bluuebunny/crossref_metadata_2025_split huggingface dataset:
Untersuchungen zur Induktion der Lac‐Enzyme
Authors: Boos W. , Wallenfels K. 
Published: March 2005

1‐O‐β‐d‐Galactopyranosyl‐d‐glycerol was shown in a previous publication [1] to be an abnormal inducer. It has a maximal activity even at 10−7 M [2] whereby no autocatalytic phase can be observed. On addition of galactose the quoted abnormal behaviour of the inducer galactosyl glycerol is normalized. From these data it was concluded that for this particular case galactose competes with galactosyl glycerol for a lac‐operon independent permease.We could now show that the abnormal behaviour of the inducer galactosyl glycerol also disappears when a bacterial strain is used which lacks the gen MGP for the methyl galactoside permease. This gen maps outside the lac operon of the Escherichia coli chromosome [4] and his expression is constitutive under the conditions of the experiment. In order to prove the responsibility of the methyl galactoside permease for the abnormal behaviour of galactosyl glycerol as inducer we measured the accumulation of galactosyl glycerol in uninduced cells of E. coli K 12 W 3100 and W 3092i, MGP+‐ and MGP−‐strains respectively. It could be shown that in fact the strain W 3100 accumulates galactosyl glycerol whereas the strain W 3092i does not.Since derivatives of galactosyl glycerol are probably the most abundant galactosides in nature it seems likely that galactosyl glycerol is the main natural galactoside substrate during the evolution of the “Lac” operon.
Modification of Folic Acid‐Induced Changes in Renal Nucleic Acid and Protein Synthesis by Actinomycin D and Cycloheximide
Authors: Threlfall G. , Taylor D. M. 
Published: March 2005

Parenteral administration of folic acid to rats produces marked increases in the rates of synthesis of protein, RNA and DNA in the kidney. Basic nuclear protein synthesis is increased within 1 hour of folate administration with a sharper increase appearing about 18 hours and reaching a maximum about 26 hours. RNA synthesis increases to reach a maximum at 12 hours after folate before declining to normal levels at 24 hours. The increase in the rate of DNA synthesis commences at about 18 hours and reaches a maximum, about 20 times above control levels, about 32 hours after folate.Using the increased rate of DNA synthesis normally seen 26 hours after folate as a reference point, actinomycin D was found to produce a very marked depression of DNA synthesis when administered between 0 and 4 hours after folate; at longer time intervals this depression became less marked and when actinomycin D was given at 20 hours no effect was observed. Actinomycin D, given at the same time as folic acid, also abolished the increase in the rate of RNA synthesis normally seen 12 hours after folate.In contrast to the time dependent effect of actinomycin D, cycloheximide produced a similarly profound decrease in the rate of DNA synthesis, measured 26 hours after folate, when the drug was given at any time between 0 and 25 hours after folate.These results suggest that the complete requirement for increased RNA synthesis has been met by the time that increased DNA synthesis begins at 18 hours after folate administration, but that there is continuous need for newly synthesised protein both before and during the period of increased DNA synthesis.
Interactions of Glucagon and Insulin on the Metabolism of Perfused Livers from Fasted Rats
Authors: Menahan L. A. , Wieland O. 
Published: March 2005

Glucagon (28 nM) stimulated gluconeogenesis, urea production and ketogenesis in perfused livers from fasted rats. Since the livers were perfused without added substrate, liver protein is the source of carbon of the glucose synthesis. Addition of N6, O2′‐dibutyryl cyclic adenosine 3′:5′‐monophosphate in concentrations of 100 and 10 μM to the perfusion medium resulted in a response similar to that of glucagon. It is suggested that cyclic adenosine 3′:5′‐monophosphate is the mediator of glucagon action in liver.Preperfusion of the isolated livers with insulin diminished the glucagon effects. The glucagon‐stimulation of glucose and urea production was completely suppressed, while the increased ketogenesis was inhibited by 60% in the presence of insulin. Since all three glucagon responses were inhibited, this supports the concept that insulin lowers, in some way, the elevation of cyclic adenosine 3′:5′‐phosphate which occurs following glucagon administration. That insulin does not exert its effect subsequent to cyclic adenosine 3′:5′‐phosphate is suggested by the observation that insulin, under the same conditions which inhibited the response of liver to glucagon, had little or no effect on the increases in gluconeogenesis, ureogenesis, and ketogenesis following, dibutyryl cyclic adenosine‐3′:5′‐phosphate. Since an effect of insulin on cyclic adenosine 3′:5′‐phosphate phosphodiesterase seems unlikely, it is suggested that the inhibition of glucagon responses by insulin is the result of an interaction at the adenyl cyclase or one of the step(s) between binding of the hormone and the enzyme.
Mise en évidence du mécanisme d'action de l'éthacrynate de sodium sur des mitochondries de foie de rat
Authors: Foucher B. , Geyssant A. , Goldschmidt D. , Gaudemer Y. 
Published: March 2005

