bluuebunny/crossref_metadata_2025_split huggingface dataset:
Steroids in Germfree and Conventional Rats
Authors: Eriksson Håkan 
Published: March 2005

Gas chromatography‐mass spectrometry and radio‐gas chromatography were used to identify metabolites of [14C]corticosterone and [14C]pregnenolone in faeces and urine from germfree and conventional male rats. The metabolites were generally more polar than those in female rats and the main part of those which could be identified were found in the free steroid fraction. In the conventional male rats a number of pregnane‐3,11,16,20,21‐pentol isomers constituted the major corticosterone metabolites identified both in urine and in faeces. In addition 3α(and 3β),20β‐dihydroxy‐5α‐pregnan‐11‐one and 5α‐pregnane‐3α(and 3β),11β,20β,21‐tetrol were excreted in faeces. In the germfree male rats, minor amounts of some C19O3 and C21O3 steroids were excreted as monosulphates in faeces. However, 5α‐pregnane‐3α(and 3β),11β,21‐tetrols were the predominant steroids in this fraction. These compounds also constituted the major part of steroids identified in the disulphate fraction, which also contained 3α(and 3β),11β,21‐trihydroxy‐5α‐pregnan‐20‐one. All radioactive steroids excreted in the urine of germfree male rats were unconjugated. Although none of these compounds could be fully identified evidence was obtained for the presence of several C19O5, C21O4, C21O5, C21O6 and C21O7 steroids.The findings are discussed in relation to previous information on the steroid metabolizing activities of the intestinal flora and sex differences in the metabolism of steroids in rats.
The Kinetics of Light Induced Carotenoid Changes in Rhodopseudomonas spheroides and their Relation to Electrical Field Generation across the Chromatophore Membrane
Authors: Jackson J. Barry , Crofts Antony R. 
Published: March 2005

The shift of the carotenoid absorption spectrum in chromatophores prepared from Rhodo pseudomonas spheroides induced by different types of actinic illumination has been resolved into several distinct, kinetic phases. A saturating 20 ns pulse from a Q‐switched ruby laser elicited a spectral change more rapid than the response time of the mesuring apparatus (1 μs). A rapid change 10–20% greater than this was produced during a saturating 200 μs xenon flash. Additional slower phases (half‐resetimes approximately 300 μs and 5 ms) could be distingushed after the xenon flash. Continuous illumination produced a rapid change of similar extent to that produced by xenon flash but with a risetime limited by the light intensity, and an equally extensive slow change of half‐risetime approximately 83 ms. During prolonged illumination the carotenoid shift decayed by about 50% with an approximate half‐decay time of 30 s.
The effects of certain electron‐transport inhibitors, uncoupling agents, ion‐transporting antibotics and permeant anions on these phases and upon the decay after illumination have been investigated. None of these agents markedly affected the rapid phase of the shift induced by flash illumination. The relation of this phase to membrane potential was indicated by the fact that its decay was stimulated during electrophoretic ion flux. These observations are consistent with the suggestion tht the rapid phase of the carotenoid shift is in response to separation of charge across the chromatophore membrane, between reaction cente bacteriochlorophyll and the primary acceptor. The effects of these specific chemical modifies on the slower pahses of the carotenoid shift were complex. They are discussed in terms of a model in which thes phases reflect the generation of a membrane potential as a result of electrogenic oxidation‐reduction processees. Antimycin A partly inhibited electron flow through such an electrogenic site(s). Valinomycin delayed the formation of the membrane potential by catalysing an initial, electrophoretic K+ efflux. Uncoupling agents causeed a partial but permanent collapse of the electrical field. Permeant anions produced a slight lowering of the steady‐state electrical field by raising the membrane conductivity.
The contribution of the membrane potential to the high‐energy state leading to ATP synthesis is discussed.
Evidence of an Enzymatic Degradation of Insulin in Blood in vitro
Authors: Brodal Björn P. 
Published: March 2005

Haemolyzed red cells from human and rat blood possess the ability to split enzymastically the insulin molecule into its A and B chain without further degradation.The splitting of insulin incubated with different blood preparations, has been studied as a function of the degree of haemolysis, by the use of a trichloroacetic acid precipitation technique using 125I‐labelled insulin. Kinetic data are obtained using haemolysate as crude enzyme.
Formation of the Parasporal Inclusion of Bacillus thuringiensis
Authors: Somerville Hugh J. 
Published: March 2005

