bluuebunny/crossref_metadata_2025 huggingface dataset:
The distribution of glucose and [14C]glucose between erythrocytes and plasma in the rat
Authors: Heath D. F. , Rose J. G.
Published: August 2015

1. Of the glucose in rat blood 79·8±3·3% (s.d.) was in the plasma. The variance was mostly due to differences between rats. 2. The concentration of glucose in erythrocyte water was 51±8% (s.d.) of that in plasma water. 3. The ratio (specific radioactivity in plasma)/(specific radioactivity in whole blood), i.e. the P/B ratio, was estimated for glucose at intervals after intravenous injection of [U−14C]glucose and [U−14C]fructose. The ratio differed from unity by more than the standard error of a single determination of the specific radioactivity of blood or plasma glucose except from 10 to 17min. after injection of [14C]glucose and from 22 to 30min. after injection of [14C]fructose. At all other times specific radioactivities in blood had to be corrected to give specific radioactivities in plasma. How to do so is described. 4. The P/B ratios were accounted for by a turnover of glucose in erythrocytes of 0·14μmole/min./ml. of erythrocytes. 5. Metabolism of glucose in rat erythrocytes is unlikely to be a major source of lactate.
Conjugation of androsterone by the guinea-pig kidney in vitro
Authors: Dillard Morris , Bondy Philip K.
Published: August 2015

Radioactive androsterone was incubated with kidney slices from guinea pigs in a Ringer bicarbonate buffer. For analysis, the radioactivity was partitioned between chloroform and water for the separation of non-polar and polar steroids. After multiple chromatography procedures, the non-polar fraction was shown to contain androsterone and at least four other similar steroids, not identified in this study. The polar fraction yielded numerous conjugates from which androsterone glucuronide and androsterone sulphate in approximately equal quantities were isolated and characterized.
Association of inorganic pyrophosphatase activity with normal calcification of rat costal cartilage in vivo
Authors: Alcock Nancy W. , Shils Maurice E.
Published: August 2015

1. Dialysed extracts of rat costal cartilage were shown to possess an enzyme that hydrolyses inorganic pyrophosphate. 2. Inorganic pyrophosphatase activity assayed in the presence of 2mm substrate was maximal at pH6·8. 3. Mg2+ was essential for activity, which was greatest with 10mm or higher concentrations of Mg2+. 4. Extracts prepared from cartilage taken from suckling rats (<20g.) showed little or no hydrolytic activity, but as rat weight increased inorganic pyrophosphatase activity was detected, increased to a maximum in tissue from animals weighing about 40g., and then rapidly declined. 5. The increase in inorganic pyrophosphatase activity was associated with an increase in the uptake of 45Ca by the cartilage in vivo. 6. Accumulation of calcium, inorganic phosphate and magnesium occurred when inorganic pyrophosphatase activity was at its maximum. 7. Alkaline phosphatase activity, measured in the same extracts used to determine pyrophosphatase activity, was highest in the tissues of the animals weighing <20g., and decreased as inorganic pyrophosphatase activity increased to its maximum. 8. There was no direct relationship between alkaline phosphatase activity and the onset of calcification.
The separation, partial purification and some properties of isoenzymes of aldolase from guinea-pig cerebral cortex
Authors: Nicholas P. C. , Bachelard H S
Published: August 2015

1. Aldolase isoenzymes from guinea-pig cerebral cortex were partially purified and separated by ammonium sulphate fractionation and chromatography on DEAE-cellulose. 2. Each purified isoenzyme was shown to be virtually uncontaminated with other forms by starch-gel electrophoresis. The quantitative distribution of the isoenzymes was: I, 6·2%; II, 5·2%; III, 15·3%; IV, 25·7%; V, 33·3%. 3. The pH optima for the five separated isoenzymes were similar; all were in the range pH7·5–8·0. Values for pKa (6·31–6·55) and pKb (9·45–9·59) were calculated from the data and suggested the involvement of histidine and lysine residues. 4. The stabilities of the isoenzymes were shown to be I=II>III>IV>V at pH4·4 in order of decreasing stability and are discussed in terms of subunit structure. 5. The substrate activity ratios (fructose 1,6-diphosphate/fructose 1-phosphate) were measured and all were in the range 12–44.
o-Quinones formed in plant extracts. Their reactions with amino acids and peptides
Authors: Pierpoint W. S.
Published: August 2015

1. The reactions of amino acids and peptides with the o-quinones produced by the enzymic oxidation of chlorogenic acid and caffeic acid have been studied manometrically and spectrophotometrically. 2. Amino acids, except lysine and cysteine, react primarily through their α-amino groups to give red or brown products. These reactions, which compete with the polymerization of the quinones, are followed by secondary reactions that may absorb oxygen and give products with other colours. 3. The ∈-amino group of lysine reacts with the o-quinones in a similar way. The thiol group of cysteine reacts with the quinones, without absorbing oxygen, giving colourless products. 4. Peptides containing cysteine react with the o-quinones through their thiol group. 5. Other peptides, such as glycyl-leucine and leucylglycine, react primarily through their α-amino group and the overall reaction resembles that of the N-terminal amino acid except that it is quicker. 6. With some peptides, the secondary reactions differ from those that occur between the o-quinones and the N-terminal amino acids. The colours produced from carnosine resemble those produced from histidine rather than those from β-alanine, and the reactions of prolylalanine with o-quinones are more complex than those of proline.
Control of respiration and metabolism in growing Klebsiella aerogenes. The role of adenine nucleotides
Authors: Harrison D. E. F. , Maitra P. K.
Published: August 2015

