bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell-free translation of immunoglobulin messenger RNA from MOPC-315 plasmacytoma and MOPC-315 NR, a variant synthesizing only light chain.
Authors: Green M , Graves P N , Zehavi-Willner T , McInnes J , Pestka S
Published: May 2006

Total poly(A)-containing mRNA was isolated from the MOPC-315 and MOPC-315 NR plasmacytomas. The RNA was further fractionated on sodium dodecyl sulfate-sucrose gradients. The MOPC-315 mRNA fractions directed the synthesis of both the heavy chain and light chain precursor of the MOPC-315 IgA protein in a cell-free extract of Ehrlich ascites tumor cells. None of the MOPC-315 NR mRNA fractions tested programmed the synthesis of the heavy chain in this system. Analysis of cell-free products by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by immunoprecipitation demonstrated that no translatable heavy chain mRNA could be extracted from the MOPC-315 NR variant plasmacytoma.
Deduction of Semi-Optimal Mollifier for Obtaining Lower Bound for
N
0
(
T
) for Riemann's Zeta-Function
Authors: Levinson Norman
Published: May 2006

A mollifier played a key role in showing
N
0
(
T
) > 1/3
N
(
T
) for large
T
in ref. 1 [Levinson, N. (1974)
Advan. Math.
13, 383-436]. A basic problem in ref. 1 was that of obtaining an upper bound for a sum of two terms, one larger than the other. Here a deductive procedure is given for finding a mollifier that actually minimizes the larger term. An Euler-Lagrange equation is obtained. (Optimization of the sum of both the major and minor terms appears to be formidable.) The actual improvement effected by the optimized mollifier over the ad hoc mollifier of ref. 1 is unfortunately only 1.4%. To obtain a usable mollifier it is necessary to blur the optimization procedure by smoothing at several stages of the deduction. The procedure is of more interest than the particular application because of the small improvement in this case.
The structure of a yeast hexokinase monomer and its complexes with substrates at 2.7-A resolution.
Authors: Fletterick R J , Bates D J , Steitz T A
Published: May 2006

From a 2.7-A resolution electron density map we have built a model of the polypeptide backbone of a monomer of yeast hexokinase B (EC 2.7.1.1). This map was obtained from a third crystal form of hexokinase, called BIII, which exhibits space group P212121 and which contains only one monomer per asymmetric unit. The 51,000 molecular weight monomer has an elongated shape (80 A by 55 A by 50 A) and is divided into two lobes by a deep central cleft. The polypeptide chain is folded into three structural domains, one of which is predominantly alpha-helical and two of which each contain a beta-pleated sheet flanked by alpha-helices. Both glucose and AMP bind to these crystals and produce significant alterations in the protein structure. Glucose binds in the deep cleft, as was observed previously in the BII crystal of the dimeric enzyme. AMP, however, binds to a site that is different from the major intersubunit ATP binding site observed in the crystalline dimer. The AMP is found near one of the beta-pleated sheets. From our current interpretation of this electron density map we conclude that neither of the two nucleotide binding regions has the same structure as has been observed for the nucleotide binding regions of the dehydrogenases, adenylate kinase, and phosphoglycerate kinase, although some similarities exist.
The Significant Structure Theory Applied to a Mesophase System
Authors: Ma Shao-mu , Eyring H.
Published: May 2006

The significant structure theory of liquids is extended to the mesophase system with
p
-azoxyanisole as an example. This compound has two different structures, a nematic phase and an isotropic phase, in its liquid state. In this study the nematic phase is treated as subject to a second volume and temperature-dependent degeneracy formally like that due to melting. The isotropic phase is treated as a normal liquid. The specific heat, thermal expansion coefficient, compressibility, volume, entropy of transitions, and heat of transitions are calculated and compared to the observed values. This analysis differs from previous ones in including the volume dependence as well as the temperature dependence in one explicit expression for the Helmholtz free energy.
A routine method for protein-free spreading of double- and single-stranded nucleic acid molecules.
Authors: Vollenweider H J , Sogo J M , Koller T
Published: May 2006

A protein-free nucleic acid preparation method for electron microscopy is described. The basic procedure is very similar to the classical protein monolayer spreading techniques. The carrier protein (usually cytochrome c) is replaced by benzyldimethylalkylammonium chloride. Both the hypophase method and the microdiffusion or droplet method can be applied with this compound. Unlike cytochrome c, benzyldimethylalkylammonium chloride does not lead to any apparent thickening of the nucleic acid strands. Partially denatured DNA spread with this reagent shows a loosened structure with a foamy appearance in the regions previously considered to be "unmelted," which open up locally into melted loops of different size. Specifically bound proteins, such as RNA polymerase on bacteriophage T7 DNA, can be detected unambiguously.
Light-dependent absorption and selective scattering changes at 518 nm in chloroplast thylakoid membranes.
Authors: Thorne S W , Horvath G , Kahn A , Boardman N K
Published: May 2006

The light-induced absorbance change at 518 nm of isolated chloroplasts consists of a rapid phase, and a slow phase which is complete in about 20 sec. The slow component of the 518 nm absorbance change correlates with the light-induced change in 90 degrees light scattering at 518 nm. Both show a similar time course, similar pH dependence with a maximum at pH 6.0, and similar sensitivity to inhibitors and to treatment of the chloroplasts with a low concentration of glutaraldehyde. Their light minus dark difference spectra are similar with maxima at about 520 nm. It is concluded that they are manifestations of the same phenomenon, and the slow absorbance increase at 518 nm is due to enhanced scattering. It is proposed that the light-induced changes in scattering at 518 nm reflect alterations in selective dispersion, due to proton uptake and conformational changes in the chloroplast thylakoid membrane.
De novo synthesis of a polymer of deoxyadenylate and deoxythymidylate by calf thymus DNA polymerase alpha.
Authors: Henner D , Furth J J
Published: May 2006