Under given experimental conditions, a reproducible sequence of biochemical events can be measured during sporulation in Bacillus thuringiensis. Electron microscope studies reveal that, during its formation, the crystalline inclusion of Bacillus thuringiensis is closely associated with the exosporium. This association persists through several serial sections and can also be demonstrated in a mutant strain which is biochemically blocked soon after crystal formation.Two asporogenic crystalliferous strains produce a toxin active on larvae of Plutella maculipennis whereas two sporogenic, acrystalliferous strains are not toxic.Data from immunological assays and from pulse‐chase and label‐chase experiments with [14C]leucine indicate that the crystal protein is synthesized at the time of appearance of crystal antigens. It is suggested that the crystal is synthesized and assembled on the exosporium.
Characterization of the Complex Containing Rapidly Labelled RNA in EDTA‐Treated Polyribosomes from Rat Liver
Authors: Olsnes Sjur 
Published: March 2005

Polysomes were isolated from livers of rats sacrificed 30 min after an intraperitonal injection of [3H]orotic acid. The labelled material liberated from the polysomes upon treatment wth EDTA sedimented considerably more rapidly than did purified RNA from the same preparation.CsCl‐gradient centrifugation of the labelled material and sedimentation studies of the purified labelled RNA indicated that the sedimentation rate of the rapidly labelled material was correlated neither to the protein content nor to the length of the ribonucleoprotein strand.The rapidly labelled material liberated from unfragmented polysomes banded in a CsCl‐gradient as a single peak. When the polysomes were fragmented by mild RNase treatment prior to the addition of EDTA, two peaks appeared, one with buoyant density of 1.43 and another one with the same buoyant density as that of the 30 S ribosomal subunit (1.54), indicating that it represented material bound to the subunit. After extensive fragmentation most of the radioactive material banded at 1.43 and this was considered to represent ribonucleoprotein fragments with no particle attached.The labelled material with buoyant density 1.43 sedimented slowly, whereas the materila that banded with the 30 S ribosomal subunits sedimented together with the ribosomal subunits.The rapidly labelled material from polysomes treated with deoxycholate had a buoyant density which was slightly higher than that of the small ribosomal subunit, but lower than the buoyant density of the big subunit. After RNase‐treatment of the deoxycholate‐treated polysomes the liberated ribonucleoprotein fragments has a higher bouyant density than that of either ribsomal subunit, indicating that protein had been removed from the ribonucleoprotein strand.The data confirm that the rapidly labelled RNA is present in polysomes as a ribonucleoprotein strand of high protein content. The results indicate that after treatment of the polysomes with EDTA this strand remains bound to one or a few particles (presumably 30 S ribosomal subunits) which can be detached by mild RNase treatment.
Structure primaire de la caséine β bovine
Authors: Ribadeau Dumas Bruno , Grosclaude Francçois , Mercier Jean‐Claude 
Published: March 2005

In a previous communication [1] we have reported the isolation and composition of the tryptic and ‘CNBr’ peptides that account for the complete peptide chain of the bovine β‐casein A2. These peptides had been respectively numbered T1 to T14 and CN1 to CN7.The positioning of peptidde T1 at the amino terminus of the protein was elucidated by comparing the results of Edman degradations carried out on this peptide with those obtained by Kalan et al. [2] for the whole protein molecule. Peptide CN1, which gave peptide T1 by tryptic hydrolysis, accounts for the 92 amino‐terminal residues of β‐casein A2.Similarly peptide T4 is carboxyl terminal since it does not contain any lysyl or arginyl residue. Furthermore the amino acids liberated from this peptide by carboxypeptidase A are those obtained from the whole protein by Peterson et al. [3]. Peptide CN7, which has the same carboxyl terminal sequences, accounts for the 24 carboxyl terminal residues of the protein.The comparison of the fragments obtained by tryptic hydrolysis from the intact β‐casein A2 moelcule and from the ‘CNBr’ eptides have allowed to locate all these ‘CNBr’ peptides, and to assign the correct position of the tryptic fragments from CN2, CN4, CN5, CN6 and CN7, which contain two, one or none arginyl or lysyl residues.The alignment of the tryptic fragments from CN1, which contains six arginyl or lysyl residues, was elucidated by taking use of some previously obtained pptides resulting from incomplete tryptic clavages of the whole β‐casein A2 molecule.Finally the tryptic peptides from CN3, which contains three Lys or Arg residues, were positionned after analysis of fragments liberated from this ‘CNBr’ peptide by hydrolysis with thermolysin.The order of the tryptic and ‘CNBr’ peptides in the β‐casein A2 can then be written: H‐T1‐T9‐T11‐T3‐T2‐T10‐T6‐T12‐T7‐T14‐T5‐T8‐T13‐T4‐OH, and H‐CN1‐CN5‐CN6‐CN2‐CN4‐CN3‐CN7‐OH.
Studies of the Energy‐Transfer System of Submitochondrial Particles
Authors: Nordenbrand Kerstin , Ernster Lars 
Published: March 2005

