bluuebunny/crossref_metadata_2025 huggingface dataset:
Affinity labeling of gamma-glutamyl transpeptidase and location of the gamma-glutamyl binding site on the light subunit.
Authors: Tate S S , Meister A
Published: May 2006

Gamma-Glutamyl transpeptidase, which consists of two nonidentical subunits, is rapidly inactivated with respect to its transpeptidase and hydrolase activities by the gamma-glutamyl analogs 6-diazo-5-oxo-L-norleucine and L-azaserine. Inactivation, which is prevented by gamma-glutamyl substrates (but not by acceptor substrates), is accelerated by maleate, which was previously shown to enhance utilization of glutamine by transpeptidase. 6-Diazo-5-oxo--norleucine reacts specifically, covalently, and stoichiometrically at the gamma-glutamyl site of the enzyme, which was localized through studies with 6-diazo-5-OXO-[14C]norleucine to the light subunits of both the transpeptidase of rat kidney (which has subunits of molecular weights 22,000 and 46,000) and the transpeptidase of human kidney (which has subunits of molecular weights 22,000 and 62,000). The findings, which indicate that these enzymes have similar gamma-glutamyl binding subunits, are relevant to the structure-function relationships of this membrane-bound enzyme and its physiological role.
Aminoglycoside-modifying enzyme of an antibiotic-producing bacterium acts as a determinant of antibiotic resistance in Escherichia coli.
Authors: Courvalin P , Weisblum B , Davies J
Published: May 2006

Bacillus circulans NRRL B-3312, a nonpathogenic bacterium that produces the aminoglycoside antibiotic butirosin, is known to contain an aminoglycoside phosphotransferase that is similar to the neomycin phosphotransferases of clinically isolated antibiotic-resistant bacteria. Purified DNAs from B. circulans and the plasmid ColE1-ApR were digested with EcoRI endonuclease and the resulting fragments covalently joined with polynucleotide ligase. The recombined DNA was used to transform E. coli and ampicillin-neomycin resistant colonies were selected. Analysis of several clones indicated that neomycin resistance in the E. coli transformants was due to the presence of the B. circulans phosphotransferase gene. This observation is consistent with the notion that anitbiotic-modifying enzymes from antibiotic-producing organisms may be the sources of antibiotic resistance in plasmid-containing bacteria.
Rat liver preproalbumin: in vitro synthesis and partial amino acid sequence.
Authors: Strauss A W , Donohue A M , Bennett C D , Rodkey J A , Alberts A W
Published: May 2006

Rat liver poly(A)-containing RNA greatly stimulated incorporation of radioactive amino acids into protein when added to a wheat germ in vitro translation system. Approximately 7% of the labeled synthetic product was precipitated following indirect immunoprecipitation with antisera to rat serum albumin. Analysis of this material, and of the cyanogen bromide fragments derived from it, by sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed that it contained an NH2-terminal extension of about 2500 daltons when compared to rat serum albumin. Automated sequence determination of purified cell-free product labeled with various radioactive amino acids revealed the presence of 18 additional amino acids NH2-terminal to the sequence of rat proalbumin. The partial sequence of this extension was found to be: Met-X-X-X-X-Phe-Leu-Leu-Leu-Leu-Phe-X-X-X-X-X-Phe-X-proalbumin. On the basis of this evidence, the immunoprecipitable cell-free product was designated preproalbumin.
Role of sialic acid in survival of erythrocytes in the circulation: interaction of neuraminidase-treated and untreated erythrocytes with spleen and liver at the cellular level.
Authors: Aminoff D , Bruegge W F , Bell W C , Sarpolis K , Williams R
Published: May 2006

Sialidase (neuraminidase; acylneuraminyl hydrolase; EC 3.2.1.18)-treated erythrocytes obtained from different species are susceptible to rapid elimination from the circulation and are sequestered in the liver and spleen. The present studies were concerned with the mechanism of this clearance and how it may relate to the normal physiological process of removing senescent erythrocytes from the circulation. The results obtained indicate a preferential recognition of sialidase-treated as compared to normal erythrocytes by mono-nuclear spleen cells and Kupffer cells of the liver. This recognition manifests itself in both autologous and homologous systems by adhesion of the complementary cells in the form of rosettes, and as such could explain the removal of enzyme-treated erythrocytes from the circulation with their accumulation in liver and spleen. This phenomenon may represent a normal physiological mechanism for removal of senescent erythrocytes containing decreased sialic acid.
Generation of macrophage migration inhibitory activity by plasminogen activators.
Authors: Roblin R O , Hammond M E , Bensky N D , Dvorak A M , Dvorak H F , Black P H
Published: May 2006

