bluuebunny/crossref_metadata_2025 huggingface dataset:
The metabolism of aromatic acids by micro-organisms. Metabolic pathways in the fungi
Authors: Cain R B , Bilton R. F. , Darrah Josephine A.
Published: August 2015

1. The metabolic pathways of aromatic-ring fission were examined in a range of fungal genera that utilize several compounds related to lignin. 2. Most of the genera, after growth on p-hydroxybenzoate, protocatechuate or compounds that are degraded to the latter (e.g. caffeate, ferulate or vanillate), rapidly oxidized these compounds, but not catechol. 3. Such genera possessed a protocatechuate 3,4-oxygenase and accumulated β-carboxymuconate as the product of protocatechuate oxidation. This enzyme had a high pH optimum in most organisms; the Rhodotorula enzyme was competitively inhibited by catechol. 4. β-Carboxymuconate was converted by all competent fungi into β-carboxymuconolactone, which was isolated and characterized. None of the fungi produced or utilized at significant rates the corresponding bacterial intermediate γ-carboxymuconolactone. 5. The lactonizing enzymes of Rhodotorula and Neurospora crassa had a pH optimum near 5·5 and approximate molecular weights of 19000 and 190000 respectively. 6. The fungi did not degrade the isomeric (+)-muconolactone, γ-carboxymethylenebutanolide or β-oxoadipate enol lactone at significant rates, and thus differ radically from bacteria, where β-oxoadipate enol lactone is the precursor of β-oxoadipate in all strains examined. 7. The end product of β-carboxymuconolactone metabolism by extracts was β-oxoadipate. 8. Evidence for a coenzyme A derivative of β-oxoadipate was found during further metabolism of this keto acid. 9. A few anomalous fungi, after growth on p-hydroxybenzoate, had no protocatechuate 3,4-oxygenase, but possessed all the enzymes of the catechol pathway. Catechol was detected in the growth medium in one instance. 10. A strain of Penicillium sp. formed pyruvate but no β-oxoadipate from protocatechuate, suggesting the existence also of a ‘meta’ type of ring cleavage among fungi.
The preparation and kinetics of lactate dehydrogenase attached to water-insoluble particles and sheets
Authors: Wilson R. J. H. , Kay G. , Lilly M. D.
Published: August 2015

1. The preparation of lactate dehydrogenase covalently attached to anion-exchange cellulose particles and sheets by use of a dichloro-sym-triazinyl dyestuff, Procion brilliant orange MGS, is described. 2. The stability and kinetic properties of these preparations were investigated. 3. An equation is derived to describe the change in concentration of a substrate when passed through a uniform bed of a substrate-inhibited enzyme. A number of theoretical curves are shown to illustrate the system. 4. A titrimetric assay for lactate dehydrogenase is described, and shown to be stoicheiometric over the range pH5·0–9·2. 5. The results are discussed in relation to previous work, and the effects of charged groups on the support, and of the diffusion film surrounding any particle in suspension, are treated qualitatively.
Structural requirements for active intestinal sugar transport. The involvement of hydrogen bonds at C-1 and C-6 of the sugar
Authors: Barnett J. E. G. , Jarvis W. T. S. , Munday K A
Published: August 2015

1. A series of d-galactose derivatives substituted at C-1 and C-6 were tested for active accumulation by everted segments of hamster and rat intestine. 2. d-Galactose and 6-deoxy-6-fluoro-d-galactose were accumulated far more rapidly than 6-deoxy- and 6-chloro-6-deoxy-d-galactose, and this is interpreted as due to hydrogen-bonding at C-6 during the transport process. 3. 6-Bromo-6-deoxy- and 6-deoxy-6-iodo-d-galactose were not actively transported, indicating that the allowed size of substituent at C-6 lies between that of chlorine and bromine atoms. 4. Similar results were obtained at C-1. Both methyl α-d-galactopyranoside and methyl β-d-galactopyranoside were well transported, but methyl β-d-thiogalactopyranoside and 1-deoxy-d-galactose were not transported; d-galactopyranosyl fluoride was transported, but only poorly. Again hydrogen-bonding is suggested. 5. It is proposed that d-glucose is the ideal structure for active transport and that binding occurs at C-1, C-2, C-3, C-4 and C-6. Loss of two or more of these bonds usually causes loss of active transport. 6. By plotting Lineweaver–Burk plots of the rates of transport of the galactose derivatives, the apparent V and Km values were obtained. With hamster intestine both these values were very reproducible. Contrary to expectation, V varied for different sugars. 7. The Ki of some of the analogues modified at C-1 and C-6 was determined with methyl α-d-glucoside as substrate. 8. An attempt to alkylate the carrier by using methyl 3,4-anhydro-α-d-galactoside was unsuccessful. There was no evidence that this compound was bound to the carrier.
The effect of vitamin A and other dietary constituents on the activity of adenosine triphosphate sulphurylase
Authors: Levi A. S. , Geller S. , Root D. M. , Wolf G.
Published: August 2015

