ovotransferrin and serum transferrin of the hen
Authors: Williams J.
Published: August 2015

1. Glycopeptides were prepared from proteolytic digests of ovotransferrin and serum transferrin of the hen. The carbohydrate compositions and amino acid sequences of the peptides were studied. 2. The bulk of the carbohydrate of ovotransferrin is present as a single oligosaccharide composed of 4 residues of mannose and 8 residues of N-acetylglucosamine. Transferrin has most of its carbohydrate in a single unit composed of 2 residues of mannose, 2 residues of galactose, 3 residues of N-acetylglucosamine and either 1 or 2 residues of sialic acid. 3. The amino acid sequences of the glycopeptides carrying these different oligosaccharides are the same in ovotransferrin and serum transferrin, showing that the carbohydrate groups are attached to the same site on the protein molecule.
The isoelectric fractionation of hen's-egg ovotransferrin
Authors: Wenn R. V. , Williams J.
Published: August 2015

1. Hen ovotransferrin was examined by isoelectric fractionation. 2. The major component observed in starch-gel electrophoresis can be isolated from the minor component. 3. When non-saturating amounts of iron are added to ovotransferrin, isoelectric fractionation demonstrates the existence of three molecular species corresponding to the metal-free protein, the one-iron-atom–protein complex and the two-iron-atoms–protein complex. 4. Isoelectric fractionation of human serum labelled with 59Fe suggests that the transferrin of normal human serum also exists as metal-free protein, the one-iron-atom–protein complex and the two-iron-atoms–protein complex. 5. It is concluded that the binding constants for the first and second iron atoms are similar.
Enzymic studies on the biosynthesis of amino acids from lactate by Peptostreptococcus elsdenii
Authors: Somerville H. J.
Published: August 2015

Cell-free extracts of Peptostreptococcus elsdenii, a strict anaerobe from the rumen, were examined for enzymes catalysing the steps in the biosynthesis from lactate of alanine, serine, aspartate and glutamate. Extracts contain the enzymes necessary for the formation of alanine from lactate via pyruvate. The presence of enzymes catalysing the interconversion of phosphoglycerate and phosphohydroxypyruvate, the transamination of the latter to phosphoserine and the cleavage of phosphoserine to serine and inorganic phosphate was demonstrated, suggesting that serine is formed via these intermediates. ‘Malic’ enzyme, malate dehydrogenase and glutamate–oxaloacetate transaminase are present in extracts and could account for aspartate formation. The extracts catalyse all of the steps of the tricarboxylic acid pathway leading from oxaloacetate plus acetate to glutamate. Together with substantive data from previous radioactive tracer studies the results provide strong evidence that these four amino acids are synthesized in this strict anaerobe by pathways closely similar to those operating in aerobic and facultatively aerobic organisms.
Studies on the ribonucleic acids of fresh and processed tea leaves
Authors: Bhattacharyya Asok K. , Ghosh J. J.
Published: August 2015

1. A marked decrease in the total RNA content during the withering process of tea leaves was found. During the fermentation process, there was a small but significant decrease in the total RNA content. 2. During isolation of RNA from tea leaf tissues, the action of leaf ribonuclease was minimized by the addition of sodium dodecyl sulphate during extraction; 1% (w/v) sodium dodecyl sulphate in 0·2m-tris–hydrochloric acid buffer, pH8·0, containing 0·005% EDTA was found to be most efficient for the extraction and gave about 93% yield. 3. The total RNA preparations isolated from fresh, withered and fermented tea leaves were compared with regard to nucleotide composition and spectral characteristics. The total RNA preparations from all three sources contained more purines than pyrimidines (purine/pyrimidine ratio 1·47–1·52).
The chemical composition of the cyst wall of the potato cyst-nematode, Heterodera rostochiensis
Authors: Clarke A. J.
Published: August 2015

1. Cyst walls of the potato cyst-nematode (Heterodera rostochiensis Woll.) were isolated by sieving a suspension of crushed cysts. About 12mg. of dried cyst walls was obtained from 1000 cysts. 2. The cyst walls contained mainly protein (72%, calculated from nitrogen content). On acid hydrolysis about 77% of the cyst wall went into solution. Of 19 amino acids present, proline, glycine, and alanine were the most abundant, and made up about 50% by weight of the total amino acids. The amino acid composition suggested that collagen-like proteins predominated in the cyst wall and larval cuticle. 3. A small amount of glucosamine (1·5%) was present in the hydrolysates, but chitin was not detected in the cyst walls. 4. Other components of the cyst walls were lipid (2%), carbohydrate (0·5%) and a small amount of inorganic matter (ash, 5%). Polyphenols (2% by wt. of the cyst walls) occurred in the acid hydrolysates. The dark pigments of the cyst wall were not indole-containing melanins.
A study of the fatty acid metabolism of the yeast Pityrosporum ovale
Authors: Wilde Peter F. , Stewart Patrick S.
Published: August 2015