1. A rapid-sampling technique was used to obtain perchloric acid extracts of cells growing in a chemostat culture, so that meaningful values for ATP content could be obtained in spite of the fact that the turnover time for the total ATP content was about 1sec. 2. For steady-state growth, it was found that, in a glucose-limited chemostat culture, the ATP/ADP concentration ratio was approximately constant with changes in dissolved-oxygen tensions above the critical value, but fell when the culture was grown under oxygen-limited conditions and was at a minimum in anaerobically grown cultures. The steady-state ATP content was lower in cells growing under nitrogen-limited conditions with glucose in excess than in glucose-limited cells. The steady-state ATP content was independent of growth rate at growth rates over 0·1hr.−1. 3. When the respiration rate of the cells was stimulated by lowering the oxygen tension the ATP content did not increase, indicating either an increased turnover rate of ATP or a fall in the P/O ratio. The sudden addition of extra glucose or succinate to a glucose-limited culture increased the respiration rate of the cells, but the ATP content quickly returned to the steady-state value after initial perturbations. This control over ATP content is explained in terms of regulation by adenine nucleotides of the catabolism and anabolism of glucose. An exception to this control over ATP content was found when the respiration rate was stimulated by addition of an antifoam.
Biosynthesis of thyroglobulin. Incorporation of [1−14C]galactose, [1−14C]mannose and [4,5−3H2]leucine into soluble proteins by rat thyroids in vitro
Authors: Herscovics Annette
Published: August 2015

1. Rat thyroid lobes were incubated for various periods of time in Krebs–Ringer bicarbonate containing [3H]leucine and either [1−14C]galactose or [1−14C]mannose. Radioactivity in soluble proteins was determined after their separation by sucrose-gradient centrifugation. 2. The time-course of incorporation of label from [14C]-mannose into soluble thyroid proteins was parallel to that observed for [3H]leucine. There was a lag of at least 30min. before either label appeared in non-iodinated thyroglobulin (protein 17–18s). During this time both labels were detected in two fractions known to contain subunit precursors of thyroglobulin (fractions 12s and 3–8s). Radioactivity from double-labelled fractions 12s and 3–8s was transferred to protein 17–18s during subsequent incubation in an unlabelled medium. 3. In contrast, most of the [14C]galactose was immediately incorporated into protein 17–18s. 4. During the first hour of incubation, puromycin almost completely inhibited the incorporation of label from [3H]leucine and [14C]mannose into all protein fractions, but had little effect on the incorporation of [14C]galactose into protein 17–18s. 5. These results indicate that mannose is incorporated into the carbohydrate groups of protein 17–18s at an earlier stage in its formation than galactose. It is suggested that the synthesis of the carbohydrate groups of ghyroglobulin begins soon after formation of the polypeptide components, more than 30min. before these are aggregated to protein 17–18s; carbohydrate synthesis then proceeds in a stepwise manner, galactose being incorporated at about the time of aggregation of subunits to protein 17–18s. Most, if not all, the carbohydrate is added to thyroglobulin before it is iodinated.
Comparative studies of bile salts. 16-Deoxymyxinol, a second bile alcohol from hagfish
Authors: Anderson I. G. , Haslewood G. A. D.
Published: August 2015

1. Material containing the less polar sulphate previously noticed in hagfish bile salts gave, after dioxan–trichloroacetic acid cleavage, 16-deoxymyxinol [3β,7α,-26(27)-trihydroxy-5α-cholestane]. 2. Anodic coupling of 3β-hydroxy-5β-cholanoic acid and the mixed half esters of dl-methylsuccinic acid, followed by lithium aluminium hydride reduction, yielded 3β,26(27)-dihydroxy-5β-cholestane. 3. 16-Deoxymyxinol, the third known bile alcohol having the 3β-hydroxy-5α-hydrogen configuration, poses again the question of how the 3β-hydroxyl group of cholesterol can be ‘retained’ in biosynthesis of primitive bile salts.
The distribution of phospholipase D in developing and mature plants
Authors: Quarles R. H. , Dawson R. M. C.
Published: August 2015

1. The distribution of phospholipase D (phosphatidylcholine phosphatido-hydrolase, EC 3.1.4.4) was examined in the tissues of a number of plants and seeds. 2. The highest activities were found in various swollen storage tissues of certain plants: cabbage, central stalk; cauliflower, flower; celery, swollen leaf stalk; Kohl rabi, swollen stem; carrot, root; pea and marrow, seed. 3. Appreciable activity was retained in pea seeds for at least 1 year after drying. After germination and growth in the dark the total activity present in the cotyledons and also in the whole seedling decreased. 4. In the growing pea seedling (7 days old), about 3% of the total activity was in the plumule, 9% in the root and the remainder in the cotyledons. However, the activity in the root on a dry-weight basis was higher than that in the cotyledons. In both the root and the plumule the activity on a wet- or a dry-weight basis was highest in the growing tip. 5. The activity per dry weight in the roots and aerial parts of pea plants declined to low values as growth continued, but roots struck from cuttings of mature plants showed the same high activity as found in roots from young seedlings with cotyledons attached. 6. The total phospholipids present in the cotyledons of pea seeds were depleted on germination and growth. Of the individual phospholipids, phosphatidylcholine and phosphatidylethanolamine showed the same loss in 11 days as the whole phospholipid fraction, whereas phosphatidylinositol was decreased to a greater extent and cardiolipin and phosphatidylserine were not decreased. There was no increase of phosphatidic acid, as might have been expected if the phospholipids had disappeared through phospholipase D hydrolysis. 7. It is concluded that phospholipase D in plant storage tissues and seeds may be related to the rapid growth involved in their formation rather than being necessary for the utilization of their food reserve substances.
The integration of donor and recipient deoxyribonucleic acid during transformation of Bacillus subtilis
Authors: Ayad S R , Barker G R
Published: August 2015