Submitochondrial particles elicit a fluorescence of 8‐anilino‐naphthalene‐1‐sulfonate which is increased when the particles are brought into the energized state.
Various parameters of the anilino‐naphthalene sulfonate response were investigated in “EDTA particles” from beef‐heart mitochondria in the energized and non‐energized states. The results reveal striking differences between teh two types of anilino‐naphthalene sulfonate response in several respects, including the effects of pH and ionic strength, the number of binding sites, the dissociation constant, and the quantum yield.
Conditions are established which result in a maximal ratio of energy‐dependent to non‐energy‐dependent anilino‐naphthalene sulfonate response and a virtually linear relationship of both types of response to particle concentration. It is shown that, under such conditions, there is a linear inverse relationship between the steady state of energy‐dependnet anilino‐naphthalene sulfonate response and the respiratory rate of the particles as measured with succinate as substrate in the presence of oligomycin and increasing concentrations of an uncoupler. Extrapolation of this straight line to respiratory rate = 0 allows an estimation of the extent of anilinonaphthalene sulfonate response at complete respiratory control, i.e., in the maximally energized state.
Experiments with different substrates and electron‐transport inhibitors reveal that the linear relationship between the extent of energy‐dependent anilino‐naphthalene sulfonate response and the respiratory rate in the presence of increasing concentrations of uncoupler holds only when the cytochrome b‐c1 step of the respiratory chain is rate‐limiting. The available evidence indicates that the energy‐dependent anilino‐naphthalene sulfonate response originates mainly or exclusively from a restricted region or locus of the membrane, which is closely related to energy‐coupling site II of the respiratory chain.
With ATP as the source of energy, the anilino‐naphthalene sulfonate response increases with low, and decreases with high, concentrations of oligomycin, in a fashion similar to that earlier found for oxidative phosphorylation and its reversal.
Effect of Glucuronides on Glucuronide Biosnthesis
Authors: Hänninen Osmo , Marniemi Jukka 
Published: March 2005

1‐Naphthyl and phenolphthalein glucuronides were found to be potent inhibitors of p‐nitro‐phenyl glucuronide synthesis catalyzed by rat liver microsomal fraction. They did not compete with theaglycone, p‐nitrophenol, but with glucuronyl donor, UDPglucuronic acid. The free aglycones, 1‐naphthol and phenolphthalein, were, however, more powerful inhibitors. They competed with p‐nitrophenol andnot with UDPglucuronic acid.Also the o‐aminophenyl glucuronide synthesis in rat liver slices was inhibited by 1‐naphthyl and phenolphthalein glucuronides and free 1‐naphthol.The results indicate that the glucuronyl residue transfer to the aglycone totally block the affinity of the enzyme for the compound, although it is reduced. Glucuronides and their aglycones are apparently bound by different sites in the enzyme and glucuronides attach to UDPglucuronic acid binding site.
Two types of Pyruvate Kinase in Mucor rouxii
Authors: Terenzi Héctor F. , Roselino Eduardo , Passeron Susana 
Published: March 2005

Extracts of mycelium of Mucor rouxii have been shown to contain two forms of pyruvate kinase named Type I and II. They can be separated by DEAE‐cellulose chromatography and by electrophoresis in polyacrylamide gel.Extracts from ungerminated sporangiospores or yeast‐like cells contained only the Type I form. Pyruvate kinase Type II appears during aerobic germination of spores or during conversion of yeast‐like cells to mycelium.Both pyruvate kinases are similar in their molecular weight, pH range of activity, Km with respect to substrates and their response to activators (Mn++ and fructose 1,6‐diphosphate).
Structure of Pig Skin Dermatan Sulfate
Authors: Malmström Anders , Fransson Lars‐Åke 
Published: March 2005

