bluuebunny/crossref_metadata_2025 huggingface dataset:
Acetylcholine reversal of potassium inhibition of amino acid transport in rat brain cortex slices
Authors: Nakazawa S. , Quastel J. H.
Published: December 2009

Acetylcholine reverses the inhibitory action of a high potassium ion concentration on glycine uptake into rat brain cortex slices incubated in a physiological Ringer–glucose medium. The effect of acetylcholine, which may take place at 0.02 mM, is enhanced by the presence of eserine which itself is without effect. Choline and hemicholinium at equivalent concentrations are also without effect. The reversing action of acetylcholine is specific, as it cannot reverse the inhibitory action of ammonium ions, ouabain, L-glutamate, or L-glutamine on glycine transport into the brain. As the presence of acetylcholine does not affect the ATP level, it is suggested that it acts by promoting the influx of sodium ions, which have a controlling effect on the amino acid influx.
Biosynthesis of chloramphenicol. III. Phenylpropanoid intermediates
Authors: McGrath R. , Vining L. C. , Sala F. , Westlake D. W. S.
Published: December 2009

L-p-Aminophenylalanine-α-14C:α-15N was shown to be a specific precursor of the p-nitrophenylserinol moiety of chloramphenicol produced by cultures of Streptomyces species. It was incorporated with only a small change in the 14C:15N ratio. Evidence was obtained for the presence of a small intracellular pool of p-aminophenylalanine. DL-threo-p-Aminophenylserine-carboxyl-14C and α-N-dichloroacetyl-Ls-threo-p-aminophenylserinol-hydroxymethyl-14C were also incorporated into the antibiotic without randomization of the label.
Mechanism of the bentonite flocculation technique
Authors: Wallace R. , Diena B. B. , Greenberg L.
Published: December 2009

Univalent fragments of anti-H and anti-O papain-treated globulins lost agglutinating ability, but retained the ability to inhibit both the bentonite and Widal reactions by intact H and O immunoglobulins. Bentonite flocculation, therefore, requires the presence of divalent antibodies for proper flocculation.
Triglyceride synthesis from various precursors in adipose tissue of the rat during development
Authors: Hahn P. , Greenberg R. , Dobiášová M. , Drahota Z.
Published: December 2009

The rate of incorporation of glucose-1- and -6-14C, pyruvate-1- and -2-14C, acetate-2-14C, citrate-1,5-14C, and NaH14CO3 into pieces of brown and white adipose tissue of fetal, newborn, and weaned rats was studied in vitro. Data indicate that brown adipose tissue becomes less important with age while the opposite holds for white fat. Gluconeogenetic reactions (glyceride glycerol formation) are accentuated in both fats in the suckling period, but more so in white adipose tissue. Fatty acid formation is also more pronounced in white adipose tissue from suckling rats. Oxidation of substrates is greater in brown than in white adipose tissue.
The lipids of Listeria monocytogenes
Authors: Carroll K. K. , Cutts J. H. , Murray E. G. D.
Published: December 2009

The Gram-positive bacterium Listeria monocytogenes was found to contain 6–7%, based on dry weight, of chloroform-soluble lipid, which consisted of neutral and polar lipids in a ratio of about 1 to 4. Diglycerides made up most of the neutral fraction and the polar lipids were mainly phospholipids of the phosphatidylglycerol type, together with a glycolipid containing glucose and galactose. The fatty acids consisted of straight- and branched-chain saturated acids, with C15 and C17 anteiso acids accounting for about 80% of the total. The same fatty acids were found in all fractions studied, but the proportions varied somewhat in different lipid classes.
Radioisotopic studies on the biosynthesis of the glyceryl diether lipids of Halobacterium cutirubrum
Authors: Kates M. , Wassef M. K. , Kushner D. J.
Published: December 2009

Cells of the obligate halophile Halobacterium cutirubrum were grown to the stationary phase in the presence of 32P-orthophosphate, 35S-sulfate, or 14C-labelled precursors (acetate, malonate, mevalonate, glycerol). 32P was incorporated into the phosphatide components in proportion to their relative concentrations, thus: phosphatidyl glycerophosphate (diether analogue) > unidentified minor phosphatide > phosphatidyl glycerol (diether analogue). 35S-Sulfate was incorporated mostly into the glycolipid sulfate ester component, but small amounts of 35S also appeared in a more polar sulfolipid and in a minor unidentified sulfolipid.14C-Mevalonate was the most efficient precursor for the phytanyl chains, followed in decreasing order by acetate and glycerol. Only traces of 14C from the malonate precursor were incorporated, and these appeared entirely in the phytanyl groups. A considerable proportion of 14C from the glycerol precursor was found in the glycerol and sugar moieties of the lipids. Little or no labelling of the water-soluble moieties of the lipids was observed with the other carbon precursors.Only traces of 14C-labelled fatty acids were detected with any of the 14C precursors; with acetate, in particular, only 0.3% of the 14C in the total lipids was found in fatty acids. It is concluded that the predominant biosynthetic route for the lipid chains is the mevalonate pathway for synthesis of isoprenoid groups, and that the malonyl-CoA pathway for synthesis of fatty acids is operating at a very low level of activity.
Mutual solubility of the lipid components of egg yolk low-density lipoprotein
Authors: Schneider Henry , Tattrie Neil H.
Published: December 2009

