bluuebunny/crossref_metadata_2025 huggingface dataset:
An additional role for insulin in the control of fatty acid synthesis independent of glucose transport
Authors: Halperin M. L.
Published: December 2009

Glucose conversion into pyruvate and fatty acids was studied in epididymal adipose tissue incubated in vitro from normal, 36-h-fasted and fasted–refed rats.Insulin at optimal concentrations caused a 30-fold increase in the rate of glucose incorporation into fatty acids and an increased lactate/pyruvate output rate. Pyruvate, lactate, and N,N,N′,N′,-tetramethyl-p-phenylenediamine (TMPD) addition to this incubation medium resulted in a further 20–75% increase in the rate of fatty acid synthesis as well as a further increase in the pyruvate concentration of the incubation medium. These results suggested that it was the decreased pyruvate concentration secondary to the elevated NADH/NAD+ of the cytoplasm which limited further glucose conversion to fatty acid.With glucose as substrate, TMPD caused the medium pyruvate concentration to be at least as high or higher than that seen with insulin in both nutritional states. However, fatty acid synthesis rates were eightfold greater with insulin. Insulin in the absence of glucose caused a twofold increase in the fatty acid synthesis from pyruvate at a medium concentration of 250 μM in normal and 25 mM in the 36-h-fasted rat. Therefore, insulin augments the rate of fatty acid synthesis both by increasing the supply of substrate (pyruvate) and also by directly increasing pyruvate incorporation into fatty acid by a mechanism distinct from the known stimulation of glucose transport.In fat pads from fasted–refed rats incubated in the absence of exogenous substrate, the rate of fatty acid synthesis was doubled by insulin. This occurred when the rate of pyruvate output was half that in the control condition. This also suggests that insulin stimulated pyruvate conversion to fatty acid in the absence of the known augmentation of glucose transport by insulin.
Influence of the acceptor during transglucosylation by transglucosylamylase of Candida tropicalis
Authors: Nakamura L. K.
Published: December 2009

The nature of glucosidic substrates influences we fraction of glucosyl residues transferred to competing acceptors. This influence suggests that the mechanism of transglucosylation reactions catalyzed by transglucosylamylase involves the formation of intermediate ternary enzyme–glucoside–acceptor complexes. Evidence suggests that the ternary complex involving phenyl-α-D-glucose (PAG) forms and decomposes by a Random Bi Bi rather than by an Ordered Bi Bi mechanism. Polyhydroxylated compounds appear to compete better with water than do monohydroxylated substances for the acceptance of glucosyl residues that are transferred from PAG. Methanol and glycerol inhibit the breakdown of PAG noncompetitively. The alcohols have a higher affinity for the acceptor sites than does water. However, the slower decomposition rate of the alcohol ternary complex, in comparison to that of the water complex, reduces the overall breakdown rate of PAG.
Effect of phenobarbital on the development of fatty livers In choline-deficient rats
Authors: Chalvardjian A.
Published: December 2009

The increase in hepatic phospholipid pool induced by phenobarbital did not affect the hepatic accumulation of fat produced by feeding rats a choline-deficient diet for 4 days. This lack of effect suggests that phenobarbital administration does not increase the choline requirement of rats, and/or that phenobarbital and choline deficiency act on different loci within the hepatic cell independently of each other.
A magnesium-responsive defect of respiration and oxidative phosphorylation in skeletal muscle mitochondria of dystrophic hamsters
Authors: Wrogemann K. , Blanchaer M. C. , Jacobson B. E.
Published: December 2009

Skeletal muscle mitochondria were isolated in the presence and absence of the proteinase Nagarse from dystrophic hamsters of the BIO 14.6 strain, aged 45–196 days, and from normal hamsters. Mitochondria from the dystrophic animals prepared by glass-on-glass homogenization without Nagarse in 0.25 M sucrose – 1 mM EDTA, pH 7.4, did not differ from normal in their respiratory rate or capacity for oxidative phosphorylation. However, these functions were subnormal in mitochondria isolated with Nagarse from the same animals, both in the presence and absence of albumin. Respiration measured with an O2 electrode was reduced by 50–70% and the stimulation of O2 uptake normally seen after ADP addition was minimal or absent. This was most marked in mitochondria from young hamsters about 65 days old with muscle necrosis. The defect was ameliorated by addition to the Polarographie test system of an ATP trap or of Mg2+, one of the trap constituents. This ion, when added to the defective mitochondria prior to ADP and substrate, restored respiration and oxidative phosphorylation to values that did not differ significantly from those found with skeletal muscle mitochondria of normal hamsters.
Hemoglobin J Bangkok in a Chinese Canadian newborn
Authors: Pootrakul S. , Gray G. R. , Dixon G. H.
Published: December 2009

A fast (anionic) abnormal hemoglobin was detected in the cord blood of a Chinese Canadian baby of Cantonese descent, during a hemoglobin Bart's survey in newborns at the Vancouver General Hospital, B.C. The heterozygotes possessing this variant, the propositus and her father, showed normal hematological findings except for the presence of abnormal pigment. From the biochemical studies reported here it is evident that the glycine at the 56th residue in the β chain is substituted by aspartic acid, this mutation being identical to that previously designated as Hb J Bangkok (α2Aβ256 Gly→Asp).
The Effects of Sodium Bisulfite, Manganous Chloride, and 2,4-Dichlorophenol on Peroxidase-Catalyzed Oxidation of Indole-3-acetaldehyde
Authors: Yeh Ren , Hemphill Jr. Delbert , Sell Harold M.
Published: December 2009

