bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fat Transport in the Locust: The Role of Diglycerides
Authors: Tiezt A. 
Published: March 2005

An analysis of the lipids of the fat body of Locusta migratoria showed that approximately 97% are triglycerides and 2–3% diglycerides; free fatty acids and phospholipids were present only in small amounts. In the hemolymph, diglycerides and phospholipids were the major lipid components; free fatty acids were present in very small amounts, triglycerides were absent. The concentration of the diglycerides in the hemolymph was found to increase with the age of the locust and during sustained flight; the phospholipids remained constant. The concentration of the free fatty acids in the tissue and hemolymph was also increased during flight.When fat body tissue was incubated in vitro with [1‐14C]palmitate, the acid was incorporated into the di‐ and triglycerides of the tissue. The specific activity of the diglycerids was at least 50 times higher than that of the triglycerides.When prelabeled tissue was transfered into a medium containing hemolymph, diglycerides were released into the medium. The amount of diglyceride released was dependent on the time of incubation and on the amount of hemolymph which was added to the medium. Although the amount of diglycerides which was released, was greater than their concentration in the tissue, the amount of the latter did not change. However, their specific activity was very markedly reduced. When the fat body tissue was prelabeled in vivo and the specific activity of the di‐ and triglycerides was identical, the specific activity of the diglycerides was not reduced during diglyceride release.When fat body tissue of locusts after flight was incubated with [1‐14C]palmitate, incorporation of the acid into the diglycerides was very markedly reduced. This inhibition was reversed by the addition of glucose to the medium.When prelabeled tissue of locusts after flight was incubated in hemolymph obtained from the same locusts, diglycerides and free fatty acids were released into the medium.
Comparative Studies of Amino Acid Incorporation in a Cell‐free System from Psychrophilic Pseudomonas sp.412
Authors: Krajewska E. , Szer W. 
Published: March 2005

A subcellular amino acid incorporating system has been obtained from the psychrophilic bacterium Pseudomonas sp. 412. The system is active from near 0° to 45°, i. e. about 15° above the maximal growth temperature of the organism. The Mg2+ requirement of the system increases from 7 mM at 2° to 14–18 mM at 45°.
The sedimentation properties and optical density melting profiles of ribosomes from Pseudomonas sp. 412 have been found similar to those of Escherichia coli ribosomes.
The poly U‐induced leucine incorporation is negligible in this system as compared to the E. coli and Bacillus stearothermophilus systems.
The ribosomes and supernatant fractions of Pseudomonas sp. 412 and E. coli are interchangeable at 30–45° in the poly U‐promoted phenylalanine incorporation. At 2–9° only Pseudomonas sp. 412 ribosomes are active with both supernatant fractions. The ability to perform protein synthesis near 0° is related to ribosomal specificity. The E. coli soluble enzymes are active near 0° if combined with the ribosomes from the psychrophilie strain.
Études immunochimiques sur les Salmonella
Authors: Nghiem H. O. , Bagdian G. , Staub A. M. 
Published: March 2005

In a preceding publication Le Minor and Staub [8] predicted from phagic and immunological studies, that the repeating unit of the group D2 polysaccharide should be:In this paper the specific polysaccharide was prepared according to Freeman's technique and hydrolysed. High yields of 3 oligosaccharides have been obtained whose analysis gave:Periodate oxydation of the polysaccharide intact or degraded by slight hydrolysis (N CH3COOH, 4 hours at 100°), confirmed these data and showed that tyvelose is linked to carbon 3 of mannose. No O‐acetyl was found.Immunological data showed that tyvelose was the immunodominant sugar for both factors (9) and 46. No other analysis of these factors was possible since we did not posses oligosaccharides containing tyvelose. The position of the different factors of Salmonella strasbourg (3), (9), (10), (46) on the polysaccharide is schematised on Fig.6.
Infectious Nucleic Acids of Escherichia coli Bacteriophages
Authors: Benzinger R. , Delius H. , Jaenisch R. , Hofschneider P. H. 
Published: March 2005