Several aspects of the mutual solubility of the lipid components of the low-density lipoprotein of egg yolk have been investigated. The phospholipids were slightly soluble in the anhydrous triglycerides but became completely insoluble when water was present. Cholesterol showed a preference for the phospholipid phase both in the presence and absence of water. This partitioning behavior was taken to support the postulates that (i) the physicochemical properties of the lipids and their interactions with water may play a major role in controlling their spatial arrangement in the native lipoprotein, and (ii) the native lipoprotein contains a nucleus of almost pure triglyceride devoid of phospholipids which is surrounded by phospholipids and cholesterol.
Further evidence of altered adrenocortical function in hypertension. Dehydroepiandrosterone excretion rate
Authors: Nowaczynski W. , Fragachan F. , Silah J. , Millette B. , Genest J.
Published: December 2009

The excretion of dehydroepiandrosterone glucuronide and sulfate was studied in a group of patients with essential hypertension and a group of normal subjects by a new single-label isotopic-dilution procedure. A very marked decrease in excretion of the sulfate was found in the patients with essential hypertension.
Fatty acid esterifying enzymes in rat adipose tissue homogenates
Authors: Daniel Anna M. , Rubinstein David
Published: December 2009

Some characteristics of enzymes in homogenates of rat adipose tissue concerned with esterification of fatty acids have been investigated. Acyl-CoA thiokinase is the most active of the enzymes studied, with optimal concentrations of palmitate and ATP being 2 mM and 25 mM respectively. The thiokinase has a pH optimum between 8 and 10 and reacts with fatty acids ranging in chain length from C4 to C22, with the greatest activity towards palmitate. About 50% of the activity is found in the 100 000 × g supernatant. Acyl-CoA : α-glycerolphosphate acyltransferase and acyl-CoA deacylase have pH optima between 7 and 8. Albumin at a concentration of 1% activates the former, while the latter is inhibited by concentrations of albumin greater than 0.5%. Deacylase activity is found almost entirely in the 100 000 × g supernatant. Both the acyl-CoA : α-glycerolphosphate acyltransferase and the acyl-CoA : diglyceride acyltransferase lose much of their activity upon fractionation. The pH optimum of the acyl-CoA : diglyceride acyltransferase ranges from pH 7 to 9, while that of the phosphatidc acid phosphatase is 6. The latter enzyme is distributed equally between particulate and soluble portions of the homogenate. When these enzymes are assayed in homogenates from fed and fasted animals, a significant alteration is found only in the level of acyl-CoA deacylase, which is decreased. The properties of these enzymes can be related to the extent and type of esterification in homogenates from fed and fasted animals.
Intensification of the xanthine oxidase activity of rat liver homogenates on storage
Authors: Blair D. G. R. , McLennan B. D.
Published: December 2009

The xanthine oxidase activity of rat liver homogenates increased severalfold when the homogenates were stored (aged) at 4 °C for several days. The increase could be demonstrated by measuring xanthine oxidase activity by xanthine utilization or allantoin formation from xanthine. The increase in activity was not correlated with the concentrations of allantoin, uric acid, xanthine, or hypoxanthine in the homogenates, and, therefore, is not attributed to decrease of substrate inhibition, but its demonstration was partially inhibited by relatively high concentrations of xanthine in the enzyme-assay reaction medium.The increase in xanthine oxidase activity was temperature-dependent and was unaffected by the presence of glucose or adenosine 5′-triphosphate. Lysis of unbroken cells during the aging period and microbial contamination were not contributory. Dialysis of a fresh homogenate partially inhibited the increase in activity, but the addition of the dialysate of an aging homogenate to a dialyzed or fresh homogenate did not stimulate activity.The mechanism of the increase in xanthine oxidase activity has not been elucidated, but the fact that stimulation of the activity by methylene blue decreases as the homogenates age, suggests that the rate at which reduced xanthine oxidase is oxidized by air may increase with homogenate aging.
Mammalian dihydroorotate – ubiquinone reductase complex
Authors: Miller Richard W. , Kerr Carolyn T. , Curry Jack R.
Published: December 2009

An L-dihydroorotate–ubiquinone reductase system was obtained from beef liver mitochondria in the form of a high molecular weight complex. Whole mitochondrial preparations of mouse liver and electron-transport particles of beef heart exhibited some cytochrome-linked oxidation of the pyrimidine precursor. Solubilization of the complex from beef liver by deoxycholate and subsequent purification largely removed cytochrome components and yielded a complex which was incapable of reducing oxygen. Non-heme iron, flavin, ubiquinone, and lipids were present in the complex. The exact role of each of these components in the linkage of dihydroorotate oxidation with parts of the respiratory chain is not known.A convenient and sensitive spectrophotometric assay for dihydroorotate oxidation based on the coupled reduction of 2,6-dichlorophenolindophenol by ubiquinone and possibly, to a much lesser extent, by other redox components of the complex was developed. This assay procedure was applicable to the whole particles as well as submitochondrial fractions. With the purified complex, ubiquinone-30 greatly stimulated the dye reaction. Since the dye reacts rapidly with detergent-dispersed reduced ubiquinone, it is likely that the cofactor represents an intermediate electron carrier in the reduction of the dye. Ubiquinone and other 1,4-quinones were catalytically reduced by dihydroorotate in the presence of the purified complex.
The venom of the honeybee (Apis mellifera): free amino acids and peptides
Authors: Nelson David A. , O'Connor Rod
Published: December 2009

The venom of the honeybee (Apis mellifera), obtained by electrical excitation, was fractionated by solvent extraction and gel filtration. The free amino acid and peptide content was determined by automated analysis. Less than 1% of the venom consisted of 19 free amino acids, while the minimum quantity of the 14 peptides was 15%. Two histapeptides were isolated and characterized. The sequence of histapeptide A was alanyl-glycyl-prolyl-alanyl-glutaminyl-histamine.
Specific inhibition by ATP and other properties of an endonuclease of Neurospora crassa
Authors: Rabin E. Z. , Mustard M. , Fraser M. J.
Published: December 2009