Medium from cultures of simian virus 40-transformed mouse 3T3 cells (SV3T3) inhibits the migration in vitro of peritoneal exudate cells (macrophages) from guinea pigs while medium from untransformed 3T3 cultures does not [Hammond, M. E., Robbin, R. D., Dvorak, A. M., Selvaggio, S. S., Black, P. H. & Dvorak, H. F. (1974) Science 185, 955-957]. The present paper describes the generation of migration inhibitory factor (MIF)-like activity for peritoneal exudate cells from guinea pigs after incubation of a serum-free harvest fluid from SV3T3 cells with guinea pig serum. Inhibited macrophages lose a densely staining material from the cell surface coat compared with uninhibited guinea pig peritoneal exudate cells. The factor in SV3T3 harvest fluids which generates the migration inhibitory activity appears to be plasminogen activator, i.e., a serine protease, because (i) plasminogen activator activity and the factor which generates MIF-like activity copurify, and co-chromatograph on Sephadex G-200 columns, and (ii) plasminogen activator activity and capacity to generate MIF-like activity are simultaneously lost upon treatment with [3H]diisopropylfluorophosphate. In addition, a purified preparation of a known plasminogen activator, human urokinase, can also generate MIF-like activity upon reaction with guinea pig serum. Because transformation of 3T3 cells by SV40 increases their plasminogen activator secretion, enhanced secretion of plasminogen activator by SV3T3 cells may explain why formation of MIF-like activity is observed in SV3T3 but not 3T3 cultures. These results reveal a biochemical pathway whereby a product secreted by virus-transformed cells affects one function of a cell central to the host's immunological defense system.
Magnesium and calcium effects on uptake of hexoses and uridine by chick embryo fibroblasts.
Authors: Bowen-Pope D F , Rubin H
Published: May 2006

Cultures of chick embryo fibroblasts were incubated for varying periods in media containing different concentrations of Ca2+ and Mg2+-Mg2+ deprivation produced a gradual decrease in the Vmax of the glucose transport system for the D-glucose analogues 3-O-[3H]methyl-D-glucose and 2-deoxy-D-[3H]glucose and a parallel decrease in the rate of production of lactate from glucose in the medium. It greatly reduced the rates of [3H]uridine uptake and incorporation by decreasing the Vmax of the uridine transport system. Addition of Mg2+ to Mg2+-deprived cultures rapidly increased the rate of [3H]uridine uptake without requiring protein synthesis and increased the rate of 2-deoxy-D-[3H]glucose uptake without requiring RNA synthesis. These effects of changes in Mg2+ concentration qualitatively reproduce the effects of such variables as cell density and serum and insulin concentrations. Ca2+ deprivation resulted in similar, though much smaller, changes in the activities of the two transport systems, but also greatly increased the "leakiness" of the cells to the nontransported hexose L-[3H]glucose.
Identification of a purified complement-fixing antigen as the Epstein-Barr-virus determined nuclear antigen (EBNA) by its binding to metaphase chromosomes.
Authors: Ohno S , Luka J , Lindahl T , Klein G
Published: May 2006

A soluble complement-fixing antigen carried by Epstein-Barr virus (EBV)-transformed human cells has been previously extracted from cell nuclei and purified by DNA-cellulose chromatography [Luka, J., Siegert, W. & Klein, G. (1977) J. Virol., in press]. On addition of this antigen to methanol/acetic acid-fixed metaphase chrmosomes, followed by exposure to human sera containing antibodies against the EBV-determined nuclear antigen (EBNA), brilliant positive staining was obtained by anti-complement immunofluorescence. There was no staining after exposure to EBV-negative sera. Moreover, a nuclear protein fraction, prepared from an EBV-negative cell line in an analogous fashion, failed to induce the staining reaction. These data identify the soluble purified antigen as the EBV-determined nuclear antigen. The purified antigen has a molecular weight of 174,000 +/- 15,000, as determined by sucrose gradient centrifugation and gel filtration experiments. In neutral buffers containing 0.5-1.0 M NaCl, the antigen dissociates into a form of approximately one-half the original molecular weight with retained complement-fixing activity. This "monomer" has a molecular weight of 98,000 +/- 8,000.
Mapping of inverted repeated DNA sequences within the genome of simian virus 40.
Authors: Hsu M T , Jelinek W R
Published: May 2006

Single-stranded, linear DNA of simian virus 40 (SV40) created by denaturing the endonuclease EcoRI- or Hpa II-generated, linear, double-stranded products from form I DNA of SV40 was analyzed for regions of inverted repeated sequences by visualization with the electron microscope. Six hairpin loops were found at positions 0.11-0.30 (two loops forming a "rabbit ears" structure), 0.47-0.52, 0.63-0.68, 0.70-0.76, and 0.90-0.96. The nucleotide sequences within all of these inverted repeats may be related since the looped regions can crosshybridize with one another and, thus, the SV40 genome may contain regions of interspersed repeated and unique sequences. The map positions of the 3' and 5' ends of the early and late messenger RNAs, as determined by others, lie within regions of inverted repeated sequences. Previously recorded recombination events that occurred either within the SV40 genome or between SV40 DNA and other genomes have apparently occurred frequently at positions of inverted repeated sequences within the SV40 DNA.
Structural heterogeneity of C2 Complement protein and its genetic variants in man: a new polymorphism of the HLA region.
Authors: Meo T , Atkinson J P , Bernoco M , Bernoco D , Ceppellini R
Published: May 2006

A zymogram method, following thin-layer isoelectric focusing in a polyacrylamide gel, allows resolution of the lytic activity of serum C2 complement protein in a spectrum of molecular forms. This spectrum is characteristic in each of the species studied (man, rhesus monkey, guinea pig, and hamster). Moreover, two different alternative patterns are observed in man: each of the six major lytic bands characteristic of the most common pattern (herein designated C2(1) is duplicated in the least common pattern (C2(2-1), with an additional band displaced cathodally by not more than 0.04 pH unit. Distribution of phenotypes C2(1) and C2(2-1) in a Caucasion population is in agreement with the hypothesis that they are controlled by two alleles, C2(1) and C2(2), with frequencies 0.96 and 0.04 +/- 0.01. Segregation studies show that the two alleles are codominant and identify a locus in the HLA region. No recombinants with HLA-B were detected among 27 informative meioses, generating a cumulative lod score of 6.321 at equals 0. These findings suggest that the individuals with the C2-deficient trait might be interpreted as homozygotes for a third and rarest amorph C2 degrees of the same locus.
Spatial configuration of ordered polynucleotide chains: a novel double helix.
Authors: Olson W K
Published: May 2006

