bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thyrotrophin‐Induced Aggregation and Reorganization into Follicles of Isolated Porcine‐Thyroid Cells
Authors: Lissitzky Serge , Fayet Guy , Giraud Annie , Vernier Bernard , Torresani Janine 
Published: March 2005

The thyrotrophin‐induced reorganization of isolated porcine‐thyroid cells into follicles is specifically mediated by cyclic AMP. Both dibutyryl cyclic AMP and theophylline at concentrations of 0.1 mM and 0.05 mM, respectively, mimic the effect of thyrotrophin. Puromycin and cycloheximide acutely inhibit the cyclic AMP‐induced histiotypic reassociation of cells. Actinomycin‐D inhibits cell organization when added at zero‐time or 12 h after the onset of the culture but not when added 24 h later. Therefore, the intracellular increase in cyclic AMP is most likely a prerequisite to the reassociation into follicles of isolated thyroid cells. Cyclic AMP stimulates the production of new RNA(s) which, in turn, induces the synthesis of protein(s) involved in intercellular recognition.Isolated thyroid cells grow as a monolayer in the absence of thyrotrophin or cyclic AMP. Between the first and the second day of culturing, they lose the capacity to concentrate iodide. From the third to the thirteenth day neither iodide trapping nor organification can be detected. In contrast, cells organized into follicles maintain their capacity to concentrate iodide, iodinate thyroglobulin and synthesize thyroid hormones. Quantitative estimation of thyroglobulin was performed by radioimmunossay. Up to the seventh day of culture, the total amount of thyroglobulin recovered per cell in the medium and in the cell layer is roughly identical whether the cells are cultured as a monolayer or in histiotypic reassociation. Non‐iodinated thyroglobulin is secreted into the medium by monolayer cells whereas 19‐S iodinated‐thyroglobulin is found in the medium of thyrotrophin‐induced reassociated cells. We therefore conclude that thyrotrophin is necessary to maintain the differentiation of isolated thyroid cells in culture as judged by the preservation of such specific functions as the capacity to aggregate and reorganize into follicles, to concentrate and organify iodine and to synthesize thyroid hormones.
The Structure of Pig Gastric Mucus Conformational Transitions Induced by Salt
Authors: Snary David , Allen Adrian , Pain Roger H. 
Published: March 2005

The two major mucoprotein components (s025,w= 18.7 S and 4.9 S, respectively) of a watersoluble extract of hog‐gastric mucus have been investigated as to their behaviour in aqueous KCl solutions of differing concentrations. The values of viscosity for the unfractionated, watersoluble mucus extract undergo two sharp changes, one between 0 and 0.05 M KCl which is attributed to a polyelectrolyte charge‐shielding phenomenon, and one between 0.5 and 1.5 M KCl. The isolated 18.7 S and 4.9 S mucoprotein components of the mucus show no change in molecular weight when measured in 0.2 M KCl and 2.5 M KCl, but both undergo a marked change in hydrodynamic properties in this range of salt concentration.A large decrease in the ratio Ks/[η], (where Ks= (1/s0) (ds/dc) and [η] is the intrinsic viscosity at zero shear stress) is interpreted in terms of a marked increase in asymmetry accompanied by reduced solvation of the mucoproteins. This transition is only partially reversible, indicating the occurrence of definite structural changes within the molecule. The viscosity at zero shear of the 18.7 S mucoprotein becomes anomalously high at concentrations above 3 mg ml−1, reflecting the ability of mucus to form a gel structure under physiological conditions.
Subunit Composition of DNA‐Dependent RNA Polymerase of Anacystis nidulans
Authors: Herzfeld Frank , Zillig Wolfram 
Published: March 2005

DNA‐dependent RNA polymerase from the blue‐green alga Anacystis nidulans was purified by an improved method including precipitation by polymin P and elution from the precipitate.The subunit pattern of the enzyme in polyacrylamide‐gel electrophoresis in the presence of dodecylsulfate is very similar to that of the Escherichia coli enzyme. If the most basic subunit in analogy to E. coli enzyme is called β′ the molecular weights of the subunits are: β: 147000; β′: 125000, σ: 86000 and α: 39000. Separation depending on charge by electrophoresis in 6‐M‐urea‐containing buffers on cellulose acetate, however, yields a migrating order of β′, β′, β, α for A. nidulans subunits as contrasted to β′, β, α, σ for E. coli. In addition there exists a stable complex of β and β′ which migrates between σ and β. Variation of ionic strength, pH and ionic composition of the buffer did not alter the ratio of free subunits to the complex which dissociates in the presence of dodecylfate.In contrast to E. coli‐σ, A. nidulans‐σ cannot be removed from the complete A. nidulans enzyme by chromatography on phosphocellulose. A. nidulansσ‐factor prepared by electrophoresis on cellulose acetate in 6 M urea stimulates E. coli core‐enzyme to 50% of the activity reached with E. coliσ. Correspondingly, A. nidulans complete enzyme is stimulated by E. coliσ indicating a restricted efficiency of A. nidulansσ as compared to E. coliσ.Reactivation of urea‐dissociated A. nidulans enzyme requires higher ionic strength than that of E. coli enzyme.
Relationship between the Binding of Pyrophosphate by Myosin and the Protection of Its Active Centre
Authors: Kakol Irena 
Published: March 2005