An endonuclease specific for single-stranded DNA and RNA was purified from Neurospora crassa conidia by the method of Linn and Lehman (J. Biol. Chem. 240, 1287 (1965)). The activity of the enzyme was measured by following the rate of release of acid-soluble material at 37 °C from either denatured (single-stranded) or native DNA. After an initial lag period, the length of which was inversely proportional to enzyme concentration, the release of acid-soluble material occurred at a rate which was directly proportional to enzyme concentration. Freshly purified enzyme catalyzed the release of acid-soluble material from denatured DNA 50–70 times faster than from native DNA. This ratio of activities increased to approximately 200 following storage at 0–4 °C. Throughout this "ageing" period 2 × 10−4 M ATP inhibited the activity of the enzyme toward both denatured and native DNA by 50%. The following nucleoside phosphates, at a concentration of 4 × 10−4 M, had no effect on the activity of the endonuclease toward denatured DNA: ADP, AMP, ITP, XTP, CTP, dTTP, and UTP. GTP at 4 × 10−4 M inhibited this activity by 15%. Both ATP and dATP at 1 × 10−4 M inhibited endonuclease activity against denatured DNA by about 25%. The inhibition by ATP was noncompetitive over the range of concentration 0.11–0.75 mg DNA per milliliter. Specific inhibition of nuclease activity by ATP has not been previously reported.Several other properties of the endonuclease were examined. There is evidence that endonuclease action was inhibited by accumulation of the products of digestion. The enzyme lost activity toward denatured DNA in a medium containing 0.3 M NaCl but activity was partially restored in the presence of 4 × 10−3 M mercaptoethanol. The endonuclease did not digest DNA–RNA hybrid to any appreciable extent.
Renal gluconeogenesis, adenine nucleotides, and enzyme activities
Authors: Patrick S. J.
Published: December 2009

Various drugs which alter rates of glucose production by rat kidney slices from pyruvate or other substrates were found to have marked effects on the relative contents of ATP, ADP, and AMP in the kidney slices. The effects of the changes in adenine nucleotide concentrations on the activity of key enzymes concerned with glycolysis and gluconeogenesis were investigated. The results generally support the concept that the drugs affect gluconeogenesis secondarily by altering the concentrations of the adenine nucleotides in the tissue.
The Inhibition of chymotrypsins A4 and B with chloromethyl ketone reagents
Authors: Stevenson Kenneth J. , Smillie Lawrence B.
Published: December 2009

The inactivation of chymotrypsin A4 and B by the bifunctional reagents L-(1-tosylamido-2-phenyl) ethyl chloromethyl ketone (L-TPCK) and phenoxymethyl chloromethyl ketone (PMCK) has been investigated. The rate of inactivation of chymotrypsin A4 with both reagents as a function of pH has been shown to be dependent on a basic group of pK = 6.3–6.5. Chymotrypsin B inactivation appears to be dependent on a basic group with a somewhat lower pK. For each enzyme the reaction with both reagents is associated with the loss of a single histidine residue. By the isolation and identification of 3-carboxymethylhistidine from the alkylated and oxidized peptic histidine-57 peptides, it has been concluded that both enzymes are alkylated at the nitrogen-3 position of histidine-57 by L-TPCK and PMCK. Evidence for the submolar alkylation of methionine-192 of chymotrypsin A4 by L-TPCK, PMCK, D-(1-tosylamido-2-phenyl) ethyl chloromethyl ketone (D-TPCK), and N-methyl-L-TPCK is presented. There is no alkylation of the histidine of chymotrypsin A4 by D-TPCK or.N-methyl-L-TPCK.From a comparison of the structures of a number of reagents known to alkylate chymotrypsin A4, it has been concluded that the alkylation of methionine-192 is nonspecific and relatively independent of any defined stereochemistry of the reagent employed. To date the alkylation of histidine-57 has been shown to occur only with haloketones, and is dependent on the distance between the haloketone and the aromatic ring when the latter is present. Although the presence of an asymmetric α-carbon and acylamido group in straight-chain reagents is unnecessary for histidine alkylation, these must be of the L configuration if present.
5-Methyltetrahydrofolic acid and other folate derivatives in germinating pea seedlings
Authors: Roos A. J. , Spronk A. M. , Cossins E. A.
Published: December 2009

The folate derivatives present in germinating pea seedlings were isolated by chromatography on DEAE-cellulose and assayed with Lactobacillus casei, Streptococcus faecalis, and Pediococcus cerevisiae. The major folate derivative in the cotyledons, developing embryos, and young leaves was identified as 5-methyltetrahydrofolate. Smaller amounts of 10-formyltetrahydrofolate were also present in these tissues. Synthesis of these derivatives in the cotyledons was inhibited by aminopterin. Feeding experiments showed that the 5-methyl derivative was rapidly synthesized from folic acid-2-14C.
Carbamyl phosphate synthetase in the chick
Authors: Maresh Charles G. , Kwan Theodore H. , Kalman Sumner M.
Published: December 2009

Carbamyl phosphate synthetase activity is present in the liver of the chick embryo and in the young chick. This enzyme activity is not dependent upon acetylglutamate and is not present in the mitochondrial fraction. Because the urea cycle is not present in chick liver and because of the developmental pattern of the enzyme activity, we infer that this enzyme is involved in pyrimidine biosynthesis.
Post-microsomal fractions from rat brain which stimulate ribosomal amino acid incorporation
Authors: Murthy M. R. V.
Published: December 2009