In a reaction mixture containing calf thymus DNA polymerase alpha (DNA nucleotidyltransferase; deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase; EC 2.7.7.7), calf thymus DNA unwinding protein, DNA, deoxyadenosine 5'-triphosphate and deoxythymidine 5'-triphosphate, a copolymer of deoxyadenylate and deoxythymidylate is synthesized after a lag period of 1-2 hr. In the presence of the four deoxyribonucleoside triphosphates only deoxyadenylate and deoxythymidylate are incorporated into the polymer and the rate of synthesis is decreased. The reaction variably occurs in the absence of DNA or DNA unwinding protein but with a greatly entended lag period. The optimal Mg2+ concentration for synthesis of the polymer of deoxyadenylate and deoxythymidylate is 1 mM, in contrast to an optimal Mg2+ concentration of 8 mM for DNA synthesis with activated DNA as template. Characterization of the product of de novo synthesis indicates that it is the alternating copolymer, poly(dA-dT).
Magnitude of subunit inequivalence for oxygen release from hemoglobin: reinvestigation of the oxygen-pulse experiment.
Authors: Salhany J M , Castillo C L , McDonald M J , Gibson Q H
Published: May 2006

Two hypotheses have been presented to explain the grossly biphasic oxygen release kinetics observed when hemoglobins are studied with the oxygen pulse technique [Gibson (1973) Proc. Nat. Acad. Sci. USA 70, 1-4]. Hypothesis I suggests that the two phases result from cooperativity, with the fast phase being oxygen release from the low affinity (T) state and the slow phase being oxygen release from molecules that have switched to the high affinity (R) state. Hypothesis II suggests that the biphasic curves are due to a large (factor of 20-30) difference in oxygen release from the two types of subunits within deoxyhemoglobin. In order to experimentally discriminate between these two hypotheses, we reinvestigated the oxygen pulse reaction for hemoglobin Kansas (alpha2 beta2 102 Asn leads to Thr) in the absence and presence of inositol hexaphosphate, since recent high resolution nuclear magnetic resonance studies have shown that this allosteric cofactor stabilizes hemoglobin Kansas in T even when fully liganded [Ogawa, Mayer, and Shulman (1972) Biochem. Biophys. Res. Commun. 49, 1485-1491]. The results of these studies clearly favor hypothesis I over hypothesis II as being the correct interpretation for the oxygen pulse results. However, we have found evidence that suggests that oxygen release and binding in T are surprisingly faster than previously observed. Furthermore, within T, there is some spectral and kinetic heterogeneity for oxygen release from adult hemoglobin and hemoglobin Kansas. The magnitude of this kinetic heterogeneity in T appears to be about the same as that seen in the high affinity, R, state. The exchange of hypothesis II for hypothesis I more strongly favors views of cooperative oxygen binding involving both types of subunits, as required if the allosteric model of Monod, Wyman, and Changeux [(1965) J. Mol. Biol. 12, 88-118] is considered operative.
Conditions controlling commitment of differentiation in Bacillus megaterium.
Authors: Freese E B , Cooney P , Freese E
Published: May 2006

The developmental stage at which cells of Bacillus megaterium are committed to continue differentiation, i.e., sporulation, depends on both the previous growth medium and the new medium to which the cells are transferred for the commitment test. The latest "stage of no return," after which cells continue differentiation, no matter how rich in nutrients the medium, is reached as soon as the forespore is completely surrounded by a double membrane.
The extraordinary dielectric properties of biological materials and the action of enzymes.
Authors: Fröhlich H
Published: May 2006

From very general theoretical considerations it is concluded that many biomolecules (i) should have metastable excited states with very high dipole moment, and (ii) should be capable of strongly excited giant dipole vibrations with frequencies near 10(11) Hz. Experimental evidence available so far seems to support these postulates. It is suggested that the two postulates should be of importance for the action of enzymes, and relevant experiments are proposed.
Pion spectrum in decay of Ψ′(3.7) to Ψ(3.1)
Authors: Schwinger Julian , Milton Kimball A. , Tsai Wu-yang , DeRaad Lester L.
Published: May 2006

The decay of Ψ′ → Ψ + ππ is described by a chiral ε model. The general features of the observed dipion spectrum are well reproduced. Comparison with the hadronic decay ρ′ → ρ + ππ indicates that the Ψ′Ψε coupling is relatively suppressed by a factor ∼10
-2
.
In vitro synthesis of a constitutive enzyme of Escherichia coli, 6-phosphogluconate dehydrogenase.
Authors: Isturiz T , Wolf R E
Published: May 2006