The relationship between the myosin ability to bind pyrophosphate and the protective effect of pyrophosphate on the activity of Ca2+ ATPase during inactivation by 2′‐hydroxyethyl 2,4‐dinitrophenyl disulphide was studied.

The diminution of myosin ability to bind pyrophosphate when myosin is treated with 2′‐hydroxyethyl 2,4‐dinitrophenyl disulphide is correlated with the decrease of Ca2+‐ATPase activity and is more rapid if myosin is modified by this disulphide without pyrophosphate.
The presence of ADP diminishes the protective effect of pyrophosphate on myosin Ca2+‐ATPase when myosin is treated with 2′‐hydroxyethyl 2,4‐dinitrophenyl disulphide.
A correlation has been observed between the influence of ADP on the ability of myosin to bind pyrophosphate as well as on the protective effect of myosin Ca2+‐ATPase when myosin is treated with 2′‐hydroxyethyl 2,4‐dinitrophenyl disulphide.
The protective effect of pyrophosphate was observed only when the pyrophosphate binding sites of myosin seemed to be saturated.
Properties of Isoaccepting Species of Lysine tRNA from Rabbit Reticulocytes in Codon Recognition and in Haemoglobin Biosynthesis in vitro
Authors: Rudloff Eberhard , Hilse Kurt 
Published: March 2005

Four isoaccepting species of tRNALys from rabbit‐reticulocyte lysate were separated by reversed‐phase chromatography–2.
The binding of species II and III to Escherichia coli ribosomes is stimulated by the trinucleotide AAG, whereas binding of the same species stimulated by AAA is not observed. tRNALysIV, on the other hand, responds preferentially to the codon AAA.
A completely homologous system has been used for the insertion of lysine into the haemoglobin polypeptide chains. Compared to the insertion of lysine by unseparated species of tRNALys, the species II and III incorporated lysine predominantly into the α‐chain, whereas lysine from Lys‐tRNALysIV was transferred preferentially into the β‐chain.

From this the conclusion can be drawn, that the codon specificities of the three species of tRNALys from reticulocytes are not completely in line with the wobble hypothesis proposed by Crick. All species respond almost exclusively only to one of the two triplets specific for lysine. In haemoglobin‐mRNA translation the isoaccepting tRNALys species have a more differentiated function. Therefore, the multiplicity of tRNA species is not a phenomenon of mere redundancy.
Mechanism of the Exchanges Catalysed by the Oxoglutarate Translocator of Rat‐Heart Mitochondria
Authors: Sluse Francis E. , Ranson Monique , Liébecq Claude 
Published: March 2005

The kinetics of the exchange reactions between 2‐oxoglutarate, malate and malonate have been measured at 4 °C in preparations of rat‐heart mitochondria under conditions where the oxoglutarate translocator is operating exclusively. This was possible since no activity of the tricarboxylate translocator can be measured in such preparations and since the activities of the phosphate and dicarboxylate translocators may be blocked by mersalyl, to which the oxoglutarate translocator is insensitive. The metabolism of the substrates was prevented by addition of rotenone and arsenite.Measurements were made at three different external and three different internal concentrations of the substrates. The results show that the affinity of the oxoglutarate translocator is very much higher for external substrates than for the corresponding internal substrates. The Michaelis constants increase in the following order: external oxoglutarate < external malate < external malonate < internal oxoglutarate < internal malate < internal malonate. The results also show that the affinity of the translocator for a given substrate, either external or internal, is independent of the nature of the counter‐ion. This is not true of the maximal velocities of the exchange reactions.Of the various mechanism described by Cleland for two‐substrate‐two‐product enzyme‐catalysed reactions, only the so‐called mechanism of rapid‐equilibrium random bi‐bi is compatible with our experimental results. This implies that the Michaelis constants determined are the dissociation constants of the various translocator‐substrate(s) complexes.
1‐Anilinonaphthalene‐8‐sulphonate
Authors: Penzer Geoffrey R. 
Published: March 2005

