bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of leucyl-tRNA synthetase in regulation of branched-chain amino-acid transport.
Authors: Quay S C , Kline E L , Oxender D L
Published: May 2006

The regulation of the transport of leucine, isoleucine, and valine in Escherichia coli B/r was studied in a mutant with a complete deletion of the leucine biosynthetic operon and a temperature-sensitive leucyl-tRNA synthetase [L-leucine:tRNALeu ligase (AMP-forming), EC 6.1.1.4]. Under conditions of excess leucine and a functional leucyl-tRNA synthetase transport activity was repressed. Shifting the culture to a temperature at which the activation of leucine to an appropriate tRNA species became growth-rate-limiting led to a large increase in the high-affinity transport of leucine, isoleucine, and valine (system LIV-I) while the uptake of histidine and proline was unchanged. A similar increase was observed for branched-chain amino-acid binding protein activity. The temperature change did not alter the transport activity for any of these substrates or the level of the binding proteins in an isogenic strain with a normal leucyl-tRNA synthetase. The increase in transport activity observed in the mutant was prevented by inhibitors of protein and RNA synthesis and probably represents an increase in the differential rate of synthesis of the protein(s) required for transport. These experiments demonstrate that the repression of branched-chain amino-acid transport involves the interaction of leucine with its aminoacyl-tRNA synthetase and its cognate leucyl-tRNA species.
Inheritability of plasmids and population dynamics of cultured cells.
Authors: Anderson T F , Lustbader E
Published: May 2006

The compositions of growing bacterial cultures containing F' plasmids are developed in theoretical terms that will be helpful in designating experiments to determine the genetic and physiological parameters involved. The genetic parameter is the inheritability of the plasmid defined as the probability, h, that a daughter bacterium will inherit the plasmid and thus be F' rather than F-. The value of h determines the chance that the plasmid will survive in a clone initiated by a single F' bacterium. If 0 less than or equal to h less than 0.5, the probability of plasmid survival is zero, whereas if 0.5 less than h less than 1 the survival is (2h - 1)/h2. While clone sizes are demonstrated to be erratic, the proportion of F' bacteria does converge to an equilibrium value if log2 h greater than alpha - 1, where the physiological factor, alpha, is the ratio between the division times of F' and F- bacteria. A general expression of this equilibrium is derived. The two cases of alpha = 0, implying that only the F' bacteria multiply on a selective medium, and alpha = 1, implying a completely nonselective medium, are analyzed in detail. It is shown that the above considerations apply generally to growing cultures of cells in which irreversible mutations occur.
Purification and synthesis of eosinophilotactic tetrapeptides of human lung tissue: identification as eosinophil chemotactic factor of anaphylaxis.
Authors: Goetzl E J , Austen K F
Published: May 2006

Preferential eosinophil chemotactic activity exhibiting a molecular weight comparable to that released from sensitized human lung fragments challenged with specific antigen and designated eosinophil chemotactic factor of anaphylaxis has been isolated from extracts of human lung fragments by sequential purification on Sephadex G-25, Dowex-1, Sephadex G-10, and paper chromatography. Two eosinophilotactic tetrapeptides of amino acid sequence Val-Gly-Ser-Glu and Ala-Gly-Ser-Glu were recovered from the extracts in 4-12% overall yield of the low molecular weight peak from Sephadex G-25. Purified eosinophil chemotactic factor of anaphylaxis and the synthetic tetrapeptides were maximally active in amounts from 0.1 to 1.0 nmol per chemotactic chamber, and the activity was dependent on both the NH2-terminal and the COOH-terminal residues. Both natural and synthetic peptides were preferentially chemotactic for eosinophils and rendered them unresponsive to a subsequent stimulus.
A unique complement derived chemotactic factor for tumor cells.
Authors: Romualdez A G , Ward P A
Published: May 2006

A factor chemotactic for Walker carcinosarcoma and Novikoff hepatoma tumor cells can be generated by incubation of serum with an extract from tumor cells. The chemotactic factor has no activity for neutrophilic leukocytes, and three factors chemotactic for leukocytes are not chemotactic for tumor cells. By the use of complement deficient serums as well as purified complement components, the chemotactic factor for tumor cells has been found to be a fragment of the fifth component (C5) of complement and appears to result from direct interaction of C5 with an enzyme in the extract. The chemotactic factor for tumor cells can be classified as a functionally unique fragment of C5 that may significantly influence the behavior of tumor cells in vivo.
Solar abundance of platinum
Authors: Burger Harry , Aller Lawrence H.
Published: May 2006

Three lines of neutral platinum, located at λ 2997.98 Å, λ 3064.71 Å, and λ 3301.86 Å have been used to determine the solar platinum abundance by the method of spectral synthesis. On the scale, log
A
(H) = 12.00, the thus-derived solar platinum abundance is 1.75 ± 0.10, in fair accord with Cameron's value of log
A
(Pt) = 1.69 derived by Mason from carbonaceous chondrites and calculated on the assumption that log
A
(Si) = 7.55 in the sun.
Limits of zeroes of recursively defined polynomials
Authors: Beraha S. , Kahane J. , Weiss N. J.
Published: May 2006

Let {

P
n

(
z
)} be a sequence of polynomials satisfying a linear homogeneous recursion whose coefficients are polynomials in
z
. Necessary and sufficient conditions are found, subject to mild nondegeneracy conditions, that a number
x
be a limit of zeroes of {

