bluuebunny/crossref_metadata_2025 huggingface dataset:
Outstanding problems and instrumental prospects for the coming decade (A Review)
Authors: Ostriker Jeremiah P.
Published: May 2006

After a review of the discovery of external galaxies and the early classification of these enormous aggregates of stars into visually recognizable types, a new classification scheme is suggested based on a measurable physical quantity, the luminosity of the spheroidal component. It is argued that the new one-parameter scheme may correlate well both with existing descriptive labels and with underlying physical reality.

Two particular problems in extragalactic research are isolated as currently most fundamental. (
i
) A significant fraction of the energy emitted by active galaxies (approximately 1% of all galaxies) is emitted by very small central regions largely in parts of the spectrum (microwave, infrared, ultraviolet and x-ray wavelengths) that were previously inaccessible to observation. The physical processes by which regions with ≲ 10
-9
the volume of the luminous stellar parts of galaxies produce such enormous quantities of energy are currently the subject of much speculative debate. (
ii
) It appears that most of the mass of ordinary galaxies resides far from the central luminous region, with the volume containing most of this mass ≳ 10
3
times the volume containing most of the light-emitting stars; the nature, amount, and extent of this mass are quite unknown.

New instruments that will be operating in the next decade and that may be helpful in solving these two problems are briefly mentioned with particular emphasis on the advances expected in angular resolution at wavelengths for which picture-taking ability has historically been poor or nonexistent.
Rapid transmembrane movement of newly synthesized phospholipids during membrane assembly.
Authors: Rothman J E , Kennedy E P
Published: May 2006

The transbilayer distribution of phospholipids in Bacillus megaterium is asymmetrical, with twice as much phosphatidylethanolamine internally as externally (Rothaman, J. E. & Kennedy, E. P. (1977) J. Mol. Biol. 110,603-618). We now report that the biosynthesis of phosphatidylethanolamine is also asymmetrical. Newly synthesized phosphatidylethanolamine was found first on the cytoplasmic side of the membrane of pulse-labeled cells and later was redistributed until the specific radioactivity of the outer face became equal to that of the inner face of the bilayer. The rate of transmembrane movement is at least 30,000 times faster than the rate of spontaneous diffusion (flip-flop) of phosphatidylethanolamine across artificial phospholipid bilayers, indicating that transmembrane movement must be a facilitated process in living cells, perhaps involving membrane proteins.
tRNATrp (bovine) binding to the reverse transcriptase of avian myeloblastosis virus and function as a heterologous primer.
Authors: Baroudy B M , Fournier M , Labouesse J , Papas T S , Chirikjian J G
Published: May 2006

The primary structures for tTNATrp (bovine) and primer tRNATrp (avian) show only minor differences in nucleotide sequence. The heterologous tRNATrp (bovine) appears to have properties similar to the tRNATrp (avian) in its ability to bind the alphabeta from of RNA-dependent DNA nucleotidyltransferase of avian myeloblastosis virus. A stable enzyme-tRNA complex has been isolated by gel filtration. In addition, tRNATrp (bovine) can hydridize to the avian viral 35S RNA and act as a primer for transcription of the RNA. tRNATrp (bovine) can be obtained in larger amounts than the avian primer and can be used to study the interactions between the primer and the viral enzyme.
Terminal redundancy and the origin of replication of Rous sarcoma virus RNA.
Authors: Coffin J M , Haseltine W A
Published: May 2006

In vitro synthesis of Rous sarcoma virus DNA by the virion endogenous DNA polymerase activity is initiated on a tRNAtrp primer located near the 5' end of the genome. A major product of such synthesis is a piece of DNA 101 nucleotides long (strong stop DNA) which can be isolated covalently bound to the tRNA primer. Here we show that the strong stop DNA is complementary to the extreme 5' end of the genome. We also show that the 5' and 3' termini of the Rous sarcoma virus genome, excluding the cap and the poly(A), have the identical sequence. We propose that the function of this sequence is to facilitate elongation from the 3' end of DNA chains initiated elsewhere on the virus genome.
Use of a distant reporter group as evidence for a conformational change in a sensory receptor.
Authors: Zukin R S , Hartig P R , Koshland D E
Published: May 2006

A highly sensitive method for demonstrating ligand-induced conformational changes in protein molecules in solution is described. The method utilizes an environmentally sensitive reporter group that is known to be distant from the active site. In the present application a conformational change is demonstrated in the galactose receptor of Salmonella typhimurium, involved in bacterial sensing and transport, by means of an extrinsic fluorophore, 5-iodoacetamidofluorescein, attached at a single methionine residue, and the intrinsic tryptophan fluorophore. Binding of the ligand galactose perturbs the microenvironment of both the fluorescein and tryptophan, as shown by both spectral and potassium iodide quenching changes. The distance between the two dyes is established by fluorescence energy transfer methods to be 41 +/- 10A. Since only one molecule of galactose binds per molecule of receptor and since the galactose molecule is only about 5 A in length, changes at one of these sites reflect the result of an indirect effect. Hence, there must be a ligand-induced conformational change that is propagated a minimum of 30 A through the receptor molecule.
Calcium-binding protein of chorioallantoic membrane: identification and development expression.
Authors: Tuan R S , Scott W A
Published: May 2006