Structural details are reported for a novel right-handed polynucleotide double helix stabilized by vertical base stacking and hydrogen bonding. The primary difference between this duplex and the familiar Watson-Crick horizontally stabilized polynucleotide complex arises in the glycosyl rotation of the heterocyclic bases with respect to the sugar-phate backbone. In the vertical double helix the bases adopt a fairly unusual (although not sterically impossible) high-anti conformation, while in the horizontal models deduced from x-ray analyses the bases occur in the favored anti arrangement. The base pairing scheme in both duplexes is the standard Watson-Crick type. The vertical double helix is demonstrated to be a plausible model for the unusual complex formation observed between complementary synthetic polycyclonucleotides (the bases of which are fixed by a chemical linkage in the high-anti orientation) and also a potential alternative ordered structure available to naturally occurring nucleic acid systems that can adopt both anti and high-anti glycosyl arrangements.
Circular dichroism of adenosine dinucleotides.
Authors: Pettegrew J W , Miles D W , Eyring H
Published: May 2006

The circular dichroism and absorption spectra of (3'-5')ApA, (5'-5')AppA, and (5'-5')ApcpA [diadenosine(5'5') pyrophosphonate] under various ionic coditions and at various temperatures are reported. Temperature studies reveal that under the same ionic strength and solvation conditions the probability of base-base interaction is ApA greater than AppA greater than ApcpA. It is found that increasing the molar refractivity of the solvent decreases the base-base interaction for both ApA and AppA and that both compounds proceed to a monomeric state in solvents of high molar refractivity. Solvent effect studies also indicate that a major percentage of the driving force for the base-base interaction can be accounted for by London dispersion forces. Low ionic strength appears to favor the base-base interacted conformation. All compounds tend toward the same noninteracted form at high temperatures. Plots of [theta]lambda against X (where X is an experimental parameter) were constructed in order to obtain information concerning which transitions might be undergoing oscillator coupling. To a first approximation, transitions coupled to each other should have very similar deta[theta]lambda/detaX for the experimental range of X. Applying this technique to the experimental data yielded information concerning possible transition coupling.
Affinity of intact Escherichia coli for hydrophobic membrane probes is a function of the physiological state of the cells.
Authors: Nieva-Gomez D , Gennis R B
Published: May 2006

The fluorescence parameters of several common membrane probes in the presence of whole E. coli have been examined. The probes included electrically neutral lipophilic molecules N-phenyl-1-naphthylamine, pyrene, and 1,6-diphenyl-1,3,5-hexatriene as well as the negatively charged molecule 8-anilino-1-naphthalene sulfonate. It is demonstrated in each case that certain fluorescence parameters are a function of the state of energization of the cells. All the probes appear to monitor structural changes in the E. coli envelope which accompany the energization and de-energization of the cells. tthe phenomenon is completely reversible as demonstrated by re-energizing anoxic cells by the addition of oxygen, or starved cells by the addition of substrate. All the results are qualitatively consistent with an increased binding of probe by de-energized cells and a subsequent expulsion of probe when the cells are re-energized. A pyrene substituted with a photosensitive group, 1-azidopyrene, has been synthesized. Photolysis in the presence of a suspension of energized E. coli reveals a relatively small amount of probe irreversibly bound to the cells. However, in the presence of cells that have been de-energized the amount of irreversibly bound probe is dramatically increased. This molecule should be useful for localizing the regions of the bacterial envelope that are involved in the structural changes being monitored in these experiments.
In vitro assembly of pure tubulin into microtubules in the absence of microtubule-associated proteins and glycerol.
Authors: Herzog W , Weber K
Published: May 2006

Microtubule protein from porcine cerebrum was fractionate into pure tubulin and microtubule-associated proteins by chromatography on phosphocellulose. In agreement with previous studies, pure tubulin does not form microtubules to a significant extent at 37 degrees in normal assembly buffers, which are characterized by a low concentration of Mg2+ ions. If, however, the Mg2+ concentration is raised to approximately 10 mM, rapid and extensive self-assembly of pure tubulin into microtubules is observed, provided the tubulin concentration is above 2.5 mg/ml. At a protein concentration of 3 mg/ml, the lag period is 1.5 min and the assembly process is virtually complete after 6 min at 37 degrees. These microtubules are like normal microtubules--sensitive to calcium ions, colchicine, and low temperature.
Translation in vitro of rat liver messenger RNA coding for ligandin (glutathione S-transferase B).
Authors: Daniel V , Smith G J , Litwack G
Published: May 2006

Poly(A)-containing rat liver mRNA isolated from animals injected with phenobarbital and uninjected controls was translated efficiently in a wheat-germ system. The synthesis of ligandin (glutathione S-transferase B; glutathione transferase; RX-gluathione R-transferase, EC 2.5.1.18) was detected by immunoprecipitation with a highly purified monospecific ligandin antibody and analysis by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The extent of incorporation of [35S]methionine into ligandin in the translation system was similar for poly(A)-containing messages from un-infected animals and those treated with phenobarbital.
Hemolysis of human erythrocytes by transient electric field.
Authors: Kinosita K , Tsong T T
Published: May 2006

