bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Specific Radioactivities of Mononucleotides and Glycolytic Intermediates from Mouse Liver after Labelling in vivo with [32P]Orthophosphate
Authors: Till U. , Blume E. , Günther J. , Reich J.G. , Zahn D. , Klinger R. , Jaroszewicz K. , Frunder H. 
Published: March 2005

Experimental procedures and conditions are described for the determination of specific radioactivities of 16 different P‐positions in 12 phosphorylated liver compounds after labelling in vivo with [32P]orthophosphate. These data are necessary for calculations of flux rates within the mononucleotides and the glycolytic pathway.

Purification procedures for the following compounds are given: ATP, ADP, GTP, UTP, UDPG, glucose 6‐phosphate, fructose 6‐phosphate, fructose 1,6‐biphosphate, dihydroxyacetone‐phosphate, glycerol 3‐phosphate, phosphoglyceric acid and phosphoenolpyruvate.The purification of each compound consists of 3–5 chromatographic steps, in most cases including a specific enzymic conversion.
A preparation procedure is described for mouse liver which shows only a negligible artificial isotope exchange between the β‐ and γ‐P‐positions of ATP. This was proved by addition of labelled ATP to non‐labelled livers.
Five and ten min after intravenous injection of carrier‐free [32P]orthophosphate the specific radioactivities of the compounds examined show identical values, thereby excluding compartmentations with isotope kinetic relevance.
Thioredoxin. 6. The Amino Acid Sequence of the Protein from Escherichia coli B
Authors: Holmgren A. 
Published: March 2005

Peptide A, the C‐terminal cyanogen bromide fragment of thioredoxin, was degraded with chymotrypsin and pepsin. Partial sequences of 12 chymotryptic and 6 peptic peptides and the N‐terminal tryptic peptide of trifluoro‐acetylated peptide A were determined. The results were used to establish the order of the previously described tryptic peptides of peptide A and lead to the complete amino acid sequence of peptide A.Previous experiments had established the amino acid sequence of peptide B, the N‐terminal cyanogen bromide fragment of thioredoxin and the present results thus give the complete amino acid sequence of thioredoxin from Escherichia coli B. The molecule contains 108 residues in a single polypeptide chain with a molecular weight of 11,657 as calculated from the sequence. The functional group of the protein occurs in position 32 to 35 and consists of a disulfide bridge formed by two half‐cystine residues separated by a glycine and a proline residue. No metals were found as part of the functional group.
The Influence of Inorganic Phosphate, Adenosine Triphosphate and Glucose 6‐Phosphate on the Activity of Liver Glycogen Synthetase
Authors: de Wulf H. , Stalmans W. , Hers H. G. 
Published: March 2005

The important activation of liver glycogen synthetase which occurs after a load of glucose or after the administration of glucocorticoids and which could be demonstrated by assaying the enzyme in a concentrated liver homogenate [1,2], is due to the conversion of an inactive or b form of the enzyme into another form called a, which is active under physiological conditions. This conversion is similar to that previously shown to occur in vitro by Segal and his coworkers [7,8]. The native or b form is prevalent in the untreated animal and has a low affinity for UDPG and for glucose 6‐phosphate; it is active only in the presence of glucose 6‐phosphate but this activity is cancelled by Pi, sulfate, sulfite and ATP. Consequently it remains inactive in the concentrated liver homogenate, which is rich in Pi, and also in vivo, due to the intracellular concentrations of Pi and ATP. Glycogen synthetase a has a high affinity for UDPG and for glucose 6‐phosphate; it is stabilized by phosphate, sulfate and sulfite as well as by glucose 6‐phosphate. It is inhibited by ATP but this inhibition is mostly overcome by physiological amounts of Pi. It is therefore fully active in a concentrated homogenate and in vivo. Magnesium ions have on both forms of the enzyme an effect which is similar to that of glucose 6‐phosphate.Glycogen synthetase a is conveniently measured in a diluted liver homogenate in the presence of 10 mM sulfate; the activities found in these conditions correlate with those measured in a concentrated homogenate and therefore with the rate of liver glycogen synthesis in vivo. in the cell, Pi appears to be the most important activator of the enzyme, whereas glucose 6‐phosphate has only a minor role.
The Role of Glucose, Glucagon and Glucocorticoids in the Regulation of Liver Glycogen Synthesis
Authors: de Wulf H. , Hers H. G. 
Published: March 2005