1. DNA labelled with 5-bromo[3H]uracil was used to transform auxotrophic strains of Bacillus subtilis. 2. After various times of incubation, DNA was extracted from the transformed culture and subjected to equilibrium sedimentation in caesium chloride gradients. 3. In addition to heavy donor DNA and light recipient DNA, a component with an intermediate density was found and is believed to consist of a biological hybrid of donor and recipient. 4. The component of intermediate density was isolated and found to possess activity in transformation derived from both donor and recipient strains. 5. Denaturation of the component of intermediate density followed by centrifugation gave only one component, indicating that integration had occurred in both strands of the recipient DNA. 6. No integrated band was observed after uptake by competent cells of B. subtilis of heavy DNA prepared from Escherichia coli.
The action of dilute aqueous NN-dimethylhydrazine on bacterial cell walls
Authors: Anderson J. C. , Archibald A. R. , Baddiley J , Curtis M. J. , Davey N. Barbara
Published: August 2015

1. Walls of certain Gram-positive bacteria dissolved on incubation with dilute aqueous NN-dimethylhydrazine in the presence of air, by a reaction that probably involves free radicals. 2. Under the conditions described, the soluble products from the peptidoglycan were almost all non-diffusible. After brief incubation of walls of some organisms with reagent, part of the peptidoglycan component was obtained as a high-molecular-weight gel, the viscosity of which was rapidly decreased by incubation with lysozyme. 3. The extent to which peptidoglycan dissolved varied with different organisms, depending possibly on the extent of cross-linking, but the nature of the bonds that were destroyed has not been established. 4. Teichoic acids and polysaccharides were solubilized by this treatment and could be isolated in high overall yield. 5. The procedure is valuable in the examination of the distribution of heteropolymers in walls, and has been used to show that the polysaccharide present in walls of Lactobacillus arabinosus 17–5 is phosphorylated and may account for 20% of the total phosphate of the wall.
The emission of corrosive vapours by wood. Sweet-chestnut (Castanea sativa) and wychelm (Ulmus glabrau) O-acetyl-4-O-methylglucuronoxylans extracted with dimethyl sulphoxide
Authors: Cochrane G. C. , Gray J. D. , Arni P. C.
Published: August 2015

1. O-Acetylated 4-O-methylglucuronoxylans were isolated from sweet chestnut and wych elm, either green or incubated at 48° and 100% relative humidity for 36 weeks. 2. The chlorine–ethanolamine method of delignification resulted in a 50% loss of O-acetyl groups from green wych elm compared with an 18% loss from green sweet chestnut. 3. The acid–chlorite method gave an acceptable loss of O-acetyl groups in three cases, but incubated sweet chestnut showed a 44·6% loss. However, it is believed that this is due to the loss of simple O-acetylated xylose sugars resulting from glycosidic hydrolysis, rather than removal of O-acetyl groups by direct hydrolysis. Assuming that this occurs in a random manner, it is unlikely to have much structural significance. 4. Dimethyl sulphoxide extraction of chestnut holocellulose and elm holocellulose, green and incubated, yielded O-acetyl glucuronoxylans containing 10·2, 3·8, 13·1 and 7·7% O-acetyl groups respectively. 5. The location of these O-acetyl groups was determined by Bouveng's method in which phenyl isocyanate is used as a blocking group.
Compartmentation of glutamate metabolism in brain. Evidence for the existence of two different tricarboxylic acid cycles in brain
Authors: Van Den Berg C. J. , Kržalić LJ. , Mela P. , Waelsch H.
Published: August 2015

1. 14C from [1−14C]glucose injected intraperitoneally into mice is incorporated into glutamate, aspartate and glutamine in the brain to a much greater extent than 14C from [2−14C]glucose. This difference for [1−14C]glucose and [2−14C]glucose increases with time. The amount of 14C in C-1 of glutamate increases steadily with time with both precursors. It is suggested that a large part of the glutamate and aspartate pools in brain are in close contact with intermediates of a fast-turning tricarboxylic acid cycle. 2. 14C from [1−14C]acetate and [2−14C]acetate is incorporated to a much larger extent into glutamine than into glutamate. An examination of the time-course of 14C incorporated into glutamine and glutamate reveals that glutamine is not formed from the glutamate pool, labelled extensively by glucose, but from a small glutamate pool. This small glutamate pool is not derived from an intermediate of a fast-turning tricarboxylic acid cycle. 3. It is proposed that two different tricarboxylic acid cycles exist in brain.
Isolation of choline esters from aqueous solutions by extraction with sodium tetraphenylboron in organic solvents
Authors: Fonnum F.
Published: August 2015