The yeast Pityrosporum ovale, a skin saprophyte, will only grow if fatty acids of chain length greater than C10 are added to the culture medium. 9-Hydroxypalmitic acid is the major product of metabolism of even-carbon-number fatty acids; 9-hydroxystearic acid is also found. The optimum pH for this conversion is pH4·5. The hydroxy fatty acids produced are found bound in a polar form in the aqueous phase of the culture medium. Growth of the organisms is facilitated by presentation of the substrate as a two-phase liquid system.
The biosynthesis of some androst-16-enes from C21 and C19 steroids in boar testicular and adrenal tissue
Authors: Ahmad N. , Gower D B
Published: August 2015

1. The formation of androst-16-enes from [4−14C]progesterone has been investigated with long-term incubations and short-term kinetic studies. After 4hr., 1·7 and 10·3% respectively of 3α- and 3β-hydroxy-5α-androst-16-enes were formed in boar testis minces, but much smaller yields were obtained in boar adrenal. Both tissues formed small quantities of androsta-4,16-dien-3-one. 2. The amounts of androst-4-ene-3,17-dione and testosterone isolated were small, suggesting that androst-16-ene formation may occur preferentially in the boar testis. 3. In the absence of tissue no radioactive androst-16-enes were formed. 4. Incubation of both [4−14C]pregnenolone and [7α−3H]progesterone resulted in 3α- and 3β-hydroxy-5α-androst-16-enes containing 3H/14C ratios of near unity and confirmed that both C21 steroids were precursors. A similar incubation with 17α-hydroxy[4−14C]-progesterone and [7α−3H]progesterone gave the same Δ16-alcohols, but they contained only 3H, indicating that side-chain cleavage of pregnenolone and progesterone occurred before 17α-hydroxylation. 5. Dehydroepiandrosterone, testosterone, testosterone acetate and 16-dehydroprogesterone were not found to be precursors of Δ16-steroids. 6. A pathway is proposed for the biosynthesis of 3α- and 3β-hydroxy-5α-androst-16-enes from pregnenolone and progesterone; this may involve androsta-4,16-dien-3-one as an intermediate, but excludes 17α-hydroxyprogesterone, testosterone and dehydroepiandrosterone.
The effect of chemical modifications induced in insulin on the reactivity of the interchain disulphide bonds towards sodium sulphite
Authors: Massaglia A. , Pennisi F. , Rosa U. , Ronca-Testoni S. , Rossi C. A.
Published: August 2015

The reactivity of the three disulphide bridges of insulin towards sodium sulphite was studied by amperometric titration of the liberated thiol groups. In the native, acetylated or succinylated molecule two bridges react at pH7, but in the methylated or phenylcarbamoylated molecule only one bridge reacts. All three bridges react in all derivatives in 8m-urea or at pH9. Loss in biological activity parallels the loss in reactivity of one of the bridges during methylation. It is suggested that change in reactivity of the S·S bonds reflects the occurrence of a conformational modification of the protein. The possibility is discussed that the unusually high reactivity of the S·S bonds in native insulin depends strictly on the integrity of the native molecule, suggesting that S·S bonds are in some way involved in the hormone's mode of action.
Factors affecting the premature induction of phosphopyruvate carboxylase in neonatal rat liver
Authors: Yeung D. , Oliver I. T.
Published: August 2015

1. Phosphopyruvate carboxylase activity rapidly appears in the liver of prematurely delivered rats and development of activity is prevented by injection of actinomycin D just before delivery. 2. The activity is considerably decreased by puromycin and amino acid analogues and thus appears to be due to enzyme synthesis. 3. Newborn or premature animals show a transient intense phase of hypoglycaemia after delivery. 4. When the hypoglycaemic phase is prevented by glucose injection little phosphopyruvate carboxylase activity appears in the liver, but galactose, mannose and fructose, which have no effect on the blood glucose concentration, also repress enzyme development. 5. Lactate, pyruvate and glycerol injections repress the premature development of phosphopyruvate carboxylase. 6. Injections of glucagon, adrenalin and noradrenalin into the rat foetus in utero result in development of phosphopyruvate carboxylase activity. 7. These findings are discussed in relation to the mechanism of initiation of enzyme synthesis in neonatal rat liver.
Plasma corticosterone concentrations in the perinatal rat
Authors: Holt P. G. , Oliver I. T.
Published: August 2015

1. Plasma corticosterone concentrations were determined in the foetal rat during the gestational period from day 18·5 to term and in postnatal rats over the first few hours after delivery. 2. The plasma corticosterone concentrations in foetal rats are as high as six times maternal values at day 19 of gestation and are approximately equal to maternal values from day 20 to term. 3. In postnatal rats the plasma corticosterone concentrations rise 3·5-fold on average within 5hr. of delivery. 4. The results are discussed in relation to the function of adrenal steroids in postnatal liver development.
The glycosulphatase of Trichoderma viride
Authors: Lloyd A G , Large P J , Davies M , Olavesen A H , Dodgson K S
Published: August 2015

