bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of dimethylnitrosamine on enzyme induction in rat liver
Authors: Shank R. C.
Published: August 2015

1. The effects of various doses of dimethylnitrosamine on the hydrocortisone induction of tryptophan pyrrolase were studied. A single LD50 dose of dimethylnitrosamine inhibits the synthesis of the enzyme if given within the first 5hr. of the induction. A quarter of this dose also inhibits the synthesis of the enzyme, but, in addition, retards the rate of decay of the enzyme. 2. A single small dose of dimethylnitrosamine significantly inhibits the hydrocortisone induction of tryptophan pyrrolase for at least 14 days without causing widespread damage to liver substructure. 3. The inhibition by dimethylnitrosamine of induced tryptophan pyrrolase synthesis is probably independent of any action of the toxin on the synthesis of cofactors necessary for full expression of the enzyme's activity. Dimethylnitrosamine appears to act directly on the synthesis of the enzyme protein. 4. The synthesis of that form of the enzyme which is most sensitive to hydrocortisone is apparently also most susceptible to the action of dimethylnitrosamine. 5. It is suggested that the inhibition of protein synthesis by dimethylnitrosamine may be a result of methylation of messenger RNA, which then is unable to code effectively for amino acid polymerization.
‘Tanned’ gelatin spheres and granules for exclusion chromatography
Authors: Polson A. , Katz W.
Published: August 2015

1. The preparation of tanned gelatin spheres and granules from high-molecular-weight gelatin is described. This material is comparatively hard, giving high flow rates, is insoluble in water at temperatures between 0° and 100° and is resistant to digestion by trypsin and chymotrypsin. The high-molecular-weight fraction of gelatin was prepared by precipitation with polyethylene glycol, and the spheres and granules prepared from this fraction were hardened and insolubilized by tanning with either formalin or chromium salts or both. 2. The spheres and granules were used successfully for the separation of protein molecules and other protein-aceous materials ranging in molecular weight from 200 to greater than 6000000. This gel exclusion material has several properties superior to those of other products used for similar purposes. Further, it was noticed that the porosity of the spheres differed considerably from that of the granules.
Conversion of [U−14C]glucose into carbon dioxide, glycogen, cholesterol and fatty acids in liver slices from embryonic and growing chicks
Authors: Goodridge Alan G.
Published: August 2015

Incorporation of [U−14C]glucose into carbon dioxide, glycogen, cholesterol and fatty acids and of 3H2O into cholesterol and fatty acids was measured in liver slices from embryos and growing chicks. During the embryonic period, rates of incorporation were low and stable for all pathways. Fatty acid synthesis and glucose oxidation increased promptly when the chicks were fed, reaching plateau levels within 6 days. Cholesterol and glycogen synthesis increased only slightly when the birds were fed. After 5 and 11 days respectively, cholesterol and glycogen synthesis began to increase rapidly. The rate of glucose oxidation in liver slices from 4-week-old chicks was 20-fold greater than in slices of embryonic liver; glycogen, cholesterol and fatty acid synthesis had increased approximately 100-, 300- and 1000-fold respectively. The increase in the metabolism of [U−14C]glucose that occurred after hatching was probably due to the change from a high-fat non-carbohydrate diet (yolk) to a high-carbohydrate low-fat diet (mash).
A rapid simple method for the assay of renin in rabbit plasma
Authors: Ryan J W , McKenzie J. K. , Lee M. R.
Published: August 2015

1. EDTA (10mm), 2,3-dimercaptopropan-1-ol (10mm) and chlorhexidine gluconate (0·005%, w/v) cause complete inactivation of plasma enzymes that degrade angiotensin I, but have no effect on the reaction of renin with its substrate. The reagents were termed the selective inhibitors. 2. Thus it is possible to measure renin in plasma by its ability to catalyse the release of angiotensin I. 3. Sterile plasma, treated with the selective inhibitors, is incubated with renin substrate (500–1000ng. of angiotensin content/ml.) at pH6 at 42° for 6hr. 4. Under these conditions the reaction obeys first-order kinetics. Renin activity is calculated in terms of the percentage release of the angiotensin content/hr. 5. As described, the assay is sufficiently sensitive to measure renin in the plasma of all normal rabbits. By extending the length of the incubation, much lower activities can be measured.
The metabolism of N-triphenylmethylmorpholine in the dog and rat
Authors: Griffiths M. H.
Published: August 2015

1. Rats were given N-triphenyl[14C]methylmorpholine, triphenyl[14C]carbinol, N-triphenylmethyl[G−3H]morpholine or [G−3H]morpholine as single oral doses; the routes of excretion were examined. 2. Dogs were given single oral doses of N-triphenyl[14C]methylmorpholine. 3. 14C-labelled metabolites were excreted mainly in the faeces in both rats and dogs; no 14CO2 was expired and less than 3% remained in the carcass and skin after 96hr. 4. 3H-labelled metabolites were excreted rapidly in urine; part of the label was found in the expired gases and over 10% remained in the carcass and skin after 96hr. 5. Differences in excretion pattern between the sexes were noticed in rats but not in dogs. 6. N-Triphenylmethylmorpholine was rapidly hydrolysed to form triphenylcarbinol and morpholine in the stomach; morpholine was absorbed rapidly and excreted largely unchanged, though some was degraded, since some of the 3H was found in water. 7. Triphenylcarbinol was absorbed only slowly and was oxidized to p-hydroxyphenyldiphenylcarbinol. 8. Both triphenylcarbinol and its p-hydroxy derivative were found in urine, bile and faeces in the free form and conjugated with glucuronic acid. The proportion of conjugates was higher in rat bile than in faeces. 9. Traces of o-hydroxyphenyldiphenylcarbinol and m-hydroxyphenyldiphenylcarbinol were detected as metabolites both free and conjugated.
Physical and chemical studies of a low-molecular-weight form of urease
Authors: Tanis Robert J. , Naylor Aubrey W.
Published: August 2015