Enzymes of central intermediary metabolism are among the constitutive proteins of Escherichia coli. 6-Phosphogluconate dehydrogenase [6-phospho-D-gluconate: nicotinamide adenine dinucleotide phosphate 2-oxidoreductase (decarboxylating), EC 1.1.1.44-A1, an enzyme of the hexose monophosphate shunt, was synthesized in vitro in a coupled transcription-translation system directed by DNA from a specialized transducing phage carrying gnd, the structural gene. Enzyme synthesized in vitro was detected by radiochemical assay of its activity. Kinetic experiments using inhibitors of transcription and translation suggest that synthesis of the mRNA for the enzyme was initiated at the gnd promoter. Neither cyclic AMP nor cyclic GMP had any effect on the amount of enzyme synthesized in vitro.
Structure of yeast phenylalanine transfer RNA at 2.5 A resolution.
Authors: Ladner J E , Jack A , Robertus J D , Brown R S , Rhodes D , Clark B F , Klug A
Published: May 2006

The x-ray analysis of the monoclinic form of yeast tRNAPhe has been taken to a resolution of 2.5 A by the method of isomorphous replacement. The model proposed at 3 A has been confirmed and extended to reveal additional features of the tertiary structure and of the stereochemistry. An extensive hydrogen bonding network is described involving specific interactions between bases and the ribose-phosphate backbone. The structure of a G-U base pair has been solved.
Carcinoembryonic antigen: evidence for multiple antigenic determinants and isoantigens.
Authors: Vrba R , Alpert E , Isselbacher K J
Published: May 2006

Carcinoembryonic antigen (CEA) preparations, from various sources were compared by radioimmunoassay. The preparations studied included four CEA standards (CEA-Roch, CEA-Montreal, CEA-City of Hope, and CEA-British) and CEA from serum and liver metastases of a patient with cancer of the colon who had an extremely high concentration of serum CEA (more than 26,000 ng/ml). The data indicate that the CEA-Roche standard differs significantly from the other three CEA standards tested, and that the serum CEA from the patient was antigenically different from currently available CEA standards as well as from the CEA obtained from the patient's own liver metastases. These antigenic differences were reflected in radioimmunoassay inhibition curves that were different and that were not affected by perchloric acid extraction of CEA. Because of the antigenic variation in the serum CEA, markedly different CEA concentrations (varying by three orders of magnitude) were measurable by two different antisera (Roche and Montreal). All the various CEA standards and samples cochromatographed on columns of Sepharose-6B, despite the large antigenic variation. We postulate that CEA consists of a family of "isoantigens" with multiple antigenic determinants. We identified a serum CEA isoantigen that was different from the currently available standards. Consequently, we believe that results of radioimmunoassays currently used for CEA measurement may not represent absolute concentrations of serum "CEA", but may reflect the binding affinity of different isoantigens to a particular polyvalent CEA antiserum.
Aging and its relation to cell growth and differentiation in Drosophila imaginal discs: developmental response to growth restricting conditions.
Authors: Schweizer P , Bodenstein D
Published: May 2006

The development of Drosophila organ discs can be arrested by culturing them in adult male flies. These aged discs lose some of their differentiation competence and form incomplete imaginal structures. The more advanced the aging, the greater the loss of competence. Discs made to differentiate prematurely show deficiencies similar to aged discs. The age-induced defects can be repaired in a larval milieu. Special hormonal conditions, but not cell multiplication, are apparently involved in the recovery process.
Lambda repressor turns off transcription of its own gene.
Authors: Meyer B J , Kleid D G , Ptashne M
Published: May 2006

We report transcription in vitro of the lambda repressor gene, cI, using specific restriction endonuclease fragments as templates. This transcription is repressed by lambda repressor. Moreover, we report the sequence change caused by a cI promoter mutation. This change is located between two repressor binding sites in the rightward operator (OR). Transcription studies using mutant templates indicate that repressor bound to two sites in OR regulates transcription of gene tof, and repressor bound to the remaining site(s) controls transcription of cI.
Partial amino-acid sequence of NAD-specific glutamate dehydrogenase of Neurospora crassa.
Authors: Austen B M , Nyc J F , Degani Y , Smith E L
Published: May 2006

Parts of the primary structure of the NAD-specific glutamate dehydrogenase [L-glutamate:NAD oxidoreductase (deaminating), EC 1.4.1.2] from Neurospora crassa are presented. Segments of the sequence representing 886 unique amino-acid residues have been determined; the largest contains 267 residues. There are only short regions of possible homology between this enzyme and the glutamate dehydrogenases of bovine liver or the NADP-specific enzyme of Neurospora. The large size of the subunit (116,000 molecular weight) of the NAD-specific glutamate dehydrogenase is unusual when compared to other known dehydrogenases.
In vitro synthesis of full-length DNA transcripts of Rous sarcoma virus RNA by viral DNA polymerase.
Authors: Junghans R P , Duesberg P H , Knight C A
Published: May 2006

Varying the concentration of Triton X-100, a nonionic detergent used to promote the DNA polymerase activity of Rous sarcoma virus in an endogenous reaction, showed a very sharp peak at about 0.02% (vol/vol) for optimal DNA synthesis. The yield of DNA at this concentration of Triton exceeded yields obtained at concentrations above the optimum by a factor of 2-5 for the 90-min reaction. At optimal Triton concentration, about 1-7% of the DNA made in the absence of actinomycin and about 4-10% of the DNA made in the presence of actinomycin was 2.5 X 10(6) daltons or greater, as estimated by formamide polyacrylamide gel electrophoresis and by alkaline sucrose gradient sedimentation. No large DNA was obtained at higher than optimal Triton concentrations. The large DNA molecules were rendered totally resistant to single-strand specific nuclease S1 after hybridization to an excess of viral RNA. It was concluded that at optimal detergent concentration, the viral DNA polymerase can synthesize full-size DNA transcripts of viral RNA.
Three-dimensional structure of herring sperm protamine Y-I with the aid of dark field electron microscopy.
Authors: Ottensmeyer F P , Whiting R F , Korn A P
Published: May 2006