P
n

} in the sense that there is a sequence {

z
n

} with

P
n

(

z
n

) = 0,

z
n

→
x
. An application is given to a family of polynomials arising in a map-coloring problem.
Resonance Raman spectroscopic studies of the interactions between trypsin and a competitive inhibitor.
Authors: Dupaix A , Bechet J J , Yon J , Merlin J C , Delhaye M , Hill M
Published: May 2006

Raman spectroscopy was used to study the interactions between bovine trypsin and a competitive inhibitor. For this purpose, a chromophoric substrate analogue, 4-amidino-4'-dimethylamine azobenzene, was synthesized. This compound competitively inhibits the enzyme with a 1:1 stoichiometry and an inhibition constant Ki of 2.3 muM at pH 6.08 and 15 degrees. Resonance Raman spectra in aqueous solution of free or enzyme-bound inhibitor were analyzed. The main spectral changes observed upon enzyme-inhibitor complex formation were changes in the relative intensities of four bands (1171, 1206, 1315, 1608 cm-1) while no large frequency shifts occurred. The binding of the inhibitor molecule to the enzyme did not induce a twisting of the phenyl groups around the N=N bond. Some modifications of the band widths are interpreted in terms of a restriction of rotational motions in the inhibitor molecule. The possible involvement of specific interactions between trypsin and the benzamidinium ion part of the inhibitor molecule is discussed.
Influence of insertions on packaging of host sequences covalently linked to bacteriophage Mu DNA.
Authors: Bukhari A I , Taylor A L
Published: May 2006

Insertions in bacteriophage Mu DNA have been identified. These insertions are responsible for at least seven X mutations, all of which eliminate essential Mu functions. The insertions are about 800 base pairs long and are located to the left of the cleavage site of restriction endonuclease EcoRI, near the immunity end of Mu DNA. We have found that such insertions cause a reduction in the length of nonhomologous terminal sequences which are seen as split ends in denatured and renatured Mu DNA molecules. These heterogeneous sequences apparently arise from packaging of host DNA from maturation precursors in which Mu and host DNA are covalently linked. We infer that a single Mu genome length is too short to be cut during morphogenesis, and thus some host DNA is packaged into mature virions. Since the insertions increase the length of Mu DNA, they decrease the amount of host DNA needed for packaging.
Relationship between release of surface proteins and metabolic activation of sea urchin eggs at fertilization.
Authors: Johnson J D , Epel D
Published: May 2006

Macromolecular components are released from sea urchin eggs when their metabolism is activated at fertilization or by incubation in ammonia. When the released material is dialyzed, concentrated, and added back to partially activated eggs the rate of protein synthesis is suppressed to the level of the unactivated egg. The surface proteins of the unfertilized eggs can be labeled with 125I by a lactoperoxidase procedure. When fertilized or activated with various parthenogenetic agents, 15-25% of the total labeled protein is released; most of the label is associated with a 150,000-dalton glycoprotein. The extent of metabolic activation, as assessed by measuring increased protein synthesis, is correlated with the amount of surface label released. Several other proteins are released during activation but are not labeled by the lactoperoxidase procedure in the intact cell. We have not yet identified which of these components is responsible for suppressing protein synthesis, nor do we know if any of the other metabolic changes of fertilization such as K+ conductance and DNA synthesis are also suppressed. We suggest that these released components are surface molecules involved in maintaining the low metabolic state occurring at the end of oogenesis and that removal of these components during fertilization results in the release of the suppression of the egg.
Immunochemical characterization of murine H-2 controlled Ss (serum substance) protein through identification of its human homologue as the fourth component of complement.
Authors: Meo T , Krasteff T , Shreffler D C
Published: May 2006

The S region of the mouse H-2 complex is genetically defined by a series of alleles, or pseudoalleles, which control the level of a serum globulin, Ss, and of its allotypic vairatn, Slp. In contrast with the products of other genes in the complex, no homologue of the Ss protein has been found in other species, except the rat. In the present study, a component in human plasma was identified which cross-reacts with anti-mouse Ss, and which also displays electrophoretic and size similarities to the mouse Ss protein. This component was isolated and characterized immunochemically as the fourth component of human complement (C'4 or beta1E globulin). Several antisera monospecific for human C'4 cross-react with the mouse Ss protein and detect its genetically determined quantitative variations.
Chromosome puff activity and protein synthesis in larval salivary glands of Drosophila melanogaster.
Authors: Korge G
Published: May 2006

Secretion proteins from larval salivary glands of Drosophila melanogaster were analyzed with acrylamide gel electrophoresis. Four fractions were found; three showed electrophoretic variants in different wild-type stocks. Crossbreeding and cytogenetic techniques were used to localize the genes responsible for the two main fractions: The gene for fraction 3 was found to lie within a segment of the third chromosome which includes section 68C; the gene for fraction 4, Sgs-4, was found to lie within section 3C8-3D1 of the X chromosome (1 - 3-5). The puffs within these sections of the giant chromosomes are active before and during secretion synthesis and become inactive as secretion synthesis ceases. Larvae of one wild-type stock which lack protein fraction 4 do not exhibit any puffing in 3C. The relative amount of protein 4 in the salivary secretion shows a marked dependence on the dosage of the Sgs-4 gene in both duplication and deficiency genotypes. The active site within puff 3C11-12 apparently contains the structural gene for protein 4.
Genome of hepatitis B virus: restriction enzyme cleavage and structure of DNA extracted from Dane particles.
Authors: Summers J , O'Connell A , Millman I
Published: May 2006