1. A new form of enzymically active jack-bean [Canavalia ensiformis (L.) DC] urease corresponding to an S20,w value of 11·8s and a molecular weight of 260000 was investigated. 2. Conversion of 18s urease (EC 3.5.1.5) into the 12s form depends on both low protein concentration and pH. Above pH5·3 urease exists in the 18s form and below pH4·8 in the 12s form; between these two pH values a 12s–18s rapid-equilibrium process is observed. 3. Comparison of the properties of 18s and 12s urease indicated no major differences. 4. A survey of other good urease sources revealed that the 12s form can also be obtained from soya bean (Glycine soja Sieb. and Zucc. cultivar Biloxi) and the bacterium Bacillus pasteurii (Miguel) Migula, but not from watermelon (Citrullus vulgaris Schrad. cultivar Congo). 5. The 12s forms from jack bean and Bacillus pasteurii did not hybridize.
The resolution of some steps of the reactions of lactate dehydrogenase with its substrates
Authors: Heck H. D'A. , McMurray C. H. , Gutfreund H.
Published: August 2015

1. The reaction of pig heart lactate dehydrogenase (EC 1.1.1.27) with NAD+ and lactate to form pyruvate and NADH was followed by rapid spectrophotometric methods. The distinct spectrum of enzyme-bound NADH permits the measurement of the rate of dissociation of this compound. 2. The reduction of the first mole equivalent of NAD+ per mole of enzyme sites can also be observed, and is much more rapid than the steady-state rate of NADH production. 3. At pH8 the dissociation of the enzyme–NADH complex is rate-determining for the steady-state oxidation of lactate. At lower pH some other step after the interconversion of the ternary complex and before the dissociation of NADH is rate-determining. Other evidence for a compulsory-order mechanism is provided.
The catalase–hydrogen peroxide system. Role of sub-units in the thermal deactivation of bacterial catalase in the absence of substrate
Authors: Jones Peter , Suggett A.
Published: August 2015

1. Kinetic studies of the thermal deactivation of bacterial catalase in the absence of substrate suggest that the reaction involves a protonation-induced reversible dissociation of catalase into catalatically inactive sub-units, followed by an irreversible transformation of the sub-units into deactivated products. It is possible that the sub-units are mono-haem species. The rate of deactivation decreases with increasing pressure in accordance with the predictions of the proposed model. 2. The results also imply that the addition of hydrogen peroxide substrate induces the re-formation of active catalase. Under appropriate conditions the activity of catalase is found to increase with time in a manner that is quantitatively consistent with the results of deactivation studies.
Carbohydrase activities in the bovine digestive tract
Authors: Siddons R. C.
Published: August 2015

1. The carbohydrase activities of homogenates of mucosa from the abomasum, small intestine, caecum and colon, and of the pancreas of cattle were studied. 2. The disaccharidase activities were located mainly in the small intestine and showed a non-uniform pattern of distribution along the small intestine; trehalase activity was highest in the proximal part, lactase and cellobiase activities were highest in the proximal and middle parts and maltase activity was highest in the distal part. 3. The intestinal lactase and cellobiase activities were highest in the young calf and decreased with age, whereas the intestinal maltase and trehalase activities, which were very low compared with the lactase activity, did not change with age. 4. No intestinal sucrase or palatinase activity was detected in the calf or in the adult cow. 5. Homogenates of intestinal mucosa also exhibited amylase and dextranase activity. 6. Homogenates of the pancreas possessed a strong amylase activity and a weak maltase activity. The maltase activity did not change with age, whereas the amylase activity increased with age. 7. No marked differences were observed between the carbohydrase activities of calves fed solely on milk and those of calves given a concentrate–hay diet from 6 weeks of age.
Evidence for histidine in the active site of papain
Authors: Husain S. S. , Lowe G.
Published: August 2015

Papain was irreversibly inhibited by 1,3-dibromoacetone, a reagent designed to react first with the active-site cysteine residue and subsequently with a second nucleophile. The molecular weight of the inhibited enzyme was indistinguishable from that of papain itself, and no evidence of dimeric or oligomeric species was found. The optical-rotatory-dispersion curves of chloroacetone-inhibited papain and 1,3-dibromoacetone-inhibited papain were essentially similar. Amino acid analysis of the 1,3-dibromo[2−14C]acetone-inhibited enzyme and the performic acid-oxidized material clearly showed that a cysteine and histidine residue had been alkylated through the thiol and N-1 of the imidazole group respectively. These groups must therefore be within 5å of each other in the tertiary structure of papain. Possible mechanistic implications are briefly discussed.
Lysosomal phospholipases A1 and A2 of bovine adrenal medulla
Authors: Smith A D , Winkler H
Published: August 2015

