bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereochemistry of polymerization by DNA-dependent RNA-polymerase from Escherichia coli: an investigation with a diastereomeric ATP-analogue.
Authors: Eckstein F , Armstrong V W , Sternbach H
Published: May 2006

The phosphodiester bond formation by DNA-dependent RNA-polymerase (RNA nucleotidyltransferase, nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) can in principle result in retention, inversion, or racemization of configuration at the alpha-phosphorus of the nucleoside 5'-triphosphate being polymerized. As a first step in elucidating the stereochemistry of this reaction, one diastereomer (A) of adenosine 5'-O-(1-thiotriphosphate) (ATPalphaS) was polymerized with UTP in the presence of poly(dA-dT)-poly(dA-dT). The resulting polymer was enzymatically cleaved to uridine 2',3'-cyclic phosphorothioate which was determined to be the endo-isomer by comparison with an authentic sample. This shows that no reacemization had occurred and that isomer A of ATPalphaS gives a phosphorothioate diester bond with the R-configuration. Whether this represents inversion of retention of configuration awaits elucidation of the absolute configuration of isomer A for ATPalphaS.
On the mechanism of genetic recombination: electron microscopic observation of recombination intermediates.
Authors: Potter H , Dressler D
Published: May 2006

This paper deals with the nature of recombination intermediates. Using the electron microscope to study the DNA of the plasmid colicin E1, we have observed more than 800 molecules that appear to represent intermediates in the process of recombination. Specifically, after isolating colicin DNA and linearizing it with the restriction enzyme EcoRI, we find crossed molecules with twice the normal colicin DNA content. These forms consist of two genome-length elements held together at a region of DNA homology. The molecules can be recovered from wild type and Rec B-C host cells but are not present among the colicin DNA forms isolated from recombination-deficient Rec A cells. We have termed the experimentally observed molecules "chi forms" and believe that they represent the recombination intermediate of the Holliday model.
Identification of enzyme-bound activated CO2 as carbonic-phosphoric anhydride: isolation of the corresponding trimethyl derivative from the active site of glutamine-dependent carbamyl phosphate synthetase.
Authors: Powers S G , Meister A
Published: May 2006

The activated CO2 intermediate formed in the reaction catalyzed by glutamine-dependent carbamyl phosphate synthetase was identified as carbonic-phosphoric anhydride through the use of two independent procedures. The carboxy phosphate intermediate was reduced to formate by treatment with potassium borohydride. Although both free CO2 and the enzyme-bound activated CO2 are reduced to formic acid by borohydride, it was possible to selectively introduce a 14C label into the enzyme-bound activated CO2 and thus into the formic acid derived from it. Such [14C]formate formation required the presence of ATP, KCl, and the enzyme, and evidence was obtained that the [14C]formate found is not derived from carbamyl phosphate or from bicarbonate bound nonspecifically to the enzyme. When the enzyme was treated with L-2-amino-4-oxo-5-chloropentanoate (or cyanate), the formation of [14C]formate was increased about 2-fold, a finding consistent with the previous observation that such treatment effects a similar increase in the bicarbonate-dependent cleavage of ATP catalyzed by the enzyme. When reaction mixtures containing the enzyme, [gamma-32P]ATP, and [14C]bicarbonate were methylated by treatment with diazomethane, a labeled compound was formed which cochromatographed with authentic trimethyl carboxy phosphate. Equimolar quantities of 14C and 32P wer incorporated into the intermediate, thus confirming its identification as carboxy phosphate. Nonenzymatic transphosphorylation from ATP to bicarbonate to form carboxy phosphate was also detected by diazomethane trapping.
An RNA-dependent DNA polymerase, different from the known viral reverse transcriptases, in the chicken system.
Authors: Bauer G , Hofschneider P H
Published: May 2006