Various strains of Escherichia coli were grown to a titer of 5 × 108 cells/ml in peptone media. Following osmotic shocks (peptone → water → 0.4 M sucrose) or lysozyme‐EDTA treatment in hypertonic media, the spheroplasts were stored at 4° and then tested for competence with ØX 174 and M 13 phage DNA and M 12 phage RNA. Lysozyme spheroplasts proved most effective and yielded the following maximum infectivities: for one Ø× 174 DNA molecule, 5 × 10−3 infectious DNA centers; for one M 13 DNA molecule, 10−5 infectious DNA centers; and for one M 12 phage RNA molecle, 2 × 10−5 infectious RNA centers. For many spheroplast preparations competence remained nearly constant for one week. One strain, E. coli 112–12 (λh)F+, retained a constant (though low) level of competence for months when frozen in 10% (v/v) dimethyl sulfoxide.Ø× 174 DNA saturation experiments indicated that 0.05–1% of the lysozyme spheroplasts were competent. Between 12 and 20 minutes after the addition of a non‐saturating level of 32P‐labelled Ø× 174 DNA to such competent cell populations at 37°, 10–20% of the label was adsorbed. Noncompetent cell populations adsorbed no more than 4% of the added label. Prolonging the DNA adsorption time did not give a higher efficiency of DNA infection, because the cells began losing competence through a temperature‐dependent process.More than 90% of the infectious Ø× 174 DNA centers reamined sensitive to DNAase during the first 20 minutes in DNA adsorption medium. Plating Ø× 174 DNA and M 12 RNA‐infected cells on eosin methylene blue agar during this period prevented the formation of phage, whereas the plaque‐forming ability of the mature phage was not inhibited. These observations may suggest an unusual permeability of the competent cells.Inhibitors of phage RNA infection were removed by washing the competent cells. DNAase pretreatment of the spheroplasts increased their competence for infectious M 12 phage RNA.
α‐Chain and Globin: Intermediates in the Synthesis of Rabbit Hemoglobin
Authors: Baglioni C. , Campana T. 
Published: March 2005

The synthesis of hemoglobin by rabbit reticulocytes has been studied by means of pulse‐labelling and chase experiments. The reticulocyte lysate was fractionated into a top layer and a ribosomal fraction. The top layer was analysed by gel filtration on columns of Sephadex G‐75. At least two intermediates which were formed after short incubations and were chased into hemoglobin were separated by gel filtration. These intermediates have been identified with α chain and globin.α Chain and globin have also been separated by chromatography on carboxymethyl‐Sephadex. This method of analysis has been used to measure the rate of appearance of these intermediates in the top layer fraction and their rate of removal in chase experiments. The presence of complete α chains on polyribosomes has been confirmed. The rate of appearance of α chains on polyribosomes and their rate of removal in chase experiments have been determined. These rates appear to be identical, suggesting that the same biosynthetic process is responsible for these rates.The nature of the complete α chains present on polyribosomes has been investigated. These chains can be separated from peptidyl‐tRNA chains by gel filtration in a sodium dodecyl sulphate‐acetate buffer. This finding suggests that the complete chains are not bound to tRNA.The experimental results support the following scheme of assembly of the hemoglobin molecule: α chains are released from polyribosomes on completion. These chains combine with β chains which are still being synthesized on polyribosomes and for this reason complete α chains are found on polyribosomes. αβ subunits are released from polyribosomes once the synthesis of β chains is completed. The subunits then combine with heme to form hemoglobin molecules. The combination with heme may be stepwise and, in this case, intermediates containing less than one heme every peptide chain are formed. Some evidence for the existence of heme‐containing intermediates has been obtained.The significance of the combination of α chains with β chains at the polyribosome level is discussed. This phenomenon may have some regulatory function which may be of general importance in view of the similar finding that immunoglobulin light chains combine with heavy chains at the polyribosome level and that heavy chains are apparently not released independently from polyribosomes.
Conversion of Cholesterol to Bile Acids in Rat: Purification and Properties of a Δ4‐3‐Ketosteroid 5β‐Reductase and a 3α‐Hydroxysteroid Dehydrogenase
Authors: Berséus O. 
Published: March 2005