1. [32P]Lecithin and [32P]phosphatidylethanolamine were prepared by incubating rat liver mince with [32P]phosphate. With these 32P-labelled phospholipids conditions for the quantitative assay of phospholipase A activity were established. 2. The distribution of phospholipase A activity between subcellular fractions of the bovine adrenal medulla was determined. Phospholipases A1 and A2, with pH optima at 4·2 and 6·5 respectively, were found in the large-granule fraction. By means of sucrose-density-gradient centrifugation it was shown that both these phospholipases were localized in lysosomes. 3. Lysosomal phospholipase A1 catalysed the hydrolysis of [32P]lecithin and [32P]phosphatidylethanolamine at the same rate. The enzymic activity was inhibited by 70% in the presence of 10mm-calcium chloride. 4. Lysosomal phospholipase A2 catalysed the hydrolysis of [32P]phosphatidylethanolamine more rapidly than it hydrolysed [32P]lecithin. The hydrolysis of [32P]phosphatidylethanolamine, but not that of [32P]lecithin, by phospholipase A2 was activated by 0·8mm-calcium chloride. However, the hydrolysis of both substrates was inhibited by 8mm-calcium chloride. 5. The significance of the presence of phospholipase activity in lysosomes is discussed in relation to the functions of lysosomes in general and in the adrenal medulla.
Effects of the hepatotoxic agents retrorsine and aflatoxin B1 on hepatic protein synthesis in the rat
Authors: Villa-Treviño S. , Leaver D. D.
Published: August 2015

1. Aflatoxin and the pyrrolizidine alkaloid retrorsine inhibited the incorporation of labelled amino acids into rat liver and plasma proteins in vivo. Inhibition was greater and detected earlier with retrorsine (1hr.) than with aflatoxin (3hr.). 2. Both toxins affected the liver ribosomal aggregates, causing increases in the proportion of monomers plus dimers. The effect of retrorsine was greater than that of aflatoxin. 3. Incorporation of labelled amino acids into proteins of cell-free preparations of liver from rats treated with aflatoxin was lower than in control preparations. The main site of inhibition appeared to be the ribosomes. 4. Both toxins inhibited the incorporation of orotate into liver nuclear RNA 1hr. after administration.
Collagen synthesis and carbohydrate metabolism of rachitic bone
Authors: Paterson C. R. , Fourman P.
Published: August 2015

1. This paper reports studies on the metabolism of bone from normal chicks and from chicks with vitamin D-deficiency rickets. Both in vitro and in vivo there was an increased incorporation of [14C]proline into collagen hydroxyproline by rachitic bone. The proportion of the collagen that was soluble in cold salt solutions was greater with the rachitic bone. These results show that in rickets there is an increased synthesis of bone collagen, but they do not provide any evidence of a defect in the maturation of collagen. 2. Rachitic bone incubated aerobically in vitro consumed more glucose and released more lactate than normal bone. Bone from rachitic chicks treated with vitamin D 48hr. previously had rates of glycolysis that were nearly normal. Though we were unable to show any direct action of vitamin D in vitro, we consider that vitamin D probably has a direct action on bone, possibly related to matrix biosynthesis.
The fractionation of nuclei from mammalian cells by zonal centrifugation
Authors: Johnston I R , Mathias A P , Pennington F. , Ridge D.
Published: August 2015

1. Purified liver nuclei from adult rats separate into two main zones when centrifuged in the slow-speed zonal rotor. One zone contains diploid nuclei, the other tetraploid. 2. The effect of age on the pattern of rat liver ploidy was examined. Tetraploid nuclei are virtually absent from young animals. They increase in proportion steadily with age. Partial hepatectomy disturbs the pattern of ploidy. 3. The zonal centrifuge permits the separation of diploid, tetraploid, octaploid and hexadecaploid nuclei from mouse liver. 4. Rat liver nuclei are isopycnic with sucrose solutions of density 1·35 at 5°.
Post-mortem glycolysis in ox skeletal muscle. Effect of pre-rigor freezing and thawing on the intermediary metabolism
Authors: Scopes R. K. , Newbold R. P.
Published: August 2015

1. Ox sternomandibularis muscle was ‘slow-frozen’ by placing it in air at −22° or ‘fast-frozen’ by immersion in liquid air or acetone–solid carbon dioxide. In all cases muscles were frozen pre-rigor. Changes in length, pH and the concentrations of Pi, creatine phosphate, hexose monophosphate (glucose 1-phosphate+glucose 6-phosphate+fructose 6-phosphate), fructose diphosphate (fructose 1,6-diphosphate+½ triose phosphate), lactate, ATP, ADP, AMP and NAD+ during freezing and during subsequent thawing were determined. In addition some measurements were made of the changes in α-glycerophosphate, 3-phosphoglycerate, 2-phosphoglycerate, phosphoenolpyruvate and pyruvate concentrations during slow freezing. 2. Appreciable shortening and marked changes in chemical composition took place during slow freezing but not during fast freezing. 3. During slow freezing the hexose monophosphate concentration fell and fructose 1,6-diphosphate and triose phosphate increased substantially. Increases also took place in 3-phosphoglycerate, 2-phosphoglycerate and phosphoenolpyruvate, but not in pyruvate. 4. On thawing, most of the chemical changes were similar to those in unfrozen muscle post mortem, but took place much more rapidly; loss of NAD+ was particularly rapid. Fast-frozen muscle metabolized at a faster rate on thawing than did slow-frozen muscle. 5. The overall changes in length during freezing and thawing were about the same in slow-frozen as in fast-frozen muscle.
Cellulolytic enzyme system of Trichoderma koningii. Separation of components attacking native cotton
Authors: Wood T. M.
Published: August 2015

1. Cell-free culture filtrates from Trichoderma koningii were concentrated by precipitation with ammonium sulphate between the limits of 20% and 80% saturation. 2. Removal of a low-molecular-weight carboxymethylcellulase (CM-cellulase) component by chromatography on Sephadex G-75 had no effect on the ability of the enzyme complex to solubilize cotton. 3. Further chromatography on DEAE-Sephadex separated a component (C1) from the Cx (CM-cellulase) and β-glucosidase activities. Separately these components had little ability to produce soluble sugars from cotton, but when recombined in their original proportions this capacity was almost completely recovered. 4. The Cx component was further fractionated on SE-Sephadex into a fraction containing only CM-cellulase and a fraction showing CM-cellulase and β-glucosidase activities: the latter two components could be separated by heat treatment. 5. The C1 component had no swelling factor (S-factor) activity (Marsh, Merola & Simpson, 1953; Reese & Gilligan, 1954) on its own, but it had a synergistic effect on the S-factor activity associated with the CM-cellulase and β-glucosidase components.
The dependence on dicarboxylic acids and energy of citrate accumulation in depleted rat liver mitochondria
Authors: Harris E J
Published: August 2015

