bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolism of methylamine in the tea plant (Thea sinensis L.)
Authors: Suzuki Takeo
Published: August 2015

1. The metabolism of methylamine in excised shoot tips of tea was studied with micromolar amounts of [14C]methylamine. Of the [14C]methylamine supplied 57% was utilized by tea shoots during the 10h experimental period. 2. The main products of [14C]methylamine metabolism in tea shoots were serine, γ-glutamylmethylamide, theobromine, caffeine and CO2. There was also incorporation of the label into glutamate, aspartate, RNA purine nucleotides and S-adenosylmethionine. 3. The formation of methylamine from γ-glutamylmethylamide was confirmed by feeding tea shoots with γ-glutamyl[14C]methylamide. The products of γ-glutamyl[14C]methylamide metabolism in tea plants were serine, theobromine, caffeine, glutamate and aspartate. 4. The results indicate that the oxidation of methylamine to formaldehyde is the first step of methylamine utilization. Labelled formaldehyde released by the metabolism of methylamine leads to the incorporation of the label into metabolites on the C1 pathways of this compound. It is also suggested that formaldehyde is further oxidized via formate to CO2. 5. The role of γ-glutamylmethylamide in methylamine metabolism in tea plants is discussed. 6. Results support the view that theobromine is the immediate precursor of caffeine.
The effect of cycloheximide on adipose-tissue clearing-factor lipase (Short Communication)
Authors: Cryer A. , Foster Barbara , Wing D. R. , Robinson D. S.
Published: August 2015

The progressive increase in clearing-factor lipase activity that occurs during the incubation of adipose tissue from starved rats in an appropriate medium at 25°C is shown to occur in two stages. The first of these is not inhibited by cycloheximide, whereas the second is.
Galactosylserine in extensin
Authors: Lamport Derek T. A. , Katona Laura , Roerig Sandra
Published: August 2015

Cell walls obtained from tomato suspension cultures were treated at pH1 for 1h at 100°C to remove arabinose oligosaccharide substituents from the hydroxyproline residues of extensin. Tryptic attack of these acid-stripped walls yielded glycopeptides containing galactose. When one of these glycopeptides (designated S2A6; sequence NH2-Ser-Hyp-Hyp-Hyp-Hyp-Ser-Hyp-Lys-CO2H) was treated with (a) NaOH–NaBH4 or (b) NaOH–Na2SO3 some of the serine was converted into (a) alanine or (b) cysteic acid, and the peptide lost galactose. Maleylation or 3-carboxypropionylation of N-terminal serine was necessary for conversion of this residue and for complete loss of galactose. These results indicate that a single galactose residue is attached O-glycosidically to each of the two serine residues. Hydrazinolysis of peptide S2A6 or of isolated cell walls also led to destruction of serine. In control experiments non-glycosylated serine was not destroyed during hydrazinolysis. Thus the galactosylserine linkage is sensitive to N2H4.
The reaction of a histidine residue in glutamate dehydrogenase with diethyl pyrocarbonate
Authors: Wallis Robert B. , Holbrook J. John
Published: August 2015

1. One mol of diethyl pyrocarbonate will react with one mol of glutamate dehydrogenase polypeptide chains to form one mol of N1-carbethoxyhistidine. Reaction is prevented by NADH. 2. The 1:1 complex has an increased specific activity (1.4–2.0-fold). 3. The reason for the activation is discussed. The results are not consistent with NADH dissociation from the enzyme–glutamate–NADH complex being rate-limiting in the steady state measured. 4. The effects of modification on the properties of the enzyme were investigated. The effects of GTP and NAD+ on the enzyme activity are unaltered by activation. NADH binding is unaltered and there is no apparent change in the molecular weight. However, the activated enzyme can still be further activated by ADP. Ks for ADP is decreased fivefold.
Adenosine 3′:5′-cyclic monophosphate-binding protein from the cellular slime mould Dictyostelium discoideum (Short Communication)
Authors: Malkinson Al M. , Kwasniak Janet , Ashworth John M.
Published: August 2015

During the differentiation of myxamoebae of Dictyostelium discoideum strain Ax-2 grown in axenic medium there is a seven- to ten-fold increase in the specific activity of cyclic AMP-binding protein(s). Evidence is presented for the belief that cyclic AMP phosphodiesterase and cyclic AMP-binding protein are distinct molecular species.
The subunits and biological activity of polymorphic forms of tropomyosin
Authors: Cummins P. , Perry S. V.
Published: August 2015

1. Free thiol groups were shown to be essential for tropomyosin to effect maximum inhibition of the Ca2+-stimulated ATPase (adenosine triphosphatase) of desensitized actomyosin but not for its activity in the regulatory-protein system. 2. The activity of tropomyosin on the Mg2+-stimulated ATPase in the regulatory-protein system was more susceptible to enzymic digestion and thermal denaturation than its effect on the Ca2+-stimulated ATPase of actomyosin. 3. Rabbit skeletal tropomyosin migrated as two distinct electrophoretic components in the presence of sodium dodecyl sulphate and urea and as four components on isoelectric focusing in urea. 4. The two main subunits present in rabbit skeletal tropomyosin, which have been named the α- and β-chains, were separated by chromatography on CM-cellulose in urea at pH4.0. They were shown to be virtually identical in amino acid composition, except for their cysteine contents. The α2 and β2 forms of tropomyosin possessed all the biological activities characteristic of normal tropomyosin preparations. 5. In skeletal muscle the α and β components of tropomyosin were present in the proportion of 4:1. Somewhat lower ratios were obtained in skeletal muscle of sheep, pig and cow. 6. Tropomyosin isolated from cardiac muscle and Pecten maximus adductor muscle migrated as one band only. These tropomyosins possessed similar biological activities to those isolated from skeletal muscle.
Activities of hexokinase, phosphofructokinase, 3-oxo acid coenzyme A-transferase and acetoacetyl-coenzyme A thiolase in nervous tissue from vertebrates and invertebrates
Authors: Sugden P. H. , Newsholme E. A.
Published: August 2015