The conversion of liver glycogen synthetase b into a in vivo, induced by glucose or by glucocorticoids, is further enhanced when both treatments are combined. Once activated, the enzyme is rapidly inactivated by an injection of glucagon, epinephrine or cyclic AMP. When given together with glucose, these substances prevent the usual activation of the enzyme.The sensitivity of the mouse to glucagon was studied by the inactivation of liver glycogen synthetase and by the activation of liver phosphorylase; the first effect was obtained with lower doses than the second. On the other hand, about 100 times more glucagon was required to inactivate the synthetase previously activated by prednisolone than to prevent its activation by glucose. This difference in sensitivity can presumably not be explained by a different rate of destruction of cyclic AMP, as neither the total activity of the diesterase nor its affinity for the cyclic nucleotide is altered by the treatments. No evidence has been obtained suggesting that prednisolone lowers the sensitivity of the synthetase kinase towards cyclic AMP.
Effects of Ethanol Infusion on the Redox State and Metabolite Levels in Rat Liver in vivo
Authors: Rawat A. K. 
Published: March 2005

Hepatic levels of several metabolites of the Embden‐Meyerhof pathway, the citric acid cycle and oxidized and reduced substrate pairs of the lactate, α‐glycerophosphate, β‐hydroxybutyrate, malate, and glutamate dehydrogenase systems were measured in freeze clamped livers from fed male rats, before and after ethanol infusion.
Ethanol infusion in fed male rats after 30 min resulted in an increase in the levels of hexosemonophosphates, triosephosphates, fructose 1,6 diphosphate, lactate, α‐glycerophosphate, malate, β‐hydroxybutyrate, and glutamate. [Lactate]/[pyruvate] ratio increased about 3 fold, [α‐glycerophosphate]/[dihydroxyacetonephosphate] 1.5 fold, [malate]/[oxaloacetate], [β‐hydroxybutyrate]/[acetoacetate], and [glutamate]/[2‐oxoglutarate] × [NH4+] about 2 fold.
The levels of pyruvate, acetyl CoA, citrate, and ATP were decreased during ethãnol treatment.
The hepatic levels of glycogen, oxaloacetate, 2‐oxoglutarate, ammonia, aspartate, and acetoacetate remained unchanged, 30 min after ethanol infusion, as compared to values before ethanol infusion.
Hepatic glucose 6‐phosphatase activity was significantly increased after 15 min of ethanol infusion (1.5 g/kg body weight). The glucose 6‐phosphatase activity showed a maximum 15 min after ethanol infusion, the fructose 1,6 diphosphatase activity did not change significantly 15 and 30 min after ethanol infusion. Hepatic acid and alkaline phosphatase activities measured with β‐glycerophosphate as substrate showed no significant changes compared to values from normal rat livers.
The presence of ethanol (8 mM) in the incubation medium showed no significant effect on the [6‐14C]glucose incorporation into glycogen by the liver slices.
Distribution intracellulaire de ľexonucléase acide dans le foie de rat
Authors: van Dyck J. M. , Wattiaux R. 
Published: March 2005

