bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study of Possible Biochemical Mechanisms Involved in Hyperbaric Oxygen-Induced Changes in Cerebral γ-Aminobutyric Acid Levels and Accompanying Seizures
Authors: Wood J. D. , Radomski M. W. , Watson W. J.
Published: December 2009

A linear correlation was obtained between the relative rate of γ-aminobutyric acid (GABA) metabolism in chicks of different ages during a period of rapid brain development and the susceptibility of the birds to seizures induced by hyperbaric oxygen (O.H.P.). Since the changes taking place with age in the activities of the two enzymes involved in GABA metabolism (glutamic acid decarboxylase and GABA–α-ketoglutarate transaminase) were similar, the enzyme system primarily responsible for the O.H.P.-induced decreases in cerebral GABA levels and accompanying seizures could not be identified. Both enzyme systems may be involved. The possible involvement of an increased transport of GABA through cellular membranes in the production of low cerebral GABA levels could not be demonstrated in the present experiments.
Interpretation of Nonhyperbolic Behavior in Enzymic Systems. II. Quantitative Characteristics of Rate and Binding Functions
Authors: Endrenyi Laszlo , Chan Ming-Sang , Wong J. Tze-Fei
Published: December 2009

The quantitative evaluation of rate and binding functions involves first the determination of the form, or degree, of the equation, and secondly the interpretation of coefficients from the equation in terms of basic rate and binding constants of the reaction mechanism, (a) A lower limit of the degree is provided by the log v (or Y) versus log S plot and the Hill plot. In the case of the allosteric mechanisms of Monod et al., a general linear plot has been developed which permits direct estimation of the degree. In addition, standard curves relating the extreme Hill slope to ratios of fractionally saturating concentrations have been developed which uniquely characterize the behavior of second-degree systems. They can be employed for the detection of higher than second-degree behavior. Similar use can be made of a set of normalized Scatchard binding curves, (b) Concerning the quantitative interpretation of coefficients, feasibility of a procedure based on near-exhaustive testing of random sets of rate constants has been demonstrated. Its application to a substrate-modifier mechanism of Botts and Morales enables an interpretation of sigmoidal rate curves in terms of ratios of elementary rate constants, (c) Positive or negative cooperativity of binding systems is described quantitatively by a coefficient of cooperativity, γ. In a second-degree system it can be evaluated with the help of the normalized Scatchard curves, (d) Some of these methods of analysis have been applied to the measurements of Changeux et al. on succinate binding to aspartate transcarbamylase and led to the proposal of a second-degree concerted allosteric mechanism for this system.
The Energy Metabolism of Novikoff Ascites Hepatoma Cells. I. The Effects of Glucose on the Intracellular Level of Adenine Nucleotides
Authors: Gurd J. W. , Scholefield P. G.
Published: December 2009

When freshly prepared Novikoff hepatoma ascites tumor cells were incubated with glucose there was a rapid decrease in the ATP content of the cells. This was initially accompanied by an increased level of ADP but in the interval 6–10 min after the addition of glucose only 40% of the original adenine nucleotide content could be accounted for as adenosine phosphates. Analysis by thin-layer chromatography indicated breakdown via inosine 5′-phosphate (IMP), inosine, and hypoxanthine. Continued incubation led to resynthesis from hypoxanthine to IMP and thence to the adenine nucleotides.
Phospholipase A2: Action on Purified Phospholipids as Affected by Deoxycholate and Divalent Cations
Authors: Uthe J. F. , Magee W. L.
Published: December 2009

Phospholipase A2 preparations from a snake venom (Crotalus adamanteus) and from beef and human pancreas have been compared in identical reaction systems. With all of the substrates investigated the venom enzyme exhibited a higher specific activity in the presence of added sodium deoxycholate than in its absence. Under optimal conditions, the venom enzyme hydrolyzed phosphatidylcholine and phosphatidylethanolamine at equivalent rates, phosphatidylserine less well, and phosphatidylinositol more slowly still. Phosphatidylethanolamine was the preferred substrate for the pancreatic enzymes; although other phospholipids were hydrolyzed more rapidly in the presence of deoxycholate, its addition inhibited the conversion of this substrate to lysophosphatidylethanolamine.All three enzymes were stimulated by added Ca2+ ions whether phosphatidylcholine, phosphatidylethanolamine, or phosphatidylserine was employed as a substrate, the effect being quantitatively of greater significance with the reptilian as compared to the mammalian enzymes. Mg2+ ions could replace Ca2+ ions partially in some cases, especially with phosphatidylserine as substrate. Other divalent ions from the alkaline-earth and transition metal groups inhibited.The action of EDTA is complex; the results suggest that it has a direct inhibitory action on the enzymes.
Porcine Sugar Nucleotide: Glycoprotein Glycosyltransferases. II. Blood Serum and Liver Galactosyltransferase
Authors: Hudgin Roger L. , Schachter Harry
Published: December 2009