1. The maximum activities of hexokinase and phosphofructokinase in nervous tissue from 18 different animals from different phyla range from 5.1 to 17.6 and from 24.0μmol/min per g fresh wt. respectively. In any one tissue the activities of these two enzymes are, in general, very similar. The rate of glucose utilization by the brain in vivo is much lower than the activities of hexokinase or phosphofructokinase. It is suggested that the high activities of these enzymes indicate a capacity for glycolysis which may be used by the brain during hypoxia or during conditions of extreme neuronal activity. 2. The activities of 3-oxo acid CoA-transferase and acetoacetyl-CoA thiolase in the nervous tissues range from 1.1 to 15.3 and from 0.7 to 4.5μmol/min per g fresh wt. respectively. Unfortunately the activities of these enzymes cannot be used to estimate maximal flux through the ketone-body-utilization pathway, since they may catalyse reactions that are close to equilibrium. Nonetheless, the presence of these enzymes in nervous tissue from a large variety of animals suggests that the importance of ketone bodies as a fuel for nervous tissue may be widespread in the animal kingdom.
Effect of l-leucine on the nitrogen metabolism of isolated rat liver mitochondria
Authors: McGivan J. D. , Bradford Norah M. , Crompton M. , Chappell J. B.
Published: August 2015

1. l-Leucine strongly activated intramitochondrial glutamate dehydrogenase in the direction of glutamate synthesis. 2. In the deamination direction, the enzyme was not stimulated by leucine. This was probably due to a rate-limiting transport of glutamate across the mitochondrial membrane. 3. The effect of leucine on the kinetic constants of glutamate dehydrogenase in a mitochondrial sonicate was studied. 4. In isolated mitochondria, leucine did not stimulate the synthesis of citrulline with glutamate as the source of NH3. 5. Leucine very markedly stimulated the synthesis of glutamate from added 2-oxoglutarate+NH4Cl. 6. Under conditions where glutamate and citrulline could be synthesized simultaneously from added NH4Cl, leucine greatly increased glutamate synthesis at the expense of citrulline synthesis. 7. It is suggested that the intramitochondrial leucine concentration may be a factor influencing the nitrogen metabolism of the liver cell.
Isolation and properties of cholesterol esterstorage granules from ovarian tissues
Authors: Armstrong David T. , Flint Anthony P. F.
Published: August 2015

Cholesterol ester-storage granules were isolated from luteinized rat ovary and rabbit ovarian interstitial tissue by centrifugal flotation and were investigated with regard to their structure and function. Cholesterol ester, protein, phospholipid and unesterified cholesterol accounted for the dry weight of granules from luteinized rat ovary. The protein and the phospholipid were resistant to removal by washing. Substrate specificities of nucleotide phosphatase and specific radioactivities of lipid-soluble P (determined after administration of [32P]Piin vivo) were the same in granules and in a microsomal fraction from the same tissue. After administration of [32P]Piin vivo, luteinizing hormone increased the specific radioactivity of lipid-soluble P in granules, mitochondria and the microsomal fraction. Since granules did not swell in hypo-osmotic media, whereas microsomal particles did, it is suggested that adherent phospholipid and protein in granule suspensions is unlikely to result from contamination with endoplasmic reticulum. Luteinizing hormone administered in vivo increased the phospholipid and unesterified cholesterol contents of isolated granules relative to their cholesterol ester content, and also tended to raise their protein content. This treatment decreased the ability of isolated granules to act as a substrate for cholesterol esterase in vitro and increased the activity of cholesterol esterase. Cycloheximide in vivo also raised the unesterified cholesterol/cholesterol ester ratio of isolated granules, and when administered with luteinizing hormone acted synergistically to bring about a further increase. These results are considered compatible with evidence obtained by microscopy which suggests that granules may be surrounded by a membrane, that they arise by pinching off from the endoplasmic reticulum, and that they shrink on trophic stimulation of the tissue.
Adenosine 5′-sulphatophosphate kinase activity in spinach leaf tissue
Authors: Burnell J. N. , Anderson J. W.
Published: August 2015