The effects of pH, sodium bisulfite, manganous chloride, and 2,4-dichlorophenol (DCP) on horseradish peroxidase (HRP) catalyzed oxidation of indole-3-acetaldehyde (IAAld) and indole-3-acetic acid (IAA) were studied. The enzymatic system is inactive toward oxidation of these indole derivatives at neutral to alkaline pH, whereas addition of NaHSO3 restores enzymatic activity at alkaline pH. In contrast, NaHSO3 (or Na2SO3) inhibits HRP-catalyzed oxidation of IAAld at acidic pH. Some kinetic data are presented to show how the bisulfite ions are involved in HRP-catalyzed oxidation of IAAld. Manganous chloride and DCP are excellent catalysts for HRP-catalyzed oxidation of IAA but have no effect on oxidation of IAAld.
Studies on the Conformation of Glucagon
Authors: Epand Richard M.
Published: December 2009

Viscosity measurements of glucagon solutions at pH 11 demonstrate that the molecule has a compact shape in dilute aqueous solution. In more concentrated solutions gels are formed with time which have an antiparallel β-conformation, similar to that found in gels from acidic solution.
Sodium Ion Binding to Pepsin and Other Proteins
Authors: Clement G. E. , Siegel A. , Potter R.
Published: December 2009

The sodium ion binding to proteins was studied using a gel-filtration method employing coarse Sephadex G-25 and radioactive sodium 22. The proteins employed at various pH values were pepsin, pepsinogen, lysozyme, and β-lactoglobulin A and a mixture of A and B. As expected lysozyme did not exhibit sodium ion binding by this method at pH 5.45, while the sodium ion binding with β-lactoglobulin in the pH range 6–8.8 agreed quite well with previously reported data. The main emphasis of this work was to determine the sodium ion binding to pepsin in the acid pH range. At 0.01 M sodium ion concentrations, pepsin binds 0 mole sodium per mole protein at pH 3.4 and 5.0 mole sodium at pH 4.6. At comparable sodium ion concentrations, pepsinogen at pH 6.75 binds approximately three times as much sodium as pepsin. The advantages and disadvantages of employing the gel-filtration method for ion binding studies is discussed. Finally, the sodium ion binding data for pepsin will be used in the analysis of the titration curve of pepsin in the pH range 2–6 by modifying the Z value (charge on the protein at any pH) in the Linderstrøm–Lang equation.
Effect of Near-Ultraviolet Light on the Respiratory Chain of Escherichia coli
Authors: Bragg P. D.
Published: December 2009

Irradiation of a particulate fraction from E. coli with near-ultraviolet light destroyed NADH oxidase activity. This treatment did not affect markedly the levels of cytochromes b1 and o, and ubiquinone in this preparation. Cytochrome a2 was destroyed by irradiation. A progressive increase in the aerobic steady state level of cytochrome b1 reduction during irradiation confirmed that irradiation affected the cytochrome oxidase region of the respiratory chain. There was a second site of inactivation between substrate and cytochrome b1. This was indicated by lowered NADH:cytochrome b1 reductase activity. Partial reactivation of this activity was obtained by addition of ubiqumone-2 but not ubiquinone-8.
The Reactivity of the N-terminal Isoleucine of α-Chymotrypsin as a Function of Ionic Strength
Authors: Kurosky A. , Graham J. E. S. , Dixon Joan W. , Hofmann T.
Published: December 2009

The reactivity of the α-amino group of isoleucine-16 of α-chymotrypsin towards nitrous acid at pH 4.0 and 0° is strongly dependent on ionic strength. Third-order deamination rate constants at low ionic strength (μ = 0.1 M) are 500–1000 times higher than those at high ionic strength (μ = 5.0 and 6.0 M) and are independent of the nature of the ions and the chymotrypsin concentration. Extrapolation to zero ionic strength of a plot of the logarithms of the constants against ionic strength leads to a value which is the same as that for the exposed α-amino group of the model compounds isoleucylvaline and valylvaline, and of the N-terminal isoleucine of pepsin. The deamination rate constant of the dipeptide valylvaline varies only two- to three-fold between ionic strength of 0.1 M and 6 M. The results suggest that the concept of a "buried" N-terminal as shown by X-ray analysis (carried out at pH 4.2 and ionic strength 9–11 M) requires modification; at low ionic strength (0.1 M) the reactivity of the N-terminal is only little below that of an exposed amino group, a fact which suggests that the amino group is much more available than shown by the X-ray analysis. The results are interpreted in terms of an effect of the ionic strength on the equilibrium between two conformational states of the enzyme.
Alkaline and Acid Ribonucleases of Kidney and Spleen of Nephrotic Rats
Authors: Nicholls D. M. , Bishay Edward S.
Published: December 2009

Alkaline ribonuclease activity (pH 7.8) was markedly decreased in all the fractions of kidney homogenates from nephrotic rats compared to the fractions of kidney homogenates from control rats. In contrast to the active alkaline ribonuclease activity at pH 7.8, the latent alkaline ribonuclease activity at pH 7.8 was increased in fractions from homogenates of nephrotic kidney due to increased ribonuclease inhibitor activity. In liver from nephrotic rats, however, there was no decrease in pH 7.8 alkaline ribonuclease activity and no increase in alkaline ribonuclease inhibitor. Alkaline ribonuclease activity at pH 9.5 and acid ribonuclease activity (pH 5.8 and 4.8) were also decreased in fractions from homogenates of kidney from nephrotic rats but not to the same degree as pH 7.8 alkaline ribonuclease activity. In fractions from homogenates of spleen, only small changes in ribonuclease activity were noted in nephrotic rat preparations compared to control rat preparations.
Synthesis of Unsaturated Fatty Acids in Chick Embryo Liver
Authors: Donaldson W. E. , Mueller Nancy S.
Published: December 2009