Exposure of human erythrocytes, under isotonic conditions, to a high voltage pulse of a few kV/cm leads to total hemolysis of the red cells. Experiments described herein demonstrate that the hemolysis is due to the effect of electric field. Neither the effect of current nor the extent of the rapid Joule-heating to the suspending medium shows a direct correlation with the observed hemolysis. Voltage pulsation of the erythrocyte suspension can induce a transmembrane potential across the cell membrane and, at a critical point, it either opens up or creates pores in the red cells. In isotonic saline the pores are small. They allow passage of potassium and sodium ions but not sucrose and hemoglobin molecules. The pores are larger in low ionic conditions and permit permeation of sucrose molecules, but under no circumstances can hemoglobin leak out as the direct result of the voltage pulse. Kinetic measurements indicate that the hemolysis of the red cells follows a stepwise mechanism: leakage of ions leads to an osmotic imbalance which in turn causes a colloidal hemolysis of the red cells. Other effects of the voltage pulsation are also discussed.
Solid-like character of virus solutions.
Authors: Kupke D W , Beams J W
Published: May 2006

The solid-like behavior of turnip yellow mosaic virus solutions following the extrusion of viral RNA in alkali was observed with a torsion-fiber balance developed for the purpose. This method provided a direct measurement of the yield stresses required to break or liquefy these solutions. The yield stresses were found to increase and to be less time dependent with increasing concentrations of the virus and they were maximal at room temperatures. If the virus had been damaged, as by freeze-thaw, little or no solid-like behavior could be demonstrated. Purified viral capsids, with or without added RNA, were also inactive. The values for the yield stresses were of the same order as the value reported previously with the use of a magnetic suspension viscometer; hence, the apparent coherency appears unrelated to the magnetic fields generated by the latter instrument. These solutions behaved as typical liquids after the required stress was applied [about 0.005 to 0.17 dyne cm-2 (0.05 to 1.7 micronN cm-2)], these forces being smaller than those usually conferred by ordinary handling.
Thermotaxis by pseudoplasmodia of Dictyostelium discoideum.
Authors: Poff K L , Skokut M
Published: May 2006

The temperature dependence of migration rate and of the thermotactic sensitivity of pseudoplasmodia of Dictyostelium discoideum has been measured. Migration rate increases with temperature to 20 degrees, is temperature insensitive from 20 degrees to 27.5 degrees, and decreases with temperature to 29 degrees, above which point migration ceases. However, pseudoplasmodia formed from cells grown at 23.5 degrees are thermotactic only from 22 degrees to 27.5 degrees. Thus, a temperature dependence of migration rate is not sufficient to explain thermotaxis. Because random lateral movements by the pseudoplasmodia have not been observed, the measurement of the temperature gradient appears to be spatial rather than temporal, with a half-maximal thermotactic response to a temperature gradient of about 0.04 degree/cm, or 0.0004 degree across an average pseudoplasmodium. Thermotactic sensitivity is adaptive, with pseudoplasmodia formed from cells grown at 20 degrees capable of thermotaxis at temperatures lower than cells grown at 23.5 degrees.
Centers involved in the autonomic reflex reactions originating from stretching of the atria.
Authors: Koizumi K , Nishino H , Brooks C M
Published: May 2006

Stretching the atria in anesthetized dogs produces reflex changes in heart rate, and in cardiac and renal sympathetic nerve activity. Anemic decerebration, cord transection at C4-C5, and severance of vagal or sympathetic cardiac nerves was done to identify the pathways and centers essential for these reflexes. Stretching the right atrium produced an aceleration of the heart and a definite increase in sympathetic nerve activity. Left atrial-stretch caused biphasic responses: an initial sympathetic nerve inhibition and slower heartbeat folowed by sympathetic excitation and heart acceleration. The afferents responsible were carried mainly by the vagi; efferent neural control of the heart was mostly sympathetic. The reflex inhibition observed was integrated chiefly at the medullary level, but supramedullary structures contributed to the augmentation in sympathetic activity and heart rate. When central connections between vagal afferent and sympathetic efferent pathways were separated by cord transection, atrial stretch caused a decrease in heart rate due to reflex action through the vagal loop. After the cord was sectioned, we found that some afferent impulses from the atria traveling in sympathetic nerves produced a slight reflex augmentation of sympathetic efferent activity, though insufficient to affect the heart rate. Somatosympathetic reflexes evoked in cardiac and renal sympathetic nerves by stimulation of various somatic afferent pathways were also affected by atrial stretch indicating central nervous system interactions. Reflex responses to right atrial stretch were superimposed on accelerations of myogenic origin.
On differentiation of integrals
Authors: Cordoba A. , Fefferman R.
Published: May 2006

A technique is introduced to relate differentiation and covering properties of a basis. In particular, we find that the basis associated with a sparse set of directions differentiates integrals of functions locally in
L
2
.
Cytoplasmic nonpolysomal ribonucleoprotein particles in sea urchin embryos and their relationship to protein synthesis
Authors: Dworkin Mark B. , Rudensey Lyle M. , Infante Anthony A.
Published: May 2006

We have examined the relationship between the newly synthesized mRNA that enters polysomes in sea urchin embryos and the messengerlike RNA that enters the pool of ribosome-free ribonucleoprotein particles (free RNPs or informosomes). Although the RNA in the free RNPs turns over 25% more rapidly than in the polysomes, labeling kinetics indicate that the RNA containing poly(A) [poly(A)(+)RNA] and the RNA not containing poly(A) [poly(A)(-)RNA] within each cytoplasmic compartment have very similar half-lives. The poly(A)(+)RNA from both free RNPs and polysomes binds ribosomes almost equally well in a reticulocyte lysate, and this binding is sensitive to inhibitors of initiation. The poly(A)(-)RNA from polysomes initiates as well as poly(A)(+)RNA; however, poly(A)(-)RNA from free RNPs is only half as efficient in binding to ribosomes, and by this criterion is only 50% mRNA.