The growth of the mould Trichoderma viride on a defined medium containing either potassium d-glucose 6-O-sulphate or potassium d-galactose 6-O-sulphate as sole sources of both carbon and sulphur is marked by the production of an enzyme system capable of liberating inorganic SO42− ions from either of the sulphate esters. The enzyme is not produced when the organism is grown with glucose (or galactose) and potassium sulphate or with glucose and methionine as sole sources of carbon and sulphur. Experimental conditions are described whereby inorganic SO42− ions liberated from potassium glucose 6-O-sulphate by the growing mould appear in the culture medium after a constant lag period of 21–24hr. The enzyme has been shown to be a simple glycosulphatase that is active towards the 6-O-sulphate esters of d-glucose and d-galactose but not towards potassium glucose 3-O-sulphate. The properties of the crude glycosulphatase show the enzyme to be appreciably different from analogous molluscan enzymes that can degrade monosaccharide sulphate esters.
Regulation of rat liver pyruvate kinase. The effect of preincubation, pH, copper ions, fructose 1,6-diphosphate and dietary changes on enzyme activity
Authors: Bailey E. , Stirpe F. , Taylor C B
Published: August 2015

1. Preincubation of partially purified rat liver L-type pyruvate kinase at 25° for 10min. causes a marked increase in co-operativity with respect to both the substrate, phosphoenolpyruvate, and the allosteric activator, fructose 1,6-diphosphate. 2. The results are consistent with the existence of two forms of liver L-type pyruvate kinase, designated forms LA and LB. It is postulated that form LA has a low Km for phosphoenolpyruvate (about 0·1mm) and is not allosterically activated, whereas form LB is allosterically activated by fructose 1,6-diphosphate, exhibiting in the absence of the activator sigmoidal kinetics with half-maximal activity at about 1mm-phosphoenolpyruvate. In the presence of fructose 1,6-diphosphate, form LB gives Michaelis–Menten kinetics with Km less than 0·1mm. It is further postulated that preincubation converts form LA into form LB. 3. The influence of pH on the preincubation effect was studied. 4. The inhibition of pyruvate kinase by Cu2+ was studied in detail. Though phosphoenolpyruvate and fructose 1,6-diphosphate readily protect the enzyme against Cu2+ inhibition, little evidence of significant reversal of the inhibition by these compounds could be found. 5. The effects of starvation, fructose feeding and preincubation on the pyruvate kinase activity of crude homogenates of various tissues of the rat were also studied.
The effects of varying the cellular and extracellular concentrations of sodium and potassium ions on the uptake of glycine by mouse ascites-tumour cells in the presence and absence of sodium cyanide
Authors: Eddy A A
Published: August 2015

1. Tumour cells were starved to deplete them of ATP and transferred to 0·9mm-glycine in Ringer solutions containing 2mm-sodium cyanide and various Na+ and K+ concentrations. The uptake of glycine then usually reached a peak by about 10min. 2. When cellular [Na+] and extracellular [Na+] were each about 30m-equiv./l., the maximum amount of glycine absorbed increased between 1·2- and 3·0-fold on lowering extracellular [K+] from 128 to 10m-equiv./l. 3. When extracellular [Na+] was 150m-equiv./l., the ratio, R, of the cellular to extracellular glycine concentrations increased progressively, from near 1 to about 9, when cellular [Na+] was lowered from 120 to 40m-equiv./l. 4. When cellular [Na+] was almost constant, either at 45 or 70m-equiv./l., R fell about 14-fold when extracellular [Na+] varied from 150 to 16m-equiv./l. 5. Values of R near 0·2 were found when cellular [Na+] was about four times as large as extracellular [Na+]. 6. R fell about threefold when the cells were put with 12mm- instead of 0·9mm-glycine. 7. The results were taken to imply that, under these conditions, the spontaneous movements of both Na+ and K+ across the cell membrane, down their respective concentration gradients, served to concentrate the glycine in the tumour cells (Christensen's hypothesis).
Studies on the development of ornithine–keto acid aminotransferase activity in rat liver
Authors: Räihä Niels C. R. , Kekomäki M. P.
Published: August 2015

1. During the normal development of the rat, the specific activity of liver ornithine–keto acid aminotransferase exhibits a transient elevation around term, and subsequently increases to adult activity levels during the third postnatal week. 2. The synthetic glucocorticoid triamcinolone, administered as a single injection, produces a marked elevation of the ornithine–keto acid aminotransferase activity within 24hr. if given postnatally before the natural increase in ornithine–keto acid aminotransferase activity has occurred. In foetal and adult animals, triamcinolone does not induce any increase in this enzyme activity. 3. The repeated administration of puromycin completely prevents the rise in ornithine–keto acid aminotransferase activity that follows triamcinolone administration. 4. If adult rats are fed with a protein-free carbohydrate diet, or one free of arginine, the ornithine–keto acid aminotransferase activity diminishes to a fraction of the normal. When such diets are given, a single injection of triamcinolone does not increase the enzyme activity within 24hr. 5. Partial hepatectomy, and repeated injections of growth hormone, depress the ornithine–keto acid aminotransferase activity in adult rats. 6. The findings are discussed in relation to the mechanisms concerned with developmental and adaptive changes in enzyme activities in the liver.
The mechanism of the elaboration of ring b in ergosterol biosynthesis
Authors: Akhtar M , Parvez M. A.
Published: August 2015