Oxidation, synthesis, and desaturation of fatty acids were assessed in chick embryos and embryonic liver. No differences in the oxidation of palmitate-1-14C and oleate-1-14C by intact embryos and embryo-liver homogenates were found. De novo fatty acid synthesis and microsomal elongation of fatty acids were detected in embryo-liver homogenates, but the activities were low as compared with chick liver. The specific activities of the mitochondrial system of fatty acid elongation were similar in embryo and chick liver. Stimulation of the desaturation of stearic acid was achieved by the substitution of glucose for fatty acids in the culture medium and abolished by the addition of cyclopropene fatty acids to the medium. The hypothesis is advanced that in chick embryos, the rate of desaturation of fatty acids synthesized de novo is less than that of postembryonic liver, and that as a consequence, the liver of embryos cannot maintain the proportion of unsaturated to saturated fatty acids found in yolk.
Hepatic Ketogenesis During Development
Authors: Lee Leo P. K. , Fritz Irving B.
Published: December 2009

Livers from fetal rats were shown to have lower rates of ketogenesis from acetate, acetylcarnitine, pyruvate, octanoate, and palmitate than liver preparations from adult animals. The enzymes required for ketogenesis from acetyl-CoA were demonstrated to be nonlimiting in fetal livers. The maximal ketogenic activity by disrupted mitochondria incubated with an acetyl-CoA-generating system was one-third or more of that observed in liver mitochondrial fractions prepared from adult rats.The enzymes required for fatty acid oxidation were also shown to be present in liver mitochondria from fetal rats. Although rates of ketogenesis from octanoate and palmitate were low, ketogenesis from octanoylcarnitine was over 60% of that observed in liver mitochondria from adult rats.During late fetal development and shortly after birth, the maximal hepatic ketogenic-forming activity increased rapidly, with the increase occurring completely in mitochondrial and not in cytosol fractions. The enzymes involved with ketone body formation were shown to remain within mitochondrial particles which had been stripped of their outer membranes. Levels of carnitine acetyltransferase were measured in livers from developing rats, and results were compared with previous observations on changes in activities of carnitine palmitoyltransferase.
Fatty Acid Synthesis from Pyruvate in White Adipose Tissue: the Effect of Norepinephrine
Authors: Halperin M. L.
Published: December 2009

Pyruvate incorporation into fatty acids has been studied in epididymal adipose tissue taken from normal and 24-h-fasted rats. This rate was limited by the rate of cytoplasmic NADPH2 generation as suggested by three lines of evidence.(1) D-Glucose-12C increased pyruvate-U-14C incorporation into fatty acids threefold. This augmentation was independent of L-glycerol 3-phosphate concentrations as the level of this metabolite was not increased. Addition of lactate-U-14C to the pyruvate medium increased the tissue L-glycerol 3-phosphate levels but did not increase the rate of fatty acid synthesis.(2) Phenazine methosulfate (2 μM) inhibited pyruvate or pyruvate plus lactate (L/P = 3/1) conversion to fatty acids whilst stimulating fatty acid synthesis from glucose or lactate alone.(3) Norepinephrine stimulated pyruvate but not glucose or glucose plus pyruvate incorporation into fatty acids. This correlated with norepinephrine-induced glycogenosis and NADPH2 production in the pentose phosphate pathway. This was shown by increased 1-14CO2/6-14CO2 production from endogenously labelled glycogen and the absence of this effect in glycogen-depleted adipocytes (24-h-fasted rats).
Biosynthesis of β-Cyanoalanine in Vicia sativa
Authors: Nigam S. N. , McConnell W. B.
Published: December 2009

Administration of cysteine-U-14C to Vicia sativa at the time of seed maturation resulted in extensive labeling of β-cyanoalanine. As extensive incorporation also occurred when cysteine-U-14C was given to the pods through the cut ends of their stalks, it is suggested that the synthesis of β-cyanoalanine takes place in this tissue. The effect of cyanide on the incorporation of serine-U-14C into glutamyl-β-cyanoalanine in Vicia sativa seedlings was also investigated. It was found that extensive incorporation of radioactivity occurred only when cyanide was given to the seedlings along with radioactive serine. Incorporation of radioactivity was much less when cyanide was added to the medium 8 h after the administration of serine-U-14C.
Changes in the Free Nucleotide Pool During Growth in Cultures of Polytoma uvella
Authors: Mangat B. S.
Published: December 2009

The nucleotide components of Polytoma uvella grown in shaken cultures have been examined, and fluctuations in their individual concentrations assessed during the three phases of growth. The most marked change in the nucleotide pool occurs between 30–58 h (end of lag and onset of log phase), when a relatively large increase was observed in the concentration of all the components; the most significant increases were in the nucleoside 5′-triphosphates, UDP-glucose, and ADP-glucose. Before the end of log phase the concentrations of CTP, ATP, GTP, and UTP had decreased whereas those of UDP-glucose and ADP-glucose did not do so until after the onset of the stationary period. At this time the concentration of pyridine nucleotide had increased. There was a predominance of purine nucleotides throughout the growth of the cultures and further, at all stages, a preponderance of adenine and uracil nucleotides existed over those of cytosine and guanine. By 144 h (late stationary phase) the concentration of each nucleotide had fallen considerably.
Resolution of Ring-Substituted Phenylalanines by the Action of α-Chymotrypsin on their Ethyl Esters
Authors: Tong J. H. , Petitclerc C. , D'Iorio A. , Benoiton N. Leo
Published: December 2009