We have also examined the size and dynamics of shortening of the poly(A) tails of poly(A)(+)RNA from free RNPs and polysomes. Pulse-labeled poly(A) from both free RNPs and polysomes is about 180 nucleotides in length. Poly(A) shortening is very rapid in polysomes; steady-state labeled polysomal RNA is largely devoid of the 180-nucleotide-long poly(A) segments. Poly(A) shortening in free RNPs is slower; half of the poly(A) derived from steady-state free RNPs is still 180 nucleotides long. Despite this difference in the rates of poly(A) shortening, polysomes and free RNPs have very similar half-lives. There is, then, no obvious relationship between poly(A) shortening and turnover of mRNA in these embryos. The data are interpreted to mean that poly(A)(+)RNA from free RNPs is enriched for a class of mRNA that initiates less frequently
in vivo
than the bulk of the cellular mRNA.
Characterization of a rat liver factor that inhibits initiation of protein synthesis in rabbit reticulocyte lysates
Authors: Delaunay Jean , Ranu Rajinder Singh , Levin Daniel H. , Ernst Vivian , London Irving M.
Published: May 2006

Protein synthesis in rabbit reticulocytes and their lysates is regulated by heme. In heme-deficient reticulocyte lysates, protein synthesis proceeds at the initial rate for several minutes and then declines abruptly. Inhibition of protein synthesis is due to the activation of a heme-regulated translational inhibitor (HRI) which blocks the initiation of protein synthesis. Addition of the isolated HRI to hemin-supplemented lysates causes inhibition of initiation similar to that observed in heme-deficiency. HRI has been shown to be a protein kinase that specifically phosphorylates the Met-tRNA
f
binding factor (eIF-2). We have isolated an inhibitor (LI) of protein chain initiation from rat liver which displays properties similar to those of HRI: (
i
) the chromatographic behavior of LI on DEAE-Sephadex, DEAE-cellulose, and phosphocellulose is similar to that of HRI; (
ii
) both LI and HRI inhibit protein chain initiation in rabbit reticulocyte lysates with the same kinetics of inhibition—i.e., an initial period of synthesis for several minutes at the control rate followed by an abrupt decline in the rate of initiation; (
iii
) both inhibitions are prevented or reversed by eIF-2; (
iv
) GTP (2 mM) prevents, and ATP (2 mM) potentiates, the inhibition of protein synthesis induced by either inhibitor; (
v
) LI is associated with a protein kinase that also phosphorylates the 38,000-dalton subunit of elF-2. These findings indicate that a mechanism for the regulation of protein synthesis similar to that found in rabbit reticulocytes may be present in rat liver.
Cryoenzymology in mixed solvents without cosolvent effects on enzyme specific activity.
Authors: Douzou P , Balny C
Published: May 2006

Water-soluble polyelectrolytes in interaction with proteins are described. These polyelectrolytes make it possible to investigate enzyme-catalyzed reactions in cooled mixed solvents without the usual effects of their organic solvent component on enzyme specific activity. The applicability of techniques developed is illustrated by results obtained on several systems. The possibility of an electrostatic "sorting out" of solvents and its potentialities in cryoenzymology are discussed.
Nucleic acid helix-unwinding properties of ribosomal protein S1 and the role of S1 in mRNA binding to ribosomes.
Authors: Kolb A , Hermoso J M , Thomas J O , Szer W
Published: May 2006

The presence of ribosomal protein S1 in 30S ribosomes is indispensable for the formation of 30S initiation complexes with natural mRNA. The 30S subunits lacking S1 retain activity with AUG as mRNA and are also active in poly(rU)-directed binding of Phe-tRNA. Isolated protein S1 stoichiometrically disrupts the secondary structure of helical and stacked single-stranded polynucleotides and converts them into their fully or partially denatured forms. A mono-N-ethylmaleimide derivatives of S1 is nearly devoid of any RNA helix-unwinding properties but is readily incorporated into 30S subunits deficient in S1. The resulting N-ethylmaleimide-S1-containing 30S subunits are completely inactive in the binding of MS2 [3H]RNA and in the formation of an initiation complex with MS2 RNA as mRNA. They retain activity in the binding of the initiator fMet-tRNA in response to the trinucleotide AUG and in the binding of Phe-tRNA in response to poly(U). They also retain the capacity to bind 50S subunits and to form 70S couples. These results suggest that a correlation exists between the RNA helix-unwinding capacity of isolated S1 and the function of S1 in the ribosomal binding of natural mRNA when the protein becomes part of the 30S subunit.
Regulation by estrogen of the vitellogenin gene.
Authors: Skipper J K , Hamilton T H
Published: May 2006