DNA extracted from Dane particles has been characterized by gel electrophoresis and restriction enzyme cleavage with endonuclease R-HaeIII (from Hemophilus aegyptius). Dane particle DNA is proposed to be a double-stranded circular DNA approximately 3600 nucleotides in length containing a single-stranded gap of 600-2100 nucleotides. The endogenous DNA polymerase (DNA nucleotidyl-transferase; deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase; EC 2.7.7.7) reaction appears to repair this single-stranded gap.
Relationship in nucleic acid sequences between mouse mammary tumor virus variants.
Authors: Michalides R , Schlom J
Published: May 2006

Primary cultures of mouse mammary carcinomas were used as a source of both radioactively labeled and unlabeled 60-70S RNA of mouse mammary tumor virus (MMTV) obtained from various mouse strains. Competition molecular hybridization experiments revealed that, within the limits of the assay, the RNAs of the MMTVs synthesized in culture by the tumors of the mouse strains RIII, GR, A, and C3H, are identical. A comparison of the genomes of the milk-transmitted MMTV(C3H) and the vertically transmitted MMTV(C3Hf) revealed that these two viruses are approximately 75% similar. No nucleic acid sequence homology was observed between MMTV(C3H) 60-70S RNA and the RNAs of murine leukemia virus, Mason-Pfizer virus, or the BrdUrd-induced type-B quinea pig virus.
Studies on nucleic acid reassociation kinetics: reactivity of single-stranded tails in DNA-DNA renaturation.
Authors: Smith M J , Britten R J , Davidson E H
Published: May 2006

The reassociation kinetics of Escherichia coli DNA were measured by S1 nuclease resistance and hydroxyapatite binding. While the reaction assayed by hydroxyapatite displays second order kinetics, the S1 nuclease measurements follow a non-second order from, as previously reported by Morrow (Ph.D. Dissertation, Stanford University. 1974). Much of the reaction measured with S1 nuclease occurs between single stranded regions of fragments already bearing duplex structures from previous collisions, and between such regions and totally free single strands. Experimental determinations indicate that the nucleation rate of single stranded regions on fragments also containing duplexes is inhibited by an average factor of 2 to 4.
Human papillomavirus DNA: physical map.
Authors: Favre M , Orth G , Croissant O , Yaniv M
Published: May 2006

Human papillomavirus (HPV) DNA form I (supercoiled) was prepared from plantar warts. HPV DNA was cleaved with restriction enzymes obtained from the following sources: escherichia coli (EcoRI), Hemophilus influenzae strain Rd (both unfractionated Hind and aeparated HindII and HindIII enzymes) and Hemophilus parainfluenzae (HpaI). The cleavage products were analyzed by polyacrylamide gradient slab gel electrophoresis and electron microscopy. HPV DNA was cleaved into two fragments by EcoRI (87% and 13% of the genome) and into six fragments, ranging in size from 33.5 to 1.2% of the genome, by Hind endonucleases. The six Hind fragments result from the cleavage of three sequences recognized by HindII, two of which are also cleaved by HpaI, and of three sequence recognized by HindIII. The order of these fragments was determined by comparing their size with that of the fragments obtained with HindII, HindIII, HpaI, and the mixture of HindIII + Hpal. The two EcoRI cleavage sites were located on two adjacent Hind fragments and one of these sites has been taken for the zero point to construct a physical map. The treatment of superhelical HPV DNA with bacteriophage T4 gene 32 protein yields circular structures with a denaturation loop. The cleavage of these complexes with EcoRI and HindIII has shown two easily denatured regions which were located on the cleavage map.
Statistical theory of chromatography: new outlooks for affinity chromatography.
Authors: Denizot F C , Delaage M A
Published: May 2006

We have developed further the statistical approach to chromatography initiated by Giddings and Eyring, and applied it to affinity chromatography. By means of a convenient expression of moments the convergence towards the Laplace-Gauss distribution has been established. The Gaussian character is not preserved if other causes of dispersion are taken into account, but expressions of moments can be obtained in a generalized form. A simple procedure is deduced for expressing the fundamental constants of the model in terms of purely experimental quantities. Thus, affinity chromatography can be used to determine rate constants of association and dissociation in a range considered as the domain of the stopped-flow methods.
High resolution 31P nuclear magnetic resonance studies of intact yeast cells.
Authors: Salhany J M , Yamane T , Shulman R G , Ogawa S
Published: May 2006

High resolution 31P nuclear magnetic resonance (NMR) spectra at 145.7 MHZ are presented for intact yeast cells. Several peaks are resolved and assigned. They include the middle phosphate peaks from long chain or cyclic polyphosphates. Our results are consistent with the suggestion that these polyphosphates act as a phosphate store in the cell. We have also been able to measure cytoplasmic pH using the orthophosphate peak inside the cell, as compared with outside the cell. The results show that yeast cells maintain their cytoplasmic pH around 6.3. This value is considerably higher than the acidic extracellular pH at which they normally live. These preliminary results indicate that 31P NMR at 145.7 MHZ can be a rapid, informative, and non-invasive method for probing biochemical events within living cells.
Factor-VIII-related antigen: multiple molecular forms in human plasma.
Authors: Zimmerman T S , Roberts J , Edgington T S
Published: May 2006