The properties of an RNA-dependent DNA polymerase (an RNA-dependent DNA nucleotidyltransferase), which occurs ubiquitously in the allantoic fluid of uninfected, leukosis-virus-free eggs, are described. It is shown that the enzyme can synthesize faithful transcripts from natural RNA (globin mRNA). By biochemical and immunological methods, the enzyme can be clearly distinguished from the reverse transcriptases of the known chicken RNA tumor viruses and therefore seems to be a member of a so far unknown class of chicken polymerases.
Specificity of the protein kinase activity associated with the hemin-controlled repressor of rabbit reticulocyte.
Authors: Kramer G , Cimadevilla J M , Hardesty B
Published: May 2006

Highly purified preparations of hemin-controlled repressor of rabbit reticulocyte contain a 3':5'-cyclic AMP-indenpendent protein kinase activity that phosphorylates the low-molecular-weight (about 38,000) polypeptide chain of the initiation factor that forms a ternary complex with GTP and Met-tRNAf. These preparations also phosphorylate several polypeptide components of reticulocyte 40S ribosomal subunits. However, no significant levels of phosphorylation are observed when casein, histones, Artemia salina 40S ribosomal subunits, or other initiation factor fractions are used as substrates although high levels of phosphorylation are obtained with cruder preparations of the repressor. An antibody to these highly purified preparations of repressor has been obtained from the serum of immunized goats. Preincubation with immune goat IgG results in the neutralization of the inhibitory activity of the repressor, while normal IgG has no effect. Preincubation with immune IgG also abolishes the protein kinase activity responsible for the phosphorylation of the initiation factor and reticulocyte 40S subunits. Histone phosphorylation by crude repressor preparations, on the other hand, is unaffected by preincubation with immune IgG.
Mechanism of uncoupling in mitochondria: uncouplers as ionophores for cycling cations and protons.
Authors: Kessler R J , Tyson C A , Green D E
Published: May 2006

Classical uncouplers such as 2,4-dinitrophenol have been shown to be ionophores with the capability for transporting monovalent or divalent cations with equal efficiency. The conditions appropriate for the maximal expression of this ionophoric capability have been explored. Two critical factors are the polarity of the organic phase and the pH of the aqueous phase that is equilibrated with the organic phase. The demonstrated cationic ionophoric capability of uncouplers, taken in conjunction with the known ability of uncouplers to cycle protons across a membrane phase, provides the experimental basis for the thesis that uncoupling of electron flow from ATP synthesis via classical uncouplers involves the substitution of one coupled process by another. Uncoupling thus reduces to the replacement of one driven reaction (ATP synthesis) by the driven reaction (cyclical transport) mediated by the uncoupler.
Affinity purification of synthetic peptides.
Authors: Krieger D E , Erickson B W , Merrifield R B
Published: May 2006

A general strategy and a specific tactic for affinity purification of polypeptides synthesized on solid supports are desbribed and demonstrated. The desired peptide chains were distinguished from terminated peptide chains before removal from the support by attachment of an affinity reagnet (cysteinyl-methionine) bearing an affinity group (thiol) and a binding group (carboxylic acid). After cleavage from the synthetic support, the affinity-labeled peptides (Cys-Met-peptides) were bound to an affinity receptor (organomercurial-agarose) and thus separated from terminated peptides and all other peptides lacking the affinity group. The desired synthetic peptide was obtained by separation of the affinity reagent (loss of Cys-Met by cyanogen bromide cleavage). This general affinity purification strategy is independent of the length or amino acid sequence of the desired peptide. After assembly of ribonuclease-(111-124)-tetradecapeptide, using radiolabeled acetic anhudride for termination of uncoupled in termediates, essentially all (greater than 98.5%) of the acetylated delection peptides were removed by employing the organomercurial Cys-Met tactic. Similarly, the purity of crude synthetic histone H4-(1-37)-heptatriacontapeptide was increased six-fold by using this tactic to remove terminated peptides. A related dimeric Cys-Met tactic is outlined for affinity purification of peptides containing internal cysteine and methionine residues.
Nucleotide sequence of the operator-promoter region of the galactose operon of Escherichia coli.
Authors: Musso R , Di Lauro R , Rosenberg M , de Crombrugghe B
Published: May 2006