The vitellogenin gene is inactive in the liver of male Xenopus laevis, unless exogenous estrogen is administered. We have previously shown that conventional doses of estradiol-17beta result in the appearance of new hepatic messenger RNAs, some of which are encoded for vitellogenin. We now report that much higher doses of the hormone (2 mg/frog per day for 4 days) are required to elicit maximal responses. The relative levels of membrane-bound polysomes and vitellogenin mRNA were determined as a function of time and dose of hormone. Translation of total polysomal RNA in a cell-free system derived from wheat germ was used to estimate the relative levels of vitellogenin messenger RNA. Faithful translation of this messenger RNA was indicated by two lines of evidence: labeled cell-free products were immunoprecipitated with antivitellogenin antibody, and the migration of the major labeled product in sodium dodecyl sulfate/acrylamide gels was identical to that of native vitellogenin. Our results establish conditions for maximal estrogen-induced responses in this system, and are compatible with the hypothesis that a major regulatory mechanism of steroid hormones in the control of protein synthesis is that of gene activation and regulation of messenger RNA levels.
Isolation of bindin: the protein responsible for adhesion of sperm to sea urchin eggs.
Authors: Vacquier V D , Moy G W
Published: May 2006

The insoluble granular material of the acrosome vesicle of sea urchin sperm has been isolated and shown to be a single 30,500 dalton protein for which the name "bindin" is proposed. The data presented are consistent with the hypothesis that bindin is the adhesive responsible for the attachment of sperm to the vitelline layer of the egg. Experimental results suggest that bindin may act by binding to carbohydrate receptors of vitelline layer glycoproteins. The speculation is made that sperm bindins may be the general mechanism by which animal sperm attach to eggs.
Neuronal actions of endorphins and enkephalins among brain regions: a comparative microiontophoretic study.
Authors: Nicoll R A , Siggins G R , Ling N , Bloom F E , Guillemin R
Published: May 2006

The brain peptides alpha- and beta-endorphin, leucine- and methionine-enkephalin, as well as the opiate normorphine, have been evaluated by microiontophoresis for their effects on neuronal activity in several regions of the rat brain. In cerebral cortex, brainstem, caudate nucleus, and thalamus, most responsive cells were inhibited by the peptides and by normorphine, while in hippocampus all responsive cells were excited. Both inhibitory and excitatory responses were blocked by the narcotic antagonist naloxone. Occurrence of responsive cells encountered in a particular region was loosely correlated with density of stereospecific opiate binding sites as reported by others. These results are consistent with the hypothesis that the endorphins and enkephalins may represent a new class of central neurotransmitters; among other functions, these peptides may play a role in the regulation of behavior and the expression of psychopharmacological agents such as the opiate alkaloids.
Deformations of instantons
Authors: Atiyah M. F. , Hitchin N. J. , Singer I. M.
Published: May 2006

A study is made of the self-dual Yang-Mills fields in Euclidean 4-space. For SU(2) gauge theory it is rigorously shown that the solutions depend on 8
k
- 3 parameters, where
k
is the Pontrijagin index.
Molecular properties of the nerve growth factor secreted in mouse saliva.
Authors: Murphy R A , Saide J D , Blanchard M H , Young M
Published: May 2006

Some molecular properties of the nerve growth factor (NGF) secreted in mouse saliva and that present in submandibular glands have been measured for comparison with previously studied forms of NGF. The results show that mouse saliva contains two biologically active NGF species. One has a molecular weight near 114,000, and the other, a molecular weight of 13,000. The larger form is being continuously degraded to yield the smaller one, probably as a result of a slow enzymatic process. Virtually identical results were obtained with crude submandibular gland extracts. The larger NGF is neither the well-known 7S NGF nor 2.5S NGF. Our results indicate that the larger salivary NGF is the naturally occurring form of NGF as it exists in the submandibular gland and as it is secreted in saliva. Its biological properties and its function in saliva, if any, remain to be elucidated.
Escherichia coli 5S RNA binding proteins L18 and L25 interact with 5.8S RNA but not with 5S RNA from yeast ribosomes.
Authors: Wrede P , Erdmann V A
Published: May 2006

Reconstitution experiments showed that the two Escherichia coli 5S RNA binding proteins L18 and L25 form a specific complex with yeast 5.8S RNA and not with yeast 5S RNA. The yeast 5.8S RNA-E. coli protein complex was found to exhibit ATPase and GTPase activities that had previously been observed for the E. coli 5S RNA-protein complex. The tetranucleotide UpUpCpG, which is an analog of the tRNA fragment TpsipCpG, interacted strongly with 5S RNA-protein complexes from E. coli and Bacillus stearothermophilus and weakly with yeast 5.8S RNA. UpUpCpG did not bind to E. coli, B. stearothermophilus, or yeast 5S RNA or to the yeast 5.8S RNA-E. coli protein complex. It is suggested that 5.8S RNA evolved from prokaryotic 5S RNA and that the latter two RNAs are related and have similar functions in protein synthesis.
Identification of spacer tRNA genes in individual ribosomal RNA transcription units of Escherichia coli.
Authors: Morgan E A , Ikemura T , Nomura M
Published: May 2006

Transfer RNA genes ("spacer tRNA genes") are present in the spacer region between 16S and 23S rRNA genes in Escherichia coli. We have analyzed spacer tRNA genes carried by seven rRNA operons with different chromosomal locations. Six of these were isolated on plasmids and one on a transducing phage. We found that, in addition to the two previously identified genes for tRNA2Glu and tRNAIIle, there is a spacer tRNA gene which codes for tRNAIBAla. Of the seven rRNA operons studied, three had both tRNAIBAla and tRNAIIle genes, and the remaining four had the tRNA2Glu gene in their spacers. In addition, genes for tRNAIAsp were found near the distal ends of two different rRNA operons.
Polypeptides of cells transformed by RNA or DNA tumor viruses.
Authors: Strand M , August J T
Published: May 2006