The competition of ethacrynate with phosphate shown during oxidation of succinate by rat liver mitochondria [2] is confirmed by measuring [14C]ethacrynate incorporation into mitochondria: on increasing the phosphate present during preincubation, less ethacrynate is incorporated into the mitochondria and there is a decrease in the inhibition of succinate oxidation.Ethacrynate exhibits different effects according to the substrate used:a) with NAD‐linked substrates, ethacrynate inhibits the oxidation, this inhibition being insensitive to phosphate and accompanied by complete oxidation of NADH to NAD+;b) with succinate, as already mentionned, the inhibition is sensitive to phosphate; if rotenone is present during preincubation with ethacrynate, there is oxidation, but it is an uncoupled oxidation, while, with phosphate plus ethacrynate, the oxidation is still coupled. Methylene blue added during preincubation with ethacrynate and rotenone prevents the uncoupling and reestablishes the inhibition of oxidation. As with NAD‐linked substrates, the inhibition of oxidation by ethacrynate is accompanied by complete oxidation of NADH to NAD+;c) with TMPD + ascorbate (plus rotenone), ethacrynate completely uncouples oxidative phosphorylation; again phosphate prevents this effect. Ethacrynate inhibits the [32P]Pi‐ATP exchange reaction.The presence of Mg++ ions is required in order to get maximal effect of ethacrynate: the more Mg++ ions present, the greater is the inhibition (succinate oxidation measurement).The results presented in this paper are discussed on the basis that the primary action of ethacrynate is a phosphate‐sensitive uncoupling action.The fact that inhibition of NAD‐linked substrate oxidation is not sensitive to phosphate suggests that ethacrynate interferes in another way with these substrates.However, by depleting mitochondria of energy‐rich compounds, the penetration of these substrates (assumed to be an energy requiring process) would be inhibited by ethacrynate and, consequently, the oxidation of these substrates would be impossible.As a thiol reagent, ethacrynate is believed to react with specific proteic thiol groups implicated in the formation of an energy‐rich intermediate, and to compete with phosphate in the formation of a phosphorylated energy‐rich compound from a non‐phosphorylated energy‐rich compound.
Effect of Hyper‐ and Hypoinsulinism on the Metabolism of Ethanol in Rat Liver
Authors: Rawat A. K. 
Published: March 2005

Administration of insulin to normal fed male rats resulted in a significantly increased rate of ethanol oxidation by liver slices as compared to the control animals. The rate of ethanol oxidation by liver slices from alloxan diabetic and anti‐insulin serum treated rats was significantly lower than normal.
Administration of ethanol to normal, insulin treated and alloxan diabetic animals caused a similar relative increase in the NADH/NAD ratio as measured by 4 different extra‐ and intramitochondrial redox pairs. After ethanol administration to alloxan diabetic rats, the hepatic redox state was very much reduced.
Intravenous injection of ethanol (1.5 g/kg body wt.) after 30 min resulted in significantly increased concentration of plasma free fatty acids. The ethanol induced increase in plasma free fatty acid level, like that of alloxan diabetic and anti‐insulin serum treated animals was significantly lowered following insulin injection.
The total activities of hepatic alcohol dehydrogenase and aldehyde dehydrogenase were significantly decreased, after alloxan treatment. The enzyme activities in the insulin treated group were of the same magnitude as in control animals.
Partially purified rat liver alcohol dehydrogenase and aldehyde dehydrogenase were inhibited by free fatty acids. Laurate had a stronger inhibitory effect than palmitate and oleate. The inhibition of alcohol dehydrogenase was competitive with respect to alcohol and not with respect to NAD. The inhibition of aldehyde dehydrogenase was competitive with respect to aldehyde and not NAD.
Addition of laurate (0.8 mM) to liver slices caused a significant decrease in the ethanol oxidation rate.
Translocation of some Anions Cations and Acids in Rat Liver Mitochondria
Authors: Mitchell P. , Moyle J. 
Published: March 2005