Analysis of Factor-VIII-related antigen (vWAg) in normal plasma by crossed immunoelectrophoresis reveals an asymmetric pattern indicative of molecular heterogeneity. This asymmetric pattern apparently results from the presence of multiple molecular forms of VWAg with distinct, though partially overlapping, mobilities on crossed immunoelectrophoresis. Evidence for this conclusion has been obtained by separating these forms, one from another, utilizing cryoprecipitation, agarose gel chromatography, and ion-exchange chromatography. Variation in the relative destribution of VWAg forms in liver disease and disseminated intravascular coagulation suggests that the processes which govern generation and/or breakdown of these forms can be altered by disease.
Observations on impulse conduction along central axons.
Authors: Swadlow H A , Waxman S G
Published: May 2006

This note calls attention to the facts that (i) the conduction velocities of central axons may not be predicted on the basis of diameter alone, (ii) that such structure-function relations as do exist may not be invariant. Data are presented which indicate that conduction velocities of rabbit callosal axons vary with the history of impulse conduction along the fiber. Increases and decreases of conduction velocity occur. Constant latency does not, therefore, constitute a necessary condition for identification of antidromically activated neurons, and variable latency does not constitute a sufficient condition for identification of synaptically activated neurons. The results are further discussed in terms of temporal coding of information in the central nervous system.
Mutant hamster cells exhibiting a pleiotropic effect on carbohydrate metabolism.
Authors: Sun N C , Chang C C , Chu E H
Published: May 2006

Sixty-seven galactose negative (Gal minus) clones were established from survivors after treatment of Chinese hamster lung (V79) cells with 5-bromodeoxyuridine and black light. The mutational origin of these clonal isolates was inferred on the basis of the previously demonstrated mutagenic action of the combined treatment, persistence of the Gal minus phenotype in cell progeny in the absence of selection, conditional lethality of three isolates, interallelic complementation, and assignment of a homologous human gene to chromosome A2. In contrast to the parental cells, Gal minus mutants could not utilize exogenous galactose, mannose, fructose, galactose 1-phosphate, glucose 1-phosphate, or glucose 6-phosphate. Permeation of galactose into mutant cells appeared unimpaired. In intra- and interspecific cell hybrids, the mutation causing the Gal minus phenotype behaved like a recessive character. The pleiotropic nutritional response was due not to deficiency of any one specific enzyme in the Leloir pathway but to significant reduction in activities of phosphoglucomutase, NADP-dependent isocitrate dehydrogenase, and perhaps other enzymes. In temperature-sensitive Gal minus mutants grown at permissive temperature or in complementing intra- and interspecific cell hybrids, the activities of these enzymes were restored to normal levels, accompanied by a regained ability to use the particular hexoses or hexose monophosphates. We postulate that the change from Gal + to Gal minus phenotype in hamster cells could be due to mutations at a regulatory gene locus, or at a yet unknown locus with enzymic defect that causes secondary metabolic imbalances.
Cytochemical studies on golgi apparatus, GERL, and lysosomes in neurons of dorsal root ganglia in mice.
Authors: Boutry J M , Nivikoff A B
Published: May 2006

Cytochemically demonstrable thiamine pyrophosphatase activity is present in the innermost Golgi element in both small and large neurons of the dorsal root ganglia in CF1, C57 black, and C57 beige mice, thus resembling the neurons of rat dorsal root ganglia. The localization of acid phosphatase (EC 3.1.3.2) activity in the large neurons of dorsal root ganglia in these mice is also similar to that in rats; it is not demonstrable in Golgi elements but is present in GERL and in three types of lysosomes apparently derived from GERL. However, the small neurons of the mouse differ from those of the rat in showing acid phosphatase activity in all elements of the Golgi apparatus. In the mouse neurons the acid phosphatase activity of residual bodies is "latent," i.e., it is not demonstrable in well-preserved cells.
X-ray crystallographic visualization of drug-nucleic acid intercalative binding: structure of an ethidium-dinucleoside monophosphate crystalline complex, Ethidium: 5-iodouridylyl (3'-5') adenosine.
Authors: Tsai C C , Jain S C , Sobell H M
Published: May 2006

We have cocrystallized the drug ethidium bromide with the dinucleoside monophosphate 5-iodouridylyl(3'-5')adenosine and have solved the three-dimensional structure to atomic resolution by x-ray crystallography. This has allowed the direct visualization of intercalative binding by this drug to a fragment of a nucleic acid double helix.
Inequalities in Fourier Analysis on

R
n
Authors: Beckner William
Published: May 2006

This note describes two results: (
i
) a sharp Hausdorff-Young inequality for the Fourier transform on

L
p

(

R
n

) which extends an earlier result of Babenko; and (
ii
) a sharp form of Young's inequality for the convolution of functions on

R
n

. That is, best possible constants are obtained for the following

L
p

(

R
n

) inequalities: [Formula: see text]
Life history of Coelomomyces psorophorae.
Authors: Whisler H C , Zebold S L , Shemanchuk J A
Published: May 2006

The mosquito parasite, Coelomomyces psorophorae (Blastocladiales, Chytridiomycetes) alternates obligately between the larvae of Culiseta inornata and the copepod Cyclops vernalis. Isogametes, derived from heterothallic, wall-less gametangia which develop in the copepod, fuse to produce a diploid zygote that subsequently infects the mosquito host. Zoospores from the resistant sporangia which are produced in the haemocoel of the mosquito infect the copepod. A tentative life-history is proposed and implications of these discoveries for the biology, taxonomy, and possible role of Coelomomyces in biological control are discussed.
Cholinergic differentiation of presumptive adrenergic neuroblasts in interspecific chimeras after heterotopic transplantations.
Authors: Le Douarin N M , Renaud D , Teillet M A , Le Douarin G H
Published: May 2006