Methods for the preparation of [3α−3H]ergosta-7,22-dien-3β-ol (5,6-dihydro-ergosterol), [5,6−3H2]ergosta-7,22-dien-3β-ol and [3α−3H]ergosta-7,22-diene-3β,5α-diol are described. It is shown that 5,6-dihydro[3α−3H]ergosterol on incubation under aerobic conditions with whole cells of Saccharomyces cerevisiae LK2G12 is efficiently converted into ergosterol. Studies carried out with dihydro[5α,6α−3H2]-ergosterol demonstrate that the introduction of the 5,6-double bond in ergosterol biosynthesis is attended by an overall cis-elimination of two hydrogen atoms. To differentiate between a hydroxylation–dehydration mechanism and a dehydrogenation mechanism, the metabolism of [3α−3H]ergosta-7,22-diene-3β,5α-diol was studied. It was shown that this diol is converted into ergosterol only under aerobic conditions. It is therefore suggested that the introduction of the 5,6-double bond of ergosterol does not occur through a hydroxylation–dehydration mechanism.
The preparation and properties of purified 125I-labelled antibodies to insulin
Authors: Miles L. E. M. , Hales C. N.
Published: August 2015

1. A procedure is described for the preparation of an insulin-immunoadsorbent containing 105–185mg. of insulin/g. of matrix, and with an antibody-binding capacity of 660mg./g. of insulin-immunoadsorbent. 2. Purified non-precipitating 125I-labelled antibodies were prepared by iodination of the antibodies while they were isolated on the insulin-immunoadsorbent in order to protect at least one antigen-binding site. 3. The radioactive antibody was simply and rapidly separated from other radioactive material and damaging reagents, and found to be up to 94% pure as judged by its reaction with insulin-immunoadsorbent and unfixed insulin. 4. The 125I-labelled antibody preparations had iodine contents of 0·5–64atoms/mol. of protein and specific radioactivities of 0·3–125mc/mg. of protein. 5. It is suggested that this is a simple method of producing a useful reagent.
Novel heparin degradation products. Isolation and characterization of novel disaccharides and oligosaccharides produced from heparin by bacterial degradation
Authors: Dietrich Carl P.
Published: August 2015

1. Heparin was degraded by enzymes of adapted Flavobacterium heparinum. Several degradation products were separated by combined Sephadex-gel filtration and paper chromatography, and chemically analysed. 2. These products were identified as glucosamine 2,6-disulphate, saturated disaccharides constituted of uronic acid and glucosamine and containing two and three sulphate residues, and tetra- and hexa-saccharides with the same basic disaccharide units. 3. The implications of these findings with respect to the present knowledge of heparin structure and its enzymic degradation are discussed.
The metabolic fate of the products of citrate cleavage. Adenosine triphosphate citrate lyase and nicotinamide–adenine dinucleotide phosphate-linked malate dehydrogenase in foetal and adult liver from ruminants and non-ruminants
Authors: Hanson R. W. , Ballard F. J.
Published: August 2015

1. Foetal rat liver slices incorporate the C-3 of aspartate and C-2 of glutamate into fatty acids at rates equal to those observed with adult rat liver slices. Incorporation of either of these labelled carbon atoms into fatty acids would require a functioning citrate-cleavage pathway which consists of the enzymes ATP–citrate lyase, NAD–malate dehydrogenase and NADP–malate dehydrogenase. However, NADP–malate dehydrogenase is present in foetal rat liver at only 5% of the activity detectable in adult rat liver. 2. From these findings and the effect of cofactors on the formation of 14CO2 from [1,5−14C2]citrate in liver supernatant fractions (100000g), it is suggested that NADP–malate dehydrogenase limits the citrate-cleavage sequence. 3. Measurement of the citrate-cleavage pathway by incorporation studies with [3−14C]aspartate and [U−14C]glucose and by determining the activities of ATP–citrate lyase and NADP–malate dehydrogenase have shown that this sequence of reactions is present in the liver of the bovine foetus but not in the adult. However, C-2 of glutamate is not incorporated into fatty acids or non-saponifiable lipid by bovine liver slices. This finding as well as those presented above for the adult and foetal rat liver are interpreted on the basis of a competition between phosphoenolpyruvate carboxykinase and NAD–malate dehydrogenase for oxaloacetate produced by the cleavage of citrate in the cytosol.
The osmotic behaviour of Sephadex and its effects on chromatography
Authors: Edmond Elizabeth , Farquhar Susan , Dunstone J. R. , Ogston A. G.
Published: August 2015

1. Sephadex in bead form shows reversible changes of inner volume when immersed in solutions of a non-penetrating solute. These changes are in accordance with the theory of Flory (1953) for the swelling of gels. This makes possible the use of single beads for measuring the osmotic pressures of polymer solutions, up to or beyond 1kg./cm.2. 2. Measurements of the inner volume of Sephadex G-200 by equilibrium dilution, at various concentrations of dextran 500, gave values in agreement with those obtained from the dimensions of single beads. 3. Measurements by chromatography of the inner volume of Sephadex G-200 gave values that differed slightly but significantly from those obtained by the other methods. Similar small disagreements were found between the dilution and chromatographic values for bovine serum albumin measured in the presence of various concentrations of dextran 500. The major factor that affects the dependence of the chromatographic elution volume (of dextran 500) on concentration is shown to be the change of the inner volume of the Sephadex, with dynamic factors playing a minor role. 4. Contrary to the findings of Ackers (1964), the equilibrium dilution and chromatographic methods gave closely agreeing values for the distribution coefficient, Kav., of bovine serum albumin on Sephadex G-200; this cast doubt on his explanation of the nature of chromatographic separations on Sephadex.
A spectrophotometric method for the microdetermination of periodate
Authors: Fields Robert , Dixon H. B. F.
Published: August 2015