Proteins solubilized from normal BALB/3T3 cells and BALB/3T3 transformed by simian virus 40 or Kirsten sarcoma virus have been analyzed by two-dimensional gel electrophoresis and tryptic peptide mapping. A large fraction of the polypeptides of the virus-transformed cells, about 30%, were different from normal cells. In contrast to the marked differences between normal and transformed cells, the polypeptides of the DNA and RNA virus-transformed cells were almost identical. These findings were observed with polypeptides stained by Coomassie Blue, or labeled with [14C]glucosamine or [35S]methionine. Pulse-chase analysis showed that most of the polypeptides were stable during 20 hr of incubation. The identity of several polypeptides was confirmed by tryptic peptide mapping.
Importance of 5'-terminal blocking structure to stabilize mRNA in eukaryotic protein synthesis.
Authors: Shimotohno K , Kodama Y , Hashimoto J , Miura K I
Published: May 2006

The 7-methylguanylic acid residue confronting the 5'-terminal nucleotide of mRNA through two pyrophosphate linkages was completely removed by tobacco pyrophosphatase from mRNAs of cytoplasmic polyhedrosis virus, tobacco mosaic virus (viral RNA), and globin without any scission in the inner part of the RNA chain. Protein synthesis ability in a wheat germ cell-free system was lost after this treatment of all three kinds of mRNA. The initiation complexes for protein synthesis of these three RNAs were not obtained after using tobacco phosphodiesterase-treated mRNA. On incubation of mRNA in a wheat germ extract, the mRNA lacking m7G was quickly degraded from the 5' terminus in an exonucleolytic way, whereas the intact mRNA remained stable. These results show that one of the confronting nucleotide structure's functions is to stabilize the mRNA, to prevent its degradation.
Glucocorticoid-stimulated accumulation of mouse mammary tumor virus RNA: increased rate of synthesis of viral RNA.
Authors: Ringold G M , Yamamoto K R , Bishop J M , Varmus H E
Published: May 2006

Glucocorticoid hormones specifically increase the intracellular concentration of mouse mammary tumor virus (MMTV) RNA in a cultured cell line from a GR mouse mammary carcinoma (GR) and in an MMTV-infected rat hepatoma cell line (M1.19). In contrast, these steroids have no effect on the concentration of MMTV RNA in a lymphoma line, S49, from a Balb/c mouse. Using a molecular hybridization procedure to detect newly synthesized RNA, we have directly measured the effect of dexamethasone, a synthetic glucocorticoid, on the rate of MMTV RNA synthesis. In GR cells the hormone causes a 10-fold increase in the rate of synthesis of viral RNA without appreciably affecting the overall rate of cellular RNA synthesis. The transition from the basal to the maximally stimulated rate of MMTV RNA synthesis occurs within the earliest labeling period, 0-15 min after addition of the hormone. Thus, it appears that glucocorticoids regulate MMTV genes principally by this rapid and specific alteration of their rate of transcription. Similar results are obtained in M1.19 rat hepatoma cells. In contrast, dexamethasone does not affect the rate of viral RNA synthesis in S49 lymphoma cells.
Production of antibodies against influenza virus by somatic cell hybrids between mouse myeloma and primed spleen cells.
Authors: Koprowski H , Gerhard W , Croce C M
Published: May 2006

We have produced somatic cell hybrids between mouse myeloma cells and spleen cells derived from a BALB/c mouse immunized with purified influenza virus. The hybrid cells were found to produce large amounts of antibodies specific for the hemagglutinin of the virus and were able to induce tumor formation when injected into BALB/c mice.
Cholecystokinin and its COOH-terminal octapeptide in the pig brain.
Authors: Muller J E , Straus E , Yalow R S
Published: May 2006

Two components--one resembling intact cholecystokinin in size and charge and immunologic specificity, and the other resembling the COOH-terminal octapeptide of cholecystokinin--have been found in extracts of the pig cerebral cortex. The relative concentrations of the two peptides in the extracts were dependent on the extractant, boiling 0.1 M HCl being more effective than boiling water for the extraction of intact cholecystokinin but less effective for the extraction of the octapeptide. The physiologic role of these peptides in the brain has yet to be elucidated.
Quantum statistical theory of optical phenomena
Authors: Lin S. H. , Eyring H.
Published: May 2006

The purpose of this paper is to develop a density matrix formulation for optical phenomena that can be applied to both steady and transient states and to both resonance and off-resonance regions. To demonstrate the application, this theory has been applied to the steady-state one-photon and two-photon processes. We have found that, in the resonance region, the conventional equation used is incomplete; other terms that are comparable in importance have been ignored.
Primary photochemical event in vision: proton translocation.
Authors: Peters K , Applebury M L , Rentzepis P M
Published: May 2006