A Δ4‐3‐ketosteroid 5β‐reductase active on 7α‐hydroxycholest‐4‐en‐3‐one and 7α,12α‐di‐hydroxycholest‐4‐en‐3‐one and a 3α‐hydroxysteroid dehydrogenase active on 7α‐hydroxy‐5β‐cholestan‐3‐one and 7α,12α‐dihydroxy‐5β‐cholestan‐3‐one have been isolated from the soluble fraction of a rat liver homogenate and have been partially purified by chromatography on TEAE‐cellulose and Sephadex G‐75.The Δ4‐3‐ketosteroid 5β‐reductase required NADPH as cofactor and was inhibited reversibly by p‐chloromercuribenzoate. The enzyme preparation catalyzed the reduction of the double bond in a number of Δ4‐3‐ketosteroids of the C19, C21, C24, and C27 series. The reduction of 7α,12α‐dihydroxycholest‐4‐en‐3‐one in the presence of the Δ4‐3‐ketosteroid 5β‐reductase preparation was not inhibited by addition of 7α‐hydroxycholest‐4‐en‐3‐one and the reduction of 7α‐hydroxycholest‐4‐en‐3‐one was not inhibited by 7α,12α‐dihydroxycholest‐4‐en‐3‐one indicating that these substrates were reduced by different reductases present in the Δ4‐3‐ketosteroid 5β‐reductase preparation.The 3α‐hydroxysteroid dehydrogenase required reduced pyridine nucleotide, NADPH being preferred, and was inhibited reversibly by p‐chloromercuribenzoate. The enzyme preparation catalyzed the reduction of the 3‐keto group in a number of 3‐ketosteroids of the C19, C21, C24, and C27 series. The rate of reduction was faster with 3‐keto‐5β‐steroids than with the corresponding 3‐keto‐5α‐steroids.
Regulation and Function of Pyruvate Kinase and Malate Enzyme in Yeast*
Authors: Fernández Ma J. , Medrano L. , Ruiz‐Amil M. , Losada M. 
Published: March 2005

The concentrations of pyruvate kinase and malate enzyme have been determined in the yeast Rhodotorula glutinis and shown to vary considerably according to the carbon compounds consumed by the cells. The results so obtained, together with the kinetic studies of the synthesis of the enzymes, seem to indicate that pyruvate kinase is nutritionally induced by glucose whereas malate enzyme is repressed by glucose and by acetate.In R. glutinis, the function of pyruvate kinase is to form pyruvate from phosphoenolpyruvate during glycolysis and that of malate enzyme to provide pyruvate from malate. The reverse reactions probably do not play any physiological role. R. glutinis cells growing in a medium containing glucose could at the same time utilize aspartate as source of carbon. Under such conditions, asparate could not supply phosphoenolpyruvate nor pyruvate for biosynthetic and energetic purposes, because both phosphoenolpyruvate carboxykinase and malate enzyme are repressed by glucose, but could, however, provide oxaloacetate for biosynthesis and at the same time spare the pyruvate glycolytically formed by inhibiting its carboxylation. Once glucose was used up by the cells and after a clear diauxia, the yeast continued growing solely on the remaining aspartate. The disappearance of glucose from the medium determined a change in enzyme levels, pyruvate kinase being no longer induced and phosphoenolpyruvate carboxykinase and malate enzyme being no longer repressed. This enzymatic change allowed aspartate to fulfill by itself the functions of supplying energy and providing precursors for the synthesis of all cell constituents.
Structural Protein of Wild‐Type (ρ+) and Respiration‐Deficient (ρ−) Yeast Mitochondria
Authors: Tuppy H. , Swetly P. , Wolff I. 
Published: March 2005

Structural protein prepared from mitochondria of wild‐type baker's yeast contains several components which are separable by electrophoresis on polyacrylamide gels. One of these components is absent from structural protein preparations obtained from a cytoplasmic “petite” mutant.Rabbit antisera against the structural protein of yeast mitochondria are capable of agglutinating yeast mitochondria and human erythrocytes coated with yeast mitochondrial structural protein. The agglutination of coated erythrocytes can be inhibited by absorption of antisera with structural protein. With the help of this sensitive haemagglutination‐inhibition technique the antigenic properties of structural protein from mitochondria of the wild‐type yeast and the “petite” mutant were compared. It was found that at least one of the antigenic determinants present in the mitochondrial structural protein preparations from wild‐type yeast is lacking in those obtained from the mutant.
Cholinesterase of Squid Optical Ganglia
Authors: Turpaev T. M. , Abashkina L. I. , Brestkin A. P. , Brick I. L. , Grigorjeva G. M. , Pevzner D. L. , Rozengart V. J. , Rozengart E. V. , Sakharov D. A. 
Published: March 2005