1. A method is described for measuring the concentration of periodate over the range 0·2–20μm by adding 1,2-di-(p-dimethylaminophenyl)ethane-1,2-diol to a sample solution. Periodate cleaves this compound to from two molecules of p-dimethylaminobenzaldehyde, the extinction of which is then read at 352mμ. 2. The method has been used to follow the course of periodate oxidations of serine methyl ester, ribonuclease A and ribonuclease S-protein. Addition of the reagent stops further periodate reaction by reducing the remaining periodate to iodate. 3. The presence of protein does not interfere with the assay.
Determination of amino sugars in mixtures containing glucosamine, galactosamine and muramic acid
Authors: Stewart-Tull D. E. S.
Published: August 2015

A colorimetric method is described whereby the direct quantitative determination of glucosamine, galactosamine and muramic acid can be achieved without previous treatment of the cell-wall hydrolysate, for example by column chromatography. Molar ratios of hexosamines in cell-wall preparations, from a number of bacterial species, determined by this method were found to be in general agreement with previously published results.
Fractionation of a hyaluronic acid preparation in a density gradient. Some properties of the hyaluronic acid
Authors: Silpananta Panee , Dunstone J. R. , Ogston A. G.
Published: August 2015

1. Hyaluronic acid was isolated from ox synovial fluid by sedimentation equilibrium in a caesium chloride density gradient (Silpananta, Dunstone & Ogston, 1967). The product was almost free from chondroitin sulphate and from protein. 2. Its composition did not differ significantly from that of the carbohydrate part of the protein-containing material isolated by filtration. Its physicochemical properties and molecular configuration were similar, except for its viscosity, which showed markedly reduced concentration-dependence and shear-dependence. This suggests that the associated protein tends to form links between molecules of hyaluronic acid. 3. The accurate measurement of viscosity at very low velocity gradient, by use of the damping of oscillations in a Couette viscometer, is described. 4. A method is described for measuring, approximately, the thermodynamic non-ideality of a solute from the shape of its schlieren curve at sedimentation equilibrium in a density gradient. 5. A value for the partial specific volume of hyaluronic acid in dilute salt solution was calculated from its isopycnic density in a caesium chloride gradient.
Lipid composition of the isolated rat intestinal microvillus membrane
Authors: Forstner G. G. , Tanaka K. , Isselbacher K. J.
Published: August 2015

1. Rat intestinal microvillus plasma membranes were prepared from previously isolated brush borders and the lipid composition was analysed. 2. The molar ratio of cholesterol to phospholipid was greatest in the membranes and closely resembled that reported for myelin. 3. Unesterified cholesterol was the major neutral lipid. However, 30% of the neutral lipid fraction was accounted for by glycerides and fatty acid. 4. Five phospholipid components were identified and measured, including phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, sphingomyelin and lysophosphatidylcholine. Though phosphatidylethanolamine was the chief phospholipid, no plasmalogen was detected. 5. In contrast with other plasma membranes in the rat, the polar lipids of the microvillus membrane were rich in glycolipid. The cholesterol:polar lipid (phospholipid+glycolipid) ratio was about 1:3 for the microvillus membrane. Published data suggest that this ratio resembles that of the liver plasma membrane more closely than myelin or the erythrocyte membrane. 6. The fatty acid composition of membrane lipids was altered markedly by a single feeding of safflower oil. Membrane polar lipids did not contain significantly more saturated fatty acids than cellular polar lipids. Differences in the proportion of some fatty acids in membrane and cellular glycerides were noted. These differences may reflect the presence of specific membrane glycerides.
The fate of 7[14C]-methylguanine after administration to the rat
Authors: Craddock Valda M. , Mattocks A. R. , Magee P. N.
Published: August 2015

1. To assess the significance of the methylation of nucleic acids known to be caused by certain carcinogens, the metabolic fate of 7[14C]-methylguanine was studied, with special reference to its possible incorporation into RNA and DNA. 2. The major part (approx. 95%) of the dose was excreted unchanged in the urine. A small amount of N-demethylation took place, as evidenced by the formation of radioactive adenine and guanine, and expiration of 14C-labelled carbon dioxide. No evidence was obtained for the direct incorporation of 7-methylguanine into systems synthesizing nucleic acids, i.e. RNA in liver, DNA in intestine or in the foetus.
A tryptic peptide containing a unique serine phosphate residue in rabbit phosphoglucomutase
Authors: Milstein Celia. P. , Milstein C.
Published: August 2015