Post-microsomal fractions from rat brain were prepared which stimulated the synthesis of protein when endogenous mRNA was available and enhanced the synthesis of polyphenylalanine in the presence of poly-U and monomeric ribosomes. The amino-acid-activating (or transfer) enzymes did not appear to be responsible for the observed effect since the reaction mixture contained sufficient amounts of these enzymes to permit an optimum rate of amino acid incorporation. The effect was not solely due to the presence of messenger or amino acid transfer RNAs since the activity of the fractions was only partly reduced by prior treatment with ribonuclease. Heating led to complete inactivation of the fractions. Results from amino-acid-incorporation experiments and from sucrose density-gradient centrifugations indicate that the effect might be produced at two levels, one at the level of formation or preservation of polyribosomal structure and the other possibly at the level of peptide bond formation.
Human liver aldehyde dehydrogenase: partial purification and properties
Authors: Blair A. H. , Bodley F. H.
Published: December 2009

Aldehyde dehydrogenase was partially purified from human liver. During purification, activity was resolved into one major and one minor species by DEAE-cellulose column chromatography; the properties of the predominant form were investigated.Aldehydes are oxidized when NAD+, but not NADP+, is the electron acceptor, maximal activity occurring between pH 9 and 10. Several aliphatic aldehydes and hydroxyaldehydes served as substrates for the enzyme. Benzaldehyde also was oxidized, but at a comparatively low rate. Aliphatic aldehydes carrying negatively charged groups are not oxidized. The enzyme is sensitive to low concentrations of two sulfhydryl reagents, p-chloromercuribenzoate and mercuric ions; this inhibition was reversed with sulfhydryl compounds. Like other aldehyde dehydrogenases, the human liver enzyme is inhibited by arsenite and the inhibition is potentiated by mercaptoethanol. Only 35% inhibition was produced by disulfiram at 40 μM; and diethyldithiocarbamate, its metabolic reduction product, had no effect on activity below 10 mM.
The biosynthesis of 4-nydroxycoumarin by Penicillium jenseni
Authors: Spring M. S. , Stoker J. R.
Published: December 2009

Possible intermediates in the conversion of o-coumaric acid to 4-hydroxycoumarin have been fed to P. jenseni cultures. Although metabolized, none of the compounds was converted to 4-hydroxycoumarin. In addition, after feeding o-coumaric acid to cultures, 4-hydroxycoumarin was isolated but none of the postulated intermediates could be detected. It has been suggested that a β-oxidation pathway may be involved in the conversion of o-coumaric acid to 4-hydroxycoumarin, all intermediates being bound to enzymes.
A comparison of the effect of diet and of ethionine on rat liver histidine deaminase and urocanase
Authors: Kolenbrander Harold M.
Published: December 2009

Low levels of ethionine, when fed or injected, cause a marked decrease in the level of rat liver urocanase activity but produce a slight increase in the level of histidine deaminase (histidine ammonia-lyase, EC 4.3.1.3) activity. Fasting or feeding a protein-free diet results in decreased activities of both enzymes. These findings support the suggestion that ethionine does not inhibit urocanase through general inhibition of protein synthesis.Methionine, whether fed or injected, reduces the magnitude of the effect of ethionine on urocanase, but subcutaneously injected ATP and related compounds do not.
Intracellular mechanisms for the decomposition of a lipid peroxide. I. Decomposition of a lipid peroxide by metal ions, heme compounds, and nucleophiles
Authors: O'Brien P. J.
Published: December 2009

Linoleic acid hydroperoxide was prepared. Two types of mechanisms for its decomposition were found. The hydroperoxide was rapidly decomposed by certain transition metal ions, heme, and hemoprotein to a complex range of products, the decomposition being accompanied by changes in ultraviolet absorption spectra. The production of radical oxidizing species may account for these products. It was also found that the hydroperoxide could be decomposed by nucleophiles presumably in a nonradical reaction to a hydroxy acid without any change in ultraviolet spectra.The kinetics, the pH dependence, and the effects of metal-complexing agents, inhibitors, and hydrogen donors on the catalytic activity of the metal ions and heme compounds were also investigated.
Intracellular mechanisms for the decomposition of a lipid peroxide. II. Decomposition of a lipid peroxide by subcellular fractions
Authors: O'Brien P. J. , Little C.
Published: December 2009

The properties of subcellular fractions of rat liver in catalyzing the decomposition of linoleic acid hydroperoxide have been compared with those of transition salts, heme compounds, and nucleophiles. The properties compared included the range of products produced, the pH dependence of the reaction, and the effects of metal-complexing agents, inhibitors, and hydrogen donors. It was concluded that the decomposition of the hydroperoxide in the liver cell was due principally to reaction with the intracellular nucleophile glutathione by a mechanism catalyzed by the enzyme glutathione peroxidase. In the absence of glutathione, however, both the mitochondrial and microsomal fractions decomposed the hydroperoxide presumably by a radical mechanism probably involving the cytochromes.
The action spectrum of hemoprotein oxidase in Nitrobacter agilis
Authors: Hill Joan E. , Taylor C P. S.
Published: December 2009

A photochemical action spectrum for the relief by light of the carbon monoxide inhibition of respiration in Nitrobacter agilis (ATCC No. 14123) has been determined by the method of Castor and Chance, the first such determination in a chemolithotrophic organism. The cells were grown at 30 °C in liquid culture, were used when consuming 2–4 mM/ml per day of nitrite, and were concentrated by centrifuging. They respired actively at room temperature for about 3 h in air but only 75 min in the CO:O2 (4:1) mixture. Consistent γ and α bands of a hemoprotein spectrum were obtained from the combined results of two cultures. The maxima are at 432 ± 2 and 592 ± 2 nm; the γ/α height ratio is 6.4 (±22%) and the half-height width of the γ band is 15 nm. Since cytochrome a1 but not a3 has been reported in several Nitrobacter studies, the conclusion is that an a1-type cytochrome is a terminal oxidase in Nitrobacter agilis. The great scatter in the points around the β peak presumably results from the many cultures used, and possibly from differing oxidase activities in different phases of growth. The breadth of the peak could result from the presence of cytochrome o in some cultures. The possibility of more than one terminal oxidase is not excluded.
Multiple molecular forms of avian aldolases. I. Crystallization and physical properties of chicken (Gallus domesticus) breast muscle aldolase
Authors: Marquardt Ronald R.
Published: December 2009