A calcium-binding protein (CaBP) which has a molecular weight of 100,000 and an isoelectric point of 8.0 has been isolated from the chorioallantoic membrane (CAM) of the chick embryo. Expression of the CaBP occurs simultaneously with the onset of calcium absorption from the egg shell by the CAM, and the temporal increase in CaBP activity is coincident with calcium deposition in the embryo. The CAM CaBP differs in properties from the CaBPs of the adult organs, including the vitamin-D-dependent protein of intestine.
Solid tumor models for assessment of different treatment modalities: therapeutic strategy for sequential chemotherapy with radiotherapy.
Authors: Looney W B , Trefil J S , Hopkins H A , Kovacs C J , Ritenour R , Schaffner J G
Published: May 2006

A therapeutic strategy for combined radiotherapy and chemotherapy of experimental solid tumors has been devised. More effective utilization of combined chemotherapy and radiotherapy may be realized clinically if comparable information is obtained in man. The overall treatment efficiency of successive courses of treatment has been determined by a method that defines tumor response quantitatively over an entire spectrum of tumor responses. The findings of this study have shown that an individual tumor that responds well to the first course of therapy will respond well to the second and third courses of combined modality therapy. Various solid tumors in different animal species have demonstrated variability of response to treatment, analogous to the many types of response found clinically.
Cell-free synthesis of two proteins unique to RNA of transforming virions of Rous sarcoma virus.
Authors: Kamine J , Buchanan J M
Published: May 2006

We have utilized a reticulocyte lysate system to translate the 35S RNA of Rous sarcoma virus. Autoradiograms of the protein products separated on sodium dodecyl sulfate/polyacrylamide gels reveal a heterogeneous mixture of proteins of sizes ranging from 13,000 to 180,000 daltons. In comparing the translational products from 35S RNA of Prague B Rous sarcoma virus with those formed from the RNA of a transformation-defective deletion mutant derived from Prague B, we have found that two proteins, 25,000 and 18,000 daltons, are missing from the latter. Neither of these proteins is immunoprecipitated by monospecific antisera against the structural proteins of avian RNA tumor viruses. The combined atomic mass of 43,000 daltons corresponds to the amount of genetic coding capacity (40,000-50,000 daltons in terms of protein products) deleted from the RNA of the transformation-defective viruses. We propose that these proteins are coded for by the putative oncogene (onc) or sarc (src) gene and that one or both of them may be responsible for the oncogenic transformation caused by these viruses in infected cells.
Phosphohexosyl components of a lysosomal enzyme are recognized by pinocytosis receptors on human fibroblasts.
Authors: Kaplan A , Achord D T , Sly W S
Published: May 2006

Human beta-glucuronidase (beta-D-glucuronide glucuronosohydrolase, EC 3.2.1.31), like many other glycoprotein lysosomal hydrolases, is specifically taken up from the culture medium by human fibroblasts. Prior work has indicated that the enzyme exhibits charge heterogeneity and that "high-uptake" forms, i.e., those rapidly internalized by human fibroblasts, are more acidic than slowly internalized forms. Here we present two lines of evidence that the acidic group required for the high-uptake property of certain forms of the enzyme is a phosphate on, or in proximity to, a D-mannose-type carbohydrate. The first line of evidence was obtained from analysis of inhibition of enzyme pinocytosis by yeast mannans, phosphorylated sugars, and sugars. Mannans that contained phosphate were more potent inhibitors than those that did not contain phosphate. D-Mannose 6-phosphate was a more potent inhibitor than either D-mannose 1 phosphate or 2-deoxy-D-glucose 6-phosphate. D-Mannose and certain related sugars were weak pinocytosis inhibitors, while 2- and 4-epimers of mannose were noninhibitory. Competitive inhibition was demonstrated and the apparent Kis estimated for the following compounds: Saccharomyces cerevisiae mannan from mutant X2180-mnnl, 3 X 10(-6) M; mannan from wild-type S. cerebisiae, 3 X 10(-5) M; D-mannose 6-phosphate, 6 X 10(-5) M; L-fucose, 4 X 10(-2) M; and D-mannose, 6 X 10(-2) M. The second line of evidence comes from the observation that alkaline phosphatase [orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1] treatment of human platelet beta-glucuronidase abolished its "high-uptake" activity, without diminishing its catalytic activity, and converted some forms of the heterogeneous enzyme to less acidic forms.
Direction of active sliding of microtubules in Tetrahymena cilia.
Authors: Sale W S , Satir P
Published: May 2006

Axonemes of protozoan (Tetrahymena thermophila BIII) cilia, isolated by the dibucaine method, were treated briefly with trypsin after removal of the ciliary membranes by treatment with Triton X-100. After attachment to polylysine-coated surfaces, the partially digested axonemes remained mainly intact cylinders. Such attached axonemes can be treated with ATP, which induces microtubles sliding. ATP-treated preparations showed disrupted axonemes in which doublets had telescoped out of the original cylinders. These could be captured in place for electron microscopy after critical point drying. Images of this type were used to determine relative movement between adjacent doublet microtubules. Each doublet actively slid relative to its neighbors in a single direction, in which the polarity of force generation of the dynein arms was from base to tip.
Triiodothyronine stimulates specifically growth hormone mRNA in rat pituitary tumor cells.
Authors: Seo H , Vassart G , Brocas H , Refetoff S
Published: May 2006