Optical ganglia of squid (Ommatostrephes sloanei‐pacificus) possess very high cholinesterase activity.
Squid cholinesterase is located on the level of layers r2–r3 of plexiform zone in ganglion cortex.
The activity of catalytic site of squid cholinesterase was equal to 1.2 × 105 min−1.
The hydrolysis rates of acetylcholine, butyrylcholine and acetyl‐β‐methylcholine in the presence of squid cholinestarse were the same (in optimal substrate concentrations). But their Km values were different (the lowest ones for acetylcholine); squid cholinesterase did not hydrolyze benzoylcholine.
All organophosphorus inhibitors studied possessed a high activity with regard to squid cholinesterase. It was shown that O‐ethyl‐S(3,3‐dimethyl‐butyl)‐methyl‐thiophosphonate (LG‐56) is a selective inhibitor of squid cholinesterase.
Substrate and inhibitor specificity and catalytic activity of squid cholinesterase differed essentially from those of acetylcholinesterase and serum cholinesterase.
Altération par mutation de la régulation de la biosynthèse des cytochromes par les cultures anaérobies d'une bactérie anaérobie facultative
Authors: Chippaux M. , Pichinoty F. 
Published: March 2005

Starting with a wild strain of Hafnia having the phenotype: nitrate reductase A +, nitrate reductase B +, chlorate reductase C +, tetrathionate reductase +, fumarate reductase +, hydrogen lyase +, we have isolated two kinds of mutants having the following phenotypes: (1) A –, B +, C +, tetrathionate reductase +, fumarate reductase +, hydrogen lyase +; (2) A –, B –, C –, tetrathionate reductase –, fumarate reductase +, hydrogen lyase –. The wild strain and the mutants of category 1 can use nitrate, nitrite, fumarate, and tetrathionate as hydrogen acceptors under anaerobic conditions. The mutants of category 2 can also reduce nitrite and fumarate, but cannot use nitrate and tetrathionate as hydrogen acceptors.We have studied the effects of nitrate, nitrite, fumarate, and tetrathionate on the biosynthesis of cytochromes a2, b1, b‐562, and c‐550 using anaerobic cultures of the wild strain and several mutants of the above two categories. The following observations were made: (a) Wild strain. Neither tetrathionate nor fumarate have any effect. Nitrate, on the other hand, markedly reduces the levels of cytochromes a2, b‐562, and c‐550. As for nitrite, it causes a decrease in levels of cytochromes b‐562 and b1, but a strong increase in that of cytochrome c‐550. It is as though nitrate abolishes the effects of nitrite on the biosynthesis of cytochromes b1 and c‐550. (b) Mutants of category 1. Nitrate causes the cytochrome a2 band to disappear, but does not influence the biosynthesis of cytochromes b‐562 and c‐550. Apart from the effect of nitrate on the formation of cytochrome a2, the different hydrogen acceptors caused no detectable spectral changes. (c) Mutants of category 2. We obtain essentially the same spectra as with the wild strain except when the cultures are nitrite‐grown. In this case, nitrite has the same effect as nitrate because it represses the biosynthesis of cytochrome c‐550.It is clear from this work that the two mutant phenotypes studied have profound and different effects in their regulation of the biosynthesis of cytochromes.
Intramembrane pH Changes and Bromthymol Blue Translocation in Liver Mitochondria
Authors: Azzone G. F. , Piemonte G. , Massari S. 
Published: March 2005

The effect of pH and of ionic strength on the degree of binding of bromthymol blue to the mitochondria has been studied. Changes of the functional state of the mitochondria affect the degree of binding of bromthymol blue.The changes of light absorbance of bromthymol blue have been followed under conditions where translocation of ions other than protons where minimized and in media with high buffering power. The transition from the de‐energized to the energized state, due to the addition of succinate or ATP to rotenone treated mitochondria, results in a decrease of absorbance of the alkaline form of the dye whereas the transition from the energized to the de‐energized state, due to the addition of respiratory chain inhibitors or of uncouplers is accompanied by an increase of absorbance. Several parameters of the phenomenon have been investigated including the competition between uncouplers and substrate anions. The direction of the change of absorbance is inverted when the ionic strength or the buffer strength of the medium are decreased and when the pH of the medium is increased.The changes of absorbance may be expression of pK shifts of the dye, due either to membrane potential or to changes in the hydrophobic regions of the crystal membrane.
Dissoziation und Rekonstitution der Thiolase
Authors: Gehring U. , Riepertinger C. 
Published: March 2005