Aldolase (fructose 1,6-diphosphate-D-glyceraldehyde 3-phosphate lyase, EC 4.1.2.13) was purified and crystallized from chicken (Gallus domesticus) breast muscle.The crystalline enzyme is homogeneous according to the following criteria: purification to a constant specific activity, electrophoresis on cellulose acetate strips, absence of five other glycolytic enzyme activities, and immunodiffusion in agar.The sedimentation coefficient, diffusion constant, and molecular weight of the chicken enzyme are the same as for rabbit muscle aldolase. The ultraviolet spectra of the two proteins are the same. Electrophoretic comparison between the rabbit and chicken enzymes revealed a slightly different rate of migration.Antibodies directed against the pure chicken enzyme were prepared, and the reaction with pure chicken and rabbit aldolase was followed using the precipitin and double diffusion tests. A very pronounced reaction was observed between anti-serum and the chicken enzyme; the rabbit enzyme, in contrast, did not cross-react with the anti-serum.
The occurrence of a soluble glucose 6-phosphatase in cotyledon tissue of Phaseolus vulgaris during germination
Authors: Thompson J. E.
Published: December 2009

Cotyledon tissue from seedlings of Phaseolus vulgaris at various stages of germination was homogenized and fractionated under isotonic conditions. Measurement of glucose 6-phosphatase (D-glucose 6-phosphate phosphohydrolase, EC 3.1.3.9) activity in the isolated fractions showed an increase in the level of soluble enzyme with advancing age of the cotyledons, such that by late senescence (10 days of age) approximately 90% of the recovered glucose 6-phosphatase was present in the soluble fraction, and its specific activity was about twofold greater than that of the homogenate. The pH profiles of the bound and soluble enzymes were found to be closely similar. The presence of a soluble glucose 6-phosphatase has been interpreted as indicating either de novo synthesis of the soluble form of the enzyme with advancing senescence, or solubilization of normally bound enzyme which may in turn reflect a partial breakdown in the structure of endoplasmic reticulum in senescent cells.
The structure, synthesis, analysis, and occurrence of 3-deoxy-D-manno-octulosonic acid
Authors: Williams D. T. , Perry M. B.
Published: December 2009

The structure of 3-deoxy-D-manno-octulosonic acid was confirmed by its reduction to 3-deoxy-D-glycero-D-galacto-octonic acid and 3-deoxy-D-glycero-D-talo-octonic acid which were identified by comparison with authentic acids. 3-Deoxy-D-manno-octulosonic acid was synthesized in good yield by the oxidation of 3-deoxy-D-glycero-D-galacto-octonic acid and 3-deoxy-D-glycero-D-talo-octonic acid prepared by the action of sodium cyanide on 2-deoxy-D-manno-heptose.A method has been developed for the quantitative determination of 3-deoxy-D-manno-octulosonic acid, involving gas chromatographic analysis of the direct products of trimethylsilylation using bis-(trimethylsilyl)trifluoroacetamide for its conversion to volatile stable derivatives. The gas chromatographic method has been used for the identification of 3-deoxy-D-manno-octulosonic acid in several gram-negative bacterial lipopolysaccharide preparations.
Amino acid composition of salmon calcitonin
Authors: O'Dor R. K. , Parkes C. O. , Copp D. H.
Published: December 2009

Calcitonin has been extracted from salmon ultimobranchial glands and purified. The amino acid composition indicates similarities to mammalian calcitonin but the salmon hormone has 25 times the biological activity of the most active mammalian material.
Utilization of ammonium ions for purine precursor synthesis in soluble extracts of Ehrlich ascites cells
Authors: Trachewsky D. , Johnstone R. M.
Published: December 2009

In extracts of Ehrlich ascites cells the synthesis of α-N-formylglycinamide ribonucleotide (FGAR), an early intermediate in de novo purine synthesis, is enhanced by the presence of ammonium ions. Under these experimental conditions glutamine participation in FGAR formation is not obligatory. Ribonucleotides, deoxyribonucleotides, and purine analogues which inhibit glutamine-dependent FGAR synthesis also inhibit ammonium-ion-dependent FGAR synthesis. 3′-Ribonucleotides do not inhibit purine precursor formation from ammonium ions or from glutamine.
Studies on plasminogen. VIII. Species specificity of streptokinase
Authors: Wulf R. J. , Mertz E. T.
Published: December 2009

Continuous-flow electrophoresis was used to isolate purified plasminogens from the serums of 10 species. The ratios of esterolytic to caseinolytic activity in the purified plasminogens with urokinase as the activator for the following animals were: rat 9.8, cow 6.6, pig 5.7, cat 3.5, sheep 3.4, mouse 3.3, rabbit 2.7, man 2.2, monkey 2.0, and dog 1.4. Plasminogen activation with streptokinase divides the species into three groups: (a) activated with small amounts of streptokinase (man, cat, monkey), (b) activated with large amounts of streptokinase (dog, rabbit), and (c) not activated (cow, sheep, pig, mouse, and rat). Streptokinase – human globulin mixture and urokinase activated all plasminogens equally well When the euglobulin fractions of the serums of nine of the ten species were subjected to starch gel electrophoresis at pH 2.5, groups a and b gave two major plasminogen bands, whereas c gave only one.
Inhibition by viomycin of cell-free protein synthesis in sensitive and resistant strains of Rhizobium meliloti
Authors: Alexander D. C. , Jordan D. C. , McKague M.
Published: December 2009