In a cell-free protein-synthesizing system from a rabbit reticulocyte lysate, total RNA extracted from cultured rat pituitary tumor (GH3) cells directed, in a dose-related manner, the synthesis of proteins that were precipitated by antisera specific to rat growth hormone (somatotropin) and rat prolactin. A marked decrease in growth hormone secretion and growth hormone mRNA activity was observed when cells were grown in a medium deficient in thyroid hormone. Addition of triiodothyronine in physiologic amounts both prevented and completely reversed this effect within 48 hr. Thyroid hormone had no effect on prolactin secretion or prolactin mRNA activity. These data suggest that thyroid hormone may stimulate synthesis of growth hormone through induction of transcriptional activity. The possibility of an additional effect at the posttranscriptional level has not been excluded. Although thyroid hormone is believed to have a general effect on a variety of metabolic processes, some effects, at the molecular level, may be quite selective, as indicated by the observed changes in growth hormone but not prolactin mRNA activity. The GH3 cell model is useful in the study of triiodothyronine action because of independence from secondary hormonal effects caused by hypothyroidism and because simultaneous measurement of prolactin mRNA activity serves as a unique internal control.
Binding to idiotypic determinants of large proportions of thymus-derived lymphocytes in idiotypically suppressed mice.
Authors: Owen F L , Ju S T , Nisonoff A
Published: May 2006

All A/J mice immunized with a conjugate of p-azophenylarsonate groups to keyhole limpet hemocyanin produce antibodies against azophenylarsonate, some of which share a crossreactive idiotype. The appearance of the idiotype can be suppressed, without reducing the response against azophenylarsonate, by injecting rabbit anti-idiotypic antibodies prior to immunization. We have now observed that mice suppressed in this way, or by adoptive transfer of leukocytes from other suppressed mice, and then immunized with the hemocyanin-azophenylarsonate conjugate, possess high proportions (up to 14%) of lymphocytes that form rosettes with A/J erythrocytes coated with Fab fragments possessing the idiotype. Idiotypic specificity was demonstrated by various experiments. Most of all of the rosette-forming lymphocytes appear to be thymus-derived lymphocytes (T cells). Treatment of T cells with trypsin eliminated the capacity to form rosettes, which was restored on standing overnight in medium. Thus, the receptors are synthesized by the cells and are not passively adsorbed. Treatment of mice with anti-idiotypic antiserum without antigenic stimulation did not elicit substantial numbers of rosette-forming cells. The requirement for antigen suggests that antigen-idiotype complexes may be a stimulatory agent. A prolonged rest period after immunization of suppressed mice was required for the induction of high percentages of rosette-forming cells. Rosette formation provides a convenient method for studying factors that induce the formation of idiotype-specific T cells.
Suppression of immunoglobulin synthesis and secretion by peripheral blood lymphocytes from normal donors.
Authors: Schwartz S A , Shou L , Good R A , Choi Y S
Published: May 2006

Concanavalin A (Con A)-treated peripheral blood lymphocytes from healthy volunteer donors have been shown to suppress proliferative responses associated with thymus-derived lymphocytes (T-cells). The present investigations demonstrate that peripheral blood lymphocytes incubated with Con A for 48 hr can abrogate pokeweed mitogen-stimulated differentiation of bone-marrow-derived (B) lymphocytes to immunoglobulin-synthesizing and -secreting plasma cells. This effect was manifested when washed Con A-treated peripheral blood lymphocytes were added to pokeweed mitogen-stimulated cocultures containing fresh autologous or allogeneic mononuclear cells, and it did not appear to involve cytotoxicity. Parallel control cultures consisting of mononuclear leukocytes incubated for 48 hr in the absence of Con A also had immunoglobulin suppressor activity in mixing experiments. This effect, however, was most pronounced when preincubated cells were added to fresh autologous pokeweed mitogen-stimulated peripheral blood lymphocytes. Cell mixtures containing peripheral blood lymphocytes demonstrated a spectrum of immunoregulatory effects ranging from suppression to enhancement of pokeweed mitogen-stimulated immunoglobulin synthesis and secretion. Several functional subclasses of suppressor cells that reflect varying levels of specific activity have thus been demonstrated in human beings. Moreover, a degree of genetic identity appears to be required for the expression of "weak" immunoregulatory influences.
New methylcyclopentanoid terpenes from the larval defensive secretion of a chrysomelid beetle (Plagiodera versicolora).
Authors: Meinwald J , Jones T H , Eisner T , Hicks K
Published: May 2006

The defensive secretion of larvae of the chrysomelid beetle Plagiodera versicolora contains two unstable, volatile methylcyclopentanoid terpenes: a dialdehyde (chrysomelidial) isomeric with dolichodial and anisomorphal, and a closely related enol lactone (plagiolactone). Chrysomelidial and plagiolactone are shown to have structures III and IV on the basis of a detailed analysis of their spectra, coupled with chemical transformations to products of known structure.
Synthesis of opiate peptides by a clonal pituitary tumor cell line.
Authors: Giagnoni G , Sabol S L , Nirenberg M
Published: May 2006

Clonal mouse pituitary tumor cells, AtT-20, synthesize at least four species of peptides with opiate activity. The endorphin concentration of AtT-20 cells was estimated to be 300-600 pmol/mg of protein. The two most abundant endorphins with apparent molecular weights of 1800 and 2400 were purified 300- and 24-fold, respectively; additional minor components were found with apparent molecular weights of greater than 3000 and less than 750.
Location and structural significance of the oligosaccharides in human Ig-A1 and IgA2 immunoglobulins.
Authors: Toraño A , Tsuzukida Y , Liu Y S , Putnam F W
Published: May 2006