32P-labelled phosphoglucomutase was digested with trypsin after denaturation and two peptides were isolated that contained the bulk of the radioactivity bound to peptides. Both peptides appeared to derive from an identical section of the molecule. Peptic and subtilisin digests of the tryptic peptides were prepared. The resulting radioactive peptides were purified and their sequences studied. The presence of a single serine [32P]phosphate residue was clearly established. Difficulties in purification and low yields, especially of the tryptic peptide, prevented exhaustive sequence studies, but a tentative sequence is proposed as:Ala-Ile-Gly-Gly-Ile-Ile-Leu-Thr-Ala-SerP-His-Asx-Pro-Gly-Gly-Pro-(Asx2,Gly)-Phe-Gly-Ile-Lys(where SerP represents serine phosphate and Asx represents aspartic acid or asparagine). The results do not support the presence of two serine phosphate residues in the denatured enzyme, but confirm previous results of a unique sequence around a single serine phosphate residue.
Preparation and analysis of peptide fragments produced by pepsin hydrolysis of human plasma albumin and their relationship to its structure
Authors: Franglen G. , Swaniker G. R. E.
Published: August 2015

Human plasma albumin was prepared and subjected to proteolysis by pepsin at pH2·45 at 25° for 10min. with albumin/pepsin ratio 3000:1. Five peptide fragments were detected in the proteolysate by means of zone electrophoresis and gel filtration; these were separated and purified. Molecular weights, amino acid composition and disulphide bond content of the purified fragments were determined. The results show that a high proportion of the polypeptide chain of albumin appears to have a low cystine content, and at low pH values the molecule would be expected to have a considerable degree of freedom in its structure in these regions of the chain. A tripartite model for the structure of plasma albumin is proposed.
Metabolism of megestrol acetate by rat adrenal glands in vitro
Authors: Cooke B. A. , Vallance D. K.
Published: August 2015

Megestrol acetate is metabolized by homogenates of rat adrenal glands to three more polar metabolites Y2, Y3 and Y4. Their structures were investigated by microchemical reactions, paper chromatography, and ultraviolet and infrared spectroscopy. Metabolite Y3 was identified as 17α-acetoxy-11β-hydroxy-6-methyl-pregna-4,6-diene-3,20-dione, its oxidation product being identical with authentic 17α-acetoxy-6-methylpregna-4,6-diene-3,11,20-trione. It is suggested that metabolite Y2 is 17,18-dihydroxy-6-methylpregna-4,6-diene-3,20-dione and that it also exists in the form of an α-ketol formed between the 18-hydroxyl and 20-oxo groups. Metabolite Y4 is probably a tautomeric form of metabolite Y2 as they were partially interconverted on chromatography and also have similar properties.
Assay of carbonic anhydrase by titration at constant pH
Authors: McIntosh J. E. A.
Published: August 2015

1. A method is described for measuring accurately the initial velocity of the hydration reaction catalysed by the enzyme carbonic anhydrase (EC 4.2.1.1); the method depends on the titration of H+ ions at constant pH. 2. Human erythrocyte carbonic anhydrase, isoenzyme C, was used to illustrate the method. Under the experimental conditions employed (0°, pH7·0, in the presence of 45mm-sodium chloride and 5mm-sodium phosphate) isoenzyme C obeyed the Michaelis equation over the range of substrate concentration 1–16mm-carbon dioxide. The kinetic constants found were: Km=8·2mm; V/[E0]=5·0×104 sec.−1.
A new route to the imidazole-2-thiones from 2-thiohydantoins. Implications in the study of ergothioneine
Authors: Scott J. E. , Henderson Gillian
Published: August 2015

1. 2-Thiohydantoins are reduced by borohydrides to 4(5)-hydroxyimidazolidine-2-thiones, which eliminate water in acid to form imidazole-2-thiones. Both steps take place in mild conditions, in high yield. A number of imidazole-2-thiones have been synthesized by this sequence of steps, with one, two or three substituents in the 1-, 3- and 4(5)-positions. 2. 4(5)-Hydroxyimidazolidine-2-thiones are ammonium pseudo-bases, giving rise to an equilibrium mixture of amino aldehyde, carbinolamine and mesomeric ammonium cationic forms. The elimination of water is suggested to be a property of the mesomeric ammonium cation. 3. The mild conditions in which imidazole-2-thiones are formed from 4(5)-hydroxyimidazolidine-2-thiones are similar to those in which ergothioneine, a naturally occurring imidazole-2-thione of uncertain function, is normally released and measured. It is suggested that the occurrence in vivo of a precursor to ergothioneine, in the form of a 4(5)-hydroxyimidazolidine-2-thione, would explain many otherwise conflicting published data.
Studies of medium-chain fatty acyl-coenzyme A synthetase. Enzyme fraction II: mechanism of reaction and specific properties
Authors: Bar-Tana J. , Rose G.
Published: August 2015

1. The mechanism of reaction of fatty acyl-CoA synthesis catalysed by fatty acyl-CoA synthetase from ox liver (fraction II; Bar-Tana, Rose & Shapiro, 1968) was investigated by a kinetic study of CoA disappearance dependent on butyrate plus ATP or butyryl-AMP (overall and partial reaction b respectively). 2. Contrary to findings with another enzyme (fraction I), a Bi Uni Uni Bi Ping Pong mechanism (Cleland, 1963a,b,c) corresponding to Berg's (1956) scheme of reaction was eliminated and an ordered Ter Ter mechanism with an A–C–B (standing for ATP, CoA and butyrate respectively) sequence of substrate entry for the overall reaction was established for fraction II. Partial reaction (b) was found to follow the ‘Iso-Theorell–Chance’ mechanism. 3. Also, in contrast with results obtained with fraction I, no allosteric properties could be demonstrated with fraction II.
The influence of external sodium ions on the sodium pump in erythrocytes
Authors: Priestland R. N. , Whittam R.
Published: August 2015