1. ATP sulphurylase was assayed in various organs from vitamin A-deficient and pair-fed control rats at different stages of deficiency. Activity decreased slightly in the liver and markedly in the adrenal gland. Striking differences in liver activity were observed between pair-fed control and ad libitum-fed animals. This observation suggested that diet (apart from vitamin A) strongly influenced the activity of ATP sulphurylase. 2. Total starvation caused a severe decrease in activity in liver within 48hr. This was due to a lack of protein intake. 3. By feeding groups of vitamin A-deficient and pair-fed control rats on a diet containing 80% protein, the specific activity of the liver ATP sulphurylase was maintained in the pair-fed control group at the normal level of an ad libitum-fed rat, whereas it decreased by 25% (statistically significant at P<0·01) in the deficient rat. On a 20%-protein diet, there were no significant differences between vitamin A-deficient and pair-fed control rats. These relationships held also for enzyme activity expressed per g. of liver, per total liver and per g. of DNA. There were no differences in liver protein or DNA concentration between vitamin A-deficient and control rats on either protein intake. 4. Control rats on a 20%-protein diet had liver specific enzyme activities about one-half of those in control rats on an 80%-protein diet, as well as lower liver protein concentrations. 5. It is concluded that, when the effect of protein deprivation on ATP sulphurylase is separated from the effect of vitamin A deficiency, a lowering of the enzyme activity caused by the vitamin deficiency is demonstrable.
Biochemical studies of toxic agents. The isolation of premercapturic acids from the urine of animals dosed with chlorobenzene and bromobenzene
Authors: Gillham B. , Young L.
Published: August 2015

1. A premercapturic acid, i.e. a compound that yields a mercapturic acid when decomposed by acid, was isolated as a dicyclohexylammonium salt from the urine of rats and rabbits that had been dosed with bromobenzene. 2. Another premercapturic acid was isolated as its dicyclohexylammonium salt from the urine of rats that had been dosed with chlorobenzene. 3. When decomposed by acid, the premercapturic acid from the urine of animals dosed with bromobenzene gave p-bromophenylmercapturic acid, m-and p-bromophenol and NN′-diacetylcystine. 4. The premercapturic acid derived from chlorobenzene gave the corresponding chloro compounds together with NN′-diacetylcystine when decomposed by acid. 5. On the basis of these and other observations it is suggested that the premercapturic acid formed in the metabolism of bromobenzene is N-acetyl-S-(4-bromo-1,2-dihydro-2-hydroxyphenyl)-l-cysteine. 6. It is also suggested that the premercapturic acid derived from chlorobenzene has an analogous structure.
The lactose synthetase particles of lactating bovine mammary gland. Characteristics of the particles
Authors: Coffey R. G. , Reithel F. J.
Published: August 2015

1. The conditions that promoted the solubilization of particulate lactose synthetase were effective for solubilizing the thiamine pyrophosphatase of the Golgi apparatus but differed from those effective for β-glucuronidase or acid phosphatase of lysosomes. 2. Lactose synthetase-containing particles did not bind Mg2+ or Cs+ ions, suggesting that they are not related to endoplasmic reticulum membranes. 3. Intact lactose synthetase and thiamine pyrophosphatase particles banded isopycnically at a density of 1·143 in a sucrose gradient. The dissociated ‘A’ sub-unit of lactose synthetase, UDP-galactose hydrolase, p-nitrophenyl phosphate acid phosphatase, alkaline phosphatase and phosphodiesterase I were associated with particles of a broad density range from 1·12 to 1·20. Lysosomal enzymes β-glucuronidase, arylsulphatase and β-glycerophosphate acid phosphatase were associated with particles of density 1·20, 1·175 and 1·15 respectively. 4. Rate-zonal sedimentation studies indicated that lactose synthetase particles have S20,w values exceeding 24000s, corresponding to spherical particles of diameter exceeding 5·4×10−5cm. 5. Electron micrographs of lactose synthetase particles purified over 20-fold revealed small spherical bodies (0·1–0·5μ) resembling lysosomes, the smaller of which were attached to membranes, and larger heterogeneous spherical or oval bodies (0·7–1·8μ) resembling lipofuscin secretory granules. 6. The relationship between lactose synthetase particles and the Golgi origin of secretion granules is discussed.
The chemistry of flavines and flavoproteins. Photoreduction of flavines by amino acids
Authors: Penzer G. R. , Radda G. K.
Published: August 2015

1. Flavines are photoreduced through their triplet states by amines and amino acids (e.g. EDTA and dl-phenylglycine). The anaerobic photoreduction of FMN and several other flavines with dl-phenylglycine was analysed in terms of a detailed kinetic scheme. 2. The reaction produces equimolar amounts of benzaldehyde, carbon dioxide and reduced flavine. 3. The sensitivity of the rates to substituents in the dl-phenylglycine can be described by a Hammett ρ-value of −1·1. 4. Phenylacetic acid behaves differently from dl-phenylglycine or benzylamine towards a series of flavines. 5. The photoreductions are quenched by several aromatic compounds. From the effects of light-intensity and temperature, and by comparison with potassium iodide quenching, it is concluded that inhibition by the aromatic compounds is not simply a collisional process. 6. FAD reacts more slowly than FMN both in the photoreduction and in dark reduction by NADH. Urea and dimethyl sulphoxide decrease the intramolecular interaction in FAD, but they have no effect on the rate of dark reduction of FAD compared with FMN. In contrast, the photoreduction of FAD is quicker in urea.
The mechanism of thyrotrophin action in relation to lipid metabolism in thyroid tissue
Authors: Scott T. W. , Mills S. C. , Freinkel N.
Published: August 2015

1. The effects of thyrotrophin in vitro on the incorporation of [14C]-glucose, -glycerol, -palmitate and -oleate into the lipids of thyroid tissue were examined. 2. Thyrotrophin increased the incorporation of these 14C-labelled precursors into phosphatidylinositol specifically. 3. Thyrotrophin also increased the proportion of 14C radioactivity from labelled glucose, glycerol, palmitate and oleate incorporated into the 1,2-diglycerides. 4. The addition of thyrotrophin to thyroid slices for 10min., after 2hr. of prelabelling with [14C]glycerol, also increased the proportion of 14C radioactivity incorporated into the 1,2-diglyceride fraction. 5. After incubation of thyroid tissue with [1−14C]palmitate, thyrotrophin caused a two- to three-fold increase in the specific radioactivity of palmitate isolated from phosphatidylinositol and 1,2-diglycerides. In contrast, the specific radioactivity of palmitate isolated from the choline and ethanolamine phosphoglycerides, 1,3-diglycerides and triglycerides was not increased by thyrotrophin.
Hybridizable ribonucleic acid of rat brain
Authors: Bondy S. C. , Roberts Sidney
Published: August 2015