The accumulation of some organic anions in the space inaccessible to sucrose of rat liver mitochondria was measured. In untreated mitochondria anions were apparently concentrated from 1mm applied concentration by between five- and 22-fold, depending on their charge. After depletion of endogenous reserves either with uncoupling agent or with oligomycin uptakes were decreased. The accumulation of citrate was restored by combinations of a dicarboxylic acid (malate, succinate, maleate or meso-tartrate) and energy. The energy could either be provided by oxidation of a suitable dicarboxylic acid or from ascorbate in the presence of tetramethylphenylenediamine, or from ATP. The restoration of citrate uptake is not necessarily accompanied by a gain of K+, but a cation- and energy-linked citrate uptake can be induced with valinomycin. When citrate is added to mitochondria in the presence of malate the latter is competitively displaced. The anion accumulation could arise from an internal energy-linked positive potential.
Pentitols and insulin release by isolated rat islets of Langerhans
Authors: Montague W , Taylor K W
Published: August 2015

1. Insulin secretion was studied in isolated islets of Langerhans obtained by collagenase digestion of rat pancreas. In addition to responding to glucose and mannose as do whole pancreas and pancreas slices in vitro, isolated rat islets also secrete insulin in response to xylitol, ribitol and ribose, but not to sorbitol, mannitol, arabitol, xylose or arabinose. 2. Xylitol and ribitol readily reduce NAD+ when added to a preparation of ultrasonically treated islets. 3. Adrenaline (1μm) inhibits the effects of glucose and xylitol on insulin release. Mannoheptulose and 2-deoxy-glucose, however, inhibit the response to glucose but not that to xylitol. 4. The intracellular concentration of glucose 6-phosphate is increased when islets are incubated with glucose but not with xylitol, suggesting that xylitol does not promote insulin release by conversion into glucose 6-phosphate. 5. Theophylline (5mm) potentiates the effect of 20mm-glucose on insulin release from isolated rat islets of Langerhans, but has no effect on xylitol-mediated release. These results indicate that xylitol does not stimulate insulin release by alterations in the intracellular concentrations of cyclic AMP. 6. A possible role for the metabolism of hexoses via the pentose phosphate pathway in the stimulation of insulin release is discussed.
Nucleolar 4s ribonucleic acid in dipteran salivary glands in the presence of inhibitor
Authors: Sirlin J. L. , Loening U E
Published: August 2015

1. Salivary glands of insect larvae accumulate newly made transfer RNA in the nucleolus when maintained in the presence of nucleoside antagonists that inhibit RNA synthesis preferentially at the chromosome. 2. The nucleus contains precursor transfer RNA, which, on the basis of the general evidence, may originate in the chromosome and then be methylated in the nucleolus. 3. The maturation of precursor ribosomal RNA is blocked in the nucleolus during inhibition. 4. The transport of nuclear RNA to cytoplasm is also blocked. 5. It is suggested that, if the transfer RNA accumulated in the nucleolus does indeed originate in the chromosome, the accumulation may result from the blockage of an obligatory transient association of the RNA with the nucleolus.
Choline acetyltransferase binding to and release from membranes
Authors: Fonnum F.
Published: August 2015

1. The binding of non-occluded choline acetyltransferase to synaptosome membranes is a reversible process that is primarily dependent on the pH and ionic strength of the suspending medium. 2. The distribution of soluble enzyme bound to synaptosome membranes was studied by density-gradient centrifuging. 3. Choline acetyltransferase shows enzyme activity both in the free and in the membrane-bound form. 4. Varying the temperature or prolonged hypo-osmotic treatment does not release the membrane-bound enzyme. 5. The release of choline acetyltransferase from membranes by different anions, thiols, adenosine nucleotides and enzyme substrates was studied.
Isolation of crustecdysone (20R-hydroxyecdysone) from a crayfish (Jasus lalandei H. Milne-Edwards)
Authors: Horn D. H. S. , Fabbri S. , Hampshire F. , Lowe M. E.
Published: August 2015

1. A small amount (2mg.) of crustecdysone, a moulting hormone of crustaceans, was isolated from 1 ton of crayfish waste. 2. The purification procedure used was developed with the aid of crustacean and insect bioassays. 3. CM-Sephadex was found to be superior to Sephadex and very effective for the chromatographic separation of crustecdysone from other non-ionic compounds. The higher efficiency of CM-Sephadex is attributed to the greater number of carboxyl groups available for hydrogen-bonding. 4. Reversed-phase chromatography, with butan-1-ol–cyclohexane mixtures as the stationary phase and water as the flowing phase, proved superior to countercurrent distribution with these solvents for the fractionation of purified extracts. 5. A second moulting hormone, deoxycrustecdysone, and the red-concentrating hormone were obtained in a partially purified form.
Biosynthesis of cyclopropyl long-chain fatty acids from cyclopropanecarboxylic acid by mammalian tissues in vitro
Authors: Duncombe W. G. , Rising T. J.
Published: August 2015