The location, number, and kinds of oligosaccharides in human IgA1 and IgA2 immunoglobulins have been determined by amino acid sequence analysis of the alpha heavy chains. Both A2m allotypes of the alpha2 chain of IgA2 have two GlcN oligosaccharides that are absent in the alpha1 chain, but they lack GalN. The A2m(2) allotype has a fifth GlcN oligosaccharide. The alpha chains of IgA proteins also have subclass-specific and allotype-specific differences in amino acid sequence. Although other classes of human immunoglobulins differ in the number and kind of oligosaccharides, the sites are often homologous and are related to the immunoglobulin domain structure. Evolutionary preservation of the tripeptide acceptor sequence for GlcN probably indicates both a structural and biological role for carbohydrate.
Studies on nucleic acid reassociation kinetics: retarded rate of hybridization of RNA with excess DNA.
Authors: Galau G A , Smith M J , Britten R J , Davidson E H
Published: May 2006

The rate of reaction of excess double-stranded bacteriophage phiX174 and plasmid RSF2124 DNA drivers with enzymatically synthesized asymmetric RNA tracers was measured. Other reactions were carried out with excess Escherichia coli DNA and E. coli RNA labeled in vivo. RNA and DNA fragment lengths were held approximately equal. For each case it was shown that in DNA excess the rate constant for RNA-DNA hybridization is 3- to 4.5-fold lower than that of the renaturation rate constant for the driver DNA. This retardation was also observed in pseudo-first-order hybridization reactions driven by excess strand-separated RSF2124 DNA. It was concluded that the rate constant for RNA-DNA by hybridization depends partially on which species is in excess.
Use of polylysine for adsorption of nuclei acids and enzymes to electron microscope specimen films.
Authors: Williams R C
Published: May 2006

Enzymes and nucleic acids, both free and as bound in binary complexes, adsorb to electron microscope specimen films in well-distributed fashion if a dilute solution of polylysine is previously applied to the films. Electron micrographs are exhibited that demonstrate the usefulness of the technique in visualizing double- and single-stranded DNA, Escherichia coli RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) in negative stain, and polymerase complexed to poly(dA-dT) and to an 1100 base-pair restriction fragment of bacteriophage T7 DNA containing the early promoters. The base-pair spacing of DNA prepared for electron microscopy by the polylysine method was found to be 0.326 nm. Four promoter sites on the T7 fragment were located at 215, 440, 560, and 670 base-pair distances from the left terminus. When poly(dA-dT) was incubated with a 20-to-1 weight ratio of polymerase the bound enzyme particles were found to be about two-thirds as closely packed as is sterically permissible.
Terminally repeated sequences in the avian sarcoma virus RNA genome.
Authors: Collett M S , Dierks P , Cahill J F , Faras A J , Parsons J T
Published: May 2006

The initiation of DNA synthesis in vitro by RNA-directed DNA polymerase (deoxynucleosidetriphosphate: DNA deoxynucleotidyltransferase, EC 2.7.7.7) of avian oncornaviruses requires a tRNAtrp primer molecule located close to the 5' end of the viral RNA genome. DNA transcripts, 100 nucleotides in length, initiated on the tRNAtrp primer molecule contain nucleotide sequences complementary to a large (25 nucleotides) RNase T1 oligonucleotide, T-13, located at the 5' terminus of the avian sarcoma virus RNA genome. tRNAtrp-initiated DNA transcripts with a length of about 70 nucleotides contain substantially fewer nucleotide sequences complementary to this 5'-terminal oligonucleotide, suggesting that the tRNAtrp primer associated with the avian sarcoma virus RNA is located approximately 100 nucleotides from the 5' end of the RNA. In addition, we present evidence to demonstrate that DNA transcribed from avian sarcoma virus RNA sequences located at the 3' end, immediately adjacent to the poly(A), contains nucleotide sequences that are complementary to the 5'-terminal T1 oligonucleotide T-13. These data indicate that the 5' end of the viral genome contains nucleotide sequences that are repeated at the 3' end of the genome. We conclude that the avian oncornavirus RNA genome is terminally redundant.
Globin RNA synthesis in vitro by isolated erythroleukemic cell nuclei: direct evidence for increased transcription during erythroid differentiation.
Authors: Orkin S H , Swerdlow P S
Published: May 2006

Murine erythroleukemic cells accumulate cytoplasmic globin mRNA during differentiation induced in tissue culture by dimethyl sulfoxide. Cellular accumulation of globin RNA may reflect transcriptional activation of the globin genes and/or posttranscriptional stabilization of globin RNA during differentiation. To evaluate possible transcriptional controls directly; globin RNA synthesis by isolated erythroleukemic cell nuclei was studied. Conditions were established for optimal nuclear RNA synthesis in vitro in the presence of a mercurinucleotide (Hg-CTP). Mercurated RNA synthesized in vitro was purified free of endogenous RNA by affinity chromatography on sulfhydryl-Sepharose, and analyzed for the presence of newly synthesized globin RNA sequences by molecular hybridization to globin complementary [32P]DNA. The results demonstrate markedly increased synthesis of globin RNA by nuclei isolated from dimethyl sulfoxide-treated cells, even within 5 min of nuclear transcription in vitro. These findings are most consistent with transcriptional activation of the globin genes upon induction of differentiation.
Structural implications of sequence variability in immunoglobulins.
Authors: Padlan E A
Published: May 2006

Immunoglobulin sequences were compared by using a technique that takes into account the dissimilarity in physicochemical properties of amino acids. Exterior residues showed greater structural variability than interior residues. High structural variability was found at positions known from crystallographic studies to be involved in hapten binding.
Covalence of atoms in the heavier transition metals
Authors: Pauling Linus
Published: May 2006