The conformations of 1‐anilinonaphthalene‐8‐sulphonate in 2H2O and C2H3O2H have been determined by proton magnetic resonance spectroscopy, and its fluorescence spectra as a solid, in a methyl‐cellulose matrix, and in solution in water, methanol and aqueous MgCl2 have been studied.The aromatic rings of anilinonaphthalene‐sulphonate are more nearly coplanar in C2H3O2H than in 2H2O. The NH proton fails to exchange with 2H from the solvent in C2H3O2H, and its chemical shift indicates that there is a strong interaction with the sulphonate group. The solvents in which rapid exchange of the NH proton occurs are those in which the quantum yield of fluorescence of anilinonaphthalene‐sulphonate is quenched. The fluorescence emission is enhanced and blue‐shifted in strong aqueous MgCl2 solutions. Under some conditions the overall emission is composed of contributions from two separable spectra.It is argued that an efficient mechanism for quenching the first excited singlet of anilinonaphthalene‐sulphonate is through vibrations of bonds to the nitrogen, and that the shifts of emission maxima in non‐aqueous solvents may be partly a result of the molecule displaying different spectra in different conformations (rather than simply a solvent‐polarity‐induced change). There is no convincing reason for the assumption that when a fluorescence enhancement follows the binding of anilinonaphthalene‐sulphonate to a biological structure the site of interaction must be hydrophobic.
α‐Mannosidase from Phaseolus vulgaris
Authors: Paus Elisabeth , Christensen Terje B. 
Published: March 2005

A purification method for α‐mannosidase from the seeds of Phaseolus vulgaris is described. The main steps are ammonium sulfate precipitation, DEAE‐Sephadex ion‐exchange chromatography, G‐200 gel nitration, and isoelectrie focusing. Two enzymes, α‐mannosidase I and II, with isoleectric points of 5.1 and 6.1 respectively, were found.Most of the α‐mannosidase activity was present as α‐mannosidase I. This enzyme has been extensively purified. According to the criteria of disc electrophoresis and sedimentation equilibrium, the final enzyme preparation was pure. α‐Mannosidase I has a sedimentation coefficient of 11.2 S, and molecular weight of 194000. The enzyme activity was shown to depend on zinc. The pH optimum and Km value have been determined with p‐nitrophenyl‐α‐d‐mannoside as substrate.α‐Mannosidase II was only partially purified and some of its properties were studied in order to compare the two enzymes.
The Early Region of the DNA of Bacteriophage T7
Authors: Scherzinger Eberhard , Herrlich Peter , Schweiger Manfred , Schuster Heinz 
Published: March 2005

RNA polymerase from Escherichia coli transcribes on T7 DNA in vitro and in vivo a polycistronic messenger RNA of 2.2 × 106 molecular weight. This mRNA contains the information for synthesis of T7‐phage RNA polymerase, ligase and lysozyme as was demonstrated by enzyme synthesis in vitro, using the RNA synthesized in vitro as template. Bystudying the kinetics of synthesis of these enzymes in vitro and the ultraviolet‐irradiation sensitivity of enzymesynthesis rates in vivo, the location of the genes on the DNA was estimated. Phage RNA polymerase is encoded within the first half of the mRNA molecule. The information for ligase ends at approximately 5500 nucleotides (1.7 × 106 mol wt.) and the information for lysozyme is close to the 3′‐end of the mRNA.The genes for T7 RNA polymerase and ligase are transcribed by the host RNA polymerase (early region), whereas the genes for endonuclease (gene 3) and for lysozyme are read by E. coli RNA polymerase and by T7‐phage RNA polymerase (early/late region). The DNA beyond the termination signal for host RNA polymerase is transcribed by T7‐phage RNA polymerase in the late phase (late region).Genetic mapping of mutants in the ligase and in the lysozyme genes confirm the data obtained by enzyme synthesis in vitro.
Structural Features of Ring A and the Interaction of 20‐Oxosteroids with Cortisone Reductase
Authors: White Ian H. , Jeffery Jonathan 
Published: March 2005

Kinetic mesurements were made using cortisone reductase and a series of substrates which differed in size, shape and electronic character in the region around C‐3 and in shape around C‐5. This was the part of the molecule most remote from the reacting 20‐oxo group.These structural changes in the substrate resulted in relatively small changes in the apparent Km and apparent V values. It is suggested that, in the enzyme · substrate complex, ring A is probably situated at an extremity of the substrate‐binding site and that there are relatively strong interactions between the enzyme and parts of the steroid other than ring A.
Oxygen‐Dependent Cleavage of the Vinyl‐Ether Linkage of Plasmalogens
Authors: Yavin Ephraim , Gatt Shimon 
Published: March 2005