We have derived the nucleotide sequence of a segment of the operator-promoter region of the galactose operon of E. coli, by using a variety of DNA sequencing analyses. We have previously reported the sequence of the 5' terminal portion of gal mRNA [Musso, R. E., de Crombrugghe, B., Pastan, I., Sklar, J., Yot, P. & Weissman, S. (1974) Proc. Natl. Acad. Sci. USA 71, 4940-4944] and of the 59 base pairs preceding the startpoint of gal transcription (J. Sklar, S. Weissman, R. Musso, R. Di Lauro, & B. de Crombrugghe, submitted). In conjunction with those results, the present data provide the sequence of the gal operator-promoter region. This sequence is compared with similar sequences in other promoters and operators. Tentative mechanisms for the regulation of the galactose operon are discussed.
Isolation from normal and Rous sarcoma virus-transformed chicken fibroblasts of a factor that binds glucose and stimulates its transport.
Authors: Lee S G , Lipmann F
Published: May 2006

A glucose binding fraction was obtained by sucrose gradient centrifugation and Sephadex G-200 chromatopgraphy from confluent normal cells and Rous sarcoma virus-transformed fibroblasts. It was more or less loosely bound to the membrane fraction, most strongly in sarcoma cells, and most loosely in slowly growing confluent fibroblasts. In an average of three determinations, the content of binding factor was increased 2.5-fold in transformed cells, and compared reasonably well to a nearly 4-fold increase in glucose uptake. The addition of 5 mug/ml of purified glucose binding factor to the overlaying fluid in the 100-mm plates increased 7-flod the low glucose uptake of starved fibroblasts. The stimulation was an additive increment to the known stimulation by calf serum.
Mutagen-nucleic acid intercalative binding: structure of a 9-aminoacridine: 5-iodocytidylyl(3'-5')guanosine crystalline complex.
Authors: Sakore T D , Jain S C , Tsai C C , Sobell H M
Published: May 2006

9-Aminoacridine forms a crystalline complex with the dinucleoside monophosphate, 5-iodocytidylyl(3'-5')guanosine. We have solved the three-dimensional structure of this complex by x-ray crystallography and have observed two distinct intercalative binding modes by this drug to miniature Watson-Crick double helical structures. The first of these involves a pseudosymmetric stacking interaction between 9-aminoacridine molecules and guanine-cytosine base-pairs. This configuration may be used by 9-aminoacridine when intercalating into DNA. The second configuration is an asymmetric interaction, largely governed by stacking forces between acridine and guanine rings. This type of association may play an important role in the mechanism of frameshift mutagenesis.
31P nuclear magnetic resonance studies of Ehrlich ascites tumor cells.
Authors: Navon G , Ogawa S , Shulman R G , Yamane T
Published: May 2006

High-resolution 31P nuclear magnetic resonance spectra at 145.7 MHz are reported for intact Ehrlich ascites tumor cells and their perchloric acid extracts. In the extracts it was possible to assign resonances to fructose 1,6-bisphosphates, dihydroxyacetone phosphate, ATP, ADP, AMP, Pi, NAD+, phosphorylcholine, glycero-3-phosphorylcholine, glycero-3-phosphorylethanolamine, and glyceraldehyde 3-phosphate from their chemical shifts, pH behavior, and spin couplings. All but glyceraldehyde 3-phosphate were observed and assigned in the intact cells. It was possible to show that the hydrolysis of fructose 1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde 3-phosphate is in equilibrium, that the dihydroxyacetone phosphate leads to glyceraldehyde 3-phosphate reaction is not, and that in the intact cell without added oxygen or glucose the reaction 2ADP in equilibrium ATP + AMP is in equilibrium. From the known pH dependence of the Pi resonance it was possible to show that during aerobic or anerobic glycolysis the difference between intracellular and extracellular pH values was less than 0.2 pH units. Upon oxygenation the ATP concentration increased while the ADP concentration fell. Introducing deoxyglucose depleted the ATP and resulted in an AMP signal and one from deoxyglucose 6-phosphate, which is transported and phosphorylated but not catabolized.
Structure of proteins: packing of alpha-helices and pleated sheets.
Authors: Chothia C , Levitt M , Richardson D
Published: May 2006