Thiolase from pig heart shows in dilute salt solutions the following hydrodynamic properties: s°20,w= 7.88 S D°20,w= 4.2 × 10−7 cm2/sec = 0.731 ml/g From these data a molecular weight of 169,000 was calculated which is in good agreement with the value of 168,000 obtained by the Archibald method.In the presence of 5 M guanidine‐HCl the enzyme dissociates into subunits with a molecular weight in the range of 39,000–44,000 as determined by use of the Archibald method, sedimentation equilibrium analysis and combination of sedimentation velocity with viscosity and diffusion measurements.The sedimentation coefficient and the molecular weight of the subunits in 5 M urea (s°20,w= 1.86 S, mol. wt. = 43,700) and in 70% formic acid (s°20,w= 1.73 S, mol. wt. = 41,700) are comparable to those obtained in the presence of guanidine‐HCl.Treatment of the enzyme with a large excess of succinic anhydride caused a splitting into protein particles with a molecular weight of approximately 92,000, corresponding to half the size of the native enzyme.Quantitative determinations of the NH2‐terminal amino acid residues by reaction with dinitrofluorobenzene and by Edman degradation yielded 4 valine residues per mole of protein.These results indicate that thiolase from pig heart contains 4 subunits of similar size, each consisting of one polypeptide chain. The subunits are not linked by covalent bonds. Although binding studies using [1‐14C]acetyl‐CoA and iodo‐[1‐14C]acetamide have indicated the presence of at least 3 active sites per mole of enzyme, we propose that the fully active tetramer contains one active site per subunit.The dissociation of thiolase in 5 M urea is a reversible process. After dilution to a urea concentration of 0.1 M the reconstitution of the tetrameric structure can be followed by enzyme assay and sedimentation analysis. The association of the subunits is dependent on protein concentration, temperature, pH and the nature of the buffer. Under optimal conditions the original enzyme activity can be restored completely.Thiolase dissociated with 5 M guanidine‐HCl or 70% formic acid could be reactivated in similar experiments to 70% and 50% of the original activity, respectively.Denaturation by heat or treatment with trichloroacetic acid could also be partially reversed (40%, 70%) after dissolving the precipitated protein in 5 M urea.
5′‐Deoxy‐5′‐Fluoro‐Thymidine, a Biochemical Analogue of Thymidine‐5′‐Monophosphate Selectively Inhibiting DNA Synthesis
Authors: Langen P. , Kowollik G. 
Published: March 2005

5′‐Deoxy‐5′‐fluorothymidine (5′‐fluorothymidine) inhibits the DNA synthesis of cells of the Ehrlich ascites carcinoma of the mouse (carcinoma) in vitro, as estimated by the incorporation of radioactive phosphate. About 90 or 50% inhibition is obtained at concentrations of 1 mM or 70 μM, respectively. The synthesis of neither RNA nor protein is inhibited by 5′‐fluorothymidine. The inhibition of DNA synthesis cannot be reversed by thymidine.
In cell‐free extracts obtained from carcinoma cells, 5′‐fluorothymidine strongly inhibits the phosphorylation of thymidine‐5′‐monophosphate, but hardly at all that of thymidine. A large accumulation of thymidine‐5′‐monophosphate is found among the phosphorylation products derived from thymidine in the presence of 5′‐fluorothymidine. Thus, 5′‐fluorothymidine acts as inhibitory analogue of thymidine‐5′‐monophosphate in the thymidine‐5′‐monophosphate kinase reaction. The inhibition of thymidine‐5′‐monophosphate kinase is competitive. The affinity of the analogue for the enzyme is about three times higher than that of the substrate. The enzyme is also inhibited by thymidine, but its inhibitory activity is only one tenth that of 5′‐fluorothymidine. 5′‐fluorothymidine provides protection of the enzyme against inactivation brought about by incubation in the absence of the substrate.
5′‐fluorothymidine is degraded by pyrimidine phosphorylases at a rate of only one sixth that of thymidine.
5′‐fluorothymidine inhibits the multiplication of carcinoma cells in vitro either completely or by 60% at concentrations of 100 or 10 μM, respectively. The increase in fermentation, normally associated with this cell multiplication, is much less influenced by 5′‐fluorothymidine. Thus, the effect of 5′‐fluorothymidine is primarily seen in cell division, but to a less extent in the development of cytoplasmic processes (similar to unbalanced growth).
Since 5′‐fluorothymidine cannot be phosphorylated at C‐5′ it must be assumed to act unchanged as such. This is in contrast to the classical base, or nucleoside, analogues, which, for inhibitory activity, have to be transferred intracellularly into the nucleotides (lethal synthesis). The independence of 5′‐fluorothymidine of lethal synthesis should be of advantage with regard to resistance problems for a possible use of this compound in cancer chemotherapy.