Acid exonuclease activity of rat liver has been determined with the help of DNA core as substrate.The intracellular distribution of the enzyme has been investigated by differential centrifugation of homogenates and compared with those of cytochrome oxidase, acid phosphatase and glucose‐6‐phosphatase used as reference enzymes for mitochondria, lysosomes and endoplasmic reticulum respectively. Acid exonuclease is principally associated with mitochondrial fractions and exhibits a distribution pattern similar to that of acid phosphatase.After isopycnic centrifugation in a sucrose gradient of a total mitochondrial fraction, acid exonuclease like acid phosphatase shows a relatively flattened distribution curve with a median equilibrium density of about 1.2. The injection to the rat of Triton WR‐1339, which lowers the equilibrium density of lysosomal enzymes has a similar effect on acid exonuclease.Acid exonuclease exhibits the phenomenom of structure‐linked latency.It is concluded that acid exonuclease is associated with the lysosomes in rat liver. Separation between acid DNase and acid exonuclease associated with lysosomes can be performed by chromatography on hydroxyapatite of an extract of purified granules. The complementary action of the two enzymes in lysosomal digestion of DNA is illustrated.
The Abnormalities of Lysosomal Enzymes in Mucopolysaccharidoses
Authors: van Hoof F. , Hers H. G. 
Published: March 2005

The activity of acid hydrolases on 13 substrates has been measured in the liver of normal human subjects and of 32 patients with various forms of mucopolysaccharidoses. The most important abnormalities may be summarized as follows:

In 3 patients, there was a complete absence of α‐fucosidase and an excess of fucose in the mucopolysaccharide fraction. The enzymatic deficiency extended to the brain, lung, kidney and urine. In the liver there was also a large increase in the activity of several acid hydrolases, mostly of the α‐galactosidase and of the β‐xylosidase.
In 5 patients with pseudo‐Hurler disease (generalized gangliosidosis), the activity of β‐galactosidase, at pH 3.6 was absent and this defect also extended to other tissues. This enzymatic deficiency explains the known accumulation of galactose‐rich mucopolysaccharides and of galactosyl‐N‐acetylgalactosaminyl N‐acetyl‐neuraminyl)‐galactosylceramide (GM1 ganglioside) in the tissues. Several enzymatic activities were greatly elevated, mostly that of α‐fucosidase, α‐galactosidase and N‐acetyl‐β‐glucosaminidase.
In 14 patients with an usual form of Hurler syndrome, the activity of acid β‐galactosidase was markedly reduced and this abnormality extended also to the brain and the derm but not to the kidney, spleen and leucocytes. The N‐acetyl‐β‐hexosaminidases, the β‐glucuronidase and the α‐fucosidase were much more active than normally.
In two siblings only, affected by an unusual type of Hurler syndrome, there was a marked elevation of β‐galactosidase.

The etiological significance of these findings is discussed and a classification of the mucopolysaccharidoses, based on the activity of the lysosomal enzymes in the liver, is proposed.
The Subcellular Distribution of Lysophospholipase in Bovine Adrenal Medulla
Authors: HÖrtnagl Heide , Winkler H. , Hörtnagl H. 
Published: March 2005

A study was made of lysophospholipase activity in bovine adrenal medulla. Maximum hydrolysis of lysolecithin was obtained at pH 6.5. The activity of the enzyme was 5.8 μmole × g tissue−1× hour−1.
Differential centrifugation showed that about 90% of the enzyme was confined to particles. 55% of the activity present in the low speed supernatant was recovered in the “large granule fraction”. About 35% sedimented with the microsomes.
Density gradient centrifugation (1.3–2.0 M sucrose) of the large granule fraction revealed that lysosomes and chromaffin granules contained no significant lysophospholipase activity. By the use of a second gradient (1.0–1.6 M), mitochondria could be partly separated from the microsomes which contaminate the large granule fraction. Lysophospholipase appeared to be concentrated in dense microsomal elements.
It is concluded that most, if not all, of the lysophospholipase activity in bovine adrenal medulla is localised in microsomal elements.
Sterods in Newborns and Infants
Authors: Gustafsson J.‐Å. , Shackleton C. H. L. , Sjövall J. 
Published: March 2005