1. A study has been made of the interaction between Na+ and K+ on the adenosine triphosphatase activity of erythrocyte ‘ghosts’, and on the K+ influx and Na+ efflux of intact erythrocytes. The adenosine triphosphatase activity and the ion movements were greater at a low external K+ concentration in the absence of Na+ than they were in the presence of 150mm-Na+. The inhibition by external Na+ of K+ influx had an inhibitory constant of 5–10mm. 2. Activation by K+ of kidney microsomal adenosine triphosphatase was retarded by Na+, and activation by Na+ was retarded by K+. Fragmented erythrocyte membranes behaved similarly. 3. These observations suggest that there is competition between Na+ and K+ at the K+-sensitive site of the membrane.
Photosynthetic control by isolated pea chloroplasts
Authors: West K. R. , Wiskich J. T.
Published: August 2015

Isolated pea chloroplasts undergo both cyclic and non-cyclic electron flow. Both processes are coupled to photophosphorylation. During non-cyclic flow the rate of oxygen production showed ADP-governed ‘photosynthetic control’ analogous to respiratory control of isolated mitochondria. Measurements of ADP/O and photosynthetic control ratios yielded values of 1–1·3 and 2–5·7 respectively. ‘Photosynthetic control’ was shown to be dependent on the intactness of the chloroplasts.
Kinetic and spectrophotometric studies on the renaturation of deoxyribonucleic acid
Authors: Thrower K. J. , Peacocke A. R.
Published: August 2015

The kinetics of the renaturation of Escherichia coli DNA in 0·4–1·0m-sodium chloride at temperatures from 60° to 90° have been studied. The extent of renaturation was a maximum at 65° to 75° and increased with ionic strength, and the rate constant increased with both ionic strength and temperature. The energy and entropy of activation of renaturation were calculated to be 6–7kcal.mole−1 and −40cal.deg.−1mole−1 respectively. It has been shown that renaturation is a second-order process for 5hr. under most conditions. The results are consistent with a reaction in which the rate-controlling step is the diffusion together of two separated complementary DNA strands and the formation of a nucleus of base pairs between them. The kinetics of the renaturation of T7-phage DNA and Bordetella pertussis DNA have also been studied, and their rates of renaturation related quantitatively to the relative heterogeneity of the DNA samples. By analysis of the spectra of DNA at different stages during renaturation it was shown that initially the renatured DNA was rich in guanine–cytosine base pairs and non-random in base sequence, but that, as equilibrium was approached, the renatured DNA gradually resembled native DNA more closely. The rate constant for the renaturation of guanine–cytosine base pairs was slightly higher than for adenine–thymine base pairs.
The metabolism of protocatechuate by Pseudomonas testosteroni
Authors: Dagley S. , Geary P. J. , Wood J. M.
Published: August 2015

1. Protocatechuate 4,5-oxygenase, purified 21-fold from extracts of Pseudomonas testosteroni, was examined in the ultracentrifuge and assigned a mol.wt. of about 140000. 2. When diluted, the enzyme rapidly lost activity during catalysis. Inactivation was partially prevented by l-cysteine. 3. With a saturating concentration of protocatechuate (1·36mm), Km for oxygen was 0·303mm. This value is greater than the concentration of oxygen in water saturated with air at 20°. 4. Cell extracts converted protocatechuate into γ-carboxy-γ-hydroxy-α-oxovalerate, which was isolated as its lactone. 5. γ-Carboxy-γ-hydroxy-α-oxovalerate pyruvate-lyase activity was stimulated by Mg2+ ions and mercaptoethanol. Cells grown with p-hydroxybenzoate as carbon source contained higher concentrations of this enzyme than those grown with succinate.
A reappraisal of some structural features of bovine heart malate dehydrogenase
Authors: Heyde Elizabeth , Ainsworth S.
Published: August 2015

1. Malate dehydrogenase of the mitochondrial type was prepared from an acetone-prepared powder of thoroughly washed minces of whole bovine heart by previously reported methods that were modified to give higher yields of the purified enzyme. 2. Determinations of the sedimentation and diffusion coefficients showed the molecular weight of the enzyme to be approx. 63000. The amino acid composition of the enzyme was also determined. Discrepancies between these data and similar data previously reported by Davies & Kun (1957) and Siegel & Englard (1962) were resolved. 3. ‘Fingerprints’ were made from tryptic digests of heat-denatured and of reduced and alkylated enzyme. These indicated that the enzyme is composed of a number of identical or similar sub-units.
Species differences in the metabolism of sulphadimethoxine
Authors: Bridges J W , Kibby M. R. , Walker S R , Williams R T
Published: August 2015