Viomycin at a concentration of 2–10 μg/ml inhibited cell-free polypeptide synthesis in both a viomycin-sensitive and a viomycin-resistant strain of Rhizobium meliloti when either natural messenger or polyuridylic acid (poly U) was employed. Consequently, viomycin resistance in the resistant bacterium is not the result of an inherently resistant protein-synthesizing system or of an intracellular modification of the viomycin molecule. The antibiotic did not prevent the formation of active poly U – ribosome complexes, but did inhibit the passage of 14C from 14C-phenylalanine-charged transfer RNA to these complexes.
Regulation of a salt-dependent enzyme: the aspartate transcarbamylase of an extreme halophile
Authors: Liebl V. , Kaplan J. G. , Kushner D. J.
Published: December 2009

A method of assay and a partial purification of the aspartate transcarbamylase of the extreme halophile Halobacterium cutirubrum have been presented. Activity was dependent on high salt concentration, optimal activity requiring 3–4 M NaCl or KCl. The enzyme was highly sensitive to retroinhibition by cytidine triphosphate; inhibition was also dependent on high salt concentration, but was independent of temperature of assay. The regulatory site was more resistant to heat inactivation than was the activity, unlike other bacterial and fungal aspartate transcarbamylases. Kinetics were Michaelian with respect to the substrates and to the inhibitor; there was no evidence of cooperative interactions.
The rhodanese enzyme of Ferrobacillus ferrooxidans (Thiobacillus ferrooxidans)
Authors: Tabita Robert , Silver Marvin , Lundgren D. G.
Published: December 2009

Extract of sulfur-grown Ferrobacillus ferrooxidans contains the thiosulfate-splitting enzyme rhodanese. Rhodanese was purified about 40-fold and was shown to have a wide pH optimum (pH 7.5–9.0). The Km for thiosulfate and cyanide was 5.8 × 10−4 M and 1.1 × 10−2 M, respectively. The enzyme was stable at 25 °C and was inhibited by the thiol-alkylating agents iodoacetamide and N-ethylmaleimide.
Multiple molecular forms of avian aldolases. III. Tissue distribution and properties of the predominant isozymes from chicken (Gallus domesticus)
Authors: Marquardt Ronald R.
Published: December 2009

The distribution of chicken (Gallus domesticus) tissue (muscle, oviduct, heart, brain, kidney, and liver) aldolase isozymes was established electrophoretically. Each tissue, being composed of varying proportions of six isozymes, has a distinct isozyme pattern. Brain, oviduct, and heart tissue possess five isozymes of aldolase: 1, 2, 3, 4, and 5. Leg and breast muscle of adults possess aldolase 5. Kidney and liver predominantly possess aldolase 6 with traces of isozymes 1–5. Aldolase 1 corresponds to aldolase C of mammals, 5 to aldolase A, and 6 to aldolase B.Antibodies to 5 react with 2, 3, and 4, but not with 1 and 6. Aldolase 5 hybridizes in vitro with 1 to form 2, 3, and 4. Aldolase 6 also hybridizes in vitro with 1 to form three intermediate hybrids, but these hybrids have not been detected in tissues. These observations imply that aldolase 1 (C) and 5 (A) are frequently synthesized simultaneously in the cell with the formation of the 2, 3, and 4 hybrids. Aldolase 6 (B), in contrast, may not be accompanied by the synthesis of other aldolases in the same cell. Pure preparations of aldolases 1, 5, and 6 were found to have similar molecular weights but different enzymatic properties.
The permissive role of cortisol in the regulation of rat liver tyrosine aminotransferase
Authors: Mavrides C. , Lane E. A.
Published: December 2009

The daily rhythm in the activity of rat liver tyrosine aminotransferase was abolished after 3 weeks of constant illumination. The rhythm reappeared only partially in rats bilaterally adrenalectomized immediately after the 3-week period and returned to a cyclic lighting schedule. The failure of the enzyme rhythm to reappear fully did not seem to originate in dietary factors since food consumption and rate of growth were similar in the adrenalectomized and sham-operated control rats. Developmental studies showed that the adult rhythm was absent in rats up to 15 days old but present in 21-day-old rats. Although the rhythm appears to be generated in part by the rhythmic intake of dietary amino acids, a role for the endogenous glucocorticoids was suggested by the finding that physiological amounts of cortisol played a permissive role in the stimulation of enzyme activity by amino acids (casein hydrolysate) in adrenalectomized rats. These amounts of cortisol greatly stimulated enzyme activity in rats fed a protein-free diet. A regulatory role for glucocorticoids based on this permissive action is envisaged in the daily rhythm of tyrosine aminotransferase.
Relation of polysome structure to ribonuclease and ribonuclease inhibitor activities in livers of magnesium-deficient guinea pigs
Authors: Grace Neville D. , O'Dell Boyd L.
Published: December 2009