Pork serum and liver have been shown to contain UDP-galactose galactosyltransf erase activity towards both N-acetylglucosamine and sialidase- and β-galactosidase-treated α1-acid glycoprotein. The serum enzyme is soluble while the liver enzyme is membrane-bound. A soluble liver enzyme has been prepared by an organic solvent extraction method, but this preparation is unstable. Comparison of soluble and membrane-bound liver enzymes at pH 8.0–8.7 has indicated that membrane has a relatively minor modifying effect on enzyme kinetics. Comparison of serum and liver enzymes at pH 8.0–8.7 shows that both enzymes have an absolute dependence on Mn2+ ion, and have similar substrate specificities; the preparations differ in kinetic parameters to a minor extent. Thus the serum galactosyltransferase is similar but not identical to the liver enzyme; the source and function of the serum enzyme is not known. The addition of α-lactalbumin to the serum preparation and to both the soluble and membrane-bound liver enzymes results in inhibition of N-acetyllactosamine synthetase activity and the appearance of lactose synthetase activity; α-lactalbumin has no appreciable effect on the UDP-galactose:glycoprotein galactosyltransferase activity. Competition studies show that in all three preparations, N-acetylglucosamine and glycoprotein acceptor compete for a single site. It therefore appears that the same enzyme is responsible for galactosyltransferase activity towards both N-acetylglucosamine and glycoprotein, and further, that the serum and liver enzymes are similar to milk lactose synthetase A protein.
Porcine Sugar Nucleotide: Glycoprotein Glycosyltransferases. III. Blood Serum and Liver N-Acetylglucosaminyltransferase
Authors: Hudgin Roger L. , Schachter Harry
Published: December 2009

Pork liver and serum contain UDP-N-acetylglucosamine: glycoprotein N-acetylglucosaminyltransferase activity. The serum enzyme is soluble and the liver enzyme is membrane-bound; the latter can be solubilized by organic solvent extraction but the yield is low and the soluble preparation is unstable. Comparison of membrane-bound and soluble liver enzymes indicates that the membrane has only a minor modifying effect on the enzyme kinetics. Comparison of serum and liver enzymes shows that the two activities are similar but not identical; in particular, the two enzymes have similar cation requirements, substrate specificities, pH profiles, and Km values for both nucleotide sugar and glycoprotein acceptor. The source and function of the serum enzyme cannot be deduced from this information.
Destabilization of Casein Micelles by Lysozyme
Authors: Bakri M. , Wolfe Fred H.
Published: December 2009

Lysozyme has been demonstrated to bring about coagulation of casein micelles in a manner similar to the action of rennin. Both the rennin and lysozyme catalyzed reactions show similar pH optima and calcium ion dependencies. The differences in specificities of these two enzymes suggest that the carbohydrate moiety of the casein glycoprotein plays a major role in stabilization of casein micelles.
Properties of a Purified Carnitine Palmitoyltransferase, and Evidence for the Existence of Other Carnitine Acyltransferases
Authors: Kopec Bozena , Fritz Irving B.
Published: December 2009

Carnitine palmitoyltransferase (CPT) has been purified, and some of its properties are described. The purified preparations had specific activities of 10–38 μmoles/min/mg protein at 35°. The apparent molecular weight of CPT was approximately 75 000, or a multiple thereof. The K′m value for palmitoyl-CoA was 1.8 × 10−5 M, while the K′s values for (–)-carnitine, CoA–SH, and (–)-palmitoylcarnitine were estimated to be 4.5 × 10−4 M, 5.5 × 10−6 M, and 1.4 × 10−4 M, respectively. The enzyme was subject to inhibition by all substrates and products. CPT had a relatively broad fatty acyl chain-length specificity, with highest Vmax values obtained for the transfer of myristoyl and palmitoyl groups. K′m values were lowest with long-chain fatty acylcarnitinè derivatives (1.9 × 10−4 M for (–)-stearoylcarnitine versus 1.2 × 10−3 M for (–)-decanoylcarnitine).Evidence is presented demonstrating the existence of two additional protein fractions possessing carnitine acyltransferase activities with different fatty acyl chain-length specificities. One, which displayed highest relative activity towards the transfer of octanoyl groups, is tentatively designated carnitine octanoyltransferase. The other, which displayed a high specificity toward the transfer of palmitoyl and stearoyl groups from acylcarnitine when preincubated with CoA–SH, is tentatively designated carnitine palmitoyltransferase II.
Pathways of Purine Ribonucleotide Catabolism in Ehrlich Ascites Tumor Cells In Vitro
Authors: Crabtree G. W. C. , Henderson J. Frank
Published: December 2009

Ehrlich ascites tumor cells incubated in vitro with adenine-14C catabolized up to 20% of the radioactive nucleotides which were formed, principally via dephosphorylation of inosinate and xanthylate, with small amounts of adenylate and guanylate broken down. Cells incubated with hypoxanthine-14C catabolized a much larger proportion of nucleotides, principally via dephosphorylation of inosinate and xanthylate; guanylate was also broken down. Catabolic products of guanine-14C in these cells were xanthine, which was formed directly from guanine, and guanosine which at least in part was formed via dephosphorylation of guanylate.
DNA Polymerases of Newborn Rat Brain and Liver
Authors: Bharucha A. D. , Murthy M. R. V.
Published: December 2009

DNA polymerase activity was found to be present in appreciable quantities in the extracts of whole tissue (TS) as well as of nuclei (NS) isolated from newborn rat brain and liver. The NS fractions of either of the two tissues exhibited a higher specific activity per unit protein than the corresponding TS fractions. The optimum pH requirements as well as the ability to support DNA synthesis over a long period indicate that the NS fractions were also comparatively less contaminated by interfering substances than the TS fractions.The reaction requirements for the incorporation of TMP residues into DNA by the NS fractions of newborn rat brain and liver and the effect of various inhibitors and hydrolytic enzymes on this reaction were also investigated. These extracts resembled preparations from other mammalian tissues in that they exhibited absolute requirements for the primer DNA, the four complimentary deoxynucleoside triphosphates, and Mg2+ ions. When three of the four deoxynucleoside triphosphates were omitted and only TTP-2-14C was added to the reaction mixture, a limited incorporation of TMP-2-14C into DNA occurred. Other investigations such as the effect of actinomycin and of sulfhydryl compounds revealed that a large part of incorporation by the TS and NS fractions of newborn brain and liver was due to the replicative DNA nucleotidyltransferase enzyme.
Some Optical Properties of S-β-(4-Pyridylethyl)-L-Cysteine and its Wheat Gluten and Serum Albumin Derivatives
Authors: Wu Y. Victor , Cluskey James E. , Krull L. H. , Friedman Mendel
Published: December 2009