The observed magnetic properties of the heavier transition metals permit them to have larger metallic valences than their iron-group congeners. With 0.72 metallic orbital, as found for the iron-group metals, the maximum metallic valence and minimum interatomic distance would occur for 8.28 transargononic electrons. The curves of observed interatomic distances for the close-packed metals of the second and third long periods have minima at this point, supporting the assignment of high valences to these metals. Values of the single-bond radii corresponding to these valences are calculated.
Mathematical description of molecular structure: Molecular topology
Authors: Simmons H. E. , Merrifield R. E.
Published: May 2006

The concepts of the topology of finite point sets are applied to a mathematical description of molecular structure. The combinatorial properties of the “bond topology,” which arises naturally from atomic adjacency relationships within a molecule, are investigated in detail. The collection of closed sets, the cotopology, is found to be related to bonding. Combinatorial weights of bonds over the cotopology are defined and explicit expressions for a general molecule are derived. The bond weights are found to parallel molecular orbital bond orders. It is concluded that much of the variation in π bond orders is topological in origin.
Interaction between the third complement protein and cell surface macromolecules.
Authors: Law S K , Levine R P
Published: May 2006

The activated form of the third complement protein, C3b, forms a stable complex with components of plasma membranes and particulate entities such as zymosan. The complex resists the action of detergents and protein denaturants as well as extremes of temperature, salt concentration, and pH. It can, however, be broken by exposure to hydroxylamine or by ammonolysis followed by incubation with sodium dodecyl sulfate. Thus, the complex appears to result from a hydrophobic interaction as well as a bond susceptible to nucleophilic attack.
A DNA fragment containing the origin of replication of the Escherichia coli chromosome.
Authors: Marsh R C , Worcel A
Published: May 2006

A 38 kilobase pair region of the Escherichia coli K12 chromosome containing the replication origin has been physically mapped with restriction endonucleases EcoRI and HindIII. Replication starts within or very near a 1.3 kilobase pair HindIII fragment in the middle of this region and proceeds outward in both directions with apparently equal speed. This pattern was observed in both dnaA and dnaC temperature-sensitive (ts) initiation mutants at the start of the synchronous round of replication which occurs after downshift from the nonpermissive to the permissive temperature.
Isolation of transforming murine leukemia viruses from mice with a high incidence of spontaneous lymphoma.
Authors: Staal S P , Hartley J W , Rowe W P
Published: May 2006

Murine leukemia viruses capable of malignant transformation of mink tissue culture cells have been isolated from an AKR thymoma cell line and from a spontaneous reticulum cell sarcoma in an NIH Swiss mouse partially congenic for the AKR ecotropic virus-inducing locus Akv-2. In contrast to the recently described mink cell focus-inducing strains of murine leukemia virus, at least one of the two transforming strains is replication defective. Nonproducer mink cells carrying the genome of the transforming virus of AKR origin have been isolated, and pseudotype transforming viruses generated.
Electrical stimulation of preganglionic nerve increases tyrosine hydroxylase activity in sympathetic ganglia.
Authors: Zigmond R E , Ben-Ari Y
Published: May 2006

The effect of synaptic stimulation on tyrosine hydroxylase [tyrosine 3-monooxygenase: L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2] activity in the rat superior cervical ganglion was studied. The preganglionic cervical sympathetic trunk was stimulated unilaterally at 10 Hz for 30 min. Forty-eight hours later tyrosine hydroxylase activity was 33% higher on the stimulated than on the control side. The enzyme activity restimulated than on the control side. The enzyme activity remained elevated in the stimulated ganglia for 2 days. No change was observed in total ganglion protein. Comparable increases in tyrosine hydroxylase activity were observed in anesthetized and conscious animals.
Detailed electronic description of triple bonds between transition metal atoms and verification by photoelectron spectroscopy
Authors: Cotton F. Albert , Stanley George G. , Kalbacher Barbara J. , Green Jennifer C. , Seddon Elaine , Chisholm Malcolm H.
Published: May 2006

Using the SCF-Xα-SW method the ground state electronic structures of (HO)
3
Mo≡Mo(OH)
3
, (H
2
N)
3
Mo≡Mo(NH
2
)
3
, and (Me
2
N)
3
Mo≡Mo(NMe
2
) have been calculated. The results provide a detailed description of the metal-to-metal triple bonds present; some of the more important molecular orbitals are shown in detail as contour diagrams. The energy levels of all filled valence shell/molecular orbitals and the lower virtual orbitals are presented in diagrams. The π(

e
u

) and σ(
a

1
g

) orbitals which have large amounts of metal character can be identified as the orbitals primarily responsible for Mo-Mo bonding. Using the transition state technique to allow for relaxation effects, the photoelectron spectra (up to 12 eV) have been calculated for Mo
2
(OH)
6
and Mo
2
(NH
2
)
6
and found to compare very well, after applying a constant downshift to correct for inductive effects, with experimental spectra for Mo
2
[OCH
2
C(CH
3
)
3
]
6
and Mo
2
[N(CH
3
)
2
]
6
. The experimental photoelectron spectra are reported.
Presence of a putative 15S precursor to β-globin mRNA but not to α-globin mRNA in Friend cells
Authors: Curtis Peter J. , Mantei Ned , Van Den Berg Johan , Weissmann Charles
Published: May 2006