The hepatic polysomes isolated from magnesium-deficient guinea pigs did not contain the 131 S ribosomal unit found in the polysomes of control animals that consumed an adequate magnesium diet ad libitum. A 64 S particle not present in the controls appeared in the deficient polysomes. Restriction of the adequate diet to the quantity consumed by the deficient animals (pair-fed) had no effect on the polysome pattern, but restriction so as to maintain the same body weight (pair-weighted) caused dissociation similar to that of magnesium deficiency. Alkaline ribonuclease activity determined on total homogenates and expressed on the basis of nitrogen concentration was significantly higher in the livers of the magnesium-deficient and pair-weighted animals than in animals pair-fed or ad libitum fed the control diet. Acid ribonuclease activity in the magnesium-deficient animals was also significantly higher than in the pair-fed and ad libitum fed controls. Dietary treatment had no significant effect on the concentration of ribonuclease inhibitor in the liver. It was concluded that the effect of dietary magnesium deficiency in decreasing polysome stability is indirect and may be induced as well by severely reduced food intake. However, restricting food intake to the level consumed by magnesium-deficient animals did not decrease polysome size. It is postulated that this difference is due to an effect of low extracellular magnesium on nutrient transport.
Combination chemotherapy: treatment of the Ehrlich ascites carcinoma and several drug-resistant sublines with combinations of 6-mercaptopurine and 6-(methylmercapto)purine ribonucleoside
Authors: Paterson A. R. P. , Wang M. C.
Published: December 2009

The antitumor activities of 6-mercaptopurine (6MP) and 6-(methylmercapto)purine ribonucleoside (Me6MPR) are synergistically enhanced when these two agents are used together against the Ehrlich ascites carcinoma (EAC). This report describes the response of four thiopurine-resistant EAC sublines to therapy with this drug combination. The four sublines were resistant to treatment with 6MP and Me6MPR, whether these agents were used separately or together. Characteristics of the resistant sublines suggest that (a) the synergism requires the formation of ribonucleotide derivatives of both agents, (b) the cytotoxicity of the drugs in combination is achieved by the same mechanisms that are responsible for the cytotoxic of the agents used separately, and (c) the mechanisms of action of the two agents are related.
Latent o-diphenol oxidase in mushrooms (Agaricus bisporus)
Authors: Yamaguchi M. , Hwang P. M. , Campbell J. D.
Published: December 2009

An inactive or latent form of o-diphenol oxidase (EC 1.10.3.1) which can be activated by 0.1% sodium lauryl sulfate was found in cultivated mushrooms. The latent form was found in the soluble fraction of the fruiting bodies and constituted almost 95% of the total o-diphenol oxidase. Freeze-dried and acetone preparations gave the highest yields of the latent enzyme. There was more activity in the stalks than in the caps, and the activity increased with maturity. The white, golden cream, and sobexas strains of mushroom contained the latent form of the enzyme.
Oxidation processes in relation to the induction of enzymes in Jerusalem artichoke tuber slices
Authors: Bastin Marcel , Dijkmans Huguette
Published: December 2009

The effect of diethyldithiocarbamate (DIECA) and ethylenediamine tetraacetate (EDTA) on the wounding-dependent induction of phenol oxidase and peroxidase in Jerusalem artichoke tuber slices has been investigated. DIECA which is a good inhibitor of oxidase reactions inhibits the induction of enzymes. EDTA which does not affect these reactions prevents the induction only at a concentration of 5 μmoles/ml. At a concentration of 1 μmole/ml, however, which stimulates the rate of oxygen uptake by the slices, EDTA also stimulates the induction of enzymes.The induction of enzymes was enhanced when slices were cultured in the presence of compounds having two neighboring carbonyl groups (dehydroascorbate, pyruvate, and oxalate).The rate of both induction and oxygen uptake increased with increasing intensity of slicing.
Ion exchange chromatography of 2-amino-2-deoxy-D-hexoses
Authors: Yaguchi M. , Perry M. B.
Published: December 2009

An amino acid analyzer is used to separate seven 2-ammo-2-deoxy-D-hexoses (allosamine, altrosamine, glucosamine, mannosamine, gulosamine, galactosamine, and talosamine). A borate citrate buffer at pH 7.24 is used at 60 °C. Acidic and neutral amino acids, if present, are eluted before any of the hexosamines.
L'oxydation de la prégnènolone en progestérone par des préparations de tissus des Orthoptères in vitro
Authors: Lehoux J.-G. , Chapdelaine A. , Sandor T.
Published: December 2009

Incubation of isotopically labelled pregnenolone with sliced testis tissue of adult Orthoptera (Gromphadorhina portentosa, Byrsotria fumigata, and Gryllus assimilis) in vitro has shown that these insect gonads are capable of transforming pregnenolone to progesterone. In addition, leg muscle preparations of Gryllus assimilis could also effect this transformation. In one of the experiments, pregnenolone gave rise to 20β-dihydroprogesterone. These studies demonstrated the presence of enzyme systems capable of oxidizing the steroidal 5-en-3β-ol function to 4-en-3-one structure in the three species investigated.
Characterization of amino acids and low-molecular-weight peptides bound to cytoplasmic granules from the posterior pituitary
Authors: Shin Seon , LaBella Frank , Queen Gary
Published: December 2009

A number of peptides and amino acids, representing 30–40% of the total acid-extractable, ninhydrin-positive material of the tissue, were associated with cytoplasmic granules (sedimenting at 3 000 000 g-min after preliminary removal of "nuclei and debris") isolated from bovine posterior pituitary glands. Acetic acid (0.2 N) extracts of a purified neurosecretory granule fraction showed only slight differences in the pattern of peptides and amino acids from extracts of the total cell particulate fraction. Gel filtration of extracts on Sephadex G-25 yielded three major fractions: fraction I consisting of peptide material of molecular weights > 4000, fraction II of molecular weights averaging about 3000, and fraction III of molecular weights < 2000. Fraction III was further resolved by anion-exchange chromatography into 12 subfractions. Vasopressin and oxytocin were contained in subfractions 2 and 3, respectively. Each of these subfractions was in turn chromatographed on a cation-exchange resin and resolved into a total for fraction III of 22 major components: lysine, arginine, phenylalanine, ammonia, and 18 peptides. Three of the peptides contained only aspartic and glutamic acids in the ratios 8:1, 5:1, and 4:1. The sequences of four dipeptides were ascertained. Another peptide was not retarded by Dowex 50 and yielded glutamic acid upon acid hydrolysis. Still another peptide yielded tyrosine plus an unknown ninhydrin-positive component after hydrolysis. The amino acid compositions were determined for nine other peptides containing three to nine residues. Additional peptides in fraction III were detected in lesser or trace amounts. Isolated granule fractions from both bovine posterior pituitary and rat liver were dialyzed against isotonic sucrose or distilled water. The rate of loss of ninhydrin-positive material from the sample dialyzed against water indicated that a large proportion of the "free" amino acids and peptides of these tissues were contained within intracellular organelles.
Effects of glacial acetic acid on the extraction, chemical stability, and biological activities of β-LPH
Authors: Chrétien M. , Gilardeau C.
Published: December 2009