Studies of net translocation of various anions and cations and their corresponding acids and bases, using extensions of established techniques, imply that the M phase of the cristae membrane of rat liver mitochondria is very impermeable (i.e. not permitting net permeation) to the following ions: CH3COO−, H2PO4−, HPO42−, SO42−, Fe(CN)63−, Fe(CN)64−, choline+, K+, Na+ and NH4+. How‐ever, the M phase appears to be permeated rapidly by SCN− and slowly by Cl−.It has been confirmed that CH3COO− and NH4+ probably permeate as CH3COOH and NH3 respectively, and that phosphate equilibrates across the M phase by an electrically neutral mechanism equivalent to H3PO4 translocation. The possibility that phosphate is obligatorily translocated as KH2PO4 has been eliminated.Sulphate equilibrates by an electrically neutral mechanism equivalent to H2SO4 translocation.The alkali metals Na+ and K+ (and possibly NH4+) equilibrate across the M phase via specific electrically neutral H+/Na+ and H+/K+ antiport, the former being the more active at neutral pH. Choline does not participate significantly in proton‐coupled antiport.
Die “freien” Lipide aus Brucella abortus Bang
Authors: Thiele O. W. , Kehr W. 
Published: March 2005

Two different strains of Brucella abortus, strain 1119 and strain Scherle II, were grown on solid media; strain 1119 was harvested after approximately 70 h, strain Scherle II was harvested at different ages of the culture up to 72 h. The “free” total lipids were extracted and from these the neutral lipids were prepared and analyzed. The following results were obtained.Strain 1119 contains 4.5% free lipids of bacterial dry weight. Strain Scherle II contains decreasing amounts of free total lipids from approximately 6% to 1.4% as the age of the culture increases.On a weight basis the free total lipids of strain 1119 contain 8.1% neutral lipids. The neutral lipids of strain Scherle II decrease from more than 60% to approximately 24% (of free total lipids) with increasing age of the culture. The amount of phospholipids, however, remains comparatively constant (in relation to the percentage of total lipids) with increasing age of the culture of strain Scherle II. The results indicate that polar lipids other than phospholipids accumulate as the age of the culture increases, but there is no net storage of lipids.The neutral lipids of strain 1119 contain approximately 30% (on a weight basis) of ubiquinone‐50 (corresponding to 1.2 μmoles/g bacterial dry weight). Strain Scherle II also contains ubiquinone‐50, but in amounts demonstrable by thin‐layer chromatography only after an age of 36–38 h. Ubiquinone‐50 has hitherto been found only in a few bacterial species, while most bacterial species contain lower isoprenologs of ubiquinone.The neutral lipids of strain 1119 contain 51% (on a weight basis) of diglycerides, consisting of the 1,3‐ and the 1,2‐isomers. In strain Scherle II only 1,2‐diglycerides were found. The component fatty acids of the diglycerides of strain 1119 consist of approximately 55% (on a weight basis) of C19 cyclopropane acid (lactobacillic acid).The lactobacillic acid/cis‐vaccenic acid ratio is fairly independent of the age of the culture of strain Scherle II.The amount of unesterified fatty acids is lower in strain 1119 (4.9% of the neutral lipids, on a weight basis) than in strain Scherle II (49 or 67%, according to the culture conditions).Both strain 1119 and strain Scherle II contain probably small amounts of triglycerides, monoglycerides and long‐chain hydrocarbons.The possible significance of the results in the classification of Brucella is discussed.
Comparaison de la composition chimique d'une fraction lipopolysaccharidique et d'une fraction polysaccharidique isolées de Brucella melitensis
Authors: Lacave C. , Asselineau J. , Serre A. , Roux J. 
Published: March 2005

Westphal's procedure was found the most suitable for the isolation of lipopolysaccharide fractions from Brucella melitensis cells; only the fraction obtained in the aqueous layer (LPS) is studied in this paper. Beside LPS, an extracellular polysaccharide fraction (PS) was extracted from the culture medium of the bacteria, and the chemical composition of both fractions, LPS and PS, has been compared.In both cases, nucleic acid contaminants were eliminated either by alcohol precipitation or by use of cetavlon. These treatments also removed an acidic polysaccharide containing mainly galactosaminuronic acid, which might be Vi antigen.The main difference between LPS and PS is the presence of a small amount of lipid A in LPS (ca. 1%). As in the case of lipid A isolated from LPS of Enterobacteria, Brucella lipid A contains glucosamine and fatty acids, but β‐hydroxymyristic acid could not be detected.The behaviour of LPS and PS fractions on DEAE‐cellulose columns is very similar, and the small differences that could be observed may be explained by solubility changes due to the lipid moiety present in LPS.Both fractions contain 2‐keto‐3‐hydroxy‐octulosonic acid, a mixture of d‐ and l‐glycero‐d‐mannoheptoses, a high amount of glucose, galactose, a 3,6‐dideoxyhexose (colitose or abequose), and a methylated sugar behaving as a methylated derivative of dideoxyhexose. Small amounts of rhamnose in PS and of arabinose in LPS seem to be due to contaminants.
Artspezifität Polysaccharid‐haltiger Zellmembran‐Antigene von Dictyostelium discoideum
Authors: Gerisch G. , Malchow D. , Wilhelms H. , Lüderitz O. 
Published: March 2005