Dimethyl sulfoxide-induced Friend cells were labeled for periods of 5-60 min. The denatured RNA was fractionated by sucrose gradient centrifugation and the distribution of α- and β-globin-specific [
3
H]RNA was determined by hybridization to hybrid plasmids containing mouse α- and β-globin DNA, respectively. After 5 min of labeling, a 15S peak of β-globin-specific (but not α-globin-specific) [
3
H]RNA was detected, next to an equal amount of 10S β-globin [
3
H]RNA. With increasing periods of labeling, the amount of 15S β-globin [
3
H]RNA remained constant but the amount 10S β-globin [
3
H]RNA increased steadily. α-Globin-specific [
3
H]RNA sedimented at 11 S after 5 min of labeling and at 9.5 S after longer labeling periods. Analysis of 15S globin-specific [
3
H]RNA purified by the poly(dC)-cDNA method [Curtis, P. J. & Weissmann, C. (1976)
J. Mol. Biol.
106, 1061-1075] showed oligonucleotides characteristic of β-globin mRNA but not of α-globin mRNA, as well as about 20 new oligonucleotides. Our results suggest that 10S β-globin mRNA arises via a 15S precursor that has a half-life of 5 min or less; 9.5S α-globin mRNA may be derived from an 11S precursor.
Mechanism of adenylate cyclase activation by cholera toxin: Inhibition of GTP hydrolysis at the regulatory site
Authors: Cassel Dan , Selinger Zvi
Published: May 2006

Treatment of turkey erthrocyte membranes with cholera toxin caused an enhancement of the basal and catecholamine-stimulated adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activities. Both of these activities required the presence of GTP. The toxin effect on the adenylate cyclase activity concided with an inhibition of the catecholamine-stimulated guanosinetriphosphatase activity. Inhibition of the guanosinetriphosphatase, as well as enhancement of the adenylate cyclase activity, showed the same dependence on cholera toxin concentrations, and the effect of the toxin on both activities was dependent on the presence of NAD.

It is proposed that continuous GTP hydrolysis at the regulatory guanyl nucleotide site is an essential turn-off mechanism, terminating activation of the adenylate cyclase. Cholera toxin inhibits the turn-off guanosinetriphosphatase reaction and thereby causes activation of the adenylate cyclase. According to this mechanism GTP should activate the toxin-treated preparation of adenylate cyclase, as does the hydrolysis-resistant analog guanosine 5′-(β,γ-immino)triphosphate [Gpp(NH)p]. Indeed, the toxin-treated adenylate cyclase was maximally activated, in the presence of isoproternol, by either GTP or Gpp(NH)p, while adenylate cyclase not treated with toxin was stimulated by hormone plus GTP to only one-fifth of the activity achieved with hormone plus Gpp(NH)p. Furthermore, the toxin-treated adenylate cyclase activated by isoproterenol plus GTP remained active for and extended period (half-time of 3 min) upon subsequent addition of the β-adrenergic blocker, propranolol. The native enzyme, however, was refractory to propranolol only if activated by Gpp(NH)p but not by GTP.
Selective inhibition of gamma-glutamyl-cycle enzymes by substrate analogs.
Authors: Griffith O W , Meister A
Published: May 2006

Substrate analogs have been obtained that selectively inhibit the reactions of the gamma-glutamyl cycle or that are susceptible to only limited metabolism by the cycle. Thus, glutathione synthesis may be inhibited and analogs of glutathione may be synthesized that do not participate in transpeptidation. Specific inhibitors of gamma-glutamylcyclotransferase and 5-oxoprolinase have been obtained. The findings offer new approaches to the in vivo study of the cycle and also to the design of more specifically directed analogs of inhibitors such as methionine sulfoximine and 6-diazo-5-oxonorleucine.
Bacteriophage T4 RNA ligase is gene 63 product, the protein that promotes tail fiber attachment to the baseplate.
Authors: Snopek T J , Wood W B , Conley M P , Chen P , Cozzarelli N R
Published: May 2006

RNA ligase and tail fiber attachment activities, normally induced following bacteriophage T4 infection of Escherichia coli, are not induced when gene 63 amber mutants of T4 infect nonpermissive host cells. Both activities are induced when these mutants infect permissive hosts, or when revertants of these mutants infect nonpermissive hosts. When one of these mutants infects a host that carries supF, both activities are more than normally heat labile. RNA ligase, purified to homogeneity, promotes the tail fiber attachment reaction in vitro with a specific activity similar to that of the most highly purified preparations of gene 63 product isolated on the basis of tail fiber attachment activity. We conclude that T4 RNA ligase is gene 63 product. The RNA ligase and tail fiber attachment reactions differ in requirements and in response to some inhibitors, suggesting that the two activities of the gene 63 product may be mechanistically unrelated.
Tumor promoters inhibit spontaneous and induced differentiation of murine erythroleukemia cells in culture.
Authors: Yamasaki H , Fibach E , Nudel U , Weinstein I B , Rifkind R A , Marks P A
Published: May 2006

Addition of the potent tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), to murine erythroleukemia cell lines in suspension cultures inhibited both spontaneous differentiation and differentiation induced by hexamethylene bisacetamide (HMBA), dimethyl sulfoxide, or butyric acid. Inhibition was unrelated to cytotoxicity and was reversible. When several plant diterpenes were tested, there was a positive correlation between tumor-promoting activity and inhibition of differentiation. TPA inhibited HMBA-induced differentiation only if added prior to the time of commitment to differentiation, as assayed by scoring for differentiation after transfer of cells from HMBA to fresh medium without HMBA. TPA-mediated inhibition of differentiation was associated with a decrease in globin mRNA accumulation.
Secretion of mediators following T lymphocyte-macrophage interaction is regulated by the major histocompatibility complex.
Authors: Farr A G , Dorf M E , Unanue E R
Published: May 2006