The optical properties of S-β-(4-pyridylethyl)-L-cysteine (PEC) and its bovine serum albumin (BSA) and wheat gluten derivatives were studied in 0.01–0.1 N HCl. Optical rotatory dispersions (O.R.D.), circular dichroism (C.D.), ultraviolet (U.V.), and infrared (I.R.) spectra were obtained of PEC, BSA, BSA reduced with mercaptoethanol and alkylated with 4-vinylpyridine (PE-BSA), BSA reduced with mercaptoethanol and alkylated with acrylonitrile (CN-BSA), gluten, gluten reduced with mercaptoethanol and alkylated with 4-vinylpyridine (PE-gluten), and gluten reduced with mercaptoethanol and alkylated with acrylonitrile (CN-gluten). I.R. spectra of the proteins showed the presence of α-helical and unordered conformations. The U.V. absorption at 254 mμ of PEC and PE-BSA depends on pH; a pK value near 6 for the pyridyl group was obtained by spectrophotometric titration. The possible use of PEC as a conformation probe was explored. The O.R.D. of PEC depends on concentration, solvent, and pH but not on ionic strength. The O.R.D. data of proteins were analyzed by the Moffitt–Yang method to get α-helical contents. These helical contents indicate that there is not enough interaction left to support α-helix in gluten with disulfide bonds broken at pH 2.2. However, approximately one-third of the helical content of BSA persists without the aid of disulfide bonds.
Purification and Properties of Phosphoglyceromutase from Sheep Muscle
Authors: James Eric , Hurst R. O. , Flynn T. G.
Published: December 2009

Phosphoglyceromutase (2,3-diphospho-D-glycerate phosphotransferase, EC 2.7.5.3) has been purified from sheep muscle. The enzyme has a specific activity of 828 units/mg and is stable for several months at 0–2 °C in 0.1 μ phosphate buffer, pH 7.0. The Km for 2,3-diphosphoglycerate (DPGA) is 0.003 mM; the Km for 3-phosphoglycerate is 9.0 mM. A small amount of DPGA-phosphatase activity was associated with the enzyme.At pH 5.4 and 7.0 sheep phosphoglyceromutase was shown to be homogeneous by sedimenting as a single sharp peak in the ultracentrifuge and by the appearance of a single band on both disc gel and cellulose acetate electrophoresis. The sedimentation coefficient of the enzyme at pH 7.0 was 4.1 S, the diffusion constant 7.21 × 10−7 cm2/s, and the molecular weight calculated from both the-sedimentation and gel filtration data was of the order of 51 000.Disc gel electrophoresis of the enzyme at pH 9.3 revealed the presence of three protein components which were shown to be charge isomers.Titration of the enzyme with p-chloromercuribenzoate indicated that 4.0 sulfhydryl groups were present per mole. Reaction with 5,5′-dithio-bis-(2-nitrobenzoate) showed that one of the sulfhydryl groups may be an absolute requirement for enzymic activity.
An Improved Fractionation System for Pronase on CM-Sephadex
Authors: Jurášek L. , Johnson P. , Olafson R. W. , Smillie L. B.
Published: December 2009

An efficient, single-column preparative-scale fractionation of pronase on CM-Sephadex using a linear gradient of pyridine-acetate, pH 5.0, has been developed. Under these conditions excellent resolution and minimal autolysis of the component proteolytic enzymes occurs. Only three major endopeptidases with caseinolytic activity are found. Streptomyces griseus trypsin (S.G.T.) is recovered in adequate purity for amino acid sequence studies. Streptomyces griseus Protease A and Protease B have been shown to correspond to PNPase I and II previously described by Wählby. Two aminopeptidases and a carboxypeptidase have also been demonstrated. Pronase appears to be a less complex mixture of proteolytic enzymes than had previously been appreciated.
Biochemical Alterations in the Skeletal Muscle of Vitamin E Deficient Rats
Authors: Dhalla Naranjan S. , Fedelesova Margaret , Toffler Ivan
Published: December 2009

Rats were fed a vitamin E deficient diet for 5–10 weeks and the energy state of the hind leg muscle was examined. Both creatine phosphate and ATP were decreased by 64 and 22% of the control values, respectively, in the skeletal muscles of rats on the vitamin E deficient diet for 10 weeks, whereas ADP was increased by more than 100% without any significant changes in the level of AMP. The ratios ATP/ADP and ATP/AMP also declined markedly in the hind leg muscles of the rats on the vitamin E deficient diet for 10 weeks. The concentrations of NAD+ and NADPH decreased, whereas no significant changes in the levels of NADH and NADP+ were observed in the muscles of vitamin E deficient animals. Feeding a normal diet for 4 weeks to rats previously on the vitamin E deficient diet was found to restore the energy state of the muscle towards normal. Although no changes in the ultrastructure of the skeletal muscle were apparent, the levels of lactate and pyruvate as well as the lactate/pyruvate ratio were increased in vitamin E deficiency. The activities of lactate dehydrogenase and malate dehydrogenase were decreased whereas α-glycerophosphate dehydrogenase activity did not change significantly. These results indicate a dramatic alteration in skeletal muscle metabolism of vitamin E deficient rats. It is suggested that such a change may partly be due to a defect in the process of energy production.
Autooxidation of Actomyosin
Authors: Jacobson A. L. , Henderson J.
Published: December 2009