1. Cerebral RNA of adult and newborn rats was labelled in vivo by intracervical injection of [5−3H]uridine or [32P]phosphate. Hepatic RNA of similar animals was labelled by intraperitoneal administration of [6−14C]orotic acid. Nuclear and cytoplasmic fractions were isolated and purified by procedures involving extraction with phenol and repeated precipitation with ethanol. 2. The fraction of pulse-labelled RNA from cerebral nuclei that hybridized to homologous DNA exhibited a wide range of turnover values and was heterogeneous in sucrose density gradients. 3. Base composition of the hybridizable RNA was similar to that of the total pulse-labelled material; both were DNA-like. 4. Pulse-labelled cerebral nuclear RNA hybridized to a greater extent than cytoplasmic RNA for at least a week after administration of labelled precursor. This finding suggested that cerebral nuclei contained a hybridizable component that was not transferred to cytoplasm. 5. The rates of decay of the hybridizable fractions of cerebral nuclei and cytoplasm were faster in the newborn animal than in the adult. Presumably a larger proportion of labile messenger RNA molecules was present in the immature brain. 6. Cerebral nuclear and cytoplasmic RNA fractions from newborn or adult rats, labelled either in vivo for periods varying from 4min. to 7 days or in vitro by exposure to [3H]-dimethyl sulphate, uniformly hybridized more effectively than the corresponding hepatic preparation. These data suggested that a larger proportion of RNA synthesis was oriented towards messenger RNA formation in brain than in liver.
An approach to the study of phase separation in ternary aqueous systems
Authors: Edmond Elizabeth , Ogston A. G.
Published: August 2015

1. Simple thermodynamic expressions are used to describe the properties of uncharged binary and ternary polymer solutions, in particular the sedimentation equilibrium of binary systems and the osmotic pressures and ‘incompatible’ phase separations of ternary systems. 2. Sedimentation-equilibrium experiments were performed on four samples of dextran and two of polyethylene glycol. The critical points of the phase diagrams were determined for the mixed solutions of polyethylene glycol–dextran–water and of polyethylene glycol–bovine serum albumin–0·2m-sodium chloride solution. Osmotic pressures were measured on a single-phase mixed solution of a polyethylene glycol and a dextran. By use of the simple thermodynamic expressions consistent values of second virial and interaction coefficients for the materials used were obtained from these experiments. 3. The interpretation of the values of the second virial and interaction coefficients, on the basis of three models of molecular interaction, is discussed.
Interchain disulphide-bond formation in the assembly of immunoglobulin G. Heavy-chain dimer as an intermediate
Authors: Askonas Brigitte A. , Williamson Alan R.
Published: August 2015

1. The role of disulphide-bond formation in the assembly of G2a myeloma protein 5563 was studied by pulse-labelling ascitic plasma cells of tumour-line 5563 for 2–8min. with radioactive amino acids, and analysing the intracellular proteins. Myeloma-protein determinants were first purified by ion-exchange chromatography under conditions that do not dissociate non-covalently linked sub-units of immunoglobulin G. The pulse-labelled material was then analysed by electrophoresis on polyacrylamide gels in sodium dodecyl sulphate–phosphate–urea buffer, which dissociates non-covalently linked sub-units; after gel electrophoresis, radioactive protein bands were located by radioautography, and characterized immunologically after elution. 2. Two heavy-chain intermediates were detected: (i) heavy-chain dimer; (ii) the dimer with one light chain attached. Free light chains had previously been shown to be intermediates in assembly. No evidence for the presence of half-molecules (one light chain attached to one heavy chain) was obtained. The formation of the disulphide bond between the heavy chains thus appears to precede the light-chain–heavy-chain linkage in immunoglobulin G assembly.
Metal-binding sites of concanavalin A and their role in the binding of α-methyl d-glucopyranoside
Authors: Kalb A. Joseph , Levitzki Alexander
Published: August 2015

Binding of a transition metal ion to specific sites in concanavalin A induces the formation of specific Ca2+ ion-binding sites. Sites for binding α-methyl d-glucopyranoside exist only when a transition metal ion and Ca2+ ion are bound.
Hydrolysis of 125I-labelled thyroglobulin by pancreatin, Pronase and pepsin
Authors: Malan P. G.
Published: August 2015

1. Pancreatin or Pronase hydrolysis of partially purified heat-denatured 125I-labelled thyroglobulin does not release all the iodoamino acids from peptide linkage. 2. The addition of thyroidal proteases is essential to obtain maximum hydrolysis of thyroglobulin. 3. Pronase plus a fresh non-radioactive thyroid homogenate gives the best hydrolysis results, but peptide ‘mapping’ shows that about 10% of the radioactivity remains in the form of peptides. 4. These peptides have approximately the same RF as the iodotyrosines on one-dimensional chromatograms developed in butan-1-ol–2n-acetic acid (1:1, v/v). 5. Peptic hydrolysis of thyroglobulin releases virtually all of the iodothyronines but little of the iodotyrosines, in contrast with the action of pancreatin. 6. Hydrolysis of thyroglobulin with pepsin followed by Pronase plus a source of thyroidal proteases is satisfactory, but the results are not superior to those obtained by using Pronase plus a source of thyroidal proteases.
Sporulation in Bacillus subtilis. Morphological changes
Authors: Kay D. , Warren S. C.
Published: August 2015