The D- and L-isomers of the following ring-substituted phenylalanines have been prepared from the racemates in 60–80% yield: tyrosine, o-tyrosine, m-tyrosine, p-chlorophenylalanine, p-fluorophenylalanine, and 3,4-dihydroxyphenylalanine. The resolutions were effected by digestion of the racemic ethyl esters with α-chymotrypsin at pH 5.0 (pH-stat). The L-isomers were crystallized from the concentrated digests; the D-isomers were obtained by saponification of the remaining D-esters after extraction into ethyl acetate. Analysis of the isomers by column chromatography indicated optical purities greater than 99.5%. The racemic esters were prepared with ethanol/hydrogen chloride and were used without isolation.
The Reaction of Hemoglobin with the Complex Formed from Haptoglobin and Hemoglobin α-Subunits
Authors: Boyd N. D. , Smith David B. , Andrews Daniel
Published: December 2009

Mouse hemoglobin has been used to demonstrate that when hemoglobin interacts with the complex formed between haptoglobin and hemoglobin α-subunits, the α-subunits liberated are derived from the complex rather than from the added hemoglobin as had been suggested previously.
Separation and Properties of Isozymes of 3-Deoxy-D-arabino-heptulosonate-7-phosphate Synthetase from Saccharomyces cerevisiae
Authors: Takahashi Miho , Chan William W.-C.
Published: December 2009

The phenylalanine-sensitive and the tyrosine-sensitive 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthetases in yeast were separated by affinity chromatography and several properties of the separated isozymes were studied. The nature of the chromatographic process was also investigated. Both DAHP synthetases were inactivated by EDTA. The inactivation was reversed by Co2+ or Mn2+ and to a lesser extent by Zn2+. Phosphoenolpyruvate protected both enzymes from inactivation by EDTA or by heat treatment. Both enzymes showed a broad pH optimal range between 6.5 and 8.0 and a molecular weight of 65 000. The concentration of effector for 50% inhibition of each isozyme was approximately 5 × 10−5 M phenylalanine and 2 × 10−4 M tyrosine. A number of tyrosine and phenylalanine analogues also inhibited the enzyme reaction. Kinetic data were obtained for each of the separated isozymes both in the presence and in the absence of inhibitors. Considerable departure from Michaelis–Menten kinetics was observed in several instances. Our kinetic results are significantly different from those previously reported for the ammonium sulfate fractionated isozymes. These differences may be due to structural changes in the enzymes caused by the ammonium sulfate procedure.
Circular Dichroism Properties of Conalbumin and its Iron and Copper Complexes
Authors: Tan Ah-Ti
Published: December 2009

The effects of iron and copper binding on the circular dichroism (C.D.) spectrum of hen egg white conalbumin were investigated. Conalbumin showed positive C.D. bands at 251 and 191 nm and negative bands at 295, 291, 286, 276, and 210 nm. Upon binding iron, new bands at 460, 325, and 305 nm were generated and the ellipticities of the near ultraviolet (U.V.) bands were also greatly altered. No additional bands in the visible region were observed and the near U.V. bands of conalbumin were only slightly affected when complexed with copper. At neutral pH, conalbumin contained 28% helix, 32% β structure, and 40% random coil. The secondary structure of conalbumin was not affected by metal binding. The results suggest that the effects of copper and iron binding to conalbumin were only localized in the metal-combining sites.
Biosynthesis of Cardiolipin in Mitochondria
Authors: Davidson J. B. , Stanacev N. Z.
Published: December 2009

Conversion of sn-glycero-3-phosphate-2-3H to cardiolipin in mitochondria isolated from guinea pig liver has been established. Cardiolipin thus formed was isolated and characterized. Under similar conditions, microsomes were not able to catalyze the biosynthesis of cardiolipin in a detectable amount. The mechanism for the biosynthesis of cardiolipin in mitochondria, similar to that described in bacteria, is suggested. These results have established mitochondrial capability to synthesize polyglycerophosphatides.
The Influence of Starvation on Rat Liver Polysomes
Authors: Arora D. J. S. , de Lamirande G.
Published: December 2009

A 6-day starvation produced a marked effect on the ribosomal profile of rat liver by decreasing heavier polysomes and increasing lighter ones. When starved rats were refed for 24 h, a rapid formation of heavier polysomes was detected with a concurrent decrease in the lighter polysomes. On comparing the autodegradation capacity of the hepatic ribosomes of starved, starved–refed, and control animals, it was found that starved rats were about five times more active than starved–refed rats and 44% more active than the controls.
A Diagonal Paper Electrophoretic Method for the Selective Isolation of Histidyl Peptides
Authors: Cruickshank W. H. , Radhakrishnan T. M. , Kaplan H.
Published: December 2009

Thiolysis of an imidazolyl-dinitrophenyl-histidyl peptide at either pH 3.5 or 6.5 results in an increase in the net positive charge on the peptide. It is shown that this property can be used to form the basis of a diagonal paper electrophoretic purification of histidyl peptides from proteins. The amino groups of the protein are first reacted with citraconic anhydride and then the citraconyl protein is reacted with 1-fluoro-2,4-dinitrobenzene. The dinitrophenyl-citraconyl protein is digested with pepsin in 10% formic acid and, if necessary, with other proteolytic enzymes. The enzymatic digest is subjected to high-voltage paper electrophoresis at either pH 3.5 or 6.5. A guide strip is removed, thiolyzed with 2-mercaptoethanol, and subjected to electrophoresis at the same pH at right angles to the original direction of electrophoresis. The histidyl peptides are displaced off the diagonal toward the cathode. The off-diagonal peptides are isolated from the original electrophoretogram by thiolysis and electrophoresis using the diagonal electrophoretogram to locate the positions of the dinitrophenyl-histidyl peptides.
Reduction of Chymotrypsin Aα by Dithiothreitol
Authors: Stanton M. , Viswanatha T.
Published: December 2009