1. The method is based on the observation that choline esters and sodium tetraphenylboron (Kalignost) form complexes that are insoluble in water but soluble in organic solvents such as nitriles, higher ketones and benzyl alcohol. 2. The extraction procedure is an example of liquid cation exchange where tetraphenylboron is the cation-exchange group. 3. The proportion of choline esters extracted depends on the type and total amount of cation in the aqueous phase and the amount of sodium tetraphenylboron in the organic solvent. 4. The proportion of choline esters extracted is independent of the choline ester concentration, the pH (between 8 and 3) and the relative volumes of the two phases. 5. The affinity of sodium tetraphenylboron for choline esters increases with an increase in the size of the acyl group. 6. The choline ester extracted can be released into an aqueous solution by treatment with strong acids, silver salts and anion-exchange resins.
An enzymic method for the trace iodination of immunoglobulins and other proteins
Authors: Marchalonis J. J.
Published: August 2015

1. A method is described for the trace iodination of immunoglobulins and other serum proteins by a system consisting of lactoperoxidase, hydrogen peroxide and iodide. 2. γG immunoglobulin that had been labelled to a specific radioactivity of 5μc/μg. by use of carrier-free [125I]iodide gave no evidence of denaturation when analysed by electrophoresis and density-gradient ultracentrifugation. 3. Tryptic hydrolysis and peptide ‘mapping’ of a completely characterized peptide radioiodinated by this method showed that the [125I]iodide was bound to tyrosyl residues. 4. Proteins differ in their susceptibility to iodination by this method. Human γG immunoglobulin, for example, is iodinated more than ten times as readily as is human α2-macroglobulin under the same conditions. 5. Lactoperoxidase catalyses the iodination of proteins much more readily than does horseradish peroxidase.
Effect of tannic acid on the synthesis of protein and nucleic acid by rat liver
Authors: Badawy A. A.-B. , White Audrey E. , Lathe G. H.
Published: August 2015

1. As early as 1hr. after the intraperitoneal administration of tannic acid to rats, it could be demonstrated in the liver. At 3hr. the nuclear fraction contained the largest amount of tannic acid. 2. Nuclear RNA synthesis was inhibited in vivo 2hr. after the administration of tannic acid. Induction by cortisol of tryptophan pyrrolase was 90% inhibited at 24hr. 3. Incorporation of [1−14C]leucine into protein by liver slices from treated rats was decreased by 50% after 24hr. Its incorporation into postmitochondrial supernatant from treated animals was not inhibited. Incorporation into slices and postmitochondrial supernatants were inhibited in vitro by tannic acid. 4. The sequence of events: concentration of tannic acid in nuclei, inhibition of nuclear RNA synthesis, inhibition of protein synthesis and production of necrosis, is discussed.
The pH-dependence of the binding of competitive inhibitors to pepsin
Authors: Knowles J. R. , Sharp Hilary , Greenwell P.
Published: August 2015

1. The pH-dependence of the binding to pepsin of four dipeptide competitive inhibitors is reported. Values of Ki obtained from equilibrium-dialysis experiments agree closely with those from kinetic measurements. 2. The binding of uncharged N-acyl-dipeptide amides to pepsin is essentially independent of pH from 0·2 to 5·8. Values of Ki for the corresponding N-acyl-dipeptide acids rise rapidly above pH3·5, and depend on the ionization of a group of apparent pKa 3·6. 3. The data indicate that pepsin does not undergo any gross conformation change (at least none that affects binding) over the whole pH range of its catalytic activity. The pH-dependence of the dipeptide acid inhibitors indicates that the acid anions do not bind to pepsin, presumably because of electrostatic repulsion between the inhibitor anion and a negative centre at or near the active site of the enzyme. 4. The binding of all four stereoisomers of N-acetylphenylalanylphenylalanine, of the depside analogues of the l–l- and d–l-compounds and of N-acetylglycyl-l-phenylalanine and N-acetyl-l-phenylalanylglycine was studied at pH2·2. 5. These results throw further light on the binding specificity of pepsin and on the charge nature of the active site of this enzyme.
The pH-dependence of pepsin-catalysed reactions
Authors: Cornish-Bowden A. J. , Knowles J. R.
Published: August 2015

1. The pH-dependence of the pepsin-catalysed hydrolysis of three peptide substrates was studied by using a method for the continuous monitoring of the formation of ninhydrin-positive products. 2. Two peptide acid substrates, N-acetyl-l-phenylalanyl-l-phenylalanine and N-acetyl-l-phenylalanyl-l-phenylalanyl-glycine, show apparent pKa values of 1·1 and 3·5 in the plots of k0/Km versus pH. By contrast a neutral substrate, N-acetyl-l-phenylalanyl-l-phenylalanine amide, shows apparent pKa values of 1·0 and 4·7. 3. Together with the data of the preceding paper (Knowles, Sharp & Greenwell, 1969), these results are taken to indicate that the rate of pepsin-catalysed hydrolysis is controlled by the ionization of two groups, which on the free enzyme have apparent pKa values of 1·0 and 4·7. It is apparent that the anions of peptide acid substrates are not perceptibly bound to the enzyme, resulting in apparent pKa values of 3·5 for the dependence of k0/Km for these materials.
Studies on steroid metabolism in human endometrial tissue
Authors: Collins W. P. , Mansfield M. D. , Bridges C. E. , Sommerville I. F.
Published: August 2015