1. When Bacillus subtilis was grown in a medium in which sporulation occurred well-defined morphological changes were seen in thin sections of the cells. 2. Over a period of 7·5hr. beginning 2hr. after the initiation of sporulation the following major stages were observed: axial nuclear-filament formation, spore-septum formation, release of the fore-spore within the cell, development of the cortex around the fore-spore, the laying down of the spore coat and the completion of the corrugated spore coat before release of the spore from the mother cell. 3. The appearance of refractile bodies and 2,6-dipicolinic acid and the development of heat-resistance began between 5 and 6·5hr. after initiation of sporulation. 4. The appearance of 2,6-dipicolinic acid and the onset of refractility appeared to coincide with a diminution of electron density in the spore core and cortex. 5. Heat-resistance was associated with the terminal stage, the completion of the spore coat. 6. The spore coat was composed of an inner and an outer layer, each of which consisted of three or four electron-dense laminae. 7. Serial sections through cells at an early stage of sporulation showed that the membranes of each spore septum were always continuous with the membranes of a mesosome, which was itself in close contact with the bacterial or spore nucleoid. 8. These changes were correlated with biochemical events occurring during sporulation.
The effect of chondroitin sulphate–protein on the formation of collagen fibrils in vitro
Authors: Toole B. P. , Lowther D. A.
Published: August 2015

1. It was found that the precipitation of collagen fibrils at 37° from mixtures of chondroitin sulphate–protein and tropocollagen at physiological ionic strength and pH takes place in two distinct phases. The first occurs immediately on mixing either at 4° or at 37°, and the second occurs only at 37° and after a lag phase whose magnitude depends on the proportions of components. 2. When the second stage of precipitation was inhibited by mixing the reactants at 4°, the initial precipitate was found to contain ‘native-type’ collagen fibrils and chondroitin sulphate–protein. 3. On the basis of kinetic experiments it was concluded that aggregates of chondroitin sulphate–protein and tropocollagen form instantaneously and that these act as sites for the second stage of precipitation of fibrils. 4. The gels that result after continued incubation at 37° are fibrous in appearance if formed in the presence of the initial precipitate of chondroitin sulphate–protein and tropocollagen. 5. On the basis of these experiments in vitro the authors propose a sequence of events for collagen fibrogenesis in vivo.
Factors affecting the translocation of oxaloacetate and l-malate into rat liver mitochondria
Authors: Haslam J. M. , Griffiths D. E.
Published: August 2015

1. The rates of translocation of oxaloacetate and l-malate into rat liver mitochondria were measured by a direct spectrophotometric assay. 2. Penetration obeyed Michaelis–Menten kinetics, and apparent Km values were 40μm for oxaloacetate and 0·13mm for l-malate. 3. Arrhenius plots of the temperature-dependence of rates of penetration gave activation energies of +10kcal./mole for oxaloacetate and +8kcal./mole for l-malate. 4. The translocation of both oxaloacetate and l-malate was competitively inhibited by d-malate, succinate, malonate, meso-tartrate, maleate and citraconate. The Ki values of these inhibitors were similar for the penetration of both oxaloacetate and l-malate. 5. Rates of penetration were stimulated by NNN′N′-tetramethyl-p-phenylenediamine dihydrochloride plus ascorbate under aerobic conditions or by ATP under anaerobic conditions. 6. The energy-dependent stimulation of translocation was abolished by uncouplers of oxidative phosphorylation. Oligomycin A, aurovertin, octyl-guanidine and atractyloside prevented the stimulation by ATP, but did not inhibit the stimulation by NNN′N′-tetramethyl-p-phenylenediamine dihydrochloride plus ascorbate. 7. Mitochondria prepared in the presence of ethylene-dioxybis(ethyleneamino)tetra-acetic acid did not exhibit the energy-dependent translocation, but this could be restored by the addition of 50μm-calcium chloride. 8. Valinomycin or gramicidin plus potassium chloride enhanced the energy-dependent translocation of oxaloacetate and l-malate. 9. Addition of oxaloacetate stimulated the adenosine triphosphatase activity of the mitochondria, and the ratio of ‘extra’ oxaloacetate translocation to ‘extra’ adenosine triphosphatase activity was 1·6:1. 10. Possible mechanisms for the energy-dependent entry of oxaloacetate and l-malate into mitochondria are discussed in relation to the above results.
Canine submandibular-gland hyaluronidase. Purification and properties
Authors: Tan Y. H. , Bowness J. M.
Published: August 2015

1. Methods for the purification of dog submandibular-gland hyaluronidase from sedimentable and non-sedimentable portions of a homogenate and from the whole homogenate are presented. The method consists of three main steps: removal of mucin by acid precipitation or gel filtration on Sephadex G-200, ammonium sulphate precipitation and CM-cellulose chromatography. By this method specific activities of up to 1·28 and 0·78μmoles of N-acetylglucosamine/min./mg. of protein were obtained for the purified freeze-dried non-sedimentable hyaluronidase and for the sedimentable hyaluronidase respectively. 2. A comparison of some of the properties of the non-sedimentable and the sedimentable hyaluronidase preparation indicated that there was little difference between the two and that they both resembled lysosomal hyaluronidase from rat liver.
The control of fatty acid and triglyceride synthesis in rat epididymal adipose tissue. Roles of coenzyme A derivatives, citrate and l-glycerol 3-phosphate
Authors: Denton R M , Halperin M L
Published: August 2015