Treatment of chymotrypsin Aα with dithiothreitol (10 mM) at pH 9.2 in the presence of 8 M urea results in the complete reduction of the disulfide linkages of the protein. Reduction of a single disulfide bond of the enzyme can be achieved by treatment with 10 mM dithiothreitol at pH 9.2 in the presence of 100 mM hydrocinnamate. No such disulfide cleavage occurs in the case of indoleacryloyl chymotrypsin upon treatment with dithiothreitol.
Gas–Liquid Chromatographic Fractionation of Natural Diglycerides on Organosilicone-Polyester Liquid Phases
Authors: Kuksis A.
Published: December 2009

Synthetic and naturally occurring diglyceride mixtures were successfully resolved according to their carbon number and degree of unsaturation by gas chromatography on organosilicone-polyester (EGSS-X, ECNSS-M) packings containing low loads of liquid phase. The diglycerides were chromatographed as the trimethylsilyl ethers and acetates. Complete separations and apparently quantitative recoveries were achieved with both types of derivatives within 20–60 min isothermally at 250–270 °C for most diglycerides of the common fatty acids containing 0–6 double bonds per glyceride molecule. The retention times of the acetates were longer than those of the corresponding trimethylsilyl ethers by a period of time equivalent to about four methylene units. The 1,2(2,3)-diglycerides were eluted ahead of the 1,3-diglycerides of comparable molecular weight, unsaturation, and positional distribution of fatty acids.
A Proton Magnetic Resonance Study of the Molecular Conformation of a Modified Nucleoside from Transfer RNA. Dihydrouridine
Authors: Deslauriers Roxanne , Lapper R. D. , Smith Ian C. P.
Published: December 2009

The 220 MHz nuclear magnetic resonance (N.M.R.) spectra of dihydrouridine at 23 °C and 60 °C have been analyzed. From the N.M.R. data a conformational model is derived. The ribose moiety indicates a slight preference for the C3′exo and C2′endo conformations, although rapid interconversion between ring-puckered conformers is taking place. At high temperature the preference for C3′exo and C2′endo is less. The conformation of the exocyclic hydroxymethyl group is a rapid time average of all possible conformers with a preference for the gauche-gauche rotamer. By comparison with β-cyanuric acid riboside the chemical shifts of the ribose moiety in dihydrouridine are not influenced by the diamagnetic anisotropy of the keto group on the base, demonstrating that the base has the anti conformation with respect to the ribose ring. The dihydrouracil base does not exist in any of the classical puckered conformations, but manifests an average torsional angle of approximately 30° apparently due to rapid interconversion between various conformations. This distinguishes dihydrouridine from all other naturally occurring nucleosides, and may be the reason for its occurrence in almost all known tRNA species.
Specific Interaction of tRNA 3′-Terminal Nucleotidyl Transferase with Polynucleates
Authors: Igarashi S. J. , McCalla J. I.
Published: December 2009

E. coli tRNA lacking one or more of the 3′-terminal bases was prepared for use in the tRNA 3′-terminal nucleotidyl transferase system, by periodate–amine cleavage or by snake venom phosphodiesterase treatment. Optimal conditions for the transferase reaction with tRNA-pC and tRNA-pCpC and for detection of complexing of various nucleic acids to transferase were determined.Although R17 RNA-pC, R17 RNA-pCpC, and synthetic polynucleotides are unable to accept nucleoside monophosphates in the enzymic reaction, it was found that they are able to form complexes with the enzyme. The extent of binding depends inversely on the degree of base stacking in the synthetic polynucleotide. In keeping with this, melting of tRNA reduces both the CMP-accepting activity and the binding capacity. In competition studies, it was found that R17 RNA and tRNA compete with one another for binding, and that R17 RNA and to lesser extents, poly-U and poly-A, inhibit the transferase reaction with tRNA. Thermal studies, however, show that only tRNA can protect the enzyme from heat inactivation. These findings suggest that the recognition process for transferase and its nucleic acid substrate involves at least a two-step interaction. First, there is nonspecific binding which is followed by specific complex formation, an event which depends on the specific structure of tRNA.
Activity of Human Placental Sulfatase and 11β-Hydroxysteroid Dehydrogenase with Respect to Steroids of the Pregn-4-ene C-21-yl Sulfate Series
Authors: Hall C. St.-G. , Giroud C. J. P.
Published: December 2009

Sulfatase and 11β-hydroxysteroid dehydrogenase activities of human placenta were studied with respect to four steroids of the pregn-4-ene C-21-yl-sulfate series. Homogenates, as well as the microsomal fraction of placenta obtained either at midterm or at term, possessed negligible sulfatase activity with respect to the sulfates of 11-dehydrocorticosterone and corticosterone, and low but consistent activity towards 11-deoxycorticosterone sulfate. Under the same conditions dehydroepiandrosterone sulfate was hydrolyzed almost quantitatively.Placental homogenates converted cortisol to cortisone and corticosterone to 11-dehydrocorticosterone. The reaction was greatly enhanced by the addition of NADP. In contrast, the corresponding 11β-hydroxy-C-21 steroid sulfates were poor substrates with respect to placental 11β-hydroxysteroid dehydrogenase, as indicated by the low yields of the sulfates of cortisone and 11-dehydrocorticosterone, even in the presence of NADP. These findings are consistent with the pattern of steroids of the pregn-4-ene series characterized in human cord plasma.
Cytoplasmic Carboxylesterases of Human and Domestic Animal Liver: Aggregation, Dissociation and Molecular Weight Estimation
Authors: Ecobichon D. J.
Published: December 2009