The low‐molecular‐weight component of rat brain supernatant, which catalyzed the oxygen‐dependent cleavage of the vinyl‐ether linkage of plasmalogen, was purified by chromatography on SE‐Sephadex and DEAE‐Sephadex. A compound was obtained with an absorption peak at 266 nm. It catalyzed the commensurate vinyl‐ether cleavage and oxygen reduction. Evidence is presented that this purified active component is identical with, or very similar to ascorbic acid. Commercial ascorbic acid mimicked the vinyl‐ether cleaving properties of the active component of rat brain supernatant.
Contrary to the rat brain supernatant, the purified active component was unstable and lost activity on heating or storage. Furthermore, vinyl‐ether cleavage and oxygen uptake ceased after 2–3 min. Addition of a protein of rat brain, which by itself was inactive, extended the reaction time for 15–20 min.
In the course of the reaction, 3.5–4 mol oxygen were consumed and 0.3 mol of ascorbate disappeared for each mole of vinyl‐ether‐linkage cleaved. Small quantities of compounds which reacted with thiobarbituric acid were also formed in the course of the reaction.
The products of the reaction were lysolecithin and several split products produced from the aldehydogenic moiety of the plasmalogen molecule; these reacted with p‐nitrophenylhydrazine. Using silicic acid chromatography, about 10–20% of the total carbonyl‐containing compounds were eluted with chloroform—methanol (95:5, by vol.), these were identified as pentadecanal in the presence of smaller quantities of heptadecanal.
The p‐nitrophenylhydrazones of the products were prepared and separated into 3–4 spots on thin‐layer silica gel plates. The fastest moving spot was identified by infrared and mass spectrometry as a hydroxy‐aldehyde, probably α‐hydroxyhexadecanal.
A reaction mechanism is proposed as follows: A ferrous‐ascorbate complex reduces and forms an “active” oxygen. This attacks the vinyl‐ether‐linkage of the plasmalogen forming a diol. Hydrolysis of this diol yields α‐hydroxy‐hexadecanal; oxidative cleavage of this bond yields pentadecanal.
Zur Kinetik der Glucose‐Aufnahme in Erythrocyten
Authors: Lacko Ladislav , Wittke Barbara , Kromphardt Hedwig 
Published: March 2005

A method was developed which allowed the measurement of sugar uptake into red cells after only 4 sec.
The uptake of [14C]glucose from a saline‐glucose medium was followed at two temperatures (0° and 20°C) and at three different trans‐concentrations of non labelled glucose inside the cells: at equilibrium distribution with [Str] = [Scis], for non‐exchange with [Str] = zero at time zero, and for exchange with [Str] = 34 to 35 mM at time zero.
For these conditions, we found linear plots against time, which enabled us to determine the initial velocity for the uptake of label, i.e. the unidirectional influx.
Influx depended on the widely varying cis‐concentration of glucose in the medium in the manner of a simple saturation‐relationship. The parameters Jmax and Km, determined from a reciprocal plot, were different for the three chosen [Str]‐conditions. Some of these parameters were comparable to values of other papers, determined by measuring the efflux of glucose from red cells.
The results were compared with predictions derived from two models of a mobile carrier: the symmetrical model of Levine, Oxender and Stein [1] and the asymmetrical, but passive model of Geck [2]. The relationship between glucose uptake plotted against time and influx plotted against cis‐concentration corresponded to both models. Some, but not all, ratios between the measured parameters matched the predictions of the symmetrical model, whereas all ratios were compatible with the asymmetrical model.
From both models, the translocation resistance comes out to be much greater for the free carrier than for the glucose‐carrier complex: 10 to 30 fold at 20°C and circa 200 fold at 0°C. Hence, the mobility of the free carrier appears to be very much reduced in the cold.
Structure primaire de la caséine β bovine
Authors: Dumas Bruno RIBADEAU , Brignon Ghislaine , Grosclaude François , Mercier Jean‐Claude 
Published: March 2005