1. Methods are described for the extraction and assay of acetyl-CoA and of total acid-soluble and total acid-insoluble CoA derivatives in rat epididymal adipose tissue. 2. The concentration ranges of the CoA derivatives in fat pads incubated in vitro under various conditions were: total acid-soluble CoA, 0·20–0·59mm; total acid-insoluble CoA, 0·08–0·23mm; acetyl-CoA, 0·03–0·14mm. 3. An investigation was made of some postulated mechanisms of control of fatty acid and triglyceride synthesis in rat epididymal fat pads incubated in vitro. The concentrations of intermediates of possible regulatory significance were measured at various rates of fatty acid and triglyceride synthesis produced by the addition to the incubation medium (Krebs bicarbonate buffer containing glucose) of insulin, adrenaline, albumin, palmitate or acetate. 4. The whole-tissue concentrations of glucose 6-phosphate, l-glycerol 3-phosphate, citrate, acetyl-CoA, total acid-soluble CoA and total acid-insoluble CoA were assayed after 30 or 60min. incubation. The rates of fatty acid and triglyceride synthesis, calculated from the incorporation of [U−14C]glucose into fatty acids and glyceride glycerol respectively, and the rates of glucose uptake, lactate plus pyruvate output and glycerol output were measured over a 60min. incubation. 5. The rate of triglyceride synthesis could not be correlated with the concentrations of either l-glycerol 3-phosphate or long-chain fatty acyl-CoA (measured as total acid-insoluble CoA). Factor(s) other than the whole-tissue concentrations of these recognized precursors appear to be involved in the determination of the rate of triglyceride synthesis. 6. No relationship was found between the rate of fatty acid synthesis and the whole-tissue concentrations of the intermediates, citrate or acetyl-CoA, or with the two proposed effectors of acetyl-CoA carboxylase, citrate (as activator) or long-chain fatty acyl-CoA (as inhibitor). The control of fatty acid synthesis appears to reside in additional or alternative factors.
Evidence for histidine in the active sites of ficin and stem-bromelain
Authors: Husain S. S. , Lowe G.
Published: August 2015

1. Ficin and stem-bromelain are irreversibly inhibited by 1,3-dibromoacetone, a reagent designed to react first with the active-site cysteine residue and subsequently with a second nucleophile. Evidence is presented that establishes that a histidine residue is within a 5Å locus of the active-site cysteine residue in both enzymes. The histidine residue in both enzymes is alkylated at N-1 by dibromoacetone. It is suggested that, as with papain, the thiol and imidazole groups act in concert in the hydrolysis of substrates by these enzymes. 2. The inhibition of thiol-subtilisin with 1,3-dibromoacetone is shown to be due to the alkylation of a cysteine residue only.
The production of biologically active subparticles from rabbit reticulocyte ribosomes
Authors: Bonanou Sophia , Cox R A , Higginson Betty , Kanagalingam K
Published: August 2015

The effect of exposing rabbit reticulocyte ribosomes to concentrated solutions of potassium chloride was examined by: (a) dialysis against 0·5m-potassium chloride; (b) zone centrifugation through a sucrose gradient in 0·5m-potassium chloride; (c) differential centrifugation of a solution made 0·5m with respect to potassium chloride. The products of each treatment and their ability to support protein synthesis in a reticulocyte cell-free system, in the presence and in the absence of polyuridylic acid, were examined. The following results were found. (1) Exposing the polysomes to 0·5m-potassium chloride was not a sufficient condition for the complete dissociation of ribosomes into subparticles; the reaction showed a concentration-dependence, implying the existence of an equilibrium between the various ribosomal species. Disturbance of the equilibrium by removing certain products, as in zone centrifuging, can lead to complete dissociation. (2) The subparticles produced by dialysis or sucrose-gradient fractionation were biologically inactive and unstable. (3) The pellet obtained by differential centrifuging consisted of subparticles, if suspended in a Mg2+-free buffer; addition of Mg2+ converted about 30% of the material into heavier sedimenting species, and the preparation had 20–40% of the activity of the untreated control polysomes in the cell-free system. Addition of the 0·5m-potassium chloride supernatant fraction resulted in further apparent reconstitution of sub-particles into ribosomes and polysomes and in a 50–100% restoration of biological activity. When both polyuridylic acid and supernatant factors were present incorporations similar to or higher than those of the control were attained.
Glucuronidation of 3-O-methylnoradrenaline, harmalol and some related compounds
Authors: Wong Kim Ping , Sourkes Theodore L.
Published: August 2015

1. The following compounds were glucuronidated in the presence of UDP-glucuronic acid and a microsomal preparation made from guinea-pig liver: 14C-labelled 3-O-methyladrenaline, 3-O-methylnoradrenaline, 3-methoxytyramine and 4-hydroxy-3-methoxyphenethanol, as well as unlabelled harmalol and harmol. 2. [14C]Homovanillic (4-hydroxy-3-methoxyphenylacetic) acid was not a substrate for the microsomal glucuronyltransferase. 3. The Km values for harmalol and harmol were 0·69×10−4m and 0·50×10−4m respectively. 4. The Km values for UDP-glucuronic acid, in the presence of 14C-labelled 3-O-methylnoradrenaline, harmalol and harmol as aglycones, were 0·57×10−4m, 0·44×10−4m and 2·20×10−4m respectively. 5. Mg2+ added at 2·5–10mm activated glucuronyltransferase, with harmalol as substrate. Concentrations above 10mm inhibited the enzymic activity. 6. The overall, or net, transglucuronidating activity of microsomal preparations of the liver, with harmalol as substrate, was greatest for guinea pig, and very much lower for rabbit, mouse and rat.
The sterol esters of maize seedlings
Authors: Kemp R. J. , Mercer E. I.
Published: August 2015