The presence of sulfated uronic acid residues in dermatan sulfate has been known for some time. In view of the copolymeric nature of pig skin dermatan sulfate, it was of interest to see whether the extra sulfate groups were attached to iduronic acid or glucuronic acid residues.Hyaluronidase‐degraded dermatan sulfate was fractionated on Dowex‐1 to yield fractions of varying sulfate content. It was observed that the degree of sulfation was invesely proportional to the glucuronic acid content. Oversulfated dermatan sulfate was subsequently treated with chondroitinase‐AC to yield a completely glucuronic acid‐free polymeric product still bearing all the extra sulfate groups. More direct evidence for the presence of sulfated induronic acid moieties was obtained by Smith degradation of oversulfated, chondroitinse‐AC treated dermatan sulfate. A fast‐moving component isolated by preparative electrophoresis had the molar ratio sulfate; hexosamine 1.8:1 and contained exclusively L‐iduronic acid.
Les nitrate‐réductases bactériennes
Authors: Forget Pierre 
Published: March 2005

Solubilization and Purification. Crude extract is perpared from cells of Micrococcus denitrificans grown anaerobically in the presence of NO3−. Nitrate reductase A is solubilized by an alkaliacetone treatment of particles. The purification consists of four steps: ammonium sulfate precipitation at 35% saturation; Sephadex gel filtration; discontinuous elution from two successive phosphate gel columns, the first eluted by acid phophate bffer, the second by alakline. The enzyme is purified 50‐fold with a yield of 17%. Polyacrylamide gel electrophoresis and ultracentrifugation show the prepartion to be nearly homogeneous (95% purity). Properties of the Purified Enzyme. Isoelectric point: pH 4.2. Molecular weight: (filtration on Sephadex and ultracentrifugation) 160000. Presence of flavins: no FMN and FAD. Absorption spectra: purified preparations have a brown color. Absorption increases continuously from 550 to 280 nm but does not exhibit any peaks in the visible or near‐ultraviolet. In the visible, the higher the specific absorption the higher the iron content of the protein. Heavy metals: the enzyme contains iron but the content varies from one preparation to another, 4 to 8 atoms per mole (Mw= 160000). Some of the iron is lost during purification and 8 atoms sees the value closer to reality. Traces of molybdenum are revealed by analysis, but may be acontamination although we cannot discard the hypothesis that this metal is normally present in the enzyme and lost during the purification. In ths case, it must be assumed that molybdenum is not necessary for the activity of nirate reductase with the artificaial electrons donors used. Labile sulfide: approximately one labile sulfide is found per iron atom. Amino acid composition: high content in aspartic and glutamic acids; low content in cysteine residues. Electron donors: the enzyme uses the reduced forms of viologen indicators, FMNH2, FADH2 but not NADH and NADPH. Substrates: NO3−, C1O3− and BrO3− are substrates. Inhibitors: CN− and N3− are inhibitors. The observed kinetics with 33.3 and 3.33 μM N3− are those of competitive inhibition. The nitrate reductase affinity for azide is one thousand times greater than for nitrate or chlorate. Versene and 1, 10‐phenanthroline are not inhibitors. Influence of pH: activity is maximal at pH 5.6‐5.8 with NO3− and at 6.2–6.4 with C1O3−. Iron function: the following observations suggest this metal plays an essential role in nitrate reductase A catalysis: (a) the higher the iron content of the purified fraction the greater its activity; (b) the 2 inhibitors, CN− and N3−, complex heavy metals; (c) dithionite causes a lowering of the absorption between 300 and 500 nm and this effect is reversed by the addition of nitrate; (d) the competitive inhibition by azide indicates that the iron may be at the active center and may play an important role in the formation of the enzyme‐substrate complex. Conclusion. Nitrate reductase A of M. denitrificans is a non‐heme iron protein.
Binding of Aminoacyl‐tRNA to Ribosomes Programmed with Bacteriophage MS2‐RNA
Authors: Voorma Harry O. , Benne Rob , Den Hertog Tyronne J. A. 
Published: March 2005