This article is the sixth and last of a series devoted to the primary structure of bovine β‐casein [1–5]. In the preceding paper, we presented a partial sequence of this protein in which 156 out of the 209 amino‐acid residues were exactly positioned [5]. Only a few data were given on the tryptic peptides T2 and T3 [1] which corresponded to the unknown part of the molecule. In the present communication, we establish the amino‐acid sequence of these 2 peptides, and discuss the salient features of the β‐casein molecule.Bovine β‐casein A2 is a phosphoprotein constituted of a single polypeptide chain containing 209 amino‐acid residues. Among them are five phosphoseryl residues. From sequence data, it can be written: Asp4, Asn5, Thr9, Ser11, SerP5, Glu17, Gln22, Pro35, Gly5, Ala5, Val19, Met6, Ile10, Leu22, Tyr4, Phe9, Trp, Lys11, His5, Arg4. Its exact molecular weight is 23982, a little higher than that of αs1‐casein, which is 23616 [6]. The total number of 27 amide groups (Asn + Gln) agrees well with previous data obtained by Pion et al. [7] and Peterson et al. [8]. The average hydrophobicity, calculated according to Bigelow [9], is 1330 and it places β‐casein among the most hydrophobic proteins.The sequence obtained emphasizes the uneven charge distribution along the peptide chain. A high negative net charge is located in the first 50 residues. The high proline residue content (16.7%) and the rather uniform repartition of this residue exclude the possibility of a high α‐helix content. Furthermore, the complete absence of segments containing more than 2 adjacent prolyl residues seems to preclude the possibility of poly‐L‐proline structure that was expected from optical‐rotatory‐dispersion studies [10].An interesting extension of the present work is the discovery by Gordon et al [11] that γ‐, TS‐, R‐ and S‐caseins are fragments of β‐casein likely originating from tryptic‐like cleavages of the peptide chain next to the carbonyl groups of some lysyl residues. The γ‐, TS · A2‐ and S‐, TS · B‐ and R‐caseins respectively represent residues 29 to 209, 106 to 209 and 108 to 209. These results explain the occurrence of only one phosphorus atom in the γ‐caseins, the absence of phosphorus in the TS‐, R‐ and S‐caseins [12]. Localization of the substitutions which differentiate the known variants of bovine β‐casein also explains the relationship between β‐, γ‐, R‐, S‐ and TS‐caseins [12,13].The NH2‐terminal tryptic phosphopeptide, previously analyzed by Peterson et al. [14], has been sequenced independently by Manson and Annan [15]. Their results are identical to those reported in a preceding paper [4].
Conformation of Single‐Stranded Polynucleotides
Authors: Gruenwedel Dieter W. 
Published: March 2005

Sedimenting the alternating copolymer, synthetic poly[d(A‐T)], through increasing concentrations of CH3HgOH at pH 6.8 in solutions of different ionic strength reveals that there exists a critical CH3HgOH concentration at which double‐stranded poly[d(A‐T)] becomes denatured. The denaturation reaction is accompanied first by a sudden increase in the rate of sedimentation followed by as sudden a decrease. The change occurs over a narrow concentration range of added CH3HgOH indicating that the transition is highly cooperative. At CH3HgOH concentrations insufficient to induce denaturation, the organomercurial does not interact with poly[d(A‐T)] as judged from the invariance of s20,w with increasing concentrations of CH3HgOH. By contrast, s20,w of denatured poly[d(A‐T)]is strongly dependent on CH3HgOH concentration.It appears that in solvents of low ionic strength s20,w of single‐stranded poly[d(A‐T)] is determined largely by the increase in mass caused by the addition of the methylmercury group to the various binding sites of adenine and thymine. In more concentrated supporting electrolyte solutions, on the other hand, the variation of s20,w with organomercurial concentration can no longer be explained solely on the basis of a variation in molecular weight but presumably involves also changes in the frictional properties of the polymer.
Effects of Aldosterone on RNA and Protein Synthesis in the Toad Bladder
Authors: Rousseau Guy , Crabbé Jean 
Published: March 2005

The hypothesis of a stimulatory effect of aldosterone on RNA, and consequently protein synthesis has been investigated. The influence of this hormone on the incorporation of precursors into RNA and protein was examined in the toad urinary bladder through which sodium transport is stimulated by aldosterone in vitro.Aldosterone increases total nuclear RNA synthesis and also uridine uptake. Particular fractions of this RNA characterized by density gradient centrifugation might be specifically influenced. No effect of aldosterone on cytoplasmic RNA turn‐over rate or on mRNA synthesis could be demonstrated. Examination of the pattern of protein synthesis at the polysome level, of ribosome processing, and of protein turn‐over rate also failed to disclose any definite influence of aldosterone on these parameters.The proposal that the effect of aldosterone on sodium transport is mediated by its action on transcription and translation in target tissues remains therefore founded on indirect evidence to date.