High resolution electron micrographs of herring sperm protamine (clupeine) Y-I provide sufficient detail to constrain the folding of the known amino-acid sequence of the protein into a unique three-dimensional configuration. The structure consists of a loose helix of turns of various sizes held together at one edge, spread apart along the other. This form appears to represent the shape of several fish protamines.
Acquisition of a determinant for chloramphenicol resistance by coliphage lambda.
Authors: Gottesman M M , Rosner J L
Published: May 2006

A determinanat for chloramphenicol resistance, cam, initially detected on a resistance transfer factor (RTF) and since transferred to phage P1, may be acquired from P1 by coliphage lambda. Lambdapcam are obtained when a lambda prophage is induced in bacteria which also harbor P1 cam prophage. Lambdacam formation is not dependent upon host Rec or lambda Red recombination functions. Electron microscopic heteroduplex analysis shows that the cam locus in two lambdapcams is a 5% addition of DNA in the b2 region of lambda, not contiguous with att. The extent and nucloetide sequence of the DNA insertion in the two independent lambdapcam isolates appear to be the same though they are located at different sites within the b2 region. We conclude that the determinant for chloramphenicol resistance is contained on a unique piece of DNA which facilitates its insertion into a number of unrelated genomes.
The effect of acetoxycycloheximide on rate of accumulation of cerebral catecholamines from circulating tyrosine as related to its effect on memory.
Authors: Goodman R H , Flexner J B , Flexner L B
Published: May 2006

The rate of accumulation of newly synthesized catecholamines and endogenous catecholamine levels in mice were determined after an amnestic intracranial dose of acetoxycycloheximide. Rates of accumulation were found to be severly decreased for a period of 12 hr after injection. Total catecholamine levels were increased from 1 to 4 hr, then decreased 17 hr following injection. These results are discussed in terms of previous behavioral observations. It is pointed out that they weaken the assumption that acetoxycycloheximide's amnestic effects are solely due to inhibition of protein synthesis.
Genetic evidence on the organization and action of the qa-1 gene product: a protein regulating the induction of three enzymes in quinate catabolism in Neurospora crassa.
Authors: Case M E , Giles N H
Published: May 2006

The first three reactions in the catabolism of qainic acid in Neurospora crassa are under the genetic control of the qa gene cluster. This cluster consists of three structural genes encoding three inducible enzymes plus a regulatory gene (qa-1+) whose diffusible product apparently acts in a positive fashion to initiate coordinate synthesis of the three enzymes when an appropriate inducer is present. Genetic and biochemical evidence for both complementing and temperature-sensitive qa-1 alleles indicates that the product of the qa-1+ gene is an oligomeric (multimeric) protein. On the basis of cis-trans tests of appropriate double mutants (plus genetic mapping data for temperature-sensitive mutants), at least certain constitutive mutants (which produce all three qa enzymes in the absence of an inducer) are mutants in the regulatory gene and not in controlling elements such as initiators. The detection of stable (non-revertible) qa-1 intralocus deletion (multisite)mutants provides additional evidence for positive regulation in the qa system. Extensive genetic recombination data provide evidence that the two types of qa-1 mutants--slow-complementing (qa-1-s) and fast-complementing (qa-1-f)--map in discrete, non-overlapping segments of the qa-1 locus. These two distinct types of mutants are hypothesized to produce altered regulatory protein molecules that fail to interact either with a DNA initiator site (qa-1-s types) or with an inducer (qa-1-f types). The striking similarities between the qa system in this lower eukaryote and certain prokaryote operon systems are discussed.
Distribution of membrane particles and gap junctions in normal and transformed 3T3 cells studied in situ, in suspension, and treated with concanavalin A.
Authors: Pinto Da Silva P , Martinez-Palomo A
Published: May 2006

Freeze-fracture techniques were used to study the ultrastructural distribution of plasma membrane particles in cultures of normal Balb/c and Swiss 3T3 and simian virus 40- or murine sarcoma virus-transformed fibroblasts. No apparent differences were observed. Cultures fixed in situ show a seemingly random distribution of membrane particles both in normal or in transformed cells. Treatment of cell cultures in situ with concanavalin A does not result in an altered pattern of particle distribution. EDTA-induced suspension of normal or transformed cells does not result, per se, in modification of the type of membrane particle distribution seen in cells fixed in situ. However, upon further incubation, a proportion of normal or transformed cells in suspension show a varying degree of particle aggregation following a network pattern. Concanavalin A treatment of normal and transformed cells in suspension does not result in a specific change of the pattern of particle distribution. Because it has been established that treatment with concanavalin A of simian virus 40-transformed Balb/c 3T3 fibroblasts causes pronounced clustering of the concanavalin A receptors at the outer-surface, our results probably imply independence of membrane particles and concanavalin A receptors of these transformed cells.
Stimulation of DNA polymerase by factors isolated from Novikoff hepatoma.
Authors: Probst G S , Stalker D M , Mosbaugh D W , Meyer R R
Published: May 2006