The oxidation of sulfhydryl groups in actomyosin is specifically catalyzed by ferrous or cupric ions. Ferric and lead ions protect actomyosin from oxidative degradation. In the absence of O2 there is no change in the sulfhydryl content of actomyosin. Without trace metal ions and the presence of O2 there is a very slow degradation of actomyosin. Agitation markedly increases the rate of degradation.
Effects of Phospholipases on RNA Polymerase Activity in Preparations from Rat Brain
Authors: Menon I. A.
Published: December 2009

Phospholipase A and phospholipase C increased the RNA polymerase activities in presence of Mg2+ or Mn2+ of aggregate enzyme preparation from rat brain. The stimulatory effects were not observed when the RNA polymerase activities were determined in presence of 0.4 M ammonium sulfate, KCl, or NaCl. Trypsin, pronase, and papain were found to enhance the RNA polymerase activity in presence of Mn2+ whereas they had little or no effect on the activity in presence of Mg2+. The phospholipase had relatively less effect on the RNA polymerase activity of frozen and thawed or sonicated aggregate enzyme preparation. Treatment with phospholipase A solubilized approximately 50% of the RNA polymerase. The RNA polymerase activity of brain mitochondria was stimulated by treatment with the phospholipases. The results indicate that phospholipids associated with chromatin and RNA polymerase, as well as those in mitochondria, influence the activity of the RNA polymerases.
Particulate Glucan Synthetase Activity: Dependence on Acceptor, Activator, and Plant Growth Hormone
Authors: Spencer F. S. , Ziola B. , Maclachlan G. A.
Published: December 2009

Particulate fractions isolated from the growing region of the epicotyl of Pisum sativum L. var Alaska are capable of transferring glucose from uridine or guanosine diphosphate glucose-14C to buffer-insoluble products which are partly alkali-soluble and partly alkali-insoluble. Cellobiose activates the reaction; carboxymethylcellulose and cellodextrins act as competitive acceptor molecules.When the epicotyl is decapitated, glucan synthetase activity disappears from particulate fractions of the growing region within 3 days unless the hormone indoleacetic acid (IAA) is added to the tissue, in which event activity is retained. Other growth regulators (gibberellic acid, benzyladenine) have no such effect. Loss of activity is not due to a change in solubility of enzyme or product or to the absence of substrate, activator, or acceptor molecules, nor is it accompanied by comparable losses in total protein or cellulase activity from the particulate fraction. It is concluded that IAA is needed for the formation and/or protection of an essential part of the insoluble synthetase complex.
The Hepatic Chalone. I. Assay Method for the Hormone and Purification of the Rabbit Liver Chalone
Authors: Verly W. G. , Deschamps Y. , Pushpathadam J. , Desrosiers M.
Published: December 2009

Chalone from rabbit liver has been purified 450-fold; it is a polypeptide of small molecular weight. Its action on liver DNA synthesis is tissue-specific but not species-specific. The dose–effect relationship is in agreement with the theory of receptor sites in the hepatocytes with a low affinity for this hormone.
Enzymes of the Conversion of Succinate to Glutamate in Extracts of Rumen Microorganisms
Authors: Emmanuel B. , Milligan L. P.
Published: December 2009

Cell-free extracts of mixed rumen microorganisms were incubated in vitro in order to determine the existence and nature of metabolic conversions leading from succinate to glutamate. When succinate was incubated as the substrate in the presence of reduced ferredoxin (FDH), a product was formed, which reacted with 2,4-dinitrophenylhydrazine to give the hydrazone of succinic semialdehyde as determined by paper chromatography. When succinic semialdehyde was incubated in the presence of FDH and 14C-bicarbonate, fixation of label was catalyzed by the extracts. The labelled product was isolated as an organic acid and identified as 2-hydroxyglutaric acid by means of paper chromatography. In the presence of ammonia and NAD, 2-hydroxyglutarate was aminated to a ninhydrin-reactive compound that was identified as glutamate by paper chromatography.From the information obtained, a new pathway for the synthesis of glutamate in rumen microbes was proposed. This pathway entails the reduction of succinate to succinic semialdehyde, followed by reductive carboxylation of succinic semialdehyde to yield 2-hydroxyglutarate, which is then aminated to glutamate. The pathway would agree with the labelling pattern in glutamate produced in the presence of 14C-bicarbonate by mixed rumen microorganisms.
The Effect of Cortisone Acetate on Lysosomal Enzyme Levels In Rat Liver
Authors: Kyaw A. , Mellors A.
Published: December 2009

Increases in the levels of four lysosomal enzymes were measured during the induction of tyrosine transaminase in rat liver by cortisone acetate. Tyrosine transaminase showed a maximum specific activity 2 h after the injection of the steroid hormone whereas lysosomal enzyme levels reached a maximum specific activity at 4 h. The maximum increase in specific activity for 15 injected animals compared to 15 controls was 100% for tyrosine transaminase; 40% for cathepsin A, cathepsin D, and β-N-acetylglucosaminidase; and 10% for acid phosphatase. Increased specific activities from livers of cortisone-acetate-treated rats were observed when lysosomal enzymes were released both by detergent treatment and by freezing and thawing.The increased specific activities were found in the readily solubilized lysosomal enzyme fractions and not in those lysosomal enzyme fractions which remain associated with particulate matter after lysosomal disruption. Similar increased specific activities for acid phosphatase and β-N-acetylglucosaminidase were observed in cultures of Morris hepatoma cells from rat liver when incubated with cortisone acetate in vitro. Thus the response appears to be typical of single cell types.
Amino Acid Sequence Studies of Horseradish Peroxidase. II. Thermolytic Peptides
Authors: Welinder K. G. , Smillie L. B.
Published: December 2009