1. A computerized technique is described for the quantitative determination of radiometabolites from incubation studies. 2. Seven steroid substrates have been incubated with human endometrial tissue. The principal radiometabolites were identified and determined after 2hr. incubation without the addition of cofactors and after 4hr. incubation with cofactors. 3. The main products from progesterone were 20α-dihydroprogesterone and 5α-pregnanedione with lower yields of 5β-pregnanedione and 20β-dihydroprogesterone. There was no evidence for 17α-hydroxylase activity. 4. 17α-Hydroxyprogesterone was transformed into small yields of 17α,20α- and 17α,20β-dihydroxypregn-4-en-3-one. In one incubation there was evidence for conversion into androstenedione. 5. Dehydroepiandrosterone was transformed into small amounts of androstenedione, 5α-androstanedione and androsterone. 6. Androstenedione and testosterone were interconvertible, the reaction favouring the formation of androstenedione. 5α-Androstanedione and androsterone were formed from both substrates. There was no evidence for the formation of phenolic steroids. 7. Oestrone and oestradiol-17β were interconvertible, the reaction favouring the formation of oestrone.
Hormonal induction and regulation of lactose synthetase in mouse mammary gland
Authors: Palmiter Richard D.
Published: August 2015

The augmentation of lactose synthetase activity during late pregnancy and lactation was measured by using both a tissue-culture assay and a cell-free assay. The results indicated at least a 100-fold augmentation in specific activity between late pregnancy and lactation. The cell-free assay indicated that the activities of both subunits of this enzyme had increased to 20–30% of the value during lactation by the last day of pregnancy. The tissue-culture assay, however, showed activities only 3–4% of the maximum at the time of parturition. This suggests that not all the enzyme present in the tissue before lactation commenced was active. Since at all stages of pregnancy and lactation the B subunit, α-lactalbumin (which is also a milk protein), was rate-limiting, it is suggested that the rate of lactose synthesis may be linked to the rate of milk-protein synthesis. Both subunits of lactose synthetase could be induced in tissue culture by the hormones insulin+hydrocortisone+prolactin. Of the three hormones, prolactin appeared to be the ‘trigger’ that induced the synthesis of these proteins if the tissue had been stimulated previously by insulin+hydrocortisone.
The relationship between reversibility of fibril formation and subunit composition of rat skin collagen
Authors: Bannister D. W.
Published: August 2015

1. Salt-soluble rat skin collagen was precipitated from solution at neutral pH and 37°. On cooling, a portion of the collagen returned into solution. The fractions were separated, the supernatant was concentrated and the precipitate was redissolved in dilute acetic acid. 2. Solutions of supernatant and precipitate were subjected to the same fractionation procedure, giving four fractions. 3. Each fraction was examined by starch-gel electrophoresis and a relationship between subunit composition and the fractionation procedure was noted. The collagen that redissolved on cooling contained less of the more highly cross-linked components than did either the fraction remaining in the precipitate or the starting material.
Catabolite repression of the lac operon. Repression of translation
Authors: Yudkin M D , Moses V.
Published: August 2015

1. Experiments were devised to show whether catabolite repression of β-galactosidase synthesis operates at the level of transcription or of translation. Escherichia coli K12 was induced for a short period in non-repressing medium (glycerol–minimal medium), and transcription of the lac operon was terminated by either of two methods; glucose was then added as a source of the catabolite repressor during the subsequent translation of the accumulated β-galactosidase messenger RNA. 2. When induced bacteria in glycerol medium were infected with T6 phage, which is known to halt transcription, the addition of glucose up to 3min. later diminished the yield of β-galactosidase. 3. When induced bacteria in glycerol medium were removed from the inducer and resuspended in fresh medium (a process that is also known to halt transcription), the yield of enzyme was again diminished by the presence of glucose in the resuspension medium. 4. It is concluded that repression of β-galactosidase synthesis can be brought about by the presence of glucose during the translation phase only. 5. In E. coli strain 300U the effect on translation was sufficient to account for almost all the catabolite repression of β-galactosidase synthesis observed during exponential growth of the organism in glucose–minimal medium. In E. coli strain 200P, however, much more severe repression occurred during exponential growth, and an additional effect of glucose is postulated.
Phosphatidate biosynthesis in mitochondrial subfractions of rat liver
Authors: Shephard Elizabeth H. , Hübscher G.
Published: August 2015

1. After conventional fractionation of rat liver homogenates in 0·88m-sucrose the mitochondrial fraction was subjected to short-term water lysis followed by separation of the resulting membrane preparations. 2. Phosphatidate formation was measured in all subcellular fractions and subfractions and was compared with the distribution of succinate dehydrogenase, monoamine oxidase, rotenone-insensitive NADH cytochrome c reductase, arylsulphatase, urate oxidase, arylesterase and glucose 6-phosphatase. 3. The results obtained indicated that mitochondria were capable of synthesizing phosphatidate, though this activity was only about one-third of the total homogenate activity. 4. Mitochondrial phosphatidate formation was located predominantly in the outer mitochondrial membrane. Although this membrane preparation was found to be significantly contaminated by the microsomal fraction, this contamination was estimated to account for not more than about 20% of the total phosphatidate formation observed in preparations of outer mitochondrial membrane.
Effects of lysosomal collagenolytic enzymes, anti-inflammatory drugs and other substances on some properties of insoluble collagen
Authors: Anderson A. J.
Published: August 2015