In the course of studies on species‐specific cell aggregation in the cellular slime molds, the specificity of heat‐stable surface antigens was investigated. With phenol–water, antigens could be extracted from freeze‐dried amoebae of Dictyostelium discoideum, the serological reactivity of which is insensitive to ribonuclease, pronase and α‐amylase; however, it is sensitive to periodate. Serological reactivity of phenol–water extracts was traced to a fraction which contains N ‐acetyl‐glucosamine, fucose, mannose and polypeptide, and behenic acid as the principal fatty acid. The polysaccharide moieties of these compounds are considered to carry the serological specificities. In comparing the two species, Dictyostelium discoideum and Polysphondylium pallidum, it was found that the non‐dialyzable fraction of the phenol–water‐extracts contain different proportions of the three sugars (mannose–fucose–N ‐acetyl‐glucosamine in D. discoideum 1:4.5:12; in P. pallidum 1:1:2). Species‐specificity of the phenol–water extracted antigens of the two species was demonstrated by precipitation with the respective antisera.With the fluorescent antibody technique and by agglutination, species‐specific antigens which are periodate sensitive could be detected on the surface of heat‐killed (2 h; 100°) cells. As revealed by agglutination inhibition, these heat‐stable cell surface antigens are identical, at least in part, with the phenol–water extracted antigens.
L'ATP : L‐arginine phosphotransférase de poids moléculaire élevé
Authors: Lacombe G. , Thiem N. v. , Thoai N. v. 
Published: March 2005

ATP:l‐arginine phosphotransferase has been isolated from Sipunculus nudus muscle; the preparation is homogeneous to analytical centrifugation, molecular sieving on Sephadex G‐100 and electrophoresis on cellogel and on polyacrylamide discs.Treated by 8 M urea, arginine phosphokinase from Sipunculus is dissociated into two subunits having the same molecular weight whereas arginine kinase from lobster gives no dissociation evidence. Furthermore the number of peptides shown on fingerprints of the tryptic hydrolysate of the first enzyme amounts to half of its lysine plus arginine residues. The enzyme from Sipunculus is named arginine kinase type II, to be distinguished from that of molecular weight near 40 000 (arginine kinase type I) and from that of molecular weight 160 000 (arginine kinase type III).Unlike arginine kinase type I which contains 6 total SH groups and a single reactive and essential SH, arginine kinase type II is found to have 12 total thiols and 6 SH groups reacting at the same rate with 5,5′‐dithio‐bis‐(2‐nitrobenzoic) acid or with N‐ethylmaleimide. From the numerous thiols similarly exposed results the particular autooxydisability and lability of the enzyme on study. No evidence is shown of the content of the disulfide bridges.Like arginine kinase type I, arginine kinase type II is strictly specific. The kinetics of the reaction are the same for both: no cooperative effect is observed between guanidine and nucleotide substrates fixation on the enzymes.
The Subcellular Distribution of Acyltransferases which Catalyze the Synthesis of Phosphoglycerides
Authors: Eibl H. , Hill E. E. , Lands W. E. M. 
Published: March 2005

The distribution of acyltransferase activities in rat liver homogenates is described in relation to that for five other enzymes, each known to belong to a certain subcellular particle. Five different transfer reactions were studied with 1‐acyl‐sn‐glycero‐3‐phosphorylcholine, 2‐acyl‐sn‐glycero‐3‐phosphorylcholine, 1‐acyl‐sn ‐glycero‐3‐phosphoylethanolamine, 1‐acyl‐sn‐glycero‐3‐phosphate and sn‐glycero‐3‐phosphate as substrates, and different acyl‐CoA esters served as donors of acyl groups. Glucose‐6‐phosphatase and the acyltransferase activities studied were distributed with similar relative specific activities among the subfractions.The results indicated that:a) Acyltransferases were located in the microsomal membranes.b) Nuclei and mitochondria did not have acyltransferase activity under the conditions used in these experiments, which were optimal for microsomal acyltransferases.c) Plasma membranes appeared to have only a small amount of acyltransferase activity in comparison to that in the microsomal particles.d) All acyltransferase activities tested showed similar patterns of distribution.e) Acyltransferase activities may be useful in the future as marker enzymes for microsomal particles from tissues which do not contain glucose‐6‐phosphatase, but do contain the acyltransferase within the microsomal membranes.
Nuclear RNA Fractions Obtained by Sequential Extraction of Rat Liver Nuclei with Salt Solutions and their Relationship to Polysome‐Associated RNA
Authors: Drews J. 
Published: March 2005