The levels of the neural axis from which parasympathetic and orthosympathetic neurons and adrenomedullary cells are derived under normal developmental conditions were determined in avian embryos by a biological labeling technique. The technique is based on nuclear differences between two species of birds, the chick and the quail. In quail interphase nuclei a part of the chromatin is condensed in large heterochromatic masses associated with nucleolus, while in the chick, DNA is evenly dispersed in the nucleoplasm. These characteristics provide a stable nuclear marker that can be used to study cell migrations and differentiation in chimeric embryos resulting from the association of quail and chick tissues. Isotopic and heterotopic transplantations of quail neural primordium into chick before the outset of neural crest cell migration show that the autonomic ortho- and parasympathetic neuroblasts are not determined to differentiate into cholinergic or adrenergic neurons when they begin to migrate. The neurotransmitter synthesized by crest autonomic neuroblasts depends on the microenvironment in which crest cells become localized at the term of their migration. The splanchnic mesoderm induces presumptive adrenergic cells to become fully differentiated cholinergic neurons.
Measurement of human dopamine-beta-hydroxylase in serum by homologous radioimmunoassay.
Authors: Rush R A , Thomas P E , Udenfriend S
Published: May 2006

Human serum dopamine-beta-hydroxylase [3,4-dihydroxyphenylethylamine, ascorbate: oxygen oxidoreducatse (beta-hydroxylating), EC 1.14.17.1] levels have been determined in 52 samples with a newly devised radioimmunoassay that utilizes purified human enzyme and its specific antiserum. The values obtained were in excellent agreement (correlation coefficient r equals 0.98) with those obtained by measuring enzymatic activity in the same sera. Either assay technique, enzymatic or homologous radioimmunoassay, can be used for measurement of the enzyme in normal human serum.
Changes in microtubule phosphorylation during cell cycle of HeLa cells.
Authors: Piras R , Piras M M
Published: May 2006

The phosphorylation in vitro and in vivo of tubulin isolated from HeLa cells has been examined during the cell cylce. The results obtained indicate that: (a) the protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) activity present in the microtubules, and measured in vitro with exogenous casein as substrate, is maximal in M cells, whereas that present in the cytosol is nearly constant during the S, G-2, and M stages, and decreases during G-1; (b) the patterns through the cell cycle of the maximal number of tubulin sites phosphorylated in vitro and of the microtubular protein kinase activity are similar; (c) the degree of tubulin phosphorylation in vivo is 2- to 3-fold higher in the microtubules isolated from the S and M stages of the cell cycle, than those from G-1 and G-2. This variable phosphate content of tubulin through the cell cycle suggests that such covalent modification might be important to enable tubulin to carry over some of its functions during the cell cycle.
Reversible redistribution of phytochrome within the cell upon conversion to its physiologically active form.
Authors: Mackenzie J M , Coleman R A , Briggs W R , Pratt L H
Published: May 2006

The intracellular localization of phytochrome was seen in dark-grown oat (Avena sativa L., cv. Garry) and rice (Oryza sativa L., cv. unknown) shoots after various light treatments using an indirect peroxidase-antiperoxidase antibody labeling method. Phytochrome is generally distributed throughout the cytoplasm in cells of tissue that had not been exposed to light prior to fixation. Within, at most, 8 min after the onset of saturating red irradiation, phytochrome, now present in the far-red-absorbing form, becomes associated with discrete regions of the cell. These regions do not appear to be nuclei, plastids, or mitochondria. After phototransformation back to the red-absorbing form originally present, phytochrome slowly resumes its general distribution. It is possible that this discrete localization of the far-red-absorbing form of phytochrome represents a physiologically significant binding with a receptor site in the cell.
Versatile Properties of a Nonsaturable, Homogeneous Transport System in
Bacillus subtilis:
Genetic, Kinetic, and Affinity Labeling Studies
Authors: Glover George I. , D'Ambrosio Steven M. , Jensen Roy A.
Published: May 2006

The multiphasic kinetics that characterize the transport of many amino acids into
Bacillus subtilis
suggests
a priori
at least two mechanisms: (
i
) a heterogeneous mixture of two independent transport processes, or (
ii
) a single, homogeneous system that might involve a negative cooperative mechanism. The highly specific transport system for L-tyrosine and L-phenylalanine in
B. subtilis
was studied as a case in point. The possible presence of a mixed system of independent transport systems was negated by the retention of multiphasic kinetics of transport in two types of permease mutants. Furthermore, evaluation of kinetic data obtained during transport under various uptake conditions of pH and temperature, or in the presence of metabolic inhibitors, did not reveal the heterogeneity expected of mechanism (
i
). These data, taken together with characteristics of substrate specificity and affinity labeling, provide substantial support for a negative cooperative mechanism for L-tyrosine and L-phenylalanine transport.
Lack of detectable change in cyclic AMP during the cardiac inotropic response to isoproterenol immobilized on glass beads.
Authors: Venter H C , Ross J , Kaplan N O
Published: May 2006