Extracts of Novikoff hepatoma cells contain factors capable of stimulating in vitro DNA synthesis several fold. The activity can be resolved into three separate protein peaks on DEAE-Sephadex. Two of these, factors II and III, have been purified and partially characterized. Both factors increase the initial rate of DNA synthesis and allow synthesis to proceed much longer. If either factor is added after synthesis by the DNA polymerase has reached a plateau, resumption of synthesis occurs. The factors appear to have different modes of action or sites of action since they show an additive effect even when a single one is used at saturating conditions. These factors are present in normal rat liver but at a concentration less than 5% of that found in the tumor cells. When tested with several highly purified DNA polymerases (DNA nucleotidyltransferase, EC 2.7.7.7), the factors show a much greater stimulation of homologous, non-mitochondrial enzymes (rat liver nuclear-, rat liver cytoplasmic-, or Novikoff-DNA polymerases) when compared with rat liver or calf liver mitochondrial-, Escherichia coli I-, or sea urchin nuclear-DNA polymerases. The mechanism of action of these factors is not known at present. No enzymatic activity has been associated with factor III. Highly purified, but not homogeneous, preparations of factor II contain low levels of endonuclease; it has not been established whether endonuclease is a contaminant or is responsible for the stimulating activity.
D-amphetamine disaggregates brain polysomes via a dopaminergic mechanism.
Authors: Moskowitz M A , Weiss B F , Lytle L D , Munro H N , Wurtman J
Published: May 2006

Brain polysomes are disaggregated in rats given moderate to large doses of d-amphetamine sulfate; this response is rapid in onset, lasts for at least 4-6 hr, and varies with the age of the animal. Pretreatment with a dopamine receptor blocking agent, haloperidol or pimozide, blocks the amphetamine-induced disaggregation.
Regulation of RNA polymerase synthesis in Escherichia coli: a mutant unable to synthesize the enzyme at 43 degrees.
Authors: Oeschger M P , Berlyn M K
Published: May 2006

We report the isolation of a mutant of E. coli in which the capacity to synthesize RNA polymerase (EC 2.7.7.6) (the beta and beta' subunits) is rapidly lost at 43 degrees. The mutation has no effect on the stability or activity of the polymerase itself. The mutation is recessive and is closely linked to the rif locus (the structural gene for the beta subunit). Using strains carrying the mutation, we have shown that polymerase is present in excess in rapidly growing E. coli cells.
Regulation of herpesvirus macromolecular synthesis: sequential transition of polypeptide synthesis requires functional viral polypeptides.
Authors: Honess R W , Roizman B
Published: May 2006

It was previously shown that virus-specific polypeptides made in HEp-2 cells infected with herpes simplex 1 form three groups designated alpha, beta, and gamma whose synthesis is coordinately regulated and sequentially ordered. This report shows that one or more functional alpha polypeptides are necessary to turn on the synthesis of beta and gamma groups, and conversely, one or more polypeptides in the latter groups turn off the synthesis of alpha polypeptides. Specifically, infected cells maintained in medium containing either canavanine, an analogue of arginine, or azetidine-2-carboxylic acid an analogue of proline and hydroxyproline, synthesized alpha polypeptide at rates comparable to maximal rates in untreated infected cells but did not undergo the normal transition to beta and gamma polypeptide synthesis. The transition to gamma polypeptide synthesis and shut-off of synthesis of earlier polypeptide groups proceeded normally if addition of canavanine was delayed until at least 4-5 hr after infection. Addition of canavanine after the onset of beta and gamma polypeptide synthesis, i.e., between 2 and 3.5 hr after infection, resulted in sustained, simultaneous synthesis of all three polypeptide groups, a phenomenon not seen in untreated infected cells. Canavanine-treated infected cells, synthesizing alpha polypeptides, recovered the capacity to make beta and gamma polypeptides after removal of the analogue, but only after a 1-to 2-hr delay compared with infected untreated cells. The data indicate that the on and off controls inherent in the cascade regulation of viral polypeptide synthesis are mediated by one or more polypeptides in each group at transcriptional or post-transcriptional levels.
Adenine formation from adenosine by mycoplasmas: adenosine phosphorylase activity.
Authors: Hatanaka M , Del Giudice R , Long C
Published: May 2006

Mammalian cells have enzymes to convert adenosine to inosine by deamination and inosine to hypoxanthine by phosphorolysis, but they do not possess the enzymes necessary to form the free base, adenine, from adenosine. Mycoplasmas grown in broth or in cell cultures can produce adenine from adenosine. This activity was detected in a variety of mycoplasmatales, and the enzyme was shown to be adenosine phosphorylase. Adenosine formation from adenine and ribose 1-phosphate, the reverse reaction of adenine formation from adenosine, was also observed with the mycoplasma enzyme. Adenosine phosphorylase is apparently common to the mycoplasmatales but it is not universal, and the organisms can be divided into three groups on the basis of their use of adenosine as substrate. Thirteen of 16 Mycoplasma, Acholeplasma, and Siroplasma species tested exhibit adenosine phosphorylase activity. M. lipophilium differed from the other mycoplasmas and shared with mammalian cells the ability to convert adenosine to inosine by deamination. M. pneumoniae and the unclassified M. sp. 70-159 showed no reaction with adenosine. Adenosine phosphorylase activity offers an additional method for the detection of mycoplasma contamination of cells. The patterns of nucleoside metabolism will provide additional characteristics for identification of mycoplasmas and also may provide new insight into the classification of mycoplasmas.
Differentiation of clonal lines of teratocarcinoma cells: formation of embryoid bodies in vitro.
Authors: Martin G R , Evans M J
Published: May 2006