1. Radioactivity from cyclopropane[14C]carboxylic acid is incorporated into fatty acids in vitro by rat and guinea-pig adipose tissue, by rat liver slices and by the supernatant fraction of rat liver homogenate. 2. The labelled acids are different from endogenous straight-chain fatty acids, and evidence is produced that they consist of a cyclopropyl ring in the ω-position, the remainder of the chain being built up from C2 units (not derived from cyclopropanecarboxylic acid) in the normal way via the malonate pathway. 3. It is suggested that these unnatural acids have some metabolic effect related to the hypoglycaemic action of cyclopropanecarboxylic acid.
The effect of whole-body X-irradiation of guinea pigs on liver ribosomes
Authors: Hidvégi E. J. , Holland J. , Bölöni Elisabeth , Lónai P. , Antoni F. , Várterész V.
Published: August 2015

1. The size distribution of aggregates of liver ribosomes and their protein-synthesizing ability in vitro were studied shortly after X-irradiation of guinea pigs. 2. Sucrose-density-gradient analysis of the mitochondrial supernatant after treatment with deoxycholate revealed a gradual increase in the number of polysomes, reaching a maximum between 9 and 15 hr. after irradiation. At that period the amount of ribonucleoprotein particles reached a level 25–30% above the control. This finding was confirmed by analytical-ultracentrifugal analysis and electron microscopy. Experiments were conducted to exclude the possibility that the enrichment of polysomes in the irradiated animals had occurred during the isolation procedure. 3. The protein-synthesizing ability of total ribosomal particles was measured in vitro. This showed an increase in amino acid incorporation parallel to the progressive enrichment of polysomes. At radiation doses of up to 1000r. the protein-synthesizing capacity was dependent on the radiation dose: the higher the dose the higher the amino acid incorporation, reaching 40–60% above the control at the period of maximal polysome enrichment. Amino acid incorporation remained at this level after radiation doses of between 1000 and 3000r. The enhanced protein-synthesizing activity was due solely to the increase in the proportion of polysomes, since irradiation was without effect on the activity of single ribosomes. 4. The results of the experiments are discussed in the light of our knowledge of the effect of radiation on protein synthesis.
The effect of acid mucopolysaccharides and acid mucopolysaccharide–proteins on fibril formation from collagen solutions
Authors: Mathews M B , Decker L.
Published: August 2015

1. The effects of acid mucopolysaccharides and acid mucopolysaccharide–proteins on the size and rate of formation of fibril aggregates from collagen solutions in pH7·6 buffers were studied by turbidimetric and light-scattering methods. 2. Serum albumin, orosomucoid, methylated cellulose, chondroitin sulphate A and chondroitin sulphate C of molecular weight less than 20000, and hyaluronate of molecular weight less than 40000 did not influence rates of fibril formation. Chondroitin sulphate A, chondroitin sulphate C and hyaluronate of high molecular weight retarded the rate of fibril formation. This effect of high-molecular-weight chondroitin sulphate C decreased with increasing ionic strength. Heparin, though of low molecular weight (13000), was highly effective, as was also heparitin sulphate. The chondroitin sulphate–proteins of very high molecular weight were highly effective, despite the fact that for some preparations the component chondroitin sulphate chains had molecular weights much less than 20000. 3. Agents that had delayed fibril formation were also effective in producing an increase in degree of aggregation of fibrillar collagen, as indicated by dissymmetry changes observed in light-scattering experiments at low collagen concentrations. Methylated cellulose and heparin at 2·5μg./ml. were unusual in decreasing aggregation, but heparin at 0·25μg./ml. increased aggregation. Electron microscopy of gels showed fibrils and fibril aggregates with ‘normal’ collagen spacing and dimensions consistent with the light-scattering results. 4. The rates of electrical transport of agents and of solvent (electro-osmosis) through collagen gels indicated a contribution of molecular entanglement that increased with increase in molecular size of the agents. Electrostatic binding of heparin to collagen was noted. Binding to collagen during fibril formation was also found for heparitin sulphate and a chondroitin sulphate with extra sulphate groups. 5. Electrostatic binding of acid mucopolysaccharide–proteins to collagen may be an important factor in the organization and functioning of connective tissues at all stages of growth and development. Excluded-volume (molecular-entanglement) effects may also be important. These factors operate simultaneously and interact mutually so that precise assessment of their relative importance is difficult.
Aspects of the chemistry of d-glyceraldehyde 3-phosphate dehydrogenase
Authors: Trentham D. R.
Published: August 2015

Crystalline d-glyceraldehyde 3-phosphate dehydrogenase from lobster tail contains 4 moles of NAD+ bound and reacts specifically with 4 moles of iodoacetic acid/mole of tetramer. The essential thiol group of d-glyceraldehyde 3-phosphate dehydrogenase appears to react with iodoacetic acid with a rate constant for the overall process that is independent of the extent of carboxymethylation. The d-glyceraldehyde 3-phosphate dehydrogenase–NAD+ absorption band has a variable molar extinction coefficient in the presence of phosphate that may be correlated with a proton dissociation of pK 6·86. The binding of NAD+ to d-glyceraldehyde 3-phosphate dehydrogenase weakens as alkylating agents react with the enzyme, and NAD+ promotes the reactivity of the essential thiol group. It is suggested that, on binding to d-glyceraldehyde 3-phosphate dehydrogenase, NAD+ lowers the pK of the essential thiol group, resulting in a catalytic role of NAD+ in the reaction catalysed by d-glyceraldehyde 3-phosphate dehydrogenase. If this theory is correct, then it is likely that a proton will be liberated during the phosphorolysis of the acyl-enzyme rather than in the redox step.
Studies with tryptophan metabolites in vitro. Kynurenine metabolism in kidneys of mice infested with Schistosoma mansoni
Authors: Amer M. Samir , Abdel-Daim M. H. , Abdel-Tawab G. A.
Published: August 2015