1. An F−-insensitive 3′-nucleotidase was purified from spinach leaf tissue; the enzyme hydrolysed 3′-AMP, 3′-CMP and adenosine 3′-phosphate 5′-sulphatophosphate but not adenosine 5′-nucleotides nor PPi. The pH optimum of the enzyme was 7.5; Km (3′-AMP) was approx. 0.8mm and Km (3′-CMP) was approx. 3.3mm. 3′-Nucleotidase activity was not associated with chloroplasts. Purified Mg2+-dependent pyrophosphatase, free from F−-insensitive 3′-nucleotidase, catalysed some hydrolysis of 3′-AMP; this activity was F−-sensitive. 2. Adenosine 5′-sulphatophosphate kinase activity was demonstrated in crude spinach extracts supplied with 3′-AMP by the synthesis of the sulphate ester of 2-naphthol in the presence of purified phenol sulphotransferase; purified ATP sulphurylase and pyrophosphatase were also added to synthesize adenosine 5′-sulphatophosphate. Adenosine 5′-sulphatophosphate kinase activity was associated with chloroplasts and was released by sonication. 3. Isolated chloroplasts synthesized adenosine 3′-phosphate 5′-sulphatophosphate from sulphate and ATP in the presence of a 3′-nucleotide; the formation of adenosine 5′-sulphatophosphate was negligible. In the absence of a 3′-nucleotide the synthesis of adenosine 3′-phosphate 5′-sulphatophosphate was negligible, but the formation of adenosine 5′-sulphatophosphate was readily detected. Some properties of the synthesis of adenosine 3′-phosphate 5′-sulphatophosphate by isolated chloroplasts are described. 4. Adenosine 3′-phosphate 5′-sulphatophosphate, synthesized by isolated chloroplasts, was characterized by specific enzyme methods, electrophoresis and i.r. spectrophotometry. 5. Isolated chloroplasts catalysed the incorporation of sulphur from sulphate into cystine/cysteine; the incorporation was enhanced by 3′-AMP and l-serine. It was concluded that adenosine 3′-phosphate 5′-sulphatophosphate is an intermediate in the incorporation of sulphur from sulphate into cystine/cysteine.
A model study of the fructose diphosphatase–phosphofructokinase substrate cycle
Authors: Bloxham David P. , Clark Michael G. , Holland Paul C. , Lardy Henry A.
Published: August 2015

A fructose diphosphatase–phosphofructokinase substrate cycle has been reconstructed in vitro to provide a system that recycles fructose 6-phosphate and hydrolyses ATP to ADP and Pi. The concerted actions of glucose phosphate isomerase, phosphofructokinase, aldolase and triose phosphate isomerase catalysed the loss of 3H from [5-3H,U-14C]glucose 6-phosphate. This was used as the basis of a method for the estimation of the fructose diphosphatase–phosphofructokinase substrate cycle. For the reconstructed cycle, the rate of decrease of the 3H/14C ratio in [5-3H,U-14C]hexose 6-phosphate was proportional to the rate of fructose 6-phosphate substrate cycling. A detailed theoretical treatment of this relationship is developed, which enables the rate of substrate cycling to be determined in vivo.
Induction of orientation of bacterial cellulose microfibrils by a novel terpenoid from Acetobacter xylinum
Authors: Haigh W. Geoffrey , Förster Hans J. , Biemann Klaus , Tattrie Neil H. , Colvin J. Ross
Published: August 2015

1. The bacterium Acetobacter xylinum produces extracellular cellulose microfibrils that form a pellicle in the medium enmeshing the bacterial cells. These microfibrils may show some localized alignment, which can be seen as birefringence when the culture is viewed between crossed Polaroid sheets. 2. An increase in birefringence can be induced by the addition of small amounts of certain classes of lipids, particularly sterols, to the cultures. 3. A crude lipid extract from Acetobacter cells induced greatly increased birefringence when added to fresh cultures of this organism. 4. When the bacterial lipids were fractionated, most of the activity was recovered in a complex, polar lipid. The lipid is secreted into the medium during growth and is unstable. The non-saponifiable portion of this lipid is shown to be a 1:1 mixture of a saturated and a monounsaturated C35 tetrahydroxy terpene with a hopane ring system in the accompanying paper by Förster et al. (1973). The saturated molecule is referred to as tetrahydroxybacteriohopane. 5. Tetrahydroxybacteriohopane is itself capable of inducing birefringence in cultures as is 22-hydroxyhopane, which was also isolated from the non-saponifiable fraction of the total lipids. 6. The mechanism of induction of birefringence (orientation of microfibrils) is not known. This is unlikely to be a specific effect, since all the above compounds are active (intact lipid, tetrahydroxybacteriohopane, 22-hydroxyhopane), as are other classes of lipid. It is suggested, however, that a common mechanism may be involved and that similar compounds may be concerned with control of microfibril alignment in the cells of higher plants.
A comparison of the physical and chemical properties of four cytochromes c from Azotobacter vinelandii
Authors: Campbell Wilbur H. , Orme-Johnson William H. , Burris Robert H.
Published: August 2015

1. A modified method for the separation and purification of four cytochromes c from Azotobacter vinelandii is described. Two new cytochromes c have been purified and are designated cytochromes c(551) and c(555). 2. Additional evidence is presented to establish the dihaem nature of cytochrome c4. Ultracentrifugation data indicated similar molecular weights for the native and the denatured protein. Cleavage with CNBr yielded seven peptides; the amino acid compositions of the purified peptides were determined. Only one haem peptide was recovered. 3. Cytochromes c(551) and c(555) were characterized as acidic proteins of molecular weights about 12000. The spectral properties, isoelectric points, ‘maps’ of peptides from CNBr cleavage and amino acid compositions were determined for these two proteins. 4. The spectral properties, isoelectric points, molecular weights, CNBr peptide ‘maps’, amino acid compositions, relative oxidation–reduction potentials and e.p.r. (electron-paramagnetic-resonance) spectra of the four cytochromes c were compared. Cytochrome c4 and cytochrome c(551) appear to be distinct proteins. The distinction between cytochromes c5 and c(555) was not as clear, and our data are inadequate to establish firmly that they are distinct proteins. 5. The dihaem nature of cytochrome c4 is evident in its e.p.r. spectrum. The e.p.r. spectra are similar to the spectra of mammalian cytochromes c.
The molecular-weight distribution of glycosaminoglycans
Authors: Hopwood John J. , Robinson H. Clem
Published: August 2015