Horseradish peroxidase (HRP) was digested with thermolysin. On fractionation on Sephadex G-25, Fine Chromobeads type P (Dowex 50 type resin) and by high-voltage paper electrophoresis, we isolated about 120 thermolytic peptides. Some experimentation on the composition of the pyridine acetate gradient, used for elution of the cation exchanger, is reported. All peptides were characterized with respect to amino acid composition, N-terminal residue, and pH 6.5 mobility. Unknown peptides or peptides not corresponding unambiguously to previously established tryptic sequences were subjected to dansyl-Edman analysis. Thermolytic peptides accounting for all tryptic sequences except a dipeptide and a tripeptide, and unique thermolytic sequences accounting for about 100 amino acid residues, were obtained. Nine convincing and several indicative overlaps were established for known tryptic sequences. The sequences around all four disulfide bridges, the three histidine residues, and the only tryptophan residue have been elucidated. Eight sites of carbohydrate attachment have been identified. For seven of these sites we have evidence for attachment to asparagine, and for six of the sites the carbohydrate-bound asparagine was found in the well-known sequences Asn–X–Ser/Thr. The remaining two sequences, though incomplete, are compatible with this pattern. Tentatively we suggest a pyrrolidone carboxyl N-terminal for HRP. The specificity of trypsin implicates a sequence found in two varieties, differing only by a C-terminal serine residue at the C-terminus of HRP. A discussion of the possible complications of the acidic heme extraction on the results obtained is included.
Inermin Associated with Pisatin in Peas Inoculated with the Fungus Monilinia fructicola
Authors: Stoessl A.
Published: December 2009

The phytoalexin pisatin, when isolated from pea pods inoculated with the fungus Monilinia fructicola, was found to be accompanied by smaller amounts of the chemically closely related inermin. Uninoculated controls did not contain readily detectable amounts of inermin.
The Interaction of Procaine with the Nonmyelinated Nerve Axon
Authors: Simpkins Henry , Panko Elaine , Tay Sin
Published: December 2009

The interaction of procaine with the nonmyelinated nerve axon from the legs of Homarus americanus was found to produce a conformational change in the lipid structure of the membrane. This conformational change was also observed after treatment of the nerve with acetylcholine bromide but not with any of the following local anesthetics:lidocaine, carbocaine, prilocaine, and nupercaine. It was also found that procaine is a potent inhibitor of acetylcholinesterase whereas the other anesthetics at the same concentration had little effect.
An Endonuclease for Depurinated DNA in Escherichia coli B
Authors: Verly W. G. , Paquette Y.
Published: December 2009

Escherichia coli B cells contain an endonuclease which hydrolyzes apurinic sites in DNA. The enzyme has been demonstrated in vitro by the action of E. coli B41 proteins on depurinated DNA. This endonuclease probably plays a role in the molecular mechanism of the delayed inactivation of the T7 coliphage treated by monofunctional alkylating agents, which has been shown to be dependent on depurination; this endonuclease could also be a repair enzyme necessary for the first step of the repair of DNA containing apurinic sites.
Galactosamine Polymer Isolated from the Cell Wall of Neisseria sicca
Authors: Adams G. A. , Chaudhari A. S.
Published: December 2009

A D-galactosamine polymer having a molar ratio of galactosamine–acetyl–phosphorus (1.0:1.0:0.35) has been isolated from the cell wall of Neisseria sicca. Its homogeneity was established by free-boundary electrophoresis, ultracentrifugal sedimentation, and gel permeation chromatography. Molecular weight estimation by reducing end group assay gave a value of [Formula: see text] 18 500. Methylation analysis indicated that the main glycosidic linkages were (1 → 4) and (1 → 6) with a minimum of 10% branch points. The glycosidic bonds were indicated as being in the α configuration by the high positive optical rotation of the polysaccharide and also from infrared spectrum evidence. Both the acetyl and phosphate contents were relatively unchanged by the Hakamori methylation procedure. Although galactosamine polymers have been found in a number of fungi, the present instance appears to be the first report of their presence in bacteria.
Hormonal Regulation of Rat Mammary Gland Enzyme Activities and Metabolite Patterns
Authors: Korsrud G. O. , Baldwin R. L.
Published: December 2009

Activities of nine enzymes and the levels of 15 metabolites were determined in mammary glands from normal (N) and adrenalectomized–ovariectomized (AO) rats in midlactation. Mammary gland weights and mammary DNA did not change between day 11 and day 19 of lactation in N animals and were not affected appreciably by AO. Four days after AO the activities of citrate cleavage enzyme, malic enzyme, UDPglucose pyrophosphorylase, the A protein of the lactose synthetase complex, and glucose-6-phosphate dehydrogenase were decreased to 24, 59, 53, 52, and 56% of day 11 N. These same enzymes require cortisol therapy to increase in activity after adrenalectomy on the 5th day of lactation. Activities of phosphoglucomutase, 6-phosphogluconate dehydrogenase, fructose-1,6-diphosphate aldolase, and isocitrate dehydrogenase were not affected by AO. These enzymatic changes are discussed in relation to systems regulating milk synthesis. Mammary glucose levels increased 1.9-fold in AO animals. Levels of triose phosphate, α-glycerol phosphate, and aspartate in AO animals were decreased to 52, 49, and 62% of N. The proportion of high-energy phosphate bonds to total adenine nucleotides was not affected by AO. Ratios of [free NADP]/[free NADPH2] were not significantly affected by AO or stage of lactation. Metabolite patterns are discussed in relation to changes in enzyme activities and in vitro tracer data.
Influence of the Lithium Chloride Supernatant on the Maturation of E. coli 43 S Ribosomal Precursor
Authors: Reynier Max , Varricchio Frederick
Published: December 2009