1. An enzyme system present in a rat liver lysosome-rich fraction was found to liberate soluble hydroxyproline-containing products from insoluble collagen, with maximum activity at pH3·45. It was concluded that a form of cathepsin D was involved since synthetic substrates specific for trypsin were not hydrolysed. Collagenolysis was enhanced by thiol compounds and inhibited by Cu2+ ions and the anti-inflammatory drugs phenylbutazone and ibufenac. 2. The possibility that behaviour of collagen and collagenolysis were modified by various substances, either by destruction of intramolecular and intermolecular bonds in tropocollagen or by electrostatic interactions, is discussed. Insoluble collagen was found to bind electrostatically to chondromucoprotein. This interaction was inhibited by some anti-inflammatory drugs. 3. Possible roles of the lysosomal collagenolytic enzyme system in experimental lathyrism in rats given penicillamine, and in erosion of cartilage in rheumatoid arthritis, are considered. 4. Collagenolysis in vivo, which may depend on complex interrelationships between collagen, chondromucoprotein and metal ions, is discussed in relation to possible effects, both harmful and beneficial, of anti-inflammatory drugs used in rheumatoid arthritis.
The inhibition of nucleic acid synthesis by mycophenolic acid
Authors: Franklin T J , Cook Jennifer M.
Published: August 2015

1. Mycophenolic acid, an antibiotic of some antiquity that more recently has been found to have marked activity against a range of tumours in mice and rats, strongly inhibits DNA synthesis in the L strain of fibroblasts in vitro. 2. The extent of the inhibition of DNA synthesis is markedly increased by preincubation of the cells with mycophenolic acid before the addition of [14C]thymidine. 3. The inhibition of DNA synthesis by mycophenolic acid in L cells in vitro is reversed by guanine in a non-competitive manner, but not by hypoxanthine, xanthine or adenine. 4. The reversal of inhibition by guanine can be suppressed by hypoxanthine, 6-mercaptopurine and adenine. 5. Mycophenolic acid does not inhibit the incorporation of [14C]thymidine into DNA in suspensions of Landschütz and Yoshida ascites cells in vitro. 6. Mycophenolic acid inhibits the conversion of [14C]hypoxanthine into cold-acid-soluble and -insoluble guanine nucleotides in Landschütz and Yoshida ascites cells and also in L cells in vitro. There is some increase in the radioactivity of the adenine fraction in the presence of the antibiotic. 7. Mycophenolic acid inhibits the conversion of [14C]hypoxanthine into xanthine and guanine fractions in a cell-free system from Landschütz cells capable of converting hypoxanthine into IMP, XMP and GMP. 8. Preparations of IMP dehydrogenase from Landschütz ascites cells, calf thymus and LS cells are strongly inhibited by mycophenolic acid. The inhibition showed mixed type kinetics with Ki values of between 3·03×10−8 and 4·5×10−8m. 9. Evidence was also obtained for a partial, possibly indirect, inhibition by mycophenolic acid of an early stage of biosynthesis of purine nucleotides as indicated by a decrease in the accumulation of formylglycine amide ribonucleotide induced by the antibiotic azaserine in suspensions of Landschütz and Yoshida ascites cells and L cells in vitro.
Isolation of a new phospholipid, phosphatidyl-N-(2-hydroxyethyl)alanine, from rumen protozoa
Authors: Kemp P , Dawson R. M. C.
Published: August 2015

1. Phosphatidyl-N-(2-hydroxyethyl)alanine was isolated from the mixed protozoal fraction of rumen and characterized. 2. Of the fatty acids 31% was octadecenoic acid, 91% of which was the trans-Δ11-isomer, an intermediary in the ruminal hydrogenation of linolenic acid and linoleic acid.
Metabolism of sinapic acid and related compounds in the rat
Authors: Griffiths L. A.
Published: August 2015

1. Administration of sinapic acid to the rat results in the excretion of 3-hydroxy-5-methoxyphenylpropionic acid, dihydrosinapic acid, 3-hydroxy-5-methoxycinnamic acid and unchanged sinapic acid in the urine. The sinapic acid conjugate sinalbin is also catabolized to free sinapic acid and 3-hydroxy-5-methoxyphenylpropionic acid in the rat. 2. 3,4,5-Trimethoxycinnamic acid is metabolized in part to sinapic acid and 3-hydroxy-5-methoxyphenylpropionic acid. 3. 3,5-Dimethoxycinnamic acid is metabolized to 3-hydroxy-5-methoxycinnamic acid and 3-hydroxy-5-methoxyphenylpropionic acid. 4. The metabolic interrelationships of these compounds were studied by the administration of intermediates and a metabolic pathway is proposed. 5. The metabolism of the corresponding benzoic acids was studied, but these compounds and their metabolites were shown not to be intermediates or products of the metabolism of the related cinnamic acids.
Effects of light and darkness on polyphenol distribution in the tea plant (Camellia sinensis L.)
Authors: Forrest G. I.
Published: August 2015

1. Flavonoid synthesis was able to proceed in darkness in young shoots and seedlings of the tea plant, but was increased by light. 2. The initial effect of darkness was to inhibit synthesis of the A ring or its linkage to the phenylpropane moiety of the flavonoid, but later the hydroxylation state of the flavanols was affected, leading to smaller proportions of gallocatechins and of complex leucoanthocyanins. 3. The esterification of catechins with gallic acid was less affected, so that the ratio of catechin gallates to simple catechins also increased. 4. The flavylogen content of darkened stems, especially in seedlings, was much less decreased than that of leaves; however, a short subsequent light-treatment caused an increase in polymerization.
β-Alanyl-l-tyrosine. Chemical synthesis, properties and occurrence in larvae of the fleshfly Sarcophaga bullata Parker
Authors: Levenbook L. , Bodnaryk R. P. , Spande T. F.
Published: August 2015