1. The composition of the sterol ester fraction of the shoot, root, scutellum and endosperm of 10-day-old maize seedlings was investigated. 2. The scutellum and endosperm together contain 80% of the sterol ester of the seedling. 3. β-Sitosteryl linoleate is the major sterol ester of the scutellum and endosperm. 4. β-Sitosteryl and stigmasteryl palmitate, palmitoleate, oleate and linoleate are the major sterol esters of the root. 5. In the shoot phytosterol linoleate is less abundant than phytosterol myristate, palmitate, palmitoleate and oleate. 6. There is a greater proportion of cholesteryl ester in the shoot than in the other tissues of the seedling.
Studies on the sterols and sterol esters of the intracellular organelles of maize shoots
Authors: Kemp R. J. , Mercer E. I.
Published: August 2015

1. The composition of the esterified and unesterified sterols of the nuclear, chloroplastidic, mitochondrial and microsomal fractions of 21-day-old maize shoots was examined. 2. The microsomal and mitochondrial fractions contain the bulk of the sterols of the tissue. 3. Only 1% of the sterol isolated from all the organelles is esterified. 4. The nuclear fraction has the greatest proportion of esterified sterol and the microsomal fraction the least. 5. 4-Demethyl sterols constitute the bulk of both esterified and unesterified sterols in all organelle fractions. 6. Cholesterol is the major esterified 4-demethyl sterol of the nuclear and chloroplastidic fractions, but only the nuclear fraction has an appreciable proportion of unesterified cholesterol. 7. Sterol esters of linolenic acid are more abundant in the mitochondrial and microsomal fractions than in the other two fractions.
The sequence of amino acids in insulin isolated from islet tissue of the cod (Gadus callarias)
Authors: Reid K. B. M. , Grant P T , Youngson A.
Published: August 2015

1. S-Aminoethylcysteinyl derivatives of the A and B chains of cod insulin were prepared from the individual S-sulpho chains. 2. Studies on small peptides derived from the S-aminoethylated peptide chains by treatment with trypsin allowed the amino acid sequences in the region of the cysteinyl residues of the A and B peptide chains to be defined. 3. The six amide groups in cod insulin were located by complete digestion of small peptides from the A and B chains with aminopeptidase followed by amino acid analyses. 4. The results, together with previous studies on the oxidized A and B chains, define the sequences of the 51 amino acids that constitute cod insulin.
The redistribution of carbon label by the reactions involved in glycolysis, gluconeogenesis and the tricarboxylic acid cycle in rat liver
Authors: Heath D. F.
Published: August 2015

A scheme is presented that shows how the reactions involved in gluconeogenesis, glycolysis and the tricarboxylic acid cycle are linked in rat liver. Equations are developed that show how label is redistributed in aspartate, glutamate and phosphopyruvate when it is introduced as specifically labelled pyruvate or glucose either at a constant rate (steady-state theory) or at a variable rate (non-steady-state theory). For steady-state theory the fractions of label introduced as specifically labelled pyruvate that are incorporated into glucose and carbon dioxide are also given, and for both theories the specific radioactivities of aspartate and glutamate relative to the specific radioactivity of the substrate. The theories allow for entry of label into the tricarboxylic acid cycle via both oxaloacetate and acetyl-CoA, for 14CO2 fixation and for loss of label from the tricarboxylic acid cycle in glutamate, but not for losses in citrate. They also allow for incomplete symmetrization of label in oxaloacetate due to incomplete equilibration with fumarate both in the extramitochondrial part of the cell and in the mitochondrion on entry of oxaloacetate into the tricarboxylic acid cycle. In the latter case failure both of oxaloacetate to equilibrate with malate and of malate to equilibrate with fumarate are considered.
Crystallization and properties of l-lactate oxidase from Mycobacterium smegmatis
Authors: Sullivan P. A.
Published: August 2015

1. An original method was devised for purifying and crystallizing l-lactate oxidase from Mycobacterium smegmatis. 2. The crystalline enzyme exhibited a single protein component (S020,w 14·7s) in the ultracentrifuge and also on electrophoresis on cellulose acetate strips. 3. The enzyme has a typical flavoprotein spectrum, and it was confirmed that the prosthetic group is FMN. 4. Preliminary studies indicated that the molecular weight is in the range 300000–400000. Since the minimum molecular weight was found to be 50000±3000, it was concluded that l-lactate oxidase contains 6–8moles of flavine/mole. 5. Other properties of the enzyme reported include the substrate specificity, an apparent Km for l-lactate, the effect of several inhibitors on the enzyme activity and the pH–activity curve.
Early effects of phytohaemagglutinin on glucose metabolism of normal human lymphocytes
Authors: Hedeskov C. J.
Published: August 2015

1. Phytohaemagglutinin induced early changes in the catabolism of glucose by normal human lymphocytes suspended in a bicarbonate buffer. During 4hr. incubation glucose utilization was almost doubled. 2. The rates of several reactions in the metabolism of glucose were estimated. Total pyruvate formation, lactate production and fatty acid synthesis were stimulated to the same degree as was glucose utilization. The pentose cycle and the glycogen synthesis were also stimulated but less than was glucose utilization. The pentose cycle was found to account for 1·4% and 0·9% of the total glucose utilization without and with phytohaemagglutinin respectively. In these cells rates of triose phosphate iso-merization were at least six to seven times the rate of glucose phosphorylation. On an average 55–60% of the total carbon dioxide evolved was derived from decarboxylation of pyruvate, 25–30% from the tricarboxylic acid cycle and about 15% from the pentose cycle. Observed ratios of 14C specific yields in glycogen from [1−14C]- and [6−14C]-glucose could possibly be explained by assuming the existence of two separate glucose 6-phosphate pools. 3. During 4hr. incubation in bicarbonate buffer 14C from [U−14C]serine was incorporated into perchloric acid-insoluble material. This incorporation was stimulated by phytohaemagglutinin but was almost completely inhibited by puromycin. Puromycin also abolished phytohaemagglutinin-induced stimulation of glycolysis.
The dipolar origin of protein relaxation
Authors: Hendrickx H. , Verbruggen R. , Rosseneu-Motreff M. Y. , Blaton V. , Peeters H.
Published: August 2015