Particles of 43 S ribosomal precursor have been subjected to the reconstitution procedure developed for reconstituting LiCl particles and LiCl supernatant. When the 43 S particles were dialyzed in the presence of LiCl supernatant, particles of about 50 S were obtained. If 32P 5 S RNA and LiCl supernatant were both present during reconstitution, a peak of radioactivity due to the 5 S RNA was found in the 50 S region of a sucrose gradient.
Use of a Diimidoester Cross-Linking Reagent to Examine the Submit Structure of Rabbit Muscle Pyruvate Kinase
Authors: DaVies Gregg E. , Kaplan J. Gordin
Published: December 2009

Rabbit muscle pyruvate kinase, a tetramer of highly similar or identical subunits, is known to dissociate in urea via a dimeric intermediate. To provide additional evidence regarding the structure of the native oligomer, we have treated pyruvate kinase with dimethyl pimelimidate and examined the yields of cross-linked species resolved by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Of four products resolved, predominating species are dimers and tetramers of the pyruvate kinase subunit, while monomers and trimers are present in lesser amounts. These relative yields are consistent with a dimeric structure of the tetramer.In a typical cross-linking reaction, about 86 of the 148 primary amino groups in the pyruvate kinase tetramer are amidinated. Of 53 moles of cross-linking reagent incorporated per mole of tetramer, 38% have reacted monofunctionally, with hydrolysis of the second imidoester group, and 62% have reacted bifunctionally to form intra- and intersubunit cross-links.
Purification and Properties of Phosphoribosyl-formylglycineamidine Synthetase of Ehrlich Ascites Tumor Cells
Authors: Chu Samuel Y. , Henderson J. Frank
Published: December 2009

Phosphoribosyl-formylglycineamidine synthetase was purified 56-fold from Ehrlich ascites tumor cells. The reaction required potassium ion as activator, and a combination of glutamine, magnesium chloride, and potassium chloride protected the enzyme against thermal denaturation. Ammonium ion could replace potassium ion as activator, and could replace glutamine as substrate. Studies with radioactive substrates suggest that the reaction is wholly or partially ping pong; glutamine is converted to glutamate by the free enzyme.
Kinetic Studies of Phosphoribosyl-formylglycineamidine Synthetase
Authors: Chu Samuel Y. , Henderson J. Frank
Published: December 2009

Initial velocity and product inhibition studies of phosphoribosyl-formylglycineamidine synthetase indicate that the reaction involves a fully ping pong mechanism in which glutamine binds to the free enzyme and glutamate is released before the addition of ATP. ADP is released, and phosphoribosyl-formylglycineamide then binds; the liberation of Pi is rapid, and phosphoribosyl-formylglycineamidine is the last product released from the enzyme. The Km values for glutamine, ATP, and phosphoribosyl-formylglycineamide are 1.1 × 10−4 M, 1.5 × 10−3 M, and 1.1 × 10−4 M, respectively. The Km value for ammonium chloride is 7.5 × 10−3 M, and the ratio of Vmax values with ammonium chloride and glutamine is 1/40. The inhibition constants for FGAM and Pi were calculated to be 1.3 × 10−4 M and 6.45 × 10−3 M, respectively.
Thiol–Protein Disulfide Oxidoreductase Activity in Human Placental Tissue Homogenates
Authors: Branda Luis A. , Ferrier Barbara M. , Celhoffer Lynne
Published: December 2009

Thiol–protein disulfide oxidoreductase activity was detected in the soluble cell fraction of human placental tissue homogenized in sucrose. This activity was demonstrated in the rapid reduction of oxytocin and the somewhat less rapid reduction of insulin by reduced glutathione. The apparent pH optimum of the enzymic activity for the reduction of oxytocin and insulin was found to be near pH 8.
2-Nitro-4-Azidophenyl Glycoside Affinity Labelling Agents
Authors: Perry M. B. , Heung Laura L. W.
Published: December 2009

The synthesis of the 2-nitro-4-azidophenyl glycosides of β-D-galactopyranose, β-D-glucopyranose, β-cellobiose, and 1-thio-β-D-galactopyranose is described and the properties of these photochemically active affinity labelling agents are recorded.
Mechanism of Biological Action of a New Benzindazole Compound
Authors: Chesnut R. W. , Haslam D. F. , Durham N. N. , Berlin K. D.
Published: December 2009

A new hydroxybenzindazole compound containing nitrogen in the 11 and 12 positions inhibited growth of Bacillus subtilis W23 and Escherichia coli but showed little effect on Pseudomonas fluorescens NND when added to the growth medium in concentrations up to 86 μg/ml. However, P. fluorescens cells grown in the presence of the benzindazole lysed during continued incubation. Inhibition and lysis were both concentration dependent. The benzindazole compound showed enhanced antibacterial action when used in combination with selected antibiotics. The methoxybenzindazole was an equally effective inhibitor. Results suggest that the benzindazoles act at the cell surface producing a reversible distortion in the molecular architecture which disorganizes but does not destroy the integrity of the membrane structure.
Amino Acid Metabolism in Plants. II. Transamination Reactions of Free Protein Amino Acids in Cell-Free Extracts of Cotyledons and Growing Tissues of Bushbean Seedlings (Phaseolus vulgaris L.)
Authors: Forest J. C. , Wightman F.
Published: December 2009