The steroids in faeces from infants less than one year of age have been studied. Two fractions, monosulphates and “diconjugates”, were separated by chromatography on Sephadex LH‐20. The steroids were liberated by solvolysis and were studied by thin‐layer chromatography and gas‐liquid chromatography‐mass spectrometry. Eighteen steroids, most of them having a 3β,16‐dihydroxy‐Δ5 structure, were identified in the monosulphate fraction of pooled faeces from infants 1–4 months of age. Of these, androst‐5‐ene‐3β,16β,17α(and)17β‐triols, 3β‐hydroxypregna‐5,16‐dien‐20‐one, 3β,16β‐dihydroxypregn‐5‐en‐20‐one, 3α,16α‐dihydroxy‐5β‐pregnan‐20‐one, pregn‐5‐ene‐3β,16α,20α‐triol, pregn‐5‐ene‐3β,20α,21‐triol and pregn‐5‐ene‐3β,16α,20α,21‐tetrol have not been reported as occurring in urine from infants. In addition, eight steroids were found, the stereochemistry of which was not confirmed. Four of the 16‐hydroxylated steroids were also present in the “Diconjugate” fraction.In contrast to faeces from the younger infants, pooled faeces from infants 6–12 months of age contained only small amounts of steroids, mainly pregn‐5‐ene‐3β,20α‐diol and pregn‐5‐ene‐3β,17α,20α‐triol. The results indicate that significant amounts of steroids are excreted in faeces during the first few months of life, and that metabolism of these steroids by the intestinal flora is of minor importance in this period.
Regulation of the Level of Key Enzymes of Glycolysis and Gluconeogenesis in Liver
Authors: Sillero A. , Sillero M. A. G. , Sols A. 
Published: March 2005

Diets rich in fructose, glycerol, or both were fed to normal and diabetic rats, and the activities of enzymes which catalyze irreversible steps of glycolysis and gluconeogenesis were studied in liver. With these diets, rich in precursors of triosephosphates, the activities of glucose‐6‐phosphatase and pyruvate kinase in liver were high, while those of glucokinase and phosphoenolpyruvate carboxykinase were low. A metabolic bifurcation to glycolysis and gluconeogenesis, below and above the triosephosphates level respectively, has then been shown to be easily maintained in liver.It is suggested that the induction of glucokinase and pyruvate kinase in diabetic animals after insulin administration is a sequential process that involves hormonal induction of glucokinase by insulin and secondary metabolite induction of the L isoenzyme of pyruvate kinase by some glycolytic intermediate.The occurrence of independent mechanisms for the regulation in liver of the activity of enzymes which catalyze irreversible steps of glycolysis and gluconeogenesis affords a valuable metabolic plasticity.
The Proportion of the Incorporation of Leucine into Albumin to that into Total Protein in Rat Liver and Hepatoma Morris 5123 TC*
Authors: Schreiber G. , Rotermund H.‐M. , Maeno H. , Weigand K. , Lesch R. 
Published: March 2005

Labelled serum protein appeared in the blood of normal and Morris hepatoma 5123 TC bearing rats 14 to 15 min after intracaval injection of radioactive leucine. Within this time albumin synthesis can be studied separately in vivo in liver and hepatomas.
Tumor bearing rats were killed within 10 to 14 min after injection of [3H] or [14C]leucine. Postmitochondrial supernatants were prepared from 14C‐labelled liver and 3H‐labelled tumor, treated with sodium deoxycholate and combined. Albumin was purified from the mixture. The ratio [3H]protein to [14C]protein decreased during purification from 7 to 1.2, suggesting that the tumor synthesized less albumin compared to total protein than the liver.
Radiochemically pure albumin was isolated from liver and tumor homogenates from rats killed within 12 to 14 min after injection of l‐[1‐14C]leucine. The specific radioactivity in albumin isolated from liver was 13 times higher than in that from tumor.
The proportion of the incorporation of l‐[1‐14C]leucine into albumin to that into total protein was found to be 3.3% for liver and 0.8% for hepatoma homogenates.
Die Synthese verschiedener Carbonsäuren durch den Multienzymkomplex der Fettsäuresynthese aus Hefe und die Erklärung ihrer Bildung
Authors: Sumper M. , Riepertinger C. , Lynen F. , Oesterhelt D. 
Published: March 2005