1. A set of parameters is proposed to check the interpretation of the dielectric behaviour of protein solutions as a rigid-dipole relaxation of prolate ellipsoids of revolution in the frequency range between 20 kHz and 10 MHz. Besides the δb-function of Scheraga, another analogous function (δa) is presented to establish size and shape of globular proteins. A study of the influence of solvent viscosity on the dielectric dispersion also gives strong evidence in favour of rigid-dipole relaxation. 2. Measurements of the dielectric dispersion of monomer solutions of bovine serum albumin and transferrin are reported. Monomers of bovine serum albumin were obtained by fractionation on Sephadex G-150. Low-conductivity solutions of both proteins are obtained by passage through an ion-exchange resin. 3. Computer analysis of the experimental dispersion curves by use of a two-term Debye dispersion gives valuable information about transferrin and leads to an axial ratio 4·5 for a prolate ellipsoid of revolution. The dielectric increment of bovine serum albumin is very low and no conclusive results have yet been obtained.
The membrane lipids of Halobacterium halobium
Authors: Marshall Carolyn L. , Brown A. D.
Published: August 2015

The lipid content of the cell membrane of Halobacterium halobium increased from about 15% to 21% during exponential growth of the organism. Total lipid phosphorus more than doubled during the growth cycle. The mixture of membrane lipids from stationary-phase organisms was similar to lipid mixtures from whole cells of other halobacteria inasmuch as 80% of the lipid phosphorus occurred in a diether analogue of phosphatidylglycerophosphate and an additional 7·5% occurred in the ether analogue of phosphatidylglycerol. The lipid mixture was more complex than those reported for other halophils, however, 12 components being recognized in the acetone-insoluble fraction and 17 in the acetone-soluble fraction. There were major changes in the proportions of some minor components of the acetone-insoluble fraction during a growth cycle. Three nitrogenous lipids were recognized in the acetone-insoluble fraction, but all were present in relatively low proportion. One, which was not a phospholipid, contained a bound peptide. Of the 17 acetonesoluble compounds, 15 were pigments. The major carotenoids were α- and β-bacteriorubrin. The carotenoid pigments occurred at maximal concentration after 6–7 days' growth.
The membrane teichoic acid of Staphylococcus lactis I3
Authors: Archibald A. R. , Baddiley J , Button D.
Published: August 2015

1. Teichoic acid was isolated by extraction with trichloroacetic acid of the membrane fraction of disrupted cells of Staphylococcus lactis I3. 2. The purified material contains glycerol, phosphate and alanine, but little or no sugar or amino sugar. 3. A study of the products of hydrolysis with acid and alkali established that the membrane teichoic acid is a (1→3)-linked poly(glycerol phosphate) that differs in structure from the glycerol teichoic acid in the wall of this organism. 4. The alanine ester residues show the characteristic high lability to alkali and are thus distinguishable from the more stable alanine ester residues of the wall teichoic acid. 5. The significance of these structural features and the possible function of teichoic acids are discussed.
Multilayer formation by a compressed monolayer of poly-∈-benzyloxycarbonyl-l-lysine
Authors: Malcolm B. R.
Published: August 2015

Molecular monolayers of poly-∈-benzyloxycarbonyl-l-lysine were studied at the air/water interface. Deuterium-exchange measurements and the surface area of the monolayer are consistent with a structure consisting of condensed ordered arrays of α-helices. Collapsed films removed from the surface and air-dried were examined by polarized infrared spectroscopy and electron diffraction and found to consist of molecules in the α-helical conformation. There is no indication of a conformational change during compression of the monolayer, and a series of transitions found in the force–area curve are interpreted as the consecutive formation of additional layers of molecules. Some of the factors that influence this almost perfect plastic behaviour are discussed.
The exopolysaccharide of Klebsiella aerogenes A 3 (Sl) (type 54). The isolation of O-acetylated octasaccharide, tetrasaccharide and trisaccharide
Authors: Sutherland I. W. , Wilkinson J. F.
Published: August 2015

The exopolysaccharide slime produced by Klebsiella aerogenes A 3 (Sl) (type 54) is an O-acetylated polysaccharide, the components of which are glucose, glucuronic acid, fucose and acetyl in the molar proportions 4:2:2:1. A phage-induced fucosidase was obtained that hydrolyses the polysaccharide to give an octasaccharide having the same constituents in the same molar proportions. This octasaccharide (O3) is considered to be the repeating unit of the polysaccharide. It is hydrolysed by other phage-induced fucosidases described earlier to release two tetrasaccharides (O1 and O2). These differ only in that tetrasaccharide O2 is acetylated. An acetylated trisaccharide of structure β-glucosylglucuronosylfucose was prepared from tetrasaccharide O2. A further unidentified group is present. Cell-free preparations were used to acetylate the disaccharide α-glucuronosylfucose. From these results the structure of the octasaccharide (O3) is postulated and its significance in the biosynthesis of the polysaccharide discussed.
The effect of age and sex on glutathione reductase and glutathione peroxidase activities and on aerobic glutathione oxidation in rat liver homogenates
Authors: Pinto R E , Bartley W
Published: August 2015