The different transaminase reactions for 22 protein amino acids were investigated in extracts of cotyledons and growing tissues of 8-day-old bushbean seedlings when either α-ketoglutarate, oxaloacetate, pyruvate, or glyoxylate was used as amino group acceptor. The results indicate that both cotyledons and growing tissues exhibited a similar pattern of transaminase activities with respect to the amino acids normally required for protein synthesis. It was found that with the exception of proline, hydroxyproline, and cystine which did not appear to be transaminated, and of serine and threonine which were transaminated only when pyruvate or glyoxylate was provided as the amino group acceptor, all the other 17 amino acids were transaminated to different extents when each of the four keto acids tested was supplied as the amino group acceptor. Glutamic acid, aspartic acid, and alanine were, by far, the best amino group donors and α-ketoglutarate was generally found to be the best amino acceptor. Consideration is given to the number and substrate specificity of the aminotransferases catalyzing the reactions demonstrated in this study.
In Vivo Incorporation of Labeled Acetate into Liver and Serum Lipids of Rate on Different Dietary Regimens
Authors: Serdarevich B. , Carroll K. K.
Published: December 2009

Incorporation of intravenously injected 1-14C-acetate into lipids of liver and serum was studied in suckling rats and in rats fed commercial or semisynthetic diets containing no added fat, 15% butter, or 15% corn oil. Incorporation into liver cholesterol was higher on commercial than on semisynthetic diets and was stimulated by addition of corn oil to either diet. Incorporation into fatty acids did not parallel incorporation into cholesterol in the different dietary groups. Serum lipids tended to show a pattern of labeling similar to that of liver. Suckling rats showed low incorporation into both cholesterol and fatty acids. In general, these results correspond to the findings of earlier in vitro studies.
Biochemical and Structural Changes in Mitochondria and Other Cellular Components of Pea Cotyledons During Germination
Authors: Solomos T. , Malhotra S. S. , Prasad S. , Malhotra S. K. , Spencer Mary
Published: December 2009

Integrated studies comprising biochemical and electron microscopic analysis suggested that the increase in respiratory activity of pea cotyledon mitochondria during germination results from further development of the original mitochondria present in dormant seeds. Electron microscopy of isolated mitochondria as well as mitochondria in situ has revealed that membranes are scarce in the mitochondria present in dormant seeds. Mitochondrial cristae become well developed during the initial stages of germination. Crude mitochondrial preparations from pea cotyledons were fractionated by sucrose density gradient centrifugation and analyzed through electron microscopy. These studies showed that, at all stages of germination, "peroxisome"-like structures were present in the fractions of higher sucrose densities than that containing mitochondria. Biochemical studies revealed that the activities of catalase (H2O2:H2O2 oxidoreductase, EC 1.11.1.6) and peroxidase (guaicol:H2O2 oxidoreductase, EC 1.11.1.7) were associated mainly with these fractions and their activities increased during germination.
Ouabain-induced Seizures in Rats: Regional and Subcellular Localization of 3H-Ouabain Associated with Na+–K+-ATPase in Brain
Authors: Donaldson J. , Minnich J. L. , Barbeau A.
Published: December 2009

Previous observations on clonic and tonic seizures in rats induced by intraventricular injections of ouabain, Zn2+, or Cu2+ have been expanded and confirmed. Tritiated ouabain was injected intraventricularly to rats and its regional distribution studied in the brain. The hippocampus and hypothalamus were found to be the regions with highest accumulation of radioactivity. This was supported by the in vitro finding that synaptosomes from both these regions demonstrate the highest uptake of the labelled ouabain. Subcellular fractionation experiments following in vivo injection of 3H-ouabain revealed that maximal radioactivity is associated with synaptosomal membrane fractions rich in Na+–K+-ATPase.
Association of Rabbit Antibody
Authors: Mamet-Bratley Margaret D.
Published: December 2009

The weak association of rabbit antibody, specific for the 2,4-dinitrophenyl group attached to lysine, proceeds through the dimer to the trimer stage and is characterized by ideal behavior.
Multiple Forms of Phosphoglyceromutase from Chicken Breast Muscle
Authors: James Eric , Hurst R. O. , Flynn T. G.
Published: December 2009

Phosphoglyceromutase (2,3-diphospho-D-glycerate: 2-phospho-D-glycerate phosphotransferase, EC 2.7.5.3) has been purified from both frozen and fresh chicken breast muscle. During purification it was found that substrate, 3-phospho-D-glycerate stabilized the enzyme against heat inactivation to almost the same extent as did the cofactor 2,3-diphospho-D-glycerate.Phosphoglyceromutase prepared from frozen chicken breast muscle separated into three peaks of activity (I, II, and III) following chromatography on DEAE-Sephadex in 0.05 μ phosphate buffer, pH 8.0, using a 0.0–0.4 M NaCl gradient. Each peak of activity was shown by polyacrylamide disc gel electrophoresis at pH 9.3 to contain two enzymically active components (isoenzymes Ia Ib, IIa IIb, and IIIa IIIb). Isoenzymes in the same peak had the same specific activity. Phosphoglyceromutase prepared from fresh chicken breast muscle yielded only one peak of activity following chromatography on DEAE-Sephadex. This peak contained two enzymically active components corresponding to isoenzymes Ia and Ib. Additional peaks of activity were not produced when phosphoglyceromutase from fresh muscle was subjected to freezing and thawing.Isoenzyme Ia and mixtures of Ia and Ib, IIa and IIb, and IIIa and IIIb were homogeneous in the ultra-centrifuge sedimenting as single peaks. The sedimentation coefficient obtained for isoenzyme Ia and for Ia and Ib combined was 4.15 S, the diffusion constant 6.62 × 10−7 cm2/s, and the molecular weight calculated from both gel filtration and sedimentation data was of the order of 59 000. These results were confirmed by charge isomer studies which also showed that the isoenzymes of phosphoglyceromutase from frozen chicken breast muscle were proteins of the same size but different net charges.
Mechanism of Oxidation of Tetrahydropterins
Authors: Archer M. C. , Vonderschmitt D. J. , Scrimgeour K. G.
Published: December 2009