The secondary and tertiary structure of bacteriophage RNA is possibly concerned in the regulation of the synthesis of the three proteins encoded by this RNA. The accessibility of the beginning of the three cistrons for ribosomes should therefore be different.We decided to use the aminocyl‐tRNA binding assay to obtain proof of difference in accessibility. Binding studies with aminoacyl‐tRNA to ribosomes, programmed with bacteriophage MS2‐RNA, revelaed that, besides formylmethionyl‐tRNA, alanyl‐tRNA is also extremely well bound to the initiation complex. This result was taken to indicate that the beginning of the coatgene is the major ribosomal binding site with intact RNA. In experiments with other aminoacyl‐tRNAs it was shown that seryl‐ and lysyl‐tRNA rection. In most experiments no significant binding of arginyl‐tRNA could be recorded. Similar experiments were performed with framented MS2‐RNA of which it is known that the secondary and tertiary structure content is much lower. Binding results with fragmented MS2‐RNA revealed that the accessibility of the beginning of the different cistrons reached similar levels as indicated by the amount of binding of the following aminoacyl‐tRNAs: alanyl‐, seryl‐, lysyl‐ and arginyl‐tRNA. The synthesis of the formylmethionyl‐peptides : F‐Met‐Ala, F‐Met‐Ser, F‐Met‐Arg, F‐Met‐Ala‐Ser and F‐Met‐Ser‐Lys does occur in this binding reaction, although the efficiency of the dipeptide reaction is different for the various dipeptides involved.
Distinct Antignic Specificities of Alanine Peptide Determinants Attanched to Protein Carriers via Terminal Amino or Carboxyl Groups
Authors: Schechter Israel , Clerrici Enrico , Zazepitzki Etti 
Published: March 2005

L‐Alanine chains, serving as haptenic groups were coupled to proteins in opposite directions. There was no cross‐precipitation reaction between “anti‐amino‐alanyl” antibodies (obtained by immunization with conjugates containing alanine chains with free α‐amino groups) and “anti‐alanyl‐carboxyl” antibodies (obtained by immunization with conjugates containing alanine chains with free α‐carboxyl groups). The properties of the combining sites of these antibodies were evaluated by means of the hapten‐inihibtion method. For the inhibition of the precipitin reaction, series of free peptides and peptide derivatives (blocked in th amino or carboxyl function) composed of L‐ and D‐alanine residues were employed. The results led to the conclusion that the overall properties of the combining sites in both systems, but not their specificity, were quite similar. The size of the combining site of “anti‐amino‐alanyl” antibodies is such as to accommodate a tripeptide, whereas that of “anti‐analy‐carboxyl” antibodies is such as to accommodate tri‐to a tetrapeptide. In both systems the most exposed portion of the antigeic determinant is immunodominant. Thus, “anti‐amino‐alanyl” antibodies bind very poorly peptides in which the amino terminal end was altered (e.g., by replacing the N‐terminal L‐alanine residue by a D‐residue, or by N‐acetylation), but will combine very effectively with amides of L‐alanine peptides. Correspondingly, “anti‐alanyl‐carboxyl” antibodies react very poorly with alanine peptides in which the aminio terminal end was altered, e.g., they do not bind amides of L‐alanine peptides. Both types of antibodies can react with free L‐alanine peptides, but in their combining sites these peptides are probably bond in oppoiste direction. Thus, antibodies with distinctly different specificities can be elicited against L‐alanine peptide determinants, depending on their mode of attachment in the immunogen.It is also shown that more precise information on the combining sites is obtained by comparing pairs of haptens of equal size which differ from one another in a particular feature, rather than from studying the effect of elongation in a homologous series of haptens.
Transfer Ribonucleic Acid from Mycoplams laidlawii A
Authors: Feldmann Horst , Falter Hermann 
Published: March 2005

tRNA and an enzyme fraction which contain aminoacyl‐tRNA‐synthetases and tanformylase, were prepared from Mycoplasma laidlawii A. After chromatography of tRNA on benzoylated‐DEAE‐cellulose, amino acid acceptor activites were determined. One or more species of tRNA were found for the following amino acid (number of isoaccepting species in brackets): alanine (1), arginine (2), cysteine (1), glycine (1), isoleucine (2), leucine (3), methionine (2), phenylalanine (1), serine (3), tyrosine (1), and valine (3). The mthionine specific tRNA was separated into a homologously formylatable and a non‐formylatable species.Cross‐reactions in heterologous systems from M. laidlawii A, Escherichia coli, and yeast were studied in some detail for methionine and phenylalanine. Aminoacylation was possible in all combinations of methionine specific tRNAs and enzymes. Transformylase of mycoplasma formylates tRNA from E. coli, but none of the methionine specific tRNAs from yeast.The content of minor nucleotides in tRNA from M. laidlawii A was determined mainly from [32P]tRNA by two‐dimensional thin layer chromatography.The findings are compared with those reported for other mycoplasma species and discussed in view of the genetic relationship of mycoplasma other microorganisms.