The conversion in vitro of kynurenine into kynurenic acid and anthranilic acid in both normal kidneys and those obtained from mice infested with Schistosoma mansoni was investigated. Normal mouse kidneys seem to possess an excess of functional pyridoxal phosphate over those obtained from infested mice. Kynureninase and kynurenine transaminase in the latter kidneys are more easily inhibited by deoxypyridoxal phosphate and tartar emetic, indicating low stores of active pyridoxal phosphate. The possible implication of these findings in relation to the role of the kidneys in producing abnormal patterns of tryptophan metabolism and possibly contributing to the production of bladder tumours in bilharzial patients is discussed.
Some physical and chemical properties of trypsin-digested nucleoprotein
Authors: Marks Dawn B. , Schumaker Verne N.
Published: August 2015

A DNA–peptide complex that is soluble in 0·2m-sodium chloride can be prepared by trypsin digestion of calf thymus nucleoprotein. The trypsin-digested nucleoprotein molecule contains about 70% of DNA and 30% of peptides by weight, and consists of one DNA molecule associated with arginine-rich peptides. A series of trypsin-digested nucleoprotein preparations differing only in molecular weight were prepared by blending. The intrinsic viscosity and average sedimentation coefficient were determined for each of these preparations. Then the DNA was isolated from each preparation and the hydrodynamic measurements were repeated on the DNA. From a comparison of these results it was concluded that the presence of the complex-forming peptides causes a large decrease in intrinsic viscosity of the DNA and an increase in sedimentation coefficient. In addition, the hydrodynamic data indicate that the DNA–peptide complex behaves like a coil in solution but is more compact than the same length of DNA. The ‘melting’ profiles, streptomycin precipitation curves and maximum viscosities obtained with ethidium bromide binding for the trypsin-digested nucleoprotein are similar to those of purified DNA, and markedly different from those of undigested nucleoprotein. These findings suggest that the peptides are not strongly associated with the DNA, and that secondary valency forces are involved in the binding.
Studies on halotolerance in a moderately halophilic bacterium. Effect of growth conditions on salt resistance of the respiratory system
Authors: Rafaeli-Eshkol Dvora
Published: August 2015

The effect of sodium chloride on the respiratory activity of a moderately halophilic halotolerant bacterium was studied. Irrespective of growth conditions, resting cells oxidized succinate at a low rate unless sodium chloride was included in the assay mixture, maximum respiratory rates being obtained for sodium chloride concentrations between 0·2m and 0·8m. Neither potassium chloride nor sucrose could replace the sodium salt. The response of the respiratory system to sodium chloride concentration above the optimum depended on growth conditions. Respiration of cells harvested from a low-salt medium was almost inhibited completely by 2·0m-sodium chloride, and that of cells grown and washed in the presence of 2·0m-sodium chloride by 30%. After preincubation with a growth medium containing 2·0m-sodium chloride, even with all multiplication suppressed by chloramphenicol, the resistance of the respiratory system of low-salt-grown organisms to high salt concentrations increased considerably and resembled that of their high-salt-grown counterparts. A similar increase in resistance occurred after preincubation with yeast extract or with choline. With labelled choline, energy-dependent accumulation of labelled material occurred, the conditions required for maximum accumulation and retention being the same as those that increased the salt resistance of the respiratory system. The chromatographic behaviour of the labelled material indicated that the substance was not choline but a derivative, possibly betaine.
Some metabolites of 1-bromobutane in the rabbit and the rat
Authors: James Sybil P. , Jeffery D. A. , Waring Rosemary H. , Wood P. B.
Published: August 2015

1. Rabbits and rats dosed with 1-bromobutane excrete in urine, in addition to butylmercapturic acid, (2-hydroxybutyl)mercapturic acid, (3-hydroxybutyl)mercapturic acid and 3-(butylthio)lactic acid. 2. Although both species excrete both the hydroxybutylmercapturic acids, only traces of the 2-isomer are excreted by the rabbit. The 3-isomer has been isolated from rabbit urine as the dicyclohexylammonium salt. 3. 3-(Butylthio)lactic acid is formed more readily in the rabbit; only traces are excreted by the rat. 4. Traces of the sulphoxide of butylmercapturic acid have been found in rat urine but not in rabbit urine. 5. In the rabbit about 14% and in the rat about 22% of the dose of 1-bromobutane is excreted in the form of the hydroxymercapturic acids. 6. Slices of rat liver incubated with S-butylcysteine or butylmercapturic acid form both (2-hydroxybutyl)mercapturic acid and (3-hydroxybutyl)mercapturic acid, but only the 3-hydroxy acid is formed by slices of rabbit liver. 7. S-Butylglutathione, S-butylcysteinylglycine and S-butylcysteine are excreted in bile by rats dosed with 1-bromobutane. 8. Rabbits and rats dosed with 1,2-epoxybutane excrete (2-hydroxybutyl)mercapturic acid to the extent of about 4% and 11% of the dose respectively. 9. The following have been synthesized: N-acetyl-S-(2-hydroxybutyl)-l-cysteine [(2-hydroxybutyl)mercapturic acid] and N-acetyl-S-(3-hydroxybutyl)-l-cysteine [(3-hydroxybutyl)mercapturic acid] isolated as dicyclohexylammonium salts, N-toluene-p-sulphonyl-S-(2-hydroxybutyl)-l-cysteine, S-butylglutathione and N-acetyl-S-butylcysteinyl-glycine ethyl ester.
The action of paraquat and diquat on the respiration of liver cell fractions
Authors: Gage J C
Published: August 2015