The cytoplasmic carboxylesterases of bovine, ovine, equine and human liver were fractionated by starch gel electrophoresis and by gel filtration on Sephadex. While species-specific, heterogeneous bands were observed in starch gel, the esterases of the bovine, ovine and equine liver were eluted from Sephadex G-100 as single peaks of activity, each with a characteristic elution volume. Gel filtration of human liver extracts yielded two peaks of activity, one containing electrophoretically slow esterases, the other electrophoretically fast esterases. Extracted equine and human hepatic carboxylesterases aggregated readily on storage or concentration, forming larger units which could be dissociated by a combination of acidic pH and high salt concentration. Molecular weight estimates of the hepatic esterases by gel filtration on Sephadex G-100 and G-200 yielded values of 65 000 for ovine, 55 000 for bovine, 96 000 and 70 000 for equine variants and 180 000 and 65 000 for human variants. The observations suggested that the cytoplasmic enzymes in relatively crude hepatic extracts had a lower molecular weight than those in concentrated or partially purified preparations which formed stable dimers or trimers.
Factors Controlling Ketogenesis by Rat Liver Mitochondria
Authors: Lee Leo P. K. , Fritz Irving B.
Published: December 2009

Factors controlling the rates of ketogenesis by intact rat liver mitochondria have been investigated. High rates of ketone body formation were obtained with (−)-palmitoylcarnitine (20–120 μM) as substrate, but much lower rates were observed when pyruvate (0.33–1.66 mM) or (−)-acetylcarnitine (0.33–1.00 mM) was substrate. Concentrations of CoA-SH, acetyl-CoA, and long-chain acyl-CoA have been determined in mitochondria incubated with each of these substrates in the absence of metabolic inhibitors. In general, rates of ketogenesis increased as CoA-SH levels fell. Although acetyl-CoA concentrations increased in mitochondria incubated in the presence of low concentrations of (−)-palmitoylcarnitine (below 40 μM), they decreased when higher concentrations of (−)-palmitoylcarnitine were employed. This lowering of acetyl-CoA levels occurred concomitantly with an increase in concentrations of long-chain acyl-CoA and a decrease in CoA-SH levels.In soluble mitochondrial fractions obtained after sonication, CoA-SH addition inhibited acetoacetate formation. The ratio of [acetyl-CoA]/[CoA-SH] and the concentrations of CoA-SH were shown to be of greater importance in the regulation of ketogenesis than was the concentration of acetyl-CoA. Additional factors controlling rates of ketogenesis are discussed in relation to data presented. For example, the [acetyl-CoA]/[CoA-SH] ratio was considerably elevated when pyruvate or (−)-acetylcarnitine was substrate, but at such ratios the rates of ketogenesis were far lower than when (−)-palmitoylcarnitine was the substrate. It was calculated that the "apparent Km" of acetoacetyl-CoA for ketone body formation in intact rat liver mitochondria was approximately 10−9 M when (−)-palmitoylcarnitine was the substrate but it was significantly higher when (−)-acetylcarnitine and pyruvate were substrates.
The Optical Activity, Scattering, and Viscosity of Erythrocyte Membranes
Authors: Verpoorte Jacob A. , Smith Frances M.
Published: December 2009

The optical properties of erythrocyte membranes prepared by osmotic hemolysis in the presence of EDTA (ethylenedinitrilotetraacetic acid) were studied and found to be dependent upon salt concentration. Changes in optical rotation and circular dichroism as a result of addition of NaCl were accompanied by an increase in turbidity and a decrease in pH and viscosity of the membrane suspensions. Solubilization of membranes by sodium dodecyl sulfate (SDS) resulted in a lower viscosity and loss in turbidity but had little effect on optical activity. n-Butanol-extracted soluble membrane proteins had optical activities similar to those of salt-free membrane suspensions. Addition of SDS to membranes or extraction with butanol completely eliminated the salt effect on the rotation and dichroism spectra. It is proposed that salt reduces electrostatic repulsions between phospholipid molecules favoring the formation of a more compact membrane structure with reduced hydration.
The Time of Synthesis of Satellite DNA in Mouse Cells (L Cells)
Authors: Cohen A. K. , Rode H. N. , Helleiner C. W.
Published: December 2009

In mouse L cells growing in suspension and synchronized with 5-fluorodeoxyuridine, the ratio of the rate of synthesis of satellite DNA to that of major DNA reaches a peak 4 h after the onset of DNA synthesis. Since the duration of the period of DNA synthesis (the S-phase) under these conditions is shortened to about 4 h, the synthesis of satellite DNA occurs late in the S-phase.
Studies on C19 Steroid Metabolism in American Bullfrog (Rana catesbeiana) Adrenal Mitochondria
Authors: Mehdi A. Z. , Sandor T.
Published: December 2009

'Mitochondrial' preparations from adrenals of the American bullfrog (Rana catesbeiana) were incubated with 14C-labelled androstenedione (Δ4A) and testosterone (T) as model substrates in the presence of an NADPH-generating system. The conversion of Δ4A to 11β-OH-Δ4A and T was 1.4% and 0.8%, respectively. T was metabolized to 11β-OH-Δ4A (1.7%), 11β-OH-T (0.9%), and Δ4A (3.3%). All the above-mentioned metabolites were identified by isotope dilution techniques. From these results it appears that bullfrog adrenal 'mitochondria' possess 17β-hydroxysteroid oxidoreductase, though the adrenal tissue itself lacks 17α-hydroxy-lase activity.
Acetyl-1-14C-l-carnitine Oxidation, Carnitine Acetyltransferase Activity, and CoA Content in Skeletal Muscle Mitochondria from Normal and Dystrophic Mice (Strain 129)
Authors: Jato-Rodriguez J. J. , Lin C. H. , Hudson A. J. , Strickland K. P.
Published: December 2009