Picosecond studies of rhodopsin in low-temperature glasses have been carried out in order to observe directly the risetime of prelumirhodopsin, the first intermediate in the visual pathway. Only at 20 K or below can the risetime of this intermediate be resolved and even at 4 K it is astoundingly rapid, about 36 psec. An examination of the Arrhenius dependence on temperature of the rate of formation of prelumirhodopsin shows a strong deviation from linearity at low temperatures, i.e., non-Arrhenius behavior. This marked non-linear behavior is characteristic of a quantum mechanical tunneling event such as the translocation of hydrogen. An excellent candidate for the tunnelling process is the hydrogen of the protonated Schiff base formed between opsin and its retinal chromophore. Deuterium-exchanged rhodopsin, in which the Schiff base hydrogen is replaced by a deuterium, also shows a marked non-Arrhenius temperature dependence at low temperatures, consistent with tunneling. The rate of formation of prelumirhodopsin in deuterium-exchanged samples is much slower and a deuterium isotope effect kH/kD approximately or equal to 7 is observed. The data support a model in which the formation of prelumirhodopsin involves translocation of a proton toward the Schiff base nitrogen of the retinal chromophore.
State of prophage Mu DNA upon induction.
Authors: Ljungquist E , Bukhari A I
Published: May 2006

We have compared the process of prophage lambda induction with that of prophage Mu. According to the Campbell model, rescue of lambda DNA from the host DNA involves reversal of lambda integration such that the prophage DNA is excised from the host chromosome. We have monitored this event by locating the prophage DNA with a technique in which DNA of the lysogenic cells is cleaved with a restriction endonuclease and fractionated in agarose gels. The DNA fragments are denatured in gels, transferred to a nitrocellulose paper, and hybridized with 32P-labeled mature phage DNA. The fragments containing prophage DNA become visible after autoradiography. Upon prophage lambda induction, the phage-host junction fragments disappear and the fragment containing the lambda att site appears. No such excision is seen in prophage Mu. The Mu-host junction fragments remain intact well into the lytic cycle, when Mu DNA has undergone many rounds of replication and apparently many copies of Mu DNA have been integrated into the host DNA. Therefore, we postulate that Mu DNA replicates in situ and the replication generates a form of Mu DNA active in the integrative recombination between Mu DNA and host DNA. This type of mechanism may be common to many transposable elements.
Physical properties of chemically acetylated rat liver chromatin.
Authors: Wallace R B , Sargent T D , Murphy R F , Bonner J
Published: May 2006

The physical properties of rat liver chromatin and nucleosomes acetylated with acetic anhydride were examined in order to clarify the mechanism by which chemical acetylation of histones increases template activity in vitro [Marushige, K. (1976) Proc. Natl. Acad. Sci. USA 73, 3937-3941]. Acetylation was found to have dramatic effects on the magnesium solubility, nuclease sensitivity, thermal denaturation, and sedimentation of chromatin and nucleosomes. The significance of the results to models of gene activation and chromatin replication is considered.
Mechanism of phage phiX174 DNA inactivation by benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide.
Authors: Hsu W T , Lin E J , Harvey R G , Weiss S B
Published: May 2006

A previous report from this laboratory has shown that certain derivatives of polycyclic aromatic hydrocarbons bind to phiX174 DNA and render it noninfectious. The present work describes the relationship between the extent of phiX174 DNA binding by (+/-)-anti-benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide and the effect on infectivity. The results suggest that one molecule of bound diolepoxide is sufficient to inhibit the replication of a single molecule of phiX174 DNA. DNA synthesis studies, in vitro, indicate that when phiX DNA bound by benzo[a]pyrene groups serves as template the rate of DNA polymerization is reduced and less product is formed. In addition, the propagation of synthetic DNA strands is blocked so that incomplete complementary chains are assembled. The relationship of these findings to the mutagenic and carcinogenic process associated with the action of benzo[a]pyrene-diolepoxide is discussed.
Pathways of genetic transfer from
Tripsacum
to
Zea mays
Authors: Harlan Jack R. , Wet J. M. J. De
Published: May 2006

The cytogenetic interactions in maize ×
Tripsacum
hybrid derivatives can be remarkably complex. The number of viable, somewhat female fertile chromosome combinations is astonishing. Fifty-four different combinations are listed in this paper, and others are certainly possible. In successive backcrosses to maize, chromosome numbers scale both up and down with ease, sometimes stabilizing for a few generations via apomixis, but in most cases finally generate balanced maize genomes and emerge as recovered maize. The maize, however, can produce strange and unusual phenotypes as a result of genetic transfers from
Tripsacum
. Highly tripsacoid maize lines with 2
n
= 20 chromosomes were recovered in pathways where the maize genome had first contaminated the
Tripsacum
genome in early backcross generations. In other pathways interaction of the two genomes is rare. Dominant resistances to six maize diseases were found in BC
8
populations.
Concentration of mutagens from urine by absorption with the nonpolar resin XAD-2: cigarette smokers have mutagenic urine.
Authors: Yamasaki E , Ames B N
Published: May 2006

A method is described for concentrating mutagens/carcinogens from human urine about 200-fold for subsequent assay in the Salmonella/mammalian microsome mutagenicity test. The method is also applicable for other aqueous liquids and for other in vitro tests for mutagens/carcinogens. The urine (up to 500 ml) is put through a column with a 1.5-cm3 bed volume of XAD-2 (styrene-divinylbenzene polymer) and the adsorbed material is then eluted with a few milliliters of acetone. The acetone is taken to dryness and the residue is dissolved in dimethyl sulfoxide. This is the urine concentrate that is assayed for mutagenicity. Various mutagens/carcinogens have been added to human urine and the recoveries have been measured after adsorption on XAD-2, XAD-4, and Tenax GC (diphenyl-p-phenylene oxide polymer). We propose that this method be used in monitoring the urine of human populations and of experimental animals in toxicological studies. It is shown with this procedure that cigarette smokers have mutagenic urine while nonsmokers do not.