1. Changes in liver glutathione reductase and glutathione peroxidase activities in relation to age and sex of rats were measured. Oxidation of GSH was correlated with glutathione peroxidase activity. 2. Glutathione reductase activity in foetal rat liver was about 65% of the adult value. It increased to a value slightly higher than the adult one at about 2–3 days, decreased until about 16 days and then rose after weaning to a maximum at about 31 days, finally reaching adult values at about 45 days old. 3. Weaning rats on to an artificial rat-milk diet prevented the rise in glutathione reductase activity associated with weaning on to the usual diet high in carbohydrate. 4. In male rats glutathione peroxidase activity in the liver increased steadily up to adult values. There were no differences between male and female rats until sexual maturity, when, in females, the activity increased abruptly to an adult value that was about 80% higher than that in males. 5. The rate of GSH oxidation in rat liver homogenates increased steadily from 3 days until maturity, when the rate of oxidation was about 50% higher in female than in male liver. 6. In the liver a positive correlation between glutathione peroxidase activity and GSH oxidation was found. 7. It is suggested that the coupled oxidation–reduction through glutathione reductase and glutathione peroxidase is important for determining the redox state of glutathione and of NADP, and also for controlling the degradation of hydroperoxides. 8. Changes in glutathione reductase and glutathione peroxidase activities are discussed in relation to the redox state of glutathione and NADP and to their effects on the concentration of free CoA in rat liver and its possible action on ketogenesis and lipogenesis.
The metabolism of the insecticide carbaryl (1-naphthyl N-methylcarbamate) by fat body of the blowfly larva Calliphora erythrocephala
Authors: Price G. M. , Kuhr R. J.
Published: August 2015

1. Carbaryl is metabolized more rapidly by fat body of the blowfly larva than by gut, muscle, cuticle or haemolymph. 2. Metabolism of carbaryl by the fat body is affected by the age of the larva, the pH of the incubation medium, and the concentration of magnesium chloride in the incubation medium. 3. Chloramphenicol, 2,4-dinitrophenol and 5-dimethylamino-6-nitro-1,3-benzodioxole (a carbaryl synergist) inhibit carbaryl metabolism by the fat body. 4. Subcellular fractionation of the fat body indicates that the pellet sedimenting at 30000g is the most reactive with carbaryl. 5. Probable metabolites of carbaryl formed by the fat body include the 4- and 5-hydroxy derivatives, and, possibly, the N-hydroxymethyl and 5,6-dihydrodihydroxy derivatives.
Biosynthesis of microsomal nicotinamide–adenine dinucleotide phosphate–cytochrome c reductase by membrane-bound and free polysomes from rat liver
Authors: Ragnotti G. , Lawford G. R. , Campbell P. N.
Published: August 2015

1. NADPH–ferricytochrome c oxidoreductase (EC 1.6.2.3) was purified from the endoplasmic reticulum of rat liver cells. The methods, which involved digestion of membrane with Steapsin, a crude pancreatic extract containing diastase and trypsin, gel filtration and preparative electrophoresis on polyacrylamide, provided an enzyme with a high specific activity in good yield. 2. The incorporation of 14C-labelled amino acids into the purified reductase by the incubation of various subcellular fractions was studied. The microsome fraction, bound polysomes, free polysomes and detergent-treated polysomes effected the synthesis of the enzyme. 3. The reductase that had been synthesized by the polysomes was tightly bound to preparations of smooth-surfaced endoplasmic reticulum that were added to the incubation medium. 4. Reductase activity could be detected on both free and detergent-treated polysomes. Evidence is presented to show that this activity was due, at least in part, to the presence on the ribosomes of nascent enzyme. The association of enzyme with detergent-treated polysomes did not appear to be due to contamination of the ribosomes with either membrane or cell sap but it is possible for such ribosomes to adsorb some enzyme. 5. The amount of reductase activity associated with the detergent-treated polysomes was increased when the rats from which the polysomes were derived had been previously injected with phenobarbitone. 6. The results are discussed with respect to their relevance for the question of the existence of two functionally different groups of polysomes in the liver and for current ideas on the biogenesis of membranes.
Agranular membranes in free polysome preparations and their possible interference in studies of protein biosynthesis
Authors: Murty C. N. , Hallinan T.
Published: August 2015

1. Phospholipid-rich membranous contaminants are present in free polysomes from rat liver isolated on discontinuous sucrose gradients. 2. Electron-microscopic studies indicate that the membranous contaminants are mainly agranular with very occasional granular membranes. This is confirmed by the study of their sedimentation behaviour and their initial rate of labelling with radioactive glucosamine in vivo. 3. Conventional ribosome-purification methods fail to remove the contaminants, whereas deoxycholate effectively solubilizes the membranous contaminants with little breakdown of polysomes. 4. Amino acid-incorporation studies show that these membranous contaminants may seriously interfere in assessment of the functional capacity of free polysomes in protein biosynthesis in vivo.
Uptake of monosaccharides by guinea-pig cerebral-cortex slices
Authors: Joanny P. , Corriol J. , Hillman H.
Published: August 2015

By the use of 1mm-iodoacetate to inhibit glycolysis in guinea-pig cerebral tissue slices, the kinetics of the uptake of monosaccharides on transfer of tissue from 0° to 37° were studied. d-Ribose, d-galactose, d-mannose, l-sorbose, and d-fructose showed diffusion kinetics, whereas 2-deoxy-d-glucose, d-glucose, d-arabinose and d-xylose showed saturation kinetics.