Mitochondria isolated from the hind leg muscle of normal and dystrophic mice (strain 129) were compared in their capacity to oxidize acetyl-1-14C-l-carnitine. Oxidation in the mitochondria from dystrophic animals was reduced by 80%. Carnitine acetyltransferase (EC 2.3.1.7) activity in the mitochondria was determined and showed a 35% reduction in the mitochondria from dystrophic muscle. A larger decrease (55%) was observed in the mitochondrial content of acid-soluble CoA. Although the combined decreases in carnitine acetyltransferase and CoA can largely account for the observed decrease in acetylcarnitine oxidation in the mitochondria isolated from dystrophic muscle, it is conceivable that some defect may still exist in the utilization of acetyl groups in the tricarboxylic acid cycle.
Calcium Binding Proteins in the Duodenal Mucosa of the Chick, Rat, Pig, and Human
Authors: Hitchman A. J. W. , Harrison Joan E.
Published: December 2009

A calcium binding protein has been demonstrated in human duodenal mucosa which we believe to be human vitamin D dependent CaBP. Sephadex gel filtration demonstrated that the duodenal mucosa of both the human and pig contained a calcium binding protein with a similar molecular weight to the reported vitamin D dependent rat CaBP (M.W. 12 000–13 000) but dissimilar to chick CaBP (M.W. 24 000–28 000). In addition the rat, pig, and human mucosa contained a high molecular weight calcium binding protein which is probably not vitamin D dependent.A relatively simple procedure, utilizing the tagging of CaBP by 47Ca, has been developed to partially purify normal pig CaBP by Sephadex gel filtration. Further fractionation of the 12 000–13 000 M.W. area, using disc electrophoretic procedures, separated two calcium binding proteins which had similar electrophoretic mobilities and calcium binding formation constants (3.5 and 5.5 × 106, respectively), indicating that both are forms of CaBP but that either one or both have been altered during the procedures. The electrophoretic mobilities of both of these proteins are relatively low in the presence of calcium ions but much greater when calcium ions are removed by chelation with EDTA. This finding should facilitate both the identification and purification of mammalian CaBP.
A Possible Role of Lipids in RNA Polymerase from Mammalian Cells
Authors: Menon I. A.
Published: December 2009

The effects of treatment with phospholipases and extraction with solvents on the activities of RNA polymerases from several rat tissues were studied. The RNA polymerase activity of particulate enzyme from rat liver nuclei was decreased by pretreatment of the enzyme with phospholipase A. The phospholipase decreased the RNA polymerase activity in presence of Mg2+ but not that in presence of Mn2+. The effect of phospholipase A was observed only at low ionic concentration. When the RNA polymerase activity was determined in presence of ammonium sulfate, KCl, or NaCl, phospholipase A did not decrease the RNA polymerase activity. Extraction of the RNA polymerase with ether or iso-octane decreased the RNA polymerase activity to approximately the same extent as the pretreatment with phospholipase A. Phospholipase C produced similar changes as phospholipase A but phospholipase D and lipase did not have any effect on the RNA polymerase activity. Treatment with phospholipase A as well as extraction with solvents enhanced the activity of chromatin-bound RNA polymerase from rat brain, and the RNA polymerase activities of similar preparations from spleen, kidney, heart, and lung were affected only to a relatively smaller extent.
Electron Paramagnetic Resonance Study of Single Crystals of Horse Heart Ferricytochrome c at 4.2 °K
Authors: Mailer Colin , Taylor C. P. S.
Published: December 2009

Electron paramagnetic resonance (E.P.R.) spectra from single crystals of horse heart ferricytochrome c at 4.2 °K were analyzed to obtain the orientation of the principal g values relative to the crystallographic axes. The axis of the largest principal g value (g3 = 3.06) was within 5° of the heme normal direction reported in the X-ray structure of the same crystals (Dickerson et al.: J. Biol. Chem. 246, 1511 (1971)). The other two g axes (g1 = 1.25, g2 = 2.25) lie within 5° of the N–Fe–N directions in the heme ring, in contrast to met-myoglobin azide (Helcké et al.: Proc. R. Soc. B169, 275 (1968)) and cyanide (Blumberg, W. E.: personal communication) where they lie ~ 45° from the N–Fe–N directions. A version of Eisenberger and Pershan's theory (J. Chem. Phys. 47, 327 (1967)) was used to explain the 400–2000 G variation in linewidth on crystal rotation. The results were explained by combining the broadening produced by a distribution of rhombic crystal field potential (r.m.s. deviation 11%) over the molecular population, with that from a variation in the directions of the principal g values caused by misorientation (r.m.s. deviation 1.5°) of the molecules in the crystal.
Comparison of the Transfer RNA Complements of Chick Embryos and their Supporting Membranes
Authors: Wainwright S. D. , Thompson Julia C. , Prchal J. F. , Tsay H. M.
Published: December 2009

The transfer RNA complement of 5- to 6-day chick embryos was compared with that of the associated membranes by chromatography of preparations of aminoacyl-tRNAs on columns of benzoylated diethyl-aminoethylcellulose. Profiles of all aminoacyl-tRNAs were determined under conditions selected for emphasis on the region containing a component believed to play a role in regulating onset of rapid hemoglobin synthesis in the blood islands of young blastodiscs. Differences in profile were observed only for alanyl- and glutamyl-tRNAs. A marked quantitative change in the distribution of components in the complement of glutamyl-tRNAs was in the converse direction of that required for increase in content of putative regulator and was not further investigated.Small reproducible differences in the profiles of alanyl-tRNAs were further investigated and were shown to be due to a marked increase in the content of a distinct minor component of the alanyl-tRNA complement of the membranes relative to that of the embryo.
Properties of the Endonuclease for Depurinated DNA from Escherichia coli
Authors: Paquette Y. , Crine P. , Verly W. G.
Published: December 2009

The purified Escherichia coli B41 endonuclease for depurinated DNA is strictly specific for apurinic sites; it has no action on DNA normal strands, or on strands carrying alkylated sites. The possible identity of this enzyme with endonuclease II, described as hydrolyzing alkylated and depurinated DNA, is discussed.
A High-Angle X-ray Diffraction Study of Red Cell Membranes after Treatment with Phospholipases A2 and C
Authors: Bernengo J. C. , Simpkins H.
Published: December 2009