In this study we show that T cells from mice infected with Listeria monocytogenes can interact in vitro with normal macrophages to produce a number of soluble mediators, including lymphostimulatory molecules. One of these molecules was a 15,000-dalton protein mitogenic for thymocytes. Generation of mitogenic activity was essentially completed by the first 24 hr of culture and did not require the addition of Listeria antigens. Production of mitogenic protein required contact between the lymphocytes and macrophages, because it did not occur when the two cells were separated by a cell-impermeable membrane. Optimal production of mitogenic protein occurred only when the lymphocytes and macrophages shared homologous I-A regions of the major histocompatibility complex. Once generated, the mitogenic protein did not display histocompatibility restriction and could stimulate allogeneic as well as syngeneic thymocytes. Strains of mice with the C57 background responded poorly to mitogenic protein even though those strains were capable of producing it. We conclude that an early stage in T cell immunity to Listeria involves an intimate association with macrophages regulated by the H-2 complex.
Animal cell mutants defective in sterol metabolism: A specific selection procedure and partial characterization of defects
Authors: Saito Y. , Chou S. M. , Silbert D. F.
Published: May 2006

By using a chemically defined medium, a general and highly specific procedure was devised to select for mutant cells with less abundant or structurally altered sterol in their surface membranes. Within a certain concentration range, the polyene antibiotic filipin was shown to kill only cells with normal (as opposed to decreased) membrane sterol levels. Sterol-requiring derivatives of LM cells were isolated by chemical mutagenesis, filipin treatment, and cloning followed by replica plating in soft agar. Mutants (S1 and S2) are described which, when compared to normal cells, show decreased synthesis of demosterol
in vivo
from acetate and mevalonate relative to cell number or to fatty acid synthesis. When exogenous sterol is supplied, mutants S1 and S2 grow normally in suspension culture. However, when deprived of sterol supplement, mutant S1 grows slower than wild type cells and mutant S2 lyses within one to two generations. Gas/liquid chromatography revealed that the mutants contained a normal spectrum of fatty acids including unsaturated fatty acyl groups but, unlike wildtype cells, they have less abundant (mutant S1) or no (mutant S2) desmosterol in either the presence or absence of exogenous cholesterol.
In vitro
experiments with mevalonate as the substrate suggest that the defect in both mutants is in a demethylation reaction subsequent to lanosterol synthesis. The selection method developed here may permit the isolation of mutants with defective membrane incorporation of sterols and other polyisoprenoids as well as defective synthesis of these compounds.
Interaction of L-alpha-didecanoyl phosphatidylcholine with the AI polypeptide of high density lipoprotein.
Authors: Reynolds J A , Tanford C , Stone W L
Published: May 2006

Cooperative interaction of L-alpha-didecanoyl phosphatidylcholine with the AI polypeptide from human serum high density lipoprotein results in a complex particle containing 2 molecules of AI and 190 molecules of the lipid. Binding occurs two orders of magnitude above the critical micelle concentration of the lipid and requires the simultaneous presence of low levels of single-chain amphiphiles. The present investigation and previous studies from this laboratory suggest that AI contains "pockets" capable of interacting with a fixed hydrophobic volume and that amphiphilic head groups do not affect the binding capacity.
Specialized transducing phage for the initiation factor 3 gene in Escherichia coli.
Authors: Springer M , Graffe M , Hennecke H
Published: May 2006

A previously isolated thermosensitive mutant [Springer, M., Graffe, M. & Grunberg-Manago, M. (6977) Mol. Gen. Genet. 151, 17-26] exhibits two defects in vitro, one in the initiation factor IF3 and the other in the L-phenylalanine: tRNA-Phe ligase (EC 6.1.1.20). Specialized lambda transducing phages that transduced this mutant to thermoresistance were selected. In vitro studies showed that the transductants had a normal IF3 activity. One of these transducing phages was shown to code for a protein synthesized under the control of Escherichia coli promoters, which has the same molecular weight as IF3. This protein crossreacts specifically with IF3 antisera and comigrates with pure IF3 in a two-dimensional gel system.
Neurophysin biosynthesis in normal rats and in rats with hereditary diabetes insipidus.
Authors: Brownstein M J , Gainer H
Published: May 2006

When [35S]cysteine was injected adjacent to the supraoptic nucleus (SON) in rats, it was rapidly incorporated into proteins in the SON. The [35S]cysteine-labeled proteins extracted from the SON were separated by isoelectric focusing on polyacrylamide gels. Twenty minutes after the injection of [35S]cysteine, two major labeled peaks (pI = 5.4 and 6.1) were found in the SON of normal rats; Brattleboro rats had only one major labeled peak (pI = 5.4). One hour after the injection, four major radioactive peaks were found in the SON of normal animals (pI = 5.1, 5.4, 5.6, and 6.1). Animals with diabetes insipidus had only two major labeled proteins (pI = 5.1 AND 5.4). Twenty-four hours after normal rats were injected with [35S]cysteine, all of the labeled peaks described above, except for the one with pI = 5.1, had decreased markedly in size and a small amount of labeled protein with pI about 4.8 was present in the SON. After 24 hr the posterior pituitary of normal animals contained two [35S]cysteine-labeled proteins with pI = 4.6 AND 4.8. The pituitaries of Brattleboro rats had only the pI = 4.6 labeled protein. These pulse-chase data, with data we have presented elsewhere, indicate that the vasopressin- and oxytocin-neurophysins are synthesized as parts of separate precursors (pI = 6.1 and 5.4, respectively). These precursors are converted into at least two intermediates (pI = 5.6 and 5.1) which, in turn, yield the vasopressin-neurophysin (pI = 4.8) and the oxytocin-neurophysin (pI = 4.6).
Evidence for acceleration of the rate of elongation of tyrosine aminotransferase nascent chains by dibutyryl cyclic AMP
Authors: Roper Michael D. , Wicks Wesley D.
Published: May 2006