1. Paraquat and diquat produce only a slight increase in the oxygen uptake of rat liver mitochondria, and it is likely that they do not penetrate the mitochondrial membrane. 2. In mitochondrial fragments inhibited by antimycin A or by Amytal, both substances stimulate oxygen uptake with NADH or β-hydroxybutyrate as substrate but not with succinate. The NADH dehydrogenase of the respiratory chain appears to be involved, at a site only partially inhibited by Amytal. 3. An NADPH oxidase activity is stimulated in rat liver microsomes by diquat, and to a smaller extent by paraquat; diquat also causes an NADH oxidase activity to develop. The effect is not inhibited by carbon monoxide or p-chloromercuribenzoate, and it is probable that a flavoprotein is involved by a mechanism not requiring thiol groups. 4. One molecule of oxygen can oxidize two molecules of NADPH in the stimulated microsomal system, the hydrogen peroxide produced being broken down by a catalase activity in the microsomes. 5. Diquat can stimulate NADH oxidase and NADPH oxidase activity in the postmicrosomal soluble fraction; the enzyme involved may be DT-diaphorase. 6. The mechanism of these reactions and their significance in relation to the toxicity of the dipyridilium compounds are discussed.
Radioimmunoassay for ovine, caprine and bovine prolactin in plasma and tissue extracts
Authors: Bryant Gillian D. , Greenwood F. C.
Published: August 2015

1. A radioimmunoassay for ovine prolactin is described based on the inhibition of the reaction between 131I-labelled ovine prolactin and guinea-pig or rabbit antiserum to ovine prolactin. The extent of the reaction after a 4-day incubation period is determined by chromatoelectrophoresis or by adsorption of unchanged 131I-labelled ovine prolactin on charcoal. The sensitivity is equal to 5·9ng. of prolactin/ml. of plasma with chromatoelectrophoresis, or 0·2ng. of prolactin/ml. of tissue extracts with the charcoal separation. 2. A complete cross-reaction demonstrated between ovine prolactin and caprine pituitary extracts allows the assay to be used to measure caprine prolactin. The partial cross-reactions between ovine prolactin and bovine prolactin and between ovine prolactin and bovine pituitary extract differ, and an alteration in the immunological activity of bovine prolactin during its isolation is suggested. Bovine prolactin in plasma may be measured against a bovine pituitary extract as standard. No cross-reactions were demonstrated with pituitary extracts from a number of other species. The extent of the contamination of ovine and bovine growth hormone preparations by their respective prolactins is shown. 3. Dilutions of ovine and caprine plasma inhibit the reaction between 131I-labelled ovine prolactin and antiserum with the same characteristics as ovine prolactin. 4. The immunoreactive material in plasma fractionates on Sephadex G-200 and in sucrose density gradients as a single peak similar to that shown by freshly dissolved ovine prolactin. There is no evidence that ovine prolactin is bound to a plasma protein. 5. By suppressing prolactin secretion and assaying serial samples of plasma thereafter it is shown that the immunological activity of the surviving hormone becomes progressively altered with time. It is suggested that this alteration is usually not detected but introduces an element of uncertainty into the quantitative but not the qualitative value of the measurements obtained by reference to standard ovine prolactin.
Changes in the concentrations of some phosphorylated intermediates and stimulation of glycolysis in liver slices
Authors: Gaja G. , Ragnotti G. , Cajone F. , Bernelli-Zazzera A.
Published: August 2015

1. The concentrations of some phosphorylated glycolytic intermediates and of NADH were measured in glycolysing rat liver slices. 2. In anaerobically incubated liver slices the concentration of hexose monophosphates decreases during the first 20min. of incubation, whereas the concentrations of fructose diphosphate and triose phosphates increase progressively. 3. In liver slices from fed rats, previously exposed to oxygen, the stimulated anaerobic glycolysis is accompanied by an increase in the concentration of hexose monophosphates; fructose diphosphate and triose phosphates maintain the concentrations reached at the end of the aerobic preincubation. 4. The same pattern in the concentration of glycolytic phosphorylated intermediates is seen under all conditions where aerobic preincubation brings about a stimulation of anaerobic glycolysis. A similar pattern is also found in liver slices from fed rats incubated anaerobically in the presence of fructose; these slices display a high glycolytic activity, which is not further affected by previous aerobic incubation. 5. The concentration of NADH decreases in liver slices during exposure to oxygen; during the subsequent anaerobic glycolysis the concentration increases but is always lower in preincubated than in non-preincubated liver slices. 6. The results of the present experiments suggest that the limiting step mainly affected by the preliminary exposure to oxygen might be at the level of the utilization of triose phosphates.
The displacement of calcium ions from phospholipid monolayers by pharmacologically active and other organic bases
Authors: Hauser H. , Dawson R. M. C.
Published: August 2015

1. The binding of 45Ca2+ to a monolayer of phosphatidylinositol at the air–water interface was maximal when the separation of the phospholipid head groups approximated to the diameter of a hydrated Ca2+ ion. 2. The displacement of Ca2+ adsorbed on monomolecular films of phosphatidylinositol by a series of drugs (both narcotic and excitatory) and other organic bases was related to the ability of the bases to penetrate into the film. 3. With films of phosphatidylinositol at constant area, and at an initial surface pressure of 10dynes/cm., the displacement of Ca2+ by increasing concentrations of the local anaesthetic, tetracaine, was linearly related to the change in surface pressure (Δπ) caused by the penetration of the drug. 4. Δπ and the displacement of Ca2+ showed a related fall when the initial surface pressure of the phosphatidylinositol film was increased from 4 to 40dynes/cm. both at a constant bulk tetracaine concentration and when this latter concentration was adjusted to keep it at a constant ratio to the surface density of phosphatidylinositol molecules. 5. The displacement of Ca2+ from phosphatidylinositol films by cetyltri-methylammonium ions was directly compared with the surface concentration of the base in the film, measured by using labelled base and a surface-radioactivity technique. 6. The ability of a series of straight-chain aliphatic amines to displace Ca2+ from phosphatidylinositol films increased with the number of carbon atoms up to C12. However, there was a marked jump in the displacing activity after hexylamine, and this could probably be correlated with the carbon chain's being of sufficient length to just reach the hydrophobic fatty acid chains of the orientated phospholipid molecules with the charges on both substances in juxtaposition.
The effect of N-bromosuccinimide on the sub-unit structure of avidin and its complexes with biotin
Authors: Green N. M. , Ross M. E.
Published: August 2015