1. A rapid and sensitive method for the accurate estimation of the molecular-weight distribution of keratan sulphate and chondroitin sulphate isolated from adult bovine nasal septum and intervertebral disc is described. The method utilizes gel chromatography of reductively labelled glycosaminoglycan and end-group estimation of number-average molecular weight for each fraction across the peak of eluted glycosaminoglycan. 2. Chain-length distribution data obtained by this procedure are used to evaluate mechanisms of chondroitin sulphate biosynthesis.
Conformation of the mucopolysaccharides. X-ray fibre diffraction of heparin
Authors: Nieduszynski I. A. , Atkins E. D. T.
Published: August 2015

Oriented films of the sodium salt of heparin crystallize in a triclinic unit cell. The X-ray diffraction results favour a tetrasaccharide covalent repeating sequence but the measured molecular repeat of 1.59nm is inconsistent with all α-(1→4)(1ax→4eq)-glycosidic linkages as generally accepted. Three models are proposed for the molecular shape of heparin, which depend on the chair conformation adopted by the hexuronic acid moieties. Model I has both uronic acids in the C1 chair form, model II has one uronic acid in each of the C1 and 1C chairs and model III has both in the 1C chair form. The merits of these models are discussed.
The formation of ferritin from apoferritin. Inhibition and metal ion-binding studies
Authors: Macara Ian G. , Hoy Terence G. , Harrison Pauline M.
Published: August 2015

Inhibition by Zn2+of iron uptake by apoferritin at very low substrate concentrations is shown to be competitive. It is proposed that Zn2+competes with Fe2+for sites on the protein at which the oxidation of Fe2+is catalysed. Interpretation of titration data suggests there are two independent classes of binding site for Zn2+and several other cations. Sites in one such class are probably on the external surface of the apoferritin molecule. The catalytic binding sites are presumed to be internal and may involve histidine or possibly cysteine as ligands.
Binding of oligosaccharides of hyaluronic acid to proteoglycans (Short Communication)
Authors: Hardingham Timothy E. , Muir Helen
Published: August 2015

Oligosaccharides derived from hyaluronic acid were shown to inhibit proteoglycan–hyaluronic acid interaction, as measured in a viscometer. The relative inhibition increased with the size of the oligosaccharide and the results suggested that decasaccharides were the smallest fragments able to bind strongly to the proteoglycan.
Effect of the exotoxin of Bacillus thuringiensis on normal and ecdysone-stimulated ribonucleic acid polymerase activity in intact nuclei from the fat body of Sarcophaga bullata larvae
Authors: Beebee T. J. C. , Bond R. P. M.
Published: August 2015

A nuclear preparation from the fat-body of Sarcophaga bullata was obtained which incorporates nucleotides at a steady rate. Two activities, differing in their response to α-amanitin, are present. The activities are not separated by changes in the concentration of (NH4)2SO4 as effectively as in mammalian nuclei. The activity resistant to α-amanitin is stimulated by ecdysone, and both normal and the ecdysone-stimulated activities are inhibited by the exotoxin. The amanitin-sensitive enzyme is also inhibited by exotoxin, but higher concentrations are required.
Cholesterol feeding alters the metabolism of thoracic-duct lymph lipoprotein cholesterol in rabbits but not in rats
Authors: Redgrave T. G.
Published: August 2015

1. Labelled thoracic-duct lymph was collected from rats and rabbits after test meals containing [14C]cholesterol and [2-3H]glyceryl trioleate. 2. The metabolism of labelled cholesterol and triglyceride was studied in normally fed and cholesterol-fed rats and rabbits injected with radioactive lymph from the same species. 3. In normally fed animals of both species, 10min after intravenous administration, about 80% of lymph cholesteryl ester but only about 10% of triglyceride was recovered in the liver after clearance from the plasma. This distribution is consistent with participation of ‘remnant’ particles in the metabolism of dietary lymph particles. 4. The metabolism of cleared lymph lipoprotein constituents was unchanged in cholesterol-fed rats, but the recovery of cholesteryl ester in the livers of the cholesterol-fed rabbits was decreased to 30% of the cleared dose. 5. The low recovery in cholesterol-fed rabbits was accounted for mainly by increased hydrolysis of cholesteryl ester. 6. It is proposed that differences between rats and rabbits in metabolism of dietary cholesterol might be partly due to the observed enhancement of hydrolysis of lymph lipoprotein cholesteryl ester in rabbits.
The effect of trimethoprim on macromolecular synthesis in Escherichia coli. Regulation of ribonucleic acid synthesis by ‘magic spot’ nucleotides
Authors: Smith R. J. , Midgley J. E. M.
Published: August 2015

During the inhibition of RCstr, but not RCrel mutants of Escherichia coli by trimethoprim the unusual nucleotides MSI (guanosine tetraphosphate, ppGpp) and MSII rapidly accumulated. The production of these nucleotides was not dependent on the addition of nucleotide base supplements to RCstr cultures before trimethoprim, and the MSI nucleotide concentrations in non-supplemented or purine-supplemented cultures were comparable with the concentrations obtained when the cells were inhibited with l-valine (1g/l). Rifampicin rapidly decreased MSI and MSII nucleotide concentrations in trimethoprim-inhibited cultures to the basal values. Several situations were noted, in which MS nucleotide concentrations in trimethoprim-inhibited RCstr cells could be drastically lowered without giving rise to an immediate resumption of stable RNA accumulation. If RCstr mutants were first inhibited with trimethoprim and then given purines 15min later, MS nucleotide concentrations fell rapidly, because of a temporarily enhanced rate of accumulation of stable RNA. However, after a further 5min, RNA accumulation stopped, though MS nucleotide concentrations remained low. Also, if either glycine or methionine were added to trimethoprim-inhibited cultures supplemented with purines, RNA accumulation did not resume, though MS nucleotide concentrations rapidly declined. With both amino acids present, there was both a decline in MS nucleotide concentration and a resumption in stable RNA synthesis. These findings suggest that MSI nucleotide concentrations in trimethoprim-inhibited bacteria are not the sole factors in the control of stable RNA synthesis. It is possible that, during the period when the RCstr cells contained high concentrations of MS nucleotides, some factor important in the MSI-mediated control of stable RNA synthesis was irreversibly inactivated. However, as antibiotics (e.g. chloramphenicol) both abolished high MS nucleotide concentrations and permitted a rapid resumption of stable RNA accumulation in the same conditions, it is more likely that an additional control mechanism has come into play.
Cellular reactions of O6-methylguanine, a product of some alkylating carcinogens
Authors: Miller Carolyn Thatcher , Lawley Philip D. , Shah Sudhirkumar A.
Published: August 2015