Changes in contractility and the levels of adenosine 3':5'-cyclic monophosphoric acid (cAMP) were assessed in isolated cat cardiac muscle in response to soluble isoproterenol and isoproterenol immobilized on glass beads. Drug-induced positive inotropic responses were compared to the maximum isometric force achieved with paired electrical stimulation, a potent physiological inotropic stimulus. Isoproterenol (1 muM) in solution increased the force of contraction 0.832 plus or minus 0.165 g at 60 sec in eight muscles tested, which at 60 and 120 sec averaged 65.5 plus or minus 6.5% and 82.9 plus or minus 8.8%, respectively, of the force with paired electrical stimulation. Isoproterenol immobilized on glass beads gave positive inotropic responses similar to those for the soluble form of the drug. Placement of only three isoproterenol-glass beads on the muscles increased the force of contraction 0.742 plus or minus 0.166 g at 60 sec (n equals 11), which at 60 and 120 sec averaged 45.1 plus or minus 7.0% and 58.6 plus or minus 6.4%, respectively, of the force with paired electrical stimulation. The magnitude of this response indicates that the increased force was developed by at least 60% of the cells in each muscle. Control levels of cAMP were 0.527 plus or minus 0.049 pmol/mg of tissue wet weight, n equals 11. cAMP levels 60 sec after 1 muM soluble isoproterenol was added were 1.212 plus or minus 0.085 pmol/mg; in contrast, the levels of cAMP in response to isoproterenol immobilized on glass beads at 60 sec were 0.490 plus or minus 0.060 pmol/mg, not significantly different from control levels. These data indicate that cAMP may not be involved in the propagation of the inotropic response that must have occurred in these cardiac muscles and raise questions as to the physiological significance of the large cAMP increases that occur in response to soluble drugs and hormones.
Cyclic AMP, a nonessential regulator of the cell cycle.
Authors: Coffino P , Gray J W , Tomkins G M
Published: May 2006

Flow-microfluorimetric analysis has been carried out on populations of exponentially growing S49 mouse lymphoma cells treated with dibutyryl cyclic AMP. The drug produces a specific concentration-dependent block in the G-1 phase of the cell cycle while other phases of the cycle are not perceptibly altered. The cell cycle of a line of mutant cells lacking the cyclic AMP-dependent protein kinase is not affected by the drug. Since these mutant cells have been shown to maintain a normal cell cycle, even in the presence of high levels of cyclic AMP, periodic fluctuations in the levels of the cyclic nucleotide cannot be required for or determine progression through the cell cycle.
Genetic Control of Endosperm Amylase Activity and Gibberellic Acid Responses in Standard-Height and Short-Statured Wheats
Authors: Fick Gerhardt N. , Qualset Calvin O.
Published: May 2006

In contrast to standard-height wheat genotypes, short-statured wheats having major genes for dwarfness do not show increased seedling growth after treatment with gibberellic acid. Endogenous gibberellic acid induces synthesis of amylase in the endosperm of germinating seeds, but the amount of amylase synthesized is greatly increased by exogenous gibberellic acid treatment in standard-height and in short-statured wheats that have dwarfing genes from the variety “Norin 10.” “D6899,” which has the “Tom Thumb” gene for height reduction, had about one-fourth of the amylase activity of standard-height and Norin 10-derived, short-statured wheats. This genotype showed little or no increased amylase activity after gibberellic acid treatment. Genetic analyses showed that the amount of amylase synthesized was controlled by a single gene and was dependent on the number of copies of the structural gene present in the endosperm. Dwarfism in wheat may be related to a blockage in gibberellic acid utilization because other workers have found that the amount of endogenous amylase synthesized in Norin 10-derived, short-statured wheats is not growth-limiting, but it is not known if low amylase synthesis is related to dwarfism in the Tom Thumb derivative. No recombinants were recovered in a small population, suggesting that the Tom Thumb gene may pleiotropically affect plant height and the lack of response to gibberellic acid in amylase synthesis and seedling growth.
Synthesis of DNA complementary to separated human alpha and beta globin messenger RNAs.
Authors: Forget B G , Housman D , Benz E J , McCaffrey R P
Published: May 2006

Human globulin messenger RNA, purified by oligo(dT)-cellulose column chromatography, is reproducibly separated into two bands by polyacrylamide gel electrophoresis in the presence of 99% formamide. The more rapidly migrating (fast) band is somewhat more abundant than the slow band in normal (nonthalassemic) total reticulocyte globin messenger RNA. In alpha-thalassemic (Hb H disease) messenger RNA, the slow band is 6.5 times more abundant than the fast band, whereas in beta-thalassemic messenger RNA the fast band is three times more abundant than a second band, which has a slightly greater mobility than the slow band of normal and alpha-thalassemic RNA. The RNA bands of nonthalassemic globin messenger RNA were eluted from the gel and efficiently transcribed into DNA copies by use of the RNA-dependent DAN polymerase of avian myeloblastosis virus. Hybridization of these copy DNAs to fast and slow band RANs and to nonfractionated normal, alpha-thalassemic, and geta-thalassemic messenger RNAs revealed that the eluted fast band RNA contains predominantly alpha-chain specific sequences, whereas the eluted slow band RNA contains predominantly beta-chain specific sequences. Nucleotide sequence analysis of 32-P-labeled RNA transcribed from the slow band copy DNA also indicated that the slow band RNA is beta messenger RNA.
Assessment of some problems associated with prediction of the three-dimensional structure of a protein from its amino-acid sequence.
Authors: Burgess A W , Scheraga H A
Published: May 2006