1. A naturally occurring peptide, termed sarcophagine, has been isolated from larvae of the fleshfly Sarcophaga bullata. 2. The physicochemical properties of the natural peptide are identical with those of synthetic β-alanyl-l-tyrosine. 3. During larval growth the concentration of the dipeptide increases continuously; in the fully grown larva it is the predominant non-protein ninhydrin-positive material. 4. Sarcophagine is rapidly and extensively utilized at the time of hardening and darkening of the insect puparium. 5. By virtue of its much higher solubility than that of free tyrosine, the peptide may serve as a reservoir to provide large amounts of readily available tyrosine for subsequent puparium formation.
Artificial substrates for prenyltransferase
Authors: Popják G. , Rabinowitz J. L. , Baron J. M.
Published: August 2015

Four out of 16 new allylic pyrophosphates synthesized were found to be artificial substrates for liver prenyltransferase (EC 2.5.1.1). These were the trans-and the cis-3-ethyl-3-methylallyl, the 3,3-diethylallyl and the (mixture of cis and trans) 3-methyl-3-n-propylallyl pyrophosphates. The products synthesized from these substrates and isopentenyl pyrophosphate were the appropriate homo- and bishomo-farnesyl pyrophosphates. Substitution of 3,3-dimethylallyl pyrophosphate at C-2 with a methyl group destroyed its reactivity with the enzyme. Neither the unsubstituted allyl pyrophosphate nor the cis- or trans-3-methylallyl pyrophosphate could be condensed with isopentenyl pyrophosphate. Thus the simplest allylic substrate for prenyltransferase is 3,3-dimethylallyl pyrophosphate.
The vectorial release of nascent immunoglobulin peptides
Authors: Bevan Michael J.
Published: August 2015

A microsomal preparation from a mouse plasmacytoma, MOPC 47A, that secretes immunoglobulin A was used to study the release of nascent immunoglobulin peptides in vitro. Nascent chains were released with puromycin and characterized with specific antiserum against the immunoglobulin product of the tumour. When the tissue had been prelabelled with [3H]leucine the experiments were complicated by the large background of completed radioactive polypeptides in the microsomal preparation. Up to one-third of the released radioactivity in the microsomal preparation could be recognized as immunoglobulin. With [3H]-puromycin as the radioactive label, however, the results are much easier to interpret, although the proportion of released radioactivity that can be identified as immunoglobulin is lower (up to one-tenth). Both types of experiment demonstrate that all of the recognizable nascent immunoglobulin chains remain in association with the microsomal vesicles after release from the ribosomes.
The enzymic degradation of alkyl-substituted gentisates, maleates and malates
Authors: Hopper D. J. , Chapman P. J. , Dagley S.
Published: August 2015

1. Cell-free extracts, prepared from a non-fluorescent Pseudomonas grown on m-cresol, oxidized gentisate and certain alkyl-substituted gentisates with the consumption of 1 mol of oxygen and the formation of 1 mol of pyruvate from 1 mol of substrate. 2. In addition to pyruvate, malate was formed from gentisate; citramalate was formed from 3-methylgentisate and 4-methylgentisate; 2,3-dimethylmalate was formed from 3,4-dimethylgentisate. 3. One enantiomer, d-(-)-citramalate, was formed enzymically from 3-methylgentisate, 4-methylgentisate and citraconate. l-(+)-Citramalate was formed from mesaconate by the same extracts. When examined as its dimethyl ester by gas–liquid chromatography, enzymically formed 2,3-dimethylmalate showed the same behaviour as one of the two racemates prepared from the synthetic compound. 4. Maleate, citraconate and 2,3-dimethylmaleate were rapidly hydrated by cell extracts, but ethylfumarate and 2,3-dimethylfumarate were not attacked. 5. Cell extracts oxidized 1,4-dihydroxy-2-naphthoate to give pyruvate and phthalate. 6. Alkylgentisates were oxidized by a gentisate oxygenase (EC 1.13.1.4) present in Pseudomonas 2,5. The ring-fission products were attacked by maleylpyruvase, but not by fumarylpyruvase, and their u.v.-absorption spectra were those expected for alkyl-substituted maleylpyruvates. 7. When supplemented with ATP, CoA, succinate and Mg2+ ions, an enzyme system from cells grown with 2,5-xylenol formed pyruvate from d- but not from l-citramalate. Extracts from cells grown with dl-citramalate or with itaconate attacked both d- and l-citramalate; other alkylmalates were cleaved in similar fashion to give pyruvate or 2-oxobutyrate. 8. These results accord with a general sequence of reactions in which the benzene nucleus of an alkylgentisate is cleaved to give an alkyl-substituted maleylpyruvate. The ring-fission products are hydrolysed to give pyruvate, plus alkylmalic acids which then undergo aldol fissions, probably as their CoA esters. In Pseudomonas 2,5 several homologous sequences of this general type appear to be catalysed by a single battery of enzymes with broad substrate specificities, whereas the metabolic capabilities of the fluorescent Pseudomonas 3,5 are more restricted. 9. Intact cells of both organisms metabolize d-malic acid by reactions that have not been elucidated, but are different from those which degrade alkylmalates.
The role of adenosine 3′:5′-cyclic monophosphate in the regulation of insulin release by isolated rat islets of Langerhans
Authors: Montague W. , Cook J. R.
Published: August 2015