Cultures of a purine-requiring mutant of Chinese hamster ovary cells (CHO-104b), randomly bred hamster embryo cells, or Escherichia coli Bs-1 were treated with non-toxic doses of 3H-labelled O6-methylguanine. DNA and RNA were isolated and subjected to enzymic digestion to nucleosides at pH8. The products of digestion were analysed by ion-exchange chromatography on columns of Dowex 50 (NH4+ form) at pH8.9. No 3H-labelled O6-methylguanosine was detected in nucleic acid digests. 3H-labelled O6-methylguanine was O-demethylated yielding [3H]guanine in CHO-104b cells. Radioactivity in nucleic acid digests was associated with thymidine, guanosine, deoxyguanosine and an unidentified early-eluting product. Reports of similar unidentified products from nucleic acids labelled with various agents are discussed.
The turnover rate of rabbit urinary Tamm–Horsfall glycoprotein
Authors: Grant Anne M. S. , Neuberger Albert
Published: August 2015

1. The turnover rate of urinary Tamm–Horsfall glycoprotein in rabbits was determined by two different methods. The first involved measurement of the pool size of the glycoprotein in rabbit kidney and the daily urinary excretion rate by a radioimmunoassay from which the turnover rate was calculated. 2. The second method made use of the incorporation in vivo of Na214CO3 and sodium [14C]acetate. After a single intramuscular injection of one of these compounds, urine collections were made every 24h and the glycoprotein was isolated and its specific radioactivity was determined. 3. Incorporation of the label into urinary HCO3−, urea and plasma fibrinogen was also examined. The specific radio-activities of the O-acetyl, sialic acid, aspartic acid and glutamic acid residues isolated from the Tamm–Horsfall glycoprotein were compared and their half-lives were compared with that of the intact glycoprotein. The two methods gave results in quite close agreement and indicated a half-life for the glycoprotein of approx. 9h. 4. An attempt was made to localize the glycoprotein within the kidney and within the cell. It is present throughout the kidney, but was not detected in the brush-border fraction isolated from the proximal tubules. From differential cell-centrifugation studies, the glycoprotein seemed to be predominantly present in the soluble fraction (100000g supernatant). This suggests that it is either largely a soluble cytoplasmic component or is very loosely bound to a membrane, being readily released under the gentlest homogenization procedure. 5. The half-life of Tamm–Horsfall glycoprotein in human kidney was found by the radioimmunoassay method to be approx. 16h. The similarity between the composition of Tamm–Horsfall glycoprotein and human erythropoietin is discussed.
Stimulation by vasopressin of glycogen breakdown and gluconeogenesis in the perfused rat liver
Authors: Hems Douglas A. , Whitton Patricia D.
Published: August 2015

1. Vasopressin (anti-diuretic hormone, [8-arginine]vasopressin) stimulated the breakdown of glycogen in perfused livers of fed rats, at concentrations (50–600μunits/ml) that have been reported in the blood of intact rats, especially during acute haemorrhagic shock. 2. In perfused livers from starved rats, vasopressin (30–150μunits/ml) stimulated gluconeogenesis from a mixture of lactate, pyruvate and glycerol. 3. Vasopressin prevented accumulation of liver glycogen in the perfused liver of starved rats, or in starved intact rats. 4. The action of vasopressin on hepatic carbohydrate metabolism thus resembles that of glucagon; the minimum effective circulating concentrations of these hormones are of the same order (100pg/ml). 5. The stimulation of hepatic glucose output by vasopressin is discussed in connexion with the release of glucose and water from the liver.
Inhibition by ricin of protein synthesis in vitro: 60S ribosomal subunit as the target of the toxin (Short Communication)
Authors: Sperti Simonetta , Montanaro Lucio , Mattioli Alessandro , Stirpe Fiorenzo
Published: August 2015

Poly(U)-directed polyphenylalanine synthesis by rat liver ribosomes is strongly inhibited by ricin. Experiments involving hybridization between subunits derived from normal and ricin-treated ribosomes demonstrate that the 60S subunit is the site of action of the toxin. The toxin inactivates the 60S subunit independently of the presence of the 40S subunit.
Chloride-dependent uncoupling mediated by oligomycin in rat liver mitochondria
Authors: Ariel N. , Avi-Dor Y.
Published: August 2015