The oxidation of tetrahydropterins and 7,8-dihydropterins by ferric iron has been examined by both polarographic and spectral techniques. Quinonoid dihydropterin, an intermediate in the oxidation of the tetrahydropterins, is formed rapidly, as is ferrous iron. The quinonoid dihydropterin then rearranges to 7,8-dihydropterin. The rate of oxidation of 7,8-dihydropterins is much slower than that of tetrahydropterins. The reduction potential of the reversible quinonoid dihydropterin – tetrahydropterin couple has been measured and shown to be consistent with the known chemistry of these compounds. Kinetic measurements and structural studies have been used to formulate a mechanism for the oxidation of tetrahydropterins to quinonoid dihydropterins. This mechanism involves abstraction of an electron from position 5, followed by rapid loss of two protons and the other electron.
Reduction of Folate by Ti3+
Authors: Kawai M. , Scrimgeour K. G.
Published: December 2009

Both folate and 7,8-dihydrofolate can be reduced by TiCl3, but the reduction of dihydrofolate requires a temperature above 30°. The reaction of folate with Ti3+ proceeds with rapid formation of a complex between the metal and the pterin coenzyme, with a stoichiometry of 2 Ti: 1 folate. Kinetic experiments have shown that the reduction of folate takes place as a slower reaction, after the formation of the intermediate complex. A possible structure of the intermediate and mechanism for the reduction reactions is presented.
The Conjugated Estrogens. II. A New Method for Isolating Estriol Monoglucosiduronide from Normal Human Pregnancy Urine
Authors: Cohen Saul L. , Oran Erkut
Published: December 2009

Estriol glucosiduronide has been prepared from normal pregnancy urine both as sodium salt and as the free carbonyl forms by a new and simple five-step procedure: (i) precipitation by ammonium sulfate of the conjugated estrogens from the urine; (ii) preparation of a methanol–acetone (M–A) solution of the conjugated estrogens from the ammonium sulfate precipitate; (iii) filtration through columns of Sephadex G 25 of the combined M–A residues from large batches of urine, which yielded the starting material for the work presented in this paper, namely peak four of the six estrogen peaks thus obtained; (iv) the conversion to the carbonyl form by a "Kellie" extraction at pH 2.0–2.5; and (v) crystallization of the acid or of its sodium salt from the semi-crystalline residue.
Parameter Evaluation in Second-Degree Rate Equations for Enzyme-Catalyzed Reactions
Authors: Bunting John W. , Murphy Joe
Published: December 2009

An iteration technique has been developed for fitting curves to experimental data for velocity dependence on substrate concentration in enzyme-catalyzed reactions which give rise to second-degree rate equations. Initial estimates are required for only two parameters; these estimates may differ from acceptable values for these parameters by several orders of magnitude without influencing the convergence of the iteration process. Applications of the technique to specific sets of experimental data are given, and the independence of the values for each of the final parameters on the values of the initial parameter estimates is demonstrated.
COMPARISON OF FRAMES: JORDAN VERSUS EINSTEIN FRAME FOR A NON-MINIMAL DARK ENERGY MODEL
Authors: NOZARI KOUROSH , SADATIAN S. DAVOOD
Published: December 2009

We construct a dark energy model where a scalar field non-minimally coupled to gravity plays the role of the dark component. We compare cosmological consequences of this non-minimal coupling of the scalar field and gravity in the spirit of the dark energy paradigm in Jordan and Einstein frames. Some important issues such as phantom divide line crossing, existence of the bouncing solutions and the stability of the solutions are compared in these two frames. We show that while a non-minimally coupled scalar field in the Jordan frame is a suitable dark energy component with capability to realize phantom divide line crossing, its conformal transformation in the Einstein frame does not have this capability. The conformal transformation from Jordan frame to Einstein frame transforms the equation of state parameter of the dark energy component to its minimal form with a redefined scalar field and in this case it is impossible to realize a phantom phase with possible crossing of the phantom divide line.
CYCLIC NANOINDENTATION OF SEMICONDUCTOR AND METAL THIN FILMS
Authors: FANG TE-HUA , CHANG WIN-JIN , LIN CHAO-MING , CHANG CHUN-CHIN
Published: December 2009

The nanoindentation technique was used to measure the hardness and Young's modulus of semiconductor and metal thin films on a Si(100) substrate under cyclic loading. The results showed that in all instances and at a constant cyclic load that the loading curves overlapped the previous unloading curve and had a small displacement after each cyclic nanoindentation. It was observed that the plastic energies of metal materials from the first loading–unloading cycle were much larger than that observed in semiconductor materials. Furthermore, the hardness and Young's modulus of the thin films decreased when the number of cyclic nanoindentations was increased. The effect of the cyclic loading on the hardness and Young's modulus of semiconductor material was much larger than that of the metal material. Young's modulus, the hardness and the contact stiffness of thin films conform to the relationship that Young's modulus was proportional to the contact stiffness and the square root of the thin film's hardness.