Pulse‐labeled RNA from rat liver nuclei was fractionated by sequential treatment of purified nuclei with buffered salt solutions of different ionic strength in the presence of ribonuclease inhibitor prepared from rat liver cytoplasm. Two fractions of pulse‐labeled nuclear RNA were successively extracted from rat liver nuclei with 0.14 M NaCl, 0.001 M MgCl2 at pH 7.0 and pH 8.0, respectively. The labeled material isolated at pH 7.0 sediments between 6–16 S while the pulse‐labeled RNA extracted at pH 8.0 sediments in the range of 10–34 S. Both fractions are characterized by a high content in AMP. With respect to [32P]nucleotide composition, sedimentation characteristics and hybridizability, these fractions correspond closely to non‐ribosomal RNA associated with polysomes. When a third extraction is carried out at pH 8.0 in 0.3 M NaCl another rapidly labeled RNA component is obtained. This RNA sediments above 34 S, turns over more rapidly than the RNA species extracted in 0.14 M NaCl, and contains less AMP. As judged by [32P]base‐composition, sedimentation and hybridizability, this RNA component is not present in polysomes. The pulse‐labeled RNA remaining in the nuclei after three salt extractions comprises mainly ribosomal or ribosomal precursor RNA as well as DNA‐like RNA species which show little or no nucleotide sequence homology with polysome‐associated RNA.Since nuclear RNA species clearly different from polysome‐associated cytoplasmic RNA are released from nuclei only at a relatively high ionic strength and are retained at a physiologic salt concentration it is suggested that RNA species not designated to function in cytoplasmic protein synthesis are a priori bound more tightly to nuclear structures than those types of RNA which serve as vehicles for the nucleo‐cytoplasmic transfer of genetic information.
Purification and Some Properties of a Soluble DNA‐Dependent RNA Polymerase from Nuclei of Human Placenta
Authors: Mertelsmann R. 
Published: March 2005

More than 75% of the RNA polymerase activity of isolated nuclei from human placental tissue was found in the supernatant (20 min at 40000Xg) after incubation of the nuclear suspension for 24 hours at 0°, followed by 15 min at 37° and a further 15 min at 37° in the presence of 120 mM ammonium sulphate.
Chromatography of this soluble preparation on DEAE cellulose (0.64 mequiv./g) was carried out using a linear gradient from 100 to 500 mM ammonium sulphate. RNA polymerase activity, eluted at 300 mM ammonium sulphate, was fully dependent on added DNA template.
Some properties of human RNA polymerase at various stages of purification are described.
The process of solubilization is discussed.
The Mechanism of Laccase‐Catalyzed Oxidations: Kinetic Evidence for the Involvement of Several Electron‐Accepting Sites in the Enzyme
Authors: Malmström B. G. , Finazzi Agrò A. , Antonini E. 
Published: March 2005

The anaerobic reduction of fungal laccase by quinol and ferrocyanide has been studied in a stopped‐flow apparatus by measurements of the change in the absorbancy at 610 mμ associated with the reduction of the so‐called Type 1 Cu2+. With ferrocyanide the rate of formation of product was also measured.
The reoxidation of reduced laccase by molecular oxygen has been studied by the same technique.
The kinetics of reduction and reoxidation as well as of product formation has also been investigated in a series of experiments with both the reducing substrate and oxygen present. In addition, the effect of an inhibitor, fluoride, on the kinetics has been studied.
The results confirm earlier static experiments showing that laccase contains two electronaccepting sites other than Type 1 and Type 2 Cu2+. Type 1 Cu2+ is reduced rapidly enough to involve it in the catalytic reaction. However, it appears to be rapidly reoxidized only when the other electron‐accepting sites are also occupied. A mechanism involving the cooperation of several electron‐accepting sites is consistent with the kinetic results.