The differentiation in vitro of clonal pluripotent teratocarcinoma cells is reported. The first stage of this process is the formation of simple embryoid bodies which are identical to those found in animals bearing intraperitoneal teratocarcinomas. They consist of an inner core of embryonal carcinoma cells surrounded by a layer of endodermal cells which produce Reichert's membrane. The endodermal cells become apparent shortly after the embryonal carcinoma cells have formed aggregates which are loosely attached to the substratum. One clonal teratocarcinoma line was found to produce complex cystic embryoid bodies in vitro. Following formation of the endodermal cells, extensive differentiation to a wide variety of cell types occurs. There are similarities between the process of embryoid body formation and the early events of differentiation of the mouse embryo.
Plasmid-determined tetracycline resistance in Streptococcus faecalis: evidence for gene amplification during growth in presence of tetracycline.
Authors: Clewell D B , Yagi Y , Bauer B
Published: May 2006

The tetracycline (TG)-resistant Streptococcus faecalis strain DS-5Cl harbors two plasmids designated alpha and gamma with molecular masses of approximately 6 and 35 million daltons, respectively. TC-sensitive variants were derived by storing cells at 45 degrees for 2-3 weeks. Analysis of covalently closed circular DNA from five such variants (derived independently) revealed that in each variant the alpha-plasmid, which normally sediments at 28 S (supercoiled) in a sucrose density gradient, was replaced by a 22S substance. Growth of DS-5Cl in the presence of 150 mug/ml of TC (minimum inhibitory concentration is 250 mug/ml in liquid broth) for a prolonged period of time (50-60 generations) resulted in the disappearance of 28S DNA and the appearance of a heterogeneous covalently-closed circular DNA sedimenting at about 40-48 S. This phenomenon was accompanied by an increase in the level of bacterial TC-resistance, whereby tells were subsequently grown in the absence of TC for 70-80 generations, the heterogeneous DNA disappeared and a typical 28S alpha-plasmid reappeared. The cells also became less resistant to TC, i.e., the minimum inhibitory concentration returned to 250 mug/ml. These data suggest that bacterial growth in the presence of TC results in a reversible gene amplification with respect to a TC-resistant determinant residing on the alpha-plasmid.
Determination of genes, restriction sites, and DNA sequences surrounding the 6S RNA template of bacteriophage lambda.
Authors: Sklar J , Yot P , Weissman S M
Published: May 2006

A major product of the transcription of bacteriophage lambda DNA in vitro is the 6S RNA. This article presents a detailed mapping of restriction endonuclease cleavage sites about the region of the 6S RNA template within the lambda genome. Restriction fragments defined by these sites have been used to localize the 6S RNA template within the physical and genetic maps of the lambda genome. Nucleotide sequence analysis of one of these fragments has largely confimed the nucleotide sequence of the 6S RNA reported previously and has indicated the sequence of DNA that immediately follows the 6S RNA template. This article reports the nucleotide sequence following a known site of transcription termination by RNA polymerase of Escherichia coli.
Induction of endogenous and of spleen focus-forming viruses during dimethylsulfoxide-induced differentiation of mouse erythroleukemia cells transformed by spleen focus-forming virus.
Authors: Dube S K , Pragnell I B , Kluge N , Gaedicke G , Steinheider G , Ostertag W
Published: May 2006

Spleen focus-forming virus-transformed erythroleukemic cell clones, which have been established by infection of N type mice with NB trophic Friend virus, continue to release biologically active tfriend virus of NB host range. Dimethylsulfoxide induces erythroid differentiation and a 10- to 100-fold increase in the release of biologically active Friend virus. The increase of Friend virus release is a function of the differentiating erythroleukemic cell. The induced Friend viurs is not the NB tropic Friend virus complex, but shows N host range. The induction of the Friend virus complex is due to simultaneous induction of both spleen focus-forming and endogenous viruses.
On the Possibility of a Hydrodynamic Model of the Electron
Authors: Pekeris C. L.
Published: May 2006

We explore the possibility that the mutual repulsive forces of a uniformly charged sphere could be kept in balance dynamically by a steady circulation of the material, which is assumed to be a nonconducting perfect fluid of uniform density. An exact solution is obtained of Maxwell's equations and of the hydrodynamic equations in the nonrelativistic approximation, which satisfies the boundary conditions on the surface of the sphere. In this solution all the components of the velocity and of the magnetic field are found to vanish on the surface, but not the electric field. The pressure can also be made to vanish on the surface, but in the interior it turns out to be
negative
, which makes the present solution unacceptable.
Failure of the opiate antagonist naloxone to modify hypnotic analgesia.
Authors: Goldstein A , Hilgard E R
Published: May 2006

Hypnotic analgesia in some respects resembles opiate analgesia. We tested the hypothesis that some features of hypnotic analgesia are mediated through neuronal pathways activating specific opiate receptors in brain. The opiate antagonist naloxone had no effect on hypnotic analgesia in three subjects. Thus, the hypothesis was not confirmed.
Connectivities R

i

of Fréchet Spaces in Variational Topology
Authors: Morse Marston
Published: May 2006

A global study of geodesics, joining points
A
1
[unk]
A
2
on a Riemannian manifold

N
n

, is oriented by the answers given to two questions. How does the concept of a nondegenerate geodesic enter, and what topological invariants best condition the geodesics joining
A
1
to
A
2
? We answer the first question by defining and exploiting nondegenerate point pairs
A
1
[unk]
A
2
on

N
n

. The connectivities

R
i

of

M
n

used in ordinary critical point theory should be replaced by the connectivities R

i

of the pathwise components of the Fréchet metric space [unk]

A
1

A
2

defined in this paper. These components are homeomorphic. Their connectivities R

i

condition the geodesics joining
A
1
to
A
2
on

N
n

in a way to be disclosed. Detailed proofs are found in the references listed, or will be presented later.
Permeability lesions in male Escherichia coli infected with bacteriophage T7.
Authors: Britton J R , Haselkorn R
Published: May 2006

The abortive development of bacteriophage T7 in E. coli cells carrying F factors has previously been attributed to a lack of virus-directed modification of ribosomes in such cells. We find it unnecessary to postulate such translational control to explain the failure of T7 development. Instead, there is a general cessation of macromolecular syntheses around 8 min after T7 infection of F' cells. This cessation is correlated with a sudden outflow of the entire acid-soluble pool of phosphorus-containing compounds and loss of the ability to accumulate amino acids. Manifestation of these defects requires expression of at least one T7 gene and one episomal gene.
Satellite-Rich DNA in Cucumber: Hormonal Enhancement of Synthesis and Subcellular Identification
Authors: Kadouri Avinoam , Atsmon Dan , Edelman Marvin
Published: May 2006

Cucumber hypocotyl DNA in neutral CsCl distributes into a mainband comprising 59% of the total, and two large satellite bands which contribute 41% to the DNA pattern. Organelle enrichment studies show that the densities of mitochondrial and chloroplast DNA coincide with those of the satellite bands. At least 12-19% of total cucumber DNA is associated with the cytoplasmic organelles. These values, which are several times larger than those usually quoted for higher plants, are correlated with an unusually low amount of DNA per haploid nucleus in cucumber. Synthesis of the satellite DNAs, as well as mainband DNA, is appreciably stimulated
in vivo
by application of the plant hormone, gibberellin. Endogenous and hormone-enhanced synthesis of the satellite DNAs is proportionately greater in target tissue showing a high rate of organelle synthetic activity.
Pseudoconformal Geometry of Hypersurfaces in C

n
+1
Authors: Burns D. , Shnider S.
Published: May 2006

The pseudoconformal geometry (CR structure) of a real hypersurface
M
in C

n
+1

is reviewed. We give an alternative formulation of a theorem of Cartan-Tanaka-Chern on the existence of a unique normalized Cartan connection on a principal bundle
Y
over
M
. A family of curves defined by this connection, called chains, is shown to be the projection of light rays of a conformal equivalence class of Lorentz metrics on a trivial circle bundle over
M
. The simply connected homogeneous manifolds locally CR equivalent to the sphere are classified. A theorem on moduli for deformations of the complex structure on the ball in C

n
+1

is given.
Daily periodicity in the activity of a slide used to perform immunologic reactions at a liquid-solid interface.
Authors: Rothen A
Published: May 2006

Nickel-plated slides were prepared by evaporating a nickel layer (congruent to 4000 A thick) on glass slides in the presence of a magnetic field whose lines of force were perpendicular to the surface of the slides. Such slides are called active. After being coated with a layer of bovine albumin, they could absorb a layer of antibodies 70-80 A thick. However, if the active slides before they were coated with bovine serum albumin, were submitted to a magnetic field with lines of force parallel to the surface, the layer of antibodies absorbed was only 40 A thick. They had become inactive. It has been found that slides remain active at night but that shortly after sunrise they become slowly inactivated and reach a minimum in their activity at exactly the midday period. They regain full activity at sunset. It is shown that the inactivation results from a solar radiation that can be stopped by 3.5 cm of lead. On December 13th, 1974 there was an eclipse of the sun with 65% occultation at noon (Daylight Saving Time). The activity of the slide at noon was 65% of the maximum activity (83 A) observed before sunrise. The thickness of the adsorbed layer of antibodies were 75 A instead of 63 A observed in the absence of the eclipse. The activation of the slides originates in a radiation of non-solar origin that is adsorbed by 1 can of lead.
Paleopleurocapsa wopfnerii gen. et sp. nov.:
A Late Precambrian alga and its modern counterpart
Authors: Knoll Andrew H. , Barghoorn Elso S. , Golubić Stjepko
Published: May 2006

Silicified dolomite of the approximately one billion year old Skillogalee Dolomite of the Adelaide Geosyncline, South Australia, contains organically preserved microfossils of a structurally complex, crustose pleurocapsalean cyanophyte, herein described as
Paleopleurocapsa wopfnerii
. Although actual cell contents have been degraded, lamellar sheath material faithfully preserves the morphology of the alga. Comparison with specimens of the modern genus
Pleurocapsa
Thuret demonstrates affinities at the family level and quite possibly even generic identity.
Isolation of a cationic polypeptide from human serum that stimulates proliferation of 3T3 cells.
Authors: Antoniades H N , Stathakos D , Scher C D
Published: May 2006

A basic polypeptide that stimulates DNA synthesis and cell division in confluent populations of mouse Balb/c-3T3 cells has been isolated from whole human serum, and has been separated from the heterogenous group of molecules with insulin-like activity. This highly purified basic polypeptide has a molecular weight of 1.3 x 10(4) and an isoelectric point of 9.7. Approximately 10(7) polypeptide molecules in the growth medium allow the replication of one density-inhibited cell.
Conditional-lethal mutations that suppress genetic defects in morphogenesis by altering structural proteins.
Authors: Jarvik J , Botstein D
Published: May 2006

An analysis of revertants of missense mutants in phage P22 has shown: (i) New temperature-sensitive (TS) and cold-sensitive (CS) phenotypes are often acquired concomitant with reversion. (ii) In many cases, these new phenotypes are due to second-site mutations (suppressors) that correct the original defect. (iii) Sometimes the suppressor mutation is not in the same gene as the original mutation. (iv) Extragenic suppressors are almost always in genes whose products are known to interact physically with the original gene products. (v) The suppressor mutations typically retain their TS or CS phenotypes when crossed into wild-type genetic backgrounds. (vi) Some TS and CS mutants derived by reversion can themselves be reverted to produce additional mutations. We have shown that genetic reversion of missense mutants can be of value in producing new temperature-sensitive and cold-sensitive mutations affecting related functions. We suggest that our approach can be extended to organisms with large genomes.
Cluster of genes in Escherichia coli for ribosomal proteins, ribosomal RNA, and RNA polymerase subunits.
Authors: Lindahl L , Jaskunas S R , Dennis P P , Nomura M
Published: May 2006

The transducing phage lambdarifd18 isolated by Kirschbaum and Konrad [(1973 J. Bacteriol. 116, 517-526] was found to carry structural genes for several 50S ribosomal proteins and 16S and 23S rRNA. It has previously been demonstrated [Kirschbaum & Scaife (1974) Mol. Gen. Genet. 132, 193-201] that this phage carries genes for the DNA-dependent RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase; EC 2.7.7.6) subunits beta and beta'. Thus, the region of the E. coli chromosome carried by lambdarifd18 contains a cluster of genes essential for transcription and translation.
Effects of tetraalkylammonium salts on Brdicka and presodium currénts of bovine-serum albumin.
Authors: Kolthoff I M , Yamashita K
Published: May 2006

Tetraethyl-, tetrapropyl-, and tetrabutylammonium ions are capillary-active on the interface water-mercury. In the adsorbed state they increase Brdicka and presodium currents. These currents drop sharply at potentials where tetrabutylammonium ions are desorbed, these potentials being -1.60, -1.66, -1.72, and -1.79 V versus the saturated calomel electrode (SCE) at tetrabutyla-mmonium concentrations of 0.1, 0.25, 1, and 5 mM, respectively. Indications are that tetraethylammonium ions at a concentration of 50 mM are desorbed at a potential of the order of -1.9 V (versus SCE). The increase of Brdicka currents is attributed--at least in part--to a decrease in the rate of electroreduction of cobalt(II). In the desorbed state the effect--if any--of tetrabutylammonium ions on Brdicka and presodium currents is very small. Tetrabutylammonium ions also greatly increase Brdicka currents observed with cysteine, the effect disappearing after these ions attain their desorption potential. The effect of tetraphenylarsonium on Brdicka currents is very similar to that of tetrabutylammonium, while that of diphenylguanidine is similar to that of tetraethylammonium ions.
DNA polyintercalating drugs: DNA binding of diacridine derivatives.
Authors: Le Pecq J B , Le Bret M , Barbet J , Roques B
Published: May 2006

As a first step in the synthesis and the study of DNA polyintercalating drugs, dimers of acridines have been prepared. Their DNA binding properties have been studied. It has been determined that when the chain separating the two aromatic rings is longer than a criticål distance, bisintercalation is actually observed and that the DNA binding affinity becomes quite large (greater than 10(8)-10(9) M-1). It is shown also that the optical characteristics of these molecules are dependent on the sequences of DNA. The fluorescence intensity of one of these dimers when bound to DNA varies as the fourth power of its A+T content. This derivative could be used as a fluorescent probe of DNA sequence.
Molecular mechanism for oscillation in flagella and muscle.
Authors: Brokaw C J
Published: May 2006

Two-state models for muscle cross-bridges, of the type originally detailed by Andrew Huxley, were examined. Rate functions for cross-bridge attachment and detachment can be chosen which yield a steady-state force-velocity relationship appropriate for the spontaneous generation of oscillatory contractions. Computer simulations have been used to demonstrate oscillation of such cross-bridge systems, and to demonstrate that distribution of this type of local shear oscillation along the length of a flagellum is sufficient for the generation of propagated bending waves.
Gene expression in mouse neuroblastoma cells: properties of the genome.
Authors: Zornetzer M S , Stein G S
Published: May 2006

Chromatin was prepared from isolated nuclei of proliferating and differentiated cultures of C1300 mouse neuroblastoma cells. Differentiation was induced by serum withdrawal or treatment with dibutyryl cyclic AMP. The ability to support DNA-dependent RNA synthesis when assayed in a cell-free system is three times greater for chromatin from proliferating cells. Histones isolated from proliferating and differentiated cells were fractionated electrophoretically. The relative amounts of proteins present in the five major histone fractions were similar. In contrast, there were significant differences in the nonhistone chromosomal proteins synthesized and associated with the genome of proliferating and differentiating neuroblastoma cells. Such differences are reflected by modifications in the electrophoretic banding patterns and in incorporation of [3H]tryptophan into various molecular weight classes of nonhistone chromosomal polypeptides. A functional relationship between changes in the nonhistone chromosomal proteins and variations in the transcriptional activity accompanying differentiation of neuroblastoma cells may exist.