1. Concentrations of cyclic AMP (adenosine 3′:5′-cyclic monophosphate) and rates of insulin release were measured in islets of Langerhans isolated from rat pancreas and incubated for various times in the presence of glucose, 3-isobutyl-1-methylxanthine, caffeine, theophylline, adrenaline and diazoxide. 2. Caffeine and theophylline produced small but significant increases in both cyclic AMP and release of insulin when they were incubated in the presence of 10mm-glucose. 3. 3-Isobutyl-1-methylxanthine produced a marked increase in the intracellular concentration of cyclic AMP in the presence of 5mm- and 10mm-glucose. However, insulin release was stimulated only in the presence of 10mm-glucose. 4. In response to rising concentrations of extracellular glucose (5–20mm) there was no detectable increase in the intracellular concentration of cyclic AMP even though there was a marked increase in the rate of insulin release. 5. In response to 10mm-glucose insulin release occurred in two phases and 3-isobutyl-1-methylxanthine potentiated the effect of glucose on both phases. The intracellular concentration of cyclic AMP remained constant with glucose and rose within 10min to its maximum value with 3-isobutyl-1-methylxanthine. 6. Adrenaline and diazoxide inhibited insulin release and lowered the intracellular concentration of cyclic AMP when islets were incubated with glucose or 3-isobutyl-1-methylxanthine. 7. It is suggested that glucose does not stimulate insulin release by increasing the concentration of cyclic AMP in islet cells. However, the concentration of cyclic AMP in islet cells may modulate the effect of glucose on the release process.
Albumin synthesis by the perfused rat liver. A comparison of methods with special reference to the effect of dietary protein deprivation
Authors: Hoffenberg R. , Gordon A. H. , Black E. G.
Published: August 2015

1. Isolated perfused rat livers were used to study synthesis of albumin after donors had been fed on normal or protein-free diets. 2. Methods of determining the liver's ability to produce albumin included incorporation of [14C]carbonate, [3H]lysine and [14C]arginine, as well as a direct method based on a heterologous perfusing system of rat erythrocytes and rabbit plasma. 3. Livers from protein-deprived rats were found to form extremely little urea and not to incorporate 14CO2 into [14C]urea, but they were capable of producing [14C]urea from [14C]arginine and of incorporating the latter and [3H]lysine into albumin. 4. By immunological means these lives were found to synthesize less albumin than normal, but their ability was only slightly impaired when related to body weight or liver weight. 5. These findings are consistent with a block in urea-cycle enzymes with relative integrity of arginase activity and of amino acid activation.
Incorporation of label from d-β-hydroxy-[14C]butyrate and [3-14C]acetoacetate into amino acids in rat brain in vivo
Authors: Cremer Jill E.
Published: August 2015

The metabolism of ketone bodies by rat brain was studied in vivo. Rats starved for 48h were given either d-β-hydroxy[3-14C]butyrate or [3-14C]acetoacetate by intravenous injection and killed after 3 or 10min. Total radioactivity in the acid-soluble material of the brain and the specific radioactivities of the brain amino acids glutamate, glutamine, aspartate and γ-aminobutyrate were determined. A group of fed animals were also given d-β-hydroxy[3-14C]butyrate. In the brains of all animals 14C was present in the acid-soluble material and the specific radioactivity of glutamate was greater than that of glutamine.
The control of ribonucleic acid synthesis in bacteria. The synthesis and stability of ribonucleic acid in chloramphenicol-inhibited cultures of Escherichia coli
Authors: Midgley J. E. M. , Gray W. J. H.
Published: August 2015

The rate of polymerization of ribosomal ribonucleic acid chains was estimated for steadily growing cultures of Escherichia coli M.R.E.600, from the kinetics of incorporation of exogenous [5-3H]uracil into completed 23S rRNA molecules. The analytical method of Avery & Midgley (1971) was used. Measurements were made at 37°C, in the presence or the absence of chloramphenicol, in each of three media; enriched broth, glucose–salts or sodium lactate–salts. The rate of chain elongation of 23S rRNA was virtually constant in all media at 37°C, as 24±4 nucleotides added/s. Accelerations in the rate of biosynthesis of rRNA by chloramphenicol in growth-limiting media are due primarily to an increase in the rate of initiation of new RNA chains, up to the rates existing in cultures growing rapidly in broth. Thus, in poorer media, only a small fraction of the available DNA-dependent RNA polymerase molecules are active at any given instant, since the chain-initiation rate is limiting in these conditions. In cultures growing rapidly in enriched broth, antibiotic inhibition caused a rise of some 12% in the rate of incorporation of exogenous uracil into total RNA. This small acceleration was due entirely to the partial stabilization of the mRNA fraction, which accumulated as 14′ of the RNA formed after the addition of chloramphenicol. In cultures growing more slowly in glucose–salts or lactate–salts media, chloramphenicol caused an immediate acceleration of two- to three-fold in the overall rate of RNA synthesis. Studies by DNA–RNA hybridization showed that the synthesis of mRNA was accelerated in harmony with the other affected species. However, just over half the mRNA formed after the addition of chloramphenicol quickly decayed to acid-soluble products, whereas the remainder was more stable and accumulated in the cells. The mRNA fraction constituted about 6% of the total cellular RNA after 3h inhibition. A model was suggested to explain the partial stabilization and accumulation of the mRNA fraction and the acceleration in the rate of synthesis of mRNA when chloramphenicol was added to cultures in growth-limiting media.