In rat liver mitochondria suspended in KCl medium and containing a low concentration of a K+-specific cationophore (valinomycin or Triton X-100), oligomycin was shown to induce uncoupling of oxidative phosphorylation, stimulation of adenosine triphosphatase activity, release of the respiratory control, decrease of energy-dependent changes in the fluorescence of the dye 8-anilino-1-naphthalenesulphonic acid and rapid swelling of mitochondria. Oligomycin caused none of the above effects when Br-or NO3-was substituted for Cl-as the major anionic species or when Na+replaced the K+. The same concentration of oligomycin that caused uncoupling and swelling slightly improved energy-conserving reactions when the cationophores were omitted. In the presence of KSCN, valinomycin or Triton X-100 by itself caused uncoupling and swelling which was not further enhanced by oligomycin. On the basis of the above results it is suggested that the energy dissipation resulting from the concerted action of the cationophores and oligomycin is connected with the simultaneous transport of K+and its counter ion and that oligomycin plays its role in the uncoupling by facilitating the permeation of Cl-through the cristae membrane of the mitochondria.
The diurnal response of muscle and liver protein synthesis in vivo in meal-fed rats
Authors: Garlick P. J. , Millward D. J. , James W. P. T.
Published: August 2015

1. The rate of protein synthesis in rat tissues was measured by constant intravenous infusion of [14C]tyrosine. A modification has been developed for the method of calculating the rate of protein synthesis in individual tissues from the specific radioactivity of the free and protein-bound amino acid in tissue at the end of the infusion. This technique gives greater accuracy and allows a greater choice of labelled amino acids. The specific radioactivity of free tyrosine in plasma was used to calculate the plasma tyrosine flux, an index of the rate of protein synthesis in the whole body. 2. Young male Wistar rats were allowed access to food for only 4h in every 24h. The tyrosine flux and the rate of protein synthesis in liver and muscle at different periods of time after a single feed were estimated. 3. The tyrosine flux did not alter after feeding nor even after starvation for 48h. 4. The average fractional rate of protein synthesis in muscle was 7.2%/day, i.e. the proportion of the protein mass which is replaced each day. The rate rose after eating and declined during starvation for 48h. In addition the rate of muscle protein synthesis correlated with the growth rate of the rat. 5. In liver the average fractional rate of protein synthesis was 50%/day. There was no change in the rate after eating nor after starvation for 48h. In contrast with muscle this suggests that the changes in protein mass were accompanied by changes in the rate of protein breakdown rather than synthesis.
Effects of membrane depolarization on nicotinamide nucleotide fluorescence in brain slices
Authors: Lipton Peter
Published: August 2015

1. Simultaneous measurement of tissue NAD(P)H fluorescence and respiration was used to elucidate some of the early chemical changes after depolarization of the membranes of cerebral-cortical cells. Depolarization was effected by the application of a train of short-duration voltage pulses across a slice of guinea-pig cerebral cortex. The pulses cause a biphasic change in fluorescence corresponding to an early (within 1s) oxidation and later (about 10s) reduction of nicotinamide nucleotide. The major portions of both these redox changes are unrelated to the accompanying increase in slice respiration of about 75%. 2. The early oxidation requires Ca2+and phosphate in the bathing medium and appears to be largely due to an early mitochondrial uptake of these ions. 3. The ensuing reduction occurs in the cytosol, as judged by its almost complete elimination in the presence of exogenous pyruvate. It becomes markedly attenuated with increasing time of incubation. This and the ability of exogenous 6-N-2′-O-dibutyryl cyclic AMP to cause a reduction in the absence of electrical pulses suggest that it results from a cyclic AMP-mediated activation of glycogenolysis. 4. Further results, obtained in the presence of exogenous pyruvate, indicate that in addition to the above effects a net transfer of NADH from the mitochondrial to cytosolic space (presumably via a shuttle mechanism) is activated by the electrical pulses. 5. The lack of any sizeable (more than 2% of basal fluorescence) fluorescence change associated with the respiratory increase caused by the pulses, and the fact that any change which may be associated with it corresponds to a small reduction of mitochondrial nicotinamide nucleotide, show that a simple state 4 → state 3 mitochondrial transition cannot account for the increased respiration. The results suggest, rather, a co-ordinated control of respiration, at more than one site.
A novel assay for the biosynthesis of sulphated polysaccharide and its application to studies on the effects of somatomedin on cultured cells
Authors: Wasteson Åke , Uthne Knut , Westermark Bengt
Published: August 2015

1. A simple method is described for the determination of small amounts of [35S]sulphated polysaccharide with 95–100% recovery in the range from 0.3 to 150μg of polysaccharide. 2. The method is based on precipitation with cetylpyridinium chloride of polysaccharide samples applied to filter paper. It is not significantly disturbed by the presence in the sample of a large excess of inorganic35SO42-. 3. Sulphated glucosamino- and galactosaminoglycans may be determined separately by treatment of the sample with chondroitinase ABC. 4. The method is applicable to the assay of [35S]sulphated polysaccharide biosynthesis in cell cultures. A stimulation of sulphate incorporation obeying a linear dose–response curve, was demonstrated in somatomedin-incubated fibroblast and glia cell cultures. 5. The described system provides a new assay method for somatomedin. 6. The stimulatory effect of somatomedin on the synthesis of [35S]sulphated polysaccharide appeared to be general, rather than specific, for a particular type of polysaccharide.
Calcium transport and phospholipid composition of microsomal fractions from denervated rat gastrocnemius
Authors: Hughes Beaumont P. , Yasin Rose
Published: August 2015

Total calcium uptake, but not the initial rate, and non-calcium-stimulated (basic) adenosine triphosphatase activity of rat gastrocnemius microsomal fractions 3, 7 and 14 days after denervation increased compared with contralateral controls. Microsomal sphingomyelin also increased but phosphatidylcholine plus choline plasmalogen was unchanged in amount. These results are contrasted with those reported for vincristine myopathy.
Difference in kinetic properties between hexokinase type I isoenzymes from various rat tissues with reference to the effect of a thiol inhibitor (Short Communication)
Authors: Kamikashi T. , Kizaki H. , Murakami K. , Ishibashi S.
Published: August 2015