1. The fate of sulphadimethoxine (2,4-dimethoxy-6-sulphanilamidopyrimidine) was studied in man, rhesus monkey, dog, rat, guinea pig and rabbit. 2. About 20–46% of the dose (0·1g./kg.) of the drug is excreted in the urine in 24hr. in these species, except the rat, in which only 13% is excreted. 3. In man and the monkey sulphadimethoxine N1-glucuronide is the major metabolite in the urine. In the rabbit and guinea pig N4-acetylsulphadimethoxine is the main metabolite. In the dog the drug is excreted mainly unchanged. In the rat equal amounts of the unchanged drug and its N4-acetyl derivative are the main products. 4. Small amounts of sulphadimethoxine N4-glucuronide are found in the urine of all the species. Sulphadimethoxine N1-glucuronide occurs in small amounts in the urine of rat, dog and guinea pig; none is found in rabbit urine. 5. Sulphadimethoxine N4-sulphate was synthesized and found to occur in small amounts in rat urine. 6. Monkey liver homogenates fortified with UDP-glucuronic acid are able to synthesize sulphadimethoxine N1-glucuronide with the drug as substrate. Rat liver has also this ability to a slight extent, but rabbit liver is unable to do so. 7. Sulphadimethoxine N4-glucuronide is formed spontaneously when the drug is added to human urine. 8. The biliary excretion of the drug and its metabolites was examined in rats. The drug is excreted in rat bile mainly as the N1-glucuronide. The N1- and N4-glucuronides administered as such are extensively excreted in the bile by rats.
The characterization and distribution of hexahydropolyprenyl esters in cultures of Aspergillus fumigatus Fresenius
Authors: Stone K. J. , Hemming F W
Published: August 2015

The total mycelial lipid of Aspergillus fumigatus was analysed and over half of its hexahydropolyprenol was shown to be esterified with fatty acids. Comparison of the fatty acid content of the prenyl esters with the sterol ester and the total lipid indicated a marked predominance of saturated fatty acids in the polyprenyl esters. The predominant acids esterified to the prenols were palmitic acid, linoleic acid, oleic acid, lignoceric acid, stearic acid and palmitoleic acid. Most of the unesterified polyprenol was found in the mitochondrial fraction, but the esterified prenol was equally distributed throughout the cell fractions. This distribution was unlike that found for ergosteryl ester in the same tissue.
Nitrosamine-induced carcinogenesis. The alkylation of nucleic acids of the rat by N-methyl-N-nitrosourea, dimethylnitrosamine, dimethyl sulphate and methyl methanesulphonate
Authors: Swann P. F. , Magee P. N.
Published: August 2015

1. N[14C]-Methyl-N-nitrosourea, [14C]dimethylnitrosamine, [14C]dimethyl sulphate and [14C]methyl methanesulphonate were injected into rats, and nucleic acids were isolated from several organs after various time-intervals. Radioactivity was detected in DNA and RNA, partly in major base components and partly as the methylated base, 7-methylguanine. 2. No 7-methylguanine was detected in liver DNA from normal untreated rats. 3. The specific radioactivity of 7-methylguanine isolated from DNA prepared from rats treated with [14C]dimethylnitrosamine was virtually the same as that of the dimethylnitrosamine injected. 4. The degree of methylation of RNA and DNA produced in various organs by each compound was determined, and expressed as a percentage of guanine residues converted into 7-methylguanine. With dimethylnitrosamine both nucleic acids were considerably more highly methylated in the liver (RNA, about 1% of guanine residues methylated; DNA, about 0·6% of guanine residues methylated) than in the other organs. Kidney nucleic acids were methylated to about one-tenth of the extent of those in the liver, lung showed slightly lower values and the other organs only very low values. N-Methyl-N-nitrosourea methylated nucleic acids to about the same extent in all the organs studied, the amount being about the same as that in the kidney after treatment with dimethylnitrosamine. In each case the RNA was more highly methylated than the DNA. Methyl methanesulphonate methylated the nucleic acids in several organs to about the same extent as N-methyl-N-nitrosourea, but the DNA was more highly methylated than the RNA. Dimethyl sulphate, even in toxic doses, gave considerably less methylation than N-methyl-N-nitrosourea in all the organs studied, the greatest methylation being in the brain. 5. The rate of removal of 7-methylguanine from DNA of kidneys from rats treated with dimethylnitrosamine was compared with the rate after treatment of rats with methyl methanesulphonate. No striking difference was found. 6. The results are discussed in connexion with the organ distribution of tumours induced by the compounds under study and in relation to the possible importance of alkylation of cellular components for the induction of cancer.
The rate of breakdown of methyl methanesulphonate, dimethyl sulphate and N-methyl-N-nitrosourea in the rat
Authors: Swann P. F.
Published: August 2015

1. The rates of decomposition of methyl methanesulphonate, dimethyl sulphate and N-methyl-N-nitrosourea in the rat were measured. 2. Dimethyl sulphate is no longer detectable in the blood of the rat 3min. after an intravenous dose (75mg./kg. body wt.). Methyl methanesulphonate is only just detectable in the blood 1½hr. after an intravenous dose (100mg./kg. body wt.). N-Methyl-N-nitrosourea is no longer detectable in the blood 15min. after an intravenous dose (100mg./kg. body wt.). 3. The exhalation of 14CO2 after an intragastric dose of N[14C]-methyl-N-nitrosourea (100mg./kg. body wt.) is appreciably slower than after an intravenous dose, from which it is estimated that the lifetime in the rat is 2–3hr.