It is shown that most present empirical prediction algorithms provide information about the conformational states of individual residues, but give little information about the three-dimensional structure of a protein. It is necessary to predict the conformational state of every residue before the resulting structure can serve as a starting conformation to compute the native structure. It is also shown that even a perfect five-state algorithm (which does not include long-range interactions from disulifide loop closing or solvation) will not lead to a globular structure resembling the native one. However, starting from the results of a perfect prediction algorithm, it appears that conformational energy minimization (with long-range interactions included) can lead to a structure having the general features of the native protein.
Chromosome measurement and sorting by flow systems.
Authors: Gray J W , Carrano A V , Steinmetz L L , Van Dilla M A , Moore D H , Mayall B H , Mendelsohn M L
Published: May 2006

A flow microfluorometer was used to measure metaphase chromosomes in suspension at rates up to 100,000 per min. Chromosomes from cells of the Chinese hamster M3-1 cell line were isolated, stained for DNA with the fluorescent dye ethidium bromide, and analyzed for DNA content. Nine distinct peaks were resolved that correspond well with independent chromosomal DNA measurements made with a high-resolution scanning cytophotometer. Chromosomes were sorted from each peak by an electronic cell sorter. Visual examination of each fraction indicated the purity of the sorted chromosomes. This novel technology allows separation of purified populations of individual chromosomes suitable for biochemical and biological characterizations.
Proposal concerning mechanism of evolution of the genome of Escherichia coli.
Authors: Zipkas D , Riley M
Published: May 2006

Many pairs of genes whose gene products are functionally related lie either 90 degrees or 180 degrees apart on the circular map of the E. coli chromosome. A mechanism of evolution is proposed that involves two sequential duplications of an ancestral genome, followed by mutation and divergence of function of replicate genes.
Circadian rhythm of tyrosine hydroxylase induction by short-term cold stress: modulatory action of glucocorticoids in newborn and adult rats.
Authors: Otten U , Thoenen H
Published: May 2006

The trans-synaptic induction of tyrosine hydroxylase [tyrosine 3-monooxygenase; EC 1.14.16.2, L-tyrosine, tetrahydropteridine: oxygen oxidoreductase (3-hydroxylating)] in adrenal medulla and sympathetic ganglia by short-term (1-2 hr) cold stress (4 degrees) exhibits a circadian rhythm which seems to be causally related to the diurnal changes in adrenal glucocorticoid synthesis. In induction is maximal during the morning hours, when plasma corticoid concentrations (reflecting corticoid synthesis in the adrenal cortex) are minimal. In contrast, initiation of tyrosine hydroxylase induction in sympathetic ganglia is only possible in the afternoon. These observations suggest that tyrosine hydroxylase inducibility in the adrenal medulla is optimal during periods of low corticoid synthesis (the adrenal medulla is exposed to excessively high corticoid concentrations directly originating from the adjacent cortex), whereas in sympathetic ganglia an induction is only possible during the period of high plasma corticoid concentrations. This assumption is supported by the observation that in the first postnatal weeks, when the pituitary--adrenocortical system is not yet operating and plasma corticoid concentrations are low, initiation of tyrosine hydroxylase induction in the adrenal medulla is possible at any time of the day, whereas in sympathetic ganglia it is not possible at all. However, after administration of glycocorticoids initiation of tyrosine hydroxylase induction by short-term cold stress is also possible in newborn animals and in adults during the morning hours. The importance of glucocorticoids as modulators for the initiation of trans-synaptic tyrosine hydroxylase induction can also be deduced from the observation that in sympathetic ganglia kept in organ cultures and induction of the hydroxylase by cholinomimetics is only possible when glycocorticoids are added to the culture medium.
On the question of translocation of heart cAMP-dependent protein kinase.
Authors: Keely S L , Corbin J D , Park C R
Published: May 2006

Rat hearts were perfused with epinephrine and/or 1-methyl-3-isobutylxanthine for 2 min. These agents raised the concentration of cAMP and increased the fraction of cAMP-dependent protein kinase (EC 2.7.1.70) in the active form. However, the content of cAMP-dependent protein kinase in the soluble fraction of homogenates of these hearts was reduced and the amount in the particulate fraction was increased. A similar redistribution was obtained by adding cAMP to homogenates of control hearts. The reduction in soluble protein kinase content was due to apparent binding of the free catalytic subunit of the enzyme to particulate material (12,000 times g pellet) in media of low ionic strength (smaller than 100 mM KCl). The amount bound was, therefore, proportional to the dissociation of the holoenzyme. The binding was not altered by prior boiling or trypsin treatment of the particulate material, but it was prevented or reversed by the addition of 150 mM KCl. The catalytic subunit of the protein kinase from heart also bound to particulate fractions from liver or Escherichia coli and to various denatured proteins. These findings suggest that the protein kinase activity of membranes and particulate fractions has frequently been overestimated, since isolation of particulate materials has usually been carried out at low ionic strength. The data also imply that intracellular translocation of the protein kinase catalytic subunit, at least in heart tissue, is of questionable physiological significance.
Trisomy of chromosome 15 in spontaneous leukemia of AKR mice.
Authors: Dofuku R , Biedler J L , Spengler B A , Old L J
Published: May 2006

Karyotypes of spontaneous thymomas of AKR mice were determined by trypsin-Giemsa banding methods. Trisomy of chromosome 15 occurred in 10 of 11 leukemic mice. Seven of the thymomas were predominantly trisomic for chromosome 15, one was trisomic for chromosome 12, and one exhibited multiple trisomies of chromosomes 3, 12, 15, and 17. Trisomy was not found in the norm-l AKR tissues examined.
Two classes of translational control RNA: their role in the regulation of protein synthesis.
Authors: Bester A J , Kennedy D S , Heywood S M
Published: May 2006