Hexokinase isoenzyme type I was purified from various rat tissues, and was subjected to kinetic studies in the presence or the absence of p-chloromercuribenzenesulphonate. The mode of the inhibition by the thiol inhibitor was different for the type I isoenzymes obtained from different tissues, suggesting that the type I isoenzymes from different tissues were not identical proteins.
The mechanism of phosphoglucomutase from Micrococcus lysodeikticus
Authors: Clarke John B. , Britton Hubert G.
Published: August 2015

The mechanism of the phosphoglucomutase from Micrococcus lysodeikticus was investigated. Induced-transport tests at low substrate concentrations (0.15mm) showed co-transport of the 32P label but no induced transport of the 14C label, which is in quantitative agreement with a phosphoenzyme mechanism with a rapid isomerization of the phosphoenzyme. The results excluded an intramolecular transfer of phosphate and could only have been compatible with a sequential mechanism if the Km for glucose 1-phosphate had been over 20 times smaller than the measured value. The results of induced-transport tests at intermediate concentrations (1mm) with both labels agreed quantitatively with a phosphoenzyme mechanism, and induced-transport tests with 14C-labelled substrates at high concentrations (26mm) indicated that the rate constants for isomerization of the phosphoenzyme must be greater than about 3×106s-1. Consistent with these findings is the fact that 14C label exchanged between the substrates twice as rapidly as the 32P label at chemical equilibrium. Further, since the 14C label exchanged between the substrates about ten times more rapidly than between the substrates and glucose 1,6-diphosphate, glucose 1,6-diphosphate is not an obligatory intermediate in the interconversion of the substrates. It is concluded that, contrary to previous evidence, the mechanism of the enzyme from M. lysodeikticus is essentially that of the rabbit muscle enzyme. To account for the rapid isomerization of the phosphoenzyme in both cases a mechanism is proposed in which there is no formal isomerization of the phosphoenzyme.
The type-specific substance from Pneumococcus type 33B
Authors: Watson M. J.
Published: August 2015

1. The type-specific substance, S. 33B, from Pneumococcus type 33B contains P, 2.89; hexose, 51; total sugar, 69; galactosamine, 18; and d-glucose, 20%. 2. After degradation with alkali, followed by enzymic dephosphorylation, S. 33B yielded a hexasaccharide. 3. The hexasaccharide was assigned the structure O-β-d-glucopyranosyl- (1→5)-O-β-d-galactofuranosyl- (1→3)-O-2-acetamido-2-deoxy-β-d- galactopyranosyl-(1→4)-O-[α-d- galactopyranosyl-(1→2)]-α-d-galactopyranosyl- (1→2)-ribitol. 4. Phosphate residues in S. 33B are located on the hydroxyl groups at position 5 of ribitol units and on the hydroxyl groups at position 6 of hexopyranose residues.
The detection and characterization by electron-paramagnetic-resonance spectroscopy of iron–sulphur proteins and other electron-transport components in chromatophores from the purple bacterium Chromatium
Authors: Evans Michael C. W. , Lord Anne V. , Reeves Stuart G.
Published: August 2015

Low-temperature e.p.r. (electron-paramagnetic-resonance) spectroscopy was used to detect electron-transport components in Chromatium chromatophores with e.p.r. signals in the g=2.00 region. High-potential iron protein (Em8.0=+325mV, where Em8.0 is the midpoint potential at pH8) and a second component (g=1.90, Em8.0=+285mV) are oxidized in illuminated chromatophores. Two iron–sulphur proteins (g=1.94) with Em8.0=−290mV and Em8.0=−50mV are present. One (Em8.0=−50mV) is reduced on illumination. A component (g=1.82) with Em8.0=−135mV is photoreduced at 10°K. The midpoint potential of this component is altered by o-phenanthroline and pH. The properties of this component suggest that it is the primary electron acceptor of a photochemical system. Another component (g=1.98) also has some of the properties of a primary electron acceptor, but its function cannot be completely defined. These results show that iron–sulphur proteins are present in the electron-transport system of Chromatium and indicate their role in electron transport.
Progesterone metabolism by the echinoderms Asterias rubens and Marthasterias glacialis (Short Communication)
Authors: Gaffney John , Goad L. John
Published: August 2015

The echinoderms Asterias rubens and Marthasterias glacialis metabolize injected [4-14C]progesterone to give labelled 3β-hydroxy-5α-pregnan-20-one and 3β,6α-dihydroxy-5α-pregnan-20-one. These radioactive products are converted by the animals into conjugated forms that are soluble in aqueous methanol, and which have mobilities on t.l.c. similar to the asterosaponins.
Effects of collagen and of aspirin on the concentration of guanosine 3′:5′-cyclic monophosphate in human blood platelets: measurement by a prelabelling technique (Short Communication)
Authors: Haslam R. J. , McClenaghan M. D.
Published: August 2015

A method is described for isolating cyclic [3H]GMP from platelets preincubated with [3H]guanine. Collagen increased and aspirin decreased the cyclic [3H]GMP concentration in platelets. The results are consistent with a role for cyclic GMP in the platelet release reaction.
Rate of synthesis and half-life of globin messenger ribonucleic acid. Rate of synthesis of globin messenger ribonucleic acid calculated from data of cell haemoglobin content
Authors: Hunt John A.
Published: August 2015