1. Each molecule of biotin bound to avidin protected four tryptophan residues from oxidation by N-bromosuccinimide, regardless of the occupancy of neighbouring binding sites in the four-sub-unit avidin molecule. 2. The oxidation products from avidin molecules in which some of the sites were occupied were separated on columns of Sephadex G-100. In the absence of biotin, oxidized avidin broke down into sub-units, which partly aggregated. When some of the sites were occupied by biotin, the only detectable products were completely oxidized avidin (sub-units and large aggregates) and unoxidized avidin–biotin complex (tetramer). Since the biotin-containing sub-units were randomly distributed before oxidation took place, they must have dissociated from the molecules containing oxidized sub-units and then reassociated to form the tetrameric avidin–biotin complex. 3. This reassociation still occurred in 3·5m-guanidinium chloride, which prevents the reassociation of unoccupied sub-units. During their brief existence in this medium, the sub-units of avidin–biotin complex were protected from oxidation by N-bromo-succinimide to the same extent as was the tetrameric complex. 4. It is concluded that sub-units of avidin–biotin complex do not readily lose their biotin, even in 3·5m-guanidinium chloride, and that monomeric biotin–binding species are probably present in solutions of avidin sub-units at guanidinium chloride concentrations between 3·0m and 3·5m.
Evidence of homology in a high-sulphur protein fraction (SCMK-B2) of wool and hair α-keratins
Authors: Gillespie J. M. , Haylett T. , Lindley H.
Published: August 2015

Fractions corresponding to the S-carboxymethylated high-sulphur protein component SCMK–B2 isolated by Gillespie (1963) from Merino wool were prepared from five different wool samples and also from bovine hair. The six fractions showed great similarities in amino acid composition, and also gave very similar peptide ‘maps’ after tryptic and chymotryptic digestion. Some of the peptides were isolated from the different samples, and evidence is given that suggests that a sequence of at least 21 amino acids is common to all the fraction SCMK–B2 preparations. Further, all the fractions derived from the wool samples have the same acetylated heptapeptide for the N-terminal sequence, but one extra residue may be present in this N-terminal sequence in the protein from bovine hair. The general significance of these findings is discussed.
The metabolism of [Me−14C]choline in the brain of the rat in vivo
Authors: Ansell G B , Spanner Sheila
Published: August 2015

[Me−14C]Choline was injected intracerebrally into the adult rat, and its uptake into the lipids and their water-soluble precursors in brain was studied. The radioactivity could be detected only in the choline-containing lipids and was confined to the base choline. The results indicated that initial phosphorylation of the free choline followed by the formation of CDP-choline and the subsequent transfer of the phosphorylcholine to a diglyceride is one of the principal routes by which choline lipids in brain are formed. Further evidence for this was obtained in experiments in which either phosphoryl[Me−14C]choline or [32P]orthophosphate was injected and the radioactivity in the choline-containing water-soluble and lipidbound components studied.
Studies on the glycopeptides isolated from the urinary protein in heavy-chain disease
Authors: Clamp J. R. , Dawson G. , Franklin E. C.
Published: August 2015

The urinary protein excreted in heavy-chain disease was separated by ion-exchange chromatography into two broad fractions designated Cra-1 and Cra-2. For a dimeric molecular weight of approx. 51000, Cra-1 contained 3–4 residues of 6-deoxy-l-galactose (l-fucose), 10 of d-mannose, 5–6 of d-galactose, 12 of 2-acetamido-2-deoxy-d-glucose (N-acetyl-d-glucosamine) and 4–5 of N-acetylneuraminic acid (sialic acid), whereas the corresponding values for Cra-2 were 2, 10, 7, 12 and 7. Cra-2 contained in addition 1 residue of 2-acetamido-2-deoxy-d-galactose (N-acetyl-d-galactosamine). Cra-1 contained an average of four oligosaccharide units, two of which contained 1 residue of 6-deoxy-l-galactose, 3 of d-mannose, 1 of d-galactose and 3 of 2-acetamido-2-deoxy-d-glucose, whereas the other two units contained the same proportions of 6-deoxy-l-galactose, d-mannose and 2-acetamido-2-deoxy-d-glucose but 2 residues of d-galactose and 2 of N-acetylneuraminic acid. Cra-2 also contained an average of four oligosaccharide units, but the range of glycopeptides was much wider, containing 0–1 residue of 6-deoxy-l-galactose, 2–3 of d-mannose, 2–3 of d-galactose, 2–3 of 2-acetamido-2-deoxy-d-glucose and 1–3 of N-acetylneuraminic acid. Possible reasons for this heterogeneity are discussed. Glycopeptides were also isolated from Cra-2 that contained 1 residue of d-mannose, 2 of d-galactose, 1 of 2-acetamido-2-deoxy-d-galactose and 0–3 of N-acetylneuraminic acid.