Sheep β-lipotropic hormone (β-LPH) contains within its structure the complete amino acid sequence of γ-LPH. These two molecules have a sequence of amino acid entirely similar to βSer-melanophore-stimulating hormone (MSH). We have shown that β-LPH is not likely to be degraded into γ-LPH and β-MSH during the purification procedure, or by incubation in an acetic acid/acetone mixture at 50 °C for 20 min. Results are compatible with the hypothesis that β-LPH could be the biological precursor of β-MSH and that γ-LPH is an intermediate component.
Similar effects by valine and isoleucine on threonine deaminase
Authors: Harding W. M. , Tubbs J. A. , McDaniel Deborah
Published: December 2009

Isoleucine is known to be a very effective inhibitor and stabilizer of threonine deaminase. In contrast, valine has been reported to be a positive effector for the enzyme by action on a separate site. However, the apparent increase in activity caused by valine is due to stabilization of the enzyme. When stabilization is accomplished by other means, valine exerts only an inhibitory effect. Thus, valine, like isoleucine, both stabilizes and inhibits threonine deaminase and may well do so via the isoleucine site on the enzyme.
Spectrophotometry determination of gold in biological materials
Authors: Walton R. J. , Thibert R. J. , Bozic J. , Holland W. J.
Published: December 2009

A spectrophotometry method for the determination of low levels of gold(III) with di-2-pyridylketoxime was developed. A stable 2:1 (reagent/gold) water-soluble complex is formed having an absorption maximum at 433 nm and a molar absorptivity of 1.89 × 104. The Beer–Lambert law is obeyed up to 12 p.p.m. The proposed method was applied to the determination of gold in plasma and urine. The method is simple, reproducible, and relatively rapid.
Studies on the rapid cholesterol-depleting and steroidogenic actions of luteinizing hormone in the rat ovary: effects of aminoglutethimide phosphate
Authors: Behrman Harold R. , Armstrong David T. , Greep Roy O.
Published: December 2009

Superovulated, immature rats were administered luteinizing hormone (LH) and/or aminoglutethimide phosphate (AGP), an inhibitor of cholesterol side-chain cleavage, to ascertain whether the steroidogenic action could be separated from the cholesterol-depleting action of LH. The injection of AGP [Formula: see text] and [Formula: see text] before sacrifice significantly reduced tissue levels of progesterone and 20α-dihydroprogesterone to 25–30% of normal, and increased tissue levels of free cholesterol in the absence and presence of LH given [Formula: see text] or 4 h before sacrifice. Cholesterol ester concentration was increased twofold after [Formula: see text] AGP, whereas LH injection [Formula: see text] after AGP and 4 h before sacrifice reduced the tissue concentration to the control level but not as low as that observed when only LH was given 4 h before sacrifice (50% of control level). The cholesterol ester depletion induced by LH, even though steroidogenesis was inhibited, indicates that these may represent separate events in the action of LH on luteal tissue.
Aminoacyl-tRNA synthetases of Halobacterium cutirubrum: preliminary fractionation studies
Authors: Griffiths E.
Published: December 2009

The stability, in solutions of low ionic strength, of aminoacyl-tRNA synthetases from the extremely halophilic bacterium Halobacterium cutirubrum was studied as a preliminary to their fractionation. The enzymes differed considerably in their sensitivity to such solutions. Conditions were found where reactivation from the salt-free and inactive state could be achieved. Removal of both K+ and Mg2+ together generally resulted in better stability than the removal of K+ alone. A low temperature (4°) was also important for stability in buffers of low ionic strength. In some cases the L-amino acid substrates afforded protection against inactivation in the salt-free state. Gel filtration in low ionic strength medium was found to work well as a fractionation procedure; a partial purification of phenylalanyl-tRNA synthetase was effected in this way. The use of other conventional protein fractionation procedures is now possible.
The middle ultraviolet spectra of proteins. I. Studies on model compounds
Authors: A'zary Edward P. , Bigelow Charles C.
Published: December 2009

In order to facilitate a study of the middle ultraviolet (220–250 nm) spectra of proteins, an examination of the spectral properties of model compounds (histidine, phenylalanine, tryptophan, tyrosine, and related compounds) containing protein chromophores was first undertaken. The object was to evaluate the effect of changes in the solvent composition or pH on the spectra. Considerable numerical data were collected, which permit the following conclusions, (a) The addition of ethylene glycol, urea, or salts to an aqueous solution of these chromophores causes shifts in their spectra, with resultant difference spectra. Values at the extrema of these difference spectra are usually linear functions of the solvent composition. (b) The extrema of the middle ultraviolet spectra arising from changes in pH can be used to follow the protonation of titratable groups, (c) The solvent effects observed support the conclusions that the major absorption band of the aromatic compounds is due to a π-π* transition, and that a minor transition is involved in the spectrum of tyrosine.