By the use of the favoured models defining mRNA synthesis and half-life from the preceding paper (Hunt, 1974) and the known content of globin in a reticulocyte it is possible to estimate the absolute rate of mRNA and globin synthesis and the mRNA and globin content in each type of erythroid cell. The best model requires an mRNA-synthetic rate of 3000 molecules per h/cell. This rate compares favourably with the estimated chain-extension rate of 43 nucleotides/s in Escherichia coli (Manor et al., 1969) provided that the four α- and β-chain cistrons per cell are transcribed by polymerases spaced 50 nucleotide base pairs apart. Similar calculations can be made for erythropoiesis in the chick embryo, where cell times and relative globin content at each mitosis have been measured (Campbell et al., 1971), but where no reliable estimates of mRNA half-life have been made. In this case it was estimated that a constant rate of mRNA synthesis at 10000 molecules per h/cell through six cell divisions is necessary if the mRNA half-life is 15h; after the sixth mitosis the mRNA synthesis would stop and its half-life would increase to approx. 20h. If an mRNA half-life of 4.5h is used, the synthesis rate through the six mitoses would be 21000 molecules per h/cell, ceasing at the sixth mitosis, when the half-life would need to increase to 25h. The chain-elongation rate for the four α- and β-globin cistrons per cell would be 1–2 times higher than in E. coli and would either require a greater rate, polymerases spaced between 25 and 50 nucleotide base pairs apart on the DNA, or limited gene replication. These possibilities are discussed in the light of the low values found for globin cistron multiplicity in ducks and mice.
Pig liver pyruvate carboxylase. The reaction pathway for the decarboxylation of oxaloacetate
Authors: Warren Graham B. , Tipton Keith F.
Published: August 2015

1. The reaction pathway for the decarboxylation of oxaloacetate, catalysed by pig liver pyruvate carboxylase, was studied in the presence of saturating concentrations of K+ and acetyl-CoA. 2. Free Mg2+ binds to the enzyme in an equilibrium fashion and remains bound during all further catalytic cycles. MgADP− and Pi bind randomly, at equilibrium, followed by the binding of oxaloacetate. Pyruvate is released before the ordered steay-state release of HCO3− and MgATP2−. 3. These results are entirely consistent with studies on the carboxylation of pyruvate presented in the preceding paper (Warren & Tipton, 1974b) and together they allow a quantitative description of the reaction mechanism of pig liver pyruvate carboxylase. 4. In the absence of other substrates of the back reaction pig liver pyruvate carboxylase will decarboxylate oxaloacetate in a manner that is not inhibited by avidin. 5. Reciprocal plots involving oxaloacetate are non-linear curves, which suggest a negatively co-operative interaction between this substrate and the enzyme.
The specificity of chain interactions among immunoglobulins. Combinations of γ chains with κ chains of the same subgroup as in the parent immunoglobulin G
Authors: Stevenson G. T. , Mole L. E.
Published: August 2015

1. The specificity of combination of heavy and light chains from selected human immunoglobulins was examined in the light of greater structural information than in previous studies. Heavy (γ) chains from immunoglobulin G (κ) myeloma proteins were allowed to combine with their homologous light (κ) chains or with other κ chains of the same variable-region subgroup. The affinity of each such pairing was assessed by having the test κ chain compete with a standard population of normal light chains. 2. There was a spread of affinities among the heavy–light pairings with the homologous pairings having an average affinity significantly higher than the heterologous pairings. 3. It follows that (a) the preference shown for homologous heavy–light pairings is not explicable simply in terms of the known subdivisions of the variable and constant regions of the chains, and (b) it is unlikely that those residues specifying the subgroups of κ-chain variable regions have a predominant role in the formation of interchain bonds with the γ-chain variable regions.
An investigation by dielectric methods of hydration in myoglobin solutions
Authors: Grant Edward H. , Mitton Barbara G. R. , South Gerald P. , Sheppard Rodney J.
Published: August 2015

The permittivities of three solutions of sperm-whale myoglobin of different concentrations were measured in the frequency range 300–1300MHz at 20°C by using a coaxial-line technique. These results were combined with those measured previously at frequencies below 10MHz. Two methods are described for calculating the extent of macromolecular hydration from the data. The more reliable method yields results of approx. 0.25g of H2O/g of protein, which is in satisfactory agreement with the theoretically calculated value. Agreement with the value found from the rotational motion of the molecule is not so close, which is probably caused by the different meanings that may be ascribed to the term hydration.
Endogenous steroid concentrations in human breast tumours determined by high-resolution mass fragmentography (Short Communication)
Authors: Millington D. , Jenner Diane A. , Jones T. , Griffiths K.
Published: August 2015

A pilot study of the endogenous steroid concentrations in human breast tumours was performed. The technique of high-resolution molecular-ion monitoring during combined g.l.c.–mass spectrometry was used to determine oestrone, oestradiol-17β and oestriol in concentrations above 1ng/g wet wt. of tissue, and dehydroepiandrosterone, testosterone, androsterone (3α-hydroxy-5α-androstan-17-one) and 3β-hydroxy-5α-androstan-17-one in concentrations exceeding 5ng/g, in extracts of five primary breast tumours.
A kinetic study of pig liver pyruvate kinase activated by fructose diphosphate
Authors: Macfarlane Neil , Ainsworth Stanley
Published: August 2015

The paper reports a study of the reaction between phosphoenolpyruvate, ADP and Mg2+ catalysed by pig liver pyruvate kinase when activated by fructose diphosphate and K+. The experimental results are consistent with two non-sequential mechanisms in which the substrates and products of the reaction are phosphoenolpyruvate, ADP, Mg2+, pyruvate and MgATP. Pyruvate release occurs before ADP binding. Two Mg2+ ions are involved, though the two Mg2+-binding sites cannot be occupied simultaneously. An isomerized enzyme complex forms before release of MgATP. Values were determined for the Michaelis constants of the reaction. Apparent MgATP inhibition constants are also given.