Analogs of cyclic AMP elevate the synthesis of tyrosine aminotransferase (L-tyrosine:2-oxoglutarate aminotransferase; EC 2.6.1.5) in cultured hepatoma cells and rat liver at a post-transcriptional level but have no discernible effect on total soluble protein synthesis. In order to determine whether cyclic AMP exerts its effect on a step before or after initiation of the synthesis of this enzyme, we have analyzed the ribosomal transit times for both the aminotransferase and total soluble protein in hepatoma cells incubated in the presence or absence of
N
6
,
O
2
′-dibutyryl cyclic AMP. The time required for one ribosome to translate one subunit of the “average” soluble protein (transit time) was about 2 min in cells incubated with or without the cyclic AMP analog. In contrast, the transit time for tyrosine aminotransferase was found to be reduced from 5-8 min under basal conditions to as low as 45 sec after exposure to dibutyryl cyclic AMP. Although the degree of effect varied from experiment to experiment, the relative rate of aminotransferase nascent chain elongation was found to be proportional to the stimulation of its activity. In contrast, dexamethasone did not alter the rate of aminotransferase elongation even though it elevated enzyme activity between 5- and 10-fold. These data are consistent with the hypothesis that induction of tyrosine aminotransferase with cyclic AMP analogs occurs by stimulation of the rate at which ribosomes translate pre-existing mRNA in contrast to adrenal steroids which act by increasing the level of translatable mRNA coding for this enzyme.
Specificity of the juvenile hormone binding protein: The geometrical isomers of juvenile hormone I
Authors: Goodman Walter , Schooley David A. , Gilbert Lawrence I.
Published: May 2006

The binding of the geometrical isomers (≥99% pure) of juvenile hormone I to the hemolymph juvenile hormone binding protein of
Manduca sexta
(Lepidoptera, Sphingidae) was analyzed. A technique is described for isomer separation by micropreparative high-resolution liquid chromatography. Analysis of competition was performed by using a “batch adsorption” hydroxylapatite binding assay. Competition studies indicate that the naturally occurring isomer, 2
E
,6
E
,10
cis
, is bound with the highest affinity. Optimal binding appears to depend most heavily upon the configuration of the 2,3 double bond. Juvenile hormone binding protein shows a higher affinity for the 2
E
than for the 2
Z
configuration. The 6,7 double bond is of less importance in determining binding activity, and isomerism about the epoxide appears least important in conferring binding activity. The binding site may be a groove along the surface of the binding protein interacting with the side chains of juvenile hormone, including the ester methyl group. The grouping of the side chains and the ester methyl group thus constitutes a distinct hydrophobic face, and the hydrophobic interactions are essential in maintenance of the bound ligand.
On the photosensitivity of liganded hemoproteins and their metal-substituted analogues.
Authors: Hoffman B M , Gibson Q H
Published: May 2006

We have examined the photosensitivity of low-spin liganded hemoglobin, myoglobin, and peroxidase, and their metal-substituted analogues, using three different metals (Fe, Mn, Co) in several oxidation states and employing a variety of diatomic or pseudo-diatomic ligands (L). We have discovered a number of photosensitive systems, and present an overall stereo-electronic classification scheme for these photodissociation reactions: Linear, formally d6, metal-ligand fragments [e.g., Fe(II) +/- CO; Mn(II) +/- NO] are relatively photoliable, but systems with a bent fragment, and higher electron occupancy [e.g., Fe(II) +/- O2; Co(II) +/- NO] are relatively photoinert. Photostability appears to correlate with the occurrence of long-wavelength features in the optical absorption spectra, and the classification scheme is explained by considerations of electronic structure. The discussions are further applied to d5 systems and to low-spin d6 metalloporphyrins with nitrogenous bases as axial ligands.
Mode of action of the hemin-controlled inhibitor of protein synthesis.
Authors: de Haro C , Datta A , Ochoa S
Published: May 2006

Despite the finding that the hemin-controlled translational inhibitor in reticulocyte lysates is a cyclic AMP-independent protein kinase that phosphorylates the small subunit of the initiation factor eIF-2, the mechanism of inhibition of translation remained unexplained. Whereas treatment of hemin-containing lysates with inhibitor in the presence of ATP inhibited translation, the same treatment of highly purified eIF-2 did not affect its ability to form a ternary complex with initiator Met-tRNA and GTP or a 40S initiation complex. We have isolated from ribosomal salt washes a protein (eIF-2 stimulating protein) that enhances the capacity of unphosphorylated eIF-2 to form ternary or 40S initiation complexes but has no effect on the phosphorylated factor. At low concentrations, eIF-2 is virtually inactive without this stimulating protein. Therefore, the translational inhibitor acts by converting eIF-2 to a form that is not stimulated by the stimulating protein.