Comparison of the high-angle X-ray diffraction patterns of hydrated red blood cell membranes after methanol, phospholipase A2, and phospholipase C treatment results in a more detailed understanding of the diffraction pattern obtained from untreated membranes. This study also presents more information as to the fate of the lipid and protein region of the membrane after the different phospholipase treatments. It reinforces the concept that phospholipase A2 treatment produces a structural change in the protein regions of the red cell membrane and that a structural change occurs in the lipid regions after phospholipase C treatment which may allow some of the cholesterol in the membrane to form crystallites.
Studies on the Control of Fatty Acid Synthesis in White Adipose Tissue of the Rat: Effect of Alanine
Authors: Halperin Mitchell L.
Published: December 2009

(1) Alanine resulted in inhibition of lipogenesis in adipocytes from normal fed rats incubated with glucose and insulin.(2) Two related mechanisms are suggested for the lower rates of lipogenesis caused by alanine metabolism. (a) Lower pyruvate levels were seen in the presence of alanine. This could contribute to the observed inhibition as pyruvate is an intermediate in the fatty acid synthesis pathway. Pyruvate levels were probably lowered as a result of the increased cytosol redox potential produced by high flow rates through malate dehydrogenase in this compartment, (b) Inhibition could be a consequence of depletion of malate in the cytosol which could limit the mitochondrial tricarboxylate carrier associated with citrate entry into the cytosol.(3) TMPD, an agent which lowers cytoplasmic redox potential, increased both the malate and pyruvate levels and increased the lipogenic rates nearly to normal in the presence of alanine.
EXPLORING THE COSMIC MICROWAVE BACKGROUND AS A COMPOSITION OF SIGNALS WITH KOLMOGOROV ANALYSIS
Authors: MIRZOYAN S. , POGHOSIAN E.
Published: December 2009

The problem of separation of different signals in the Cosmic Microwave Background (CMB) radiation using the difference in their statistics is analyzed. Considering samples of sequences which model the CMB as a superposition of signals, we show how the Kolmogorov stochasticity parameter acts as a relevant descriptor, either qualitatively or quantitatively, to distinguish the statistical properties of the cosmological and secondary signals.
SURFACE ANALYSIS OF MICRO-ARC OXIDIZED COATINGS DEPOSITED ON cp-Ti
Authors: KIM YEON-WOOK , NAM TAE-HYUN
Published: December 2009

The surface of commercially pure titanium (grade 4) was modified by micro-arc oxidation treatment. A porous TiO 2 coating layer was formed on the Ti surface and its crystal structure was analyzed as rutile phase. Both the thickness of the TiO 2 layer and the pore size on the surface were strongly dependent on the applied current density as well as the micro-arc oxidizing time during the oxidation treatment. When a current density of 50 mA/cm2 had been applied for 10 minutes, the thickness and the pore size of the oxide layer were 1.2 µm and 230 nm, respectively. The thickness and the pore size of the layer continued to increase with increasing the applied current density. The TiO 2 passive layer of the titanium surface can attribute to the excellent biocompatibility and the formation of nano-sized pores may maximize the interlocking between mineralized bone and the surface of the Ti implant.
A GENERAL TEMPLATE-FREE AND SURFACTANT-FREE SOLUTION-BASED ROUTE TOWARDS DENDRITIC TRANSITION-METAL SULFIDE NANOSTRUCTURES
Authors: LIU JUN , XUE DONGFENG
Published: December 2009

A template-free and surfactant-free hydrothermal method has been successfully developed to fabricate hierarchically dendritic metal sulfides ( PbS and CdS ). It has been found that the reaction temperature play important roles in the formation of well-defined sulfide dendritic nanostructures. A possible mechanism for the formation of present dendrites was proposed. The as-obtained transition-metal sulfide dendritic nanostructures may bring wide applications in optics, electricity, gas sensors, and other related fields. The synthetic route present in this work provides a new principle for the designing synthesis of dendritic metal sulfide nanomaterials and can be regarded as a general way to fabricate other metal chalcogenide materials.
EFFECT OF THE THROUGH-THE-THICKNESS TEMPERATURE DISTRIBUTION ON THE RESPONSE OF LAYERED AND COMPOSITE SHELLS
Authors: BRISCHETTO S.
Published: December 2009

This paper considers the thermal stress problem of thick and thin multilayered cylindrical and spherical shells including carbon fiber reinforced layers and/or a central soft core. The following two cases are considered: (i) the temperature distribution in thickness direction is assumed linear; (ii) the temperature distribution in thickness direction is calculated via Fourier's heat conduction equation. Carrera's Unified Formulation and the Principle of Virtual Displacements are used to obtain the governing equations in the case of shells with constant radii of curvature subjected to established temperature conditions on their upper and lower surfaces. Both Equivalent Single Layer and Layer Wise models with an order of expansion in the thickness direction from linear to fourth order are considered. The importance of refined models for a correct evaluation of displacement and stress fields in multilayered shells can be noted. Furthermore, it has been shown that results obtained assuming a linear temperature profile in the thickness direction can be meaningless.
BLOCK THRESHOLDING FOR A DENSITY ESTIMATION PROBLEM WITH A CHANGE-POINT
Authors: Chesneau Christophe
Published: December 2009

We consider a density estimation problem with a change-point. The contribution of the paper is theoretical: we develop an adaptive estimator based on wavelet block thresholding and we evaluate these performances via the minimax approach under the 𝕃p risk with p ≥ 1 over a wide range of function classes: the Besov classes, [Formula: see text] (with no particular restriction on the parameters π and r). Under this general framework, we prove that it attains near optimal rates of convergence.