The purified multienzyme complex, fatty acid synthetase of yeast, produces palmityl‐CoA and stearyl‐CoA in equal amounts under standard conditions, with adequate NADPH, and a 1:2 ratio of acetyl‐CoA and malonyl‐CoA. Based on the known enzymatic properties of fatty acid synthetase a model which rationalizes the chain termination at the level of C16 and C18‐acid is proposed.
The model is based on two assumptions that are supported by experimental evidence: (a) the probability of any covalently enzyme‐bound saturated acyl residue forming a product by transfer to CoA is determined by the relative velocities of the condensing and transferring reactions. (b) The growing alkan chain interacts with the enzyme protein only after a chain length of 13 carbon atoms has been attained; this interaction changes the relative velocities in favour of product formation by an energy increment of ‐0.9 kcal for each additional methylene group beyond the 13th.
To calculate the probability of product release at a particular chain length, an equation was derived from the model describing quantitatively the observed product distribution.
The formula suggests conditions under which either short acyl‐CoA derivatives or exclusively stearyl‐CoA can be produced. Synthesis under these conditions was examined experimentally and results indicated that the formula can be applied to a wide range of experimental conditions.
Because the condensation reaction in fatty acid synthesis is the rate limiting step under normal conditions, saturated acyl residues have the longest life‐time as intermediates and consequently the highest probability of leaving the enzyme complex as an endproduct. The reduction reactions can be made rate limiting when the NADPH level drops. Under such circumstances β‐ketoacyl‐CoA's and α,β‐unsaturated acyl‐CoA's appear as endproducts. With NADH as electron donor the first reduction is slowed to such an extent that predominantly β‐ketoacyl‐CoA's derivatives are synthesized.
The possibility that the enzyme complex catalyses synthesis of short chain fatty acids and and β‐ketoacids in vivo is discussed.
Short‐Term Effects of Calcium, Potassium, and of Ouabain on Metabolite Levels in the Frog Heart in vivo
Authors: Arese P. , Bosia A. , Rossini L. 
Published: March 2005

The short‐term effects of calcium (7.2 mM), potassium (10.7 mM), and of ouabain (0.1%) have been studied in the frog heart in vivo. No dynamic alterations occurred at 30 sec, whereas positive inotropism was observed at 60 sec in the high‐Ca and ouabain treatment; in all cases heart arrest occurred at 120 sec. 18 metabolites (glucose, glucose‐1‐P, glucose‐6‐P, fructose‐6‐P, fructose‐1,6‐P2, dihydroxyacetone‐P, glyceraldehyde‐3‐P, α‐P‐glycerol, pyruvate, lactate, oxaloacetate, malate, α‐ketoglutarate, P‐creatine, creatine, ATP, ADP, AMP) and 17 added parameters (mass‐action ratios of the phosphoglucomutase, phosphohexose isomerase, triosephosphate isomerase, phosphofructokinase, aldolase, adenylate kinase, creatine kinase; redox ratios; ratios P‐creatine/creatine, ATP/ADP; sums P‐creatine + creatine, ATP + ADP + AMP, lactate + pyruvate) were computerized by the stepwise discriminant analysis. Highly significant discrimination between control and treated hearts (thanks to the sensitivity of the statistical method employed) shows that ionic shifts and ouabain elicited modifications of the metabolite pattern which always preceded the effects on heart contractility.The most meaningful results were as follows:

High calcium effect: At 30 sec, the phosphofructokinase‐catalyzed step and the pyruvate, α‐P‐glycerol and oxaloacetate‐depleting reactions are activated; the P‐creatine and ATP balance is negative; ADP and AMP are increased. At 60 and 120 sec the phosphorylase system, phosphofructokinase, and the whole glycolytic sequence are activated.
High‐potassium effect: At 30 sec the phosphofructokinase‐step and the glycolytic flux are activated. Glucose entry into the cell is impaired. P‐creatine, ATP, AMP, ATP/ADP, P‐creatine/creatine are increased. At 60 sec, all glycolytic substrates are increased.
Ouabain effect: At 30 sec glucose extraction from the perfusing fluid decreases, lactate, pyruvate, α‐P‐glycerol and malate accumulate; P‐creatine and ATP are increased. At 60 sec there is no evidence for activation of the phosphorylase system; the glycolytic pattern points to activation of glucose extraction and of the glucose shunt, and to inhibition of the glyceraldehyde‐3‐P dehydrogenase and 3‐P‐glycerate kinase steps. P‐creatine, ATP, and AMP are decreased, creatine and ADP increased. The partial overlapping of the high‐calcium and ouabain patterns suggests that the glycoside not only raises the intracellular free‐calcium level but also depresses the glyceraldehyde‐3‐P dehydrogenase, 3‐P‐glacerate kinase and adenylate cyclase activity. The observed effects are only partially in accord with the inhibition of Na+‐K+‐dependent adenosinetriphosphatase.
Stimulation of Phospholipid Synthesis in Isolated Rat Liver Mitochondria after Treatment in vivo with Tri‐Iodothyronine
Authors: Kaiser W. , Bygrave F. L. 
Published: March 2005

The incorporation in vitro of labelled choline into mitochondria isolated from the livers of normal, hypothyroidic and hyperthyroidic rats was studied. Incorporation into the mitochondria from livers of hyperthyroidic rats was stimulated 2‐ to 3‐fold while that into mitochondria isolated from livers of hypothyroidic rats was depressed about 2‐fold.
Stimulation of choline incorporation into isolated rat liver mitochondria by administration in vivo of triiodothyronine was shown to parallel that of amino acid incorporation.
The direct addition of tri‐iodothyronine to the incubation medium did not stimulate but inhibited the incorporation in vitro of choline into mitochondria isolated from the livers of normal rats.
The data provide further evidence that the measurements of phospholipid precursor incorporation into isolated mitochondria carried out in this and in previous studies, reflect the biosynthetic activity of the organism as a whole.
Hydrolysis of Vitamin A Acetate by Unspecific Carboxylesterases from Liver and Kidney
Authors: Bertram J. , Krisch K. 
Published: March 2005

Vitamin A acetate is hydrolysed by highly purified carboxylesterases (EC 3.1.1.1) from liver and kidney of several species (pig, ox, man), whereas long‐chain fatty acid esters of vitamin A are not split.The hydrolysis of vitamin A acetate by pig liver esterase was characterized further by means of pH optimum, Km, specific and molecular activities and the behavior towards several inhibitors.
Fatty Acid Synthesis from Glucose and Acetate and the Control of Lipogenesis in Adipose Tissue
Authors: Del Boca J. , Flatt J. P. 
Published: March 2005

Epididymal fat pads of fed and 48 h fasted rats were incubated in vitro with 10 mM glucose and 0, 60, 120, or 104μunits of insulin/ml. A comparison was made of the metabolism of glucose in the absence or presence of 15 mM acetate in the incubation medium.At physiological concentrations of insulin, the addition of acetate increases glucose uptake, glucose oxidation to CO2, and incorporation of glucose‐C into fatty acids; concomitantly the rates of glycerol release and lactate production are decreased, and the lactate/pyruvate ratios are lowered. Fatty acid synthesis in the presence of glucose plus acetate was in all cases significantly higher than with glucose alone.It is concluded that, at a given insulin concentration, the conversion of carbohydrate to fat in intact adipose tissue is limited by the tissue's ability to supply acetyl‐CoA for fatty acid synthesis, and not by the enzymes directly engaged in the synthesis of fatty acid from acetyl‐CoA. The effects of acetate were of greater importance in adipose tissue from rats fasted for 48 h than from fed rats. The impairment in lipogenesis caused by fasting appears to be due primarily to a decrease in the tissue's ability to produce acetyl‐CoA from glucose.