Two classes of translation control RNA (tcRNA) have been isolated from embryonic chick muscle. One of these classes, the tcRNA isolated from messenger ribonucleoprotein particles (mRNP-tcRNA), is effective in inhibiting the translation of mRNP-mRNA while having little if any effect on polysomal mRNA. The other class, polysome-tcRNA, has no effect on mRNP-mRNA while it stimulates the translation of polysomal mRNA. The mRNP tcRNA contains approximately 50 percent uridylate residues and forms small but stable hybrids with poly (A), while polysome-tcRNA contains fewer uridylate residues and is much less effective in forming a hybrid with poly (A). A proposed model concerning the role of these two classes of tcRNA in the regulation of protein synthesis is presented.
Induction of maturation (meiosis) in Xenopus laevis oocytes by three organomercurials.
Authors: Brachet J , Baltus E , De Schutter-Pays A , Hanocq-Quertier J , Hubert E , Steinert G
Published: May 2006

Three organomercurials, p-hydroxymercuribenzoate, p-hydroxymercuriphenylsulfonate, and mersalyl, induce maturation (meiosis) in a large percentage (20-100 percent) of Xenopus laevis oocytes. Maturation takes place even when the follicle cells which surround the oocytes have been withdrawn. Organomercurial- and progesterone-induced maturations have many features in common: they do not occur when the inducer is injected into the oocytes, they require the presence of Ca++ in the medium, they are inhibited by cycloheximide but not by actinomycin D. In both cases, the maturation producing factor and the pseudomaturation inducing factor are produced. Organomercurial-treated oocytes react normally to activating stimuli; their protein synthesis increases, but uptake of amino acids is strongly inhibited. Progesterone and p-hydroxymercuriphenyl-sulfonate act synergically in inducing maturation. The main difference between the two agents is that p-hydroxymercuriphenylsulfonate must act for several hours, whereas, short contact with progesterone is sufficient to induce maturation.
Cooperative activation of action potential Na+ ionophore by neurotoxins.
Authors: Catterall W A
Published: May 2006

Four neurotoxins that activate the action potential Na+ ionophore of electrically excitable neuroblastoma cells interact with two distinct classes of sites, one specific for the alkaloids veratridine, batrachotoxin, and aconitine, and the second specific for scorpion toxin. Positive heterotropic cooperativity is observed between toxins bound at these two classes of sites. Tetrodotoxin is a noncompetitive inhibitor of activation by each of these toxins (KI = 4-8 nM). These results suggest the existence of three functionally separable components of the action potential Na+ ionophore: two regulatroy components, which bind activating neurotoxins and interact allosterically in controlling the activity of a third ion-transport component, which binds tetrodotoxin.
Distribution and virogenic effects of 5-bromodeoxyuridine in synchronized rat embryo cells.
Authors: Schwartz S A , Panem S , Kirsten W H
Published: May 2006

Rat embryo cell cultures were synchronized by a double thymidine block. The DNA replication phase (S) was divided into an early, middle, and late period. Cell cultures in the early, middle, or late S phase were pulsed with 0.1 muM 5-bromo[(3)H]deoxyuridine (BrdU) or equimolar [(3)H]dT. DNA-DNA reassociation experiments of each sample revealed that [(3)H]BrdU was more concentrated in the intermediate repetitive than the repetitive or unique DNA sequences of the early and middle S phase. In contrast, [(3)H]dT was nearly uniformly jistributed throughout all nucleotide sequences during the entire S phase. synchronized rat cells were pulsed during various portions of the S phase with unlabeled 0.1 mM or 0.1 muM BrdU and examined for sytoplasmic immumofluorescence against the 30,000 molecular weight group-specific antigen (p30) of Friend mouse leukemia virus. Equally strong fluorescence was detected 12 hr later in cells treated with each concentration of BrdU. Furthermore, incorporation of BrdU during late S phase was suffieient to elicit maximal antigen expression.
Single-strand scissions of chromosomal DNA during commitment to recombination at meiosis.
Authors: Jacobson G K , Pinon R , Esposito R E , Esposito M S
Published: May 2006

Diploid cells of the yeast Saccharomyces cerevisiae induced to undergo meiosis accumulate single-strand scissions in both template and newly synthesized DNA during commitment to genetic recombination. No evidence for accumulation of double-strand breaks during meiosis was obtained. When commitment to recombination is at the full meiotic level there are approximately 70 to 200 single-strand scissions per meiotic cell in which approximately 150 recombination events have been reported to occur.
Genetic control of endogenous C-type virus production in pancreatic acinar cells of C57BL/He and C57BL/6J mice.
Authors: Boiocchi M , Della Torre G , Della Porta G
Published: May 2006

Electron microscopy revealed very active production of C-type virus particles in the pancreatic acinar cells of untreated normal adult mice of the C57BL/He strain. In C57BL/6J mice, a similar picture was observed after a single intraperitoneal injection of dexamethasone. No viruses were observed in the pancreas of untreated or dexamethasone-treated BALB/c and C3Hf mice. F1 hybrids of both C57BL strains with C3Hf mice produced viruses in the same manner and quantity as the C57BL parents, whereas hybrids with BALB/c mice were entirely negative. Approximately 50% of mice of the first backcross generation of (BALB/c times C57BL/He)F1 hybrids with C57BL/He mice were active producers of C-type particles, while the other 50% were negative. It is suggested that a regulator gene that controls C-type virus production does not function in the pancreatic cells of either C57BL strain, and that BALB/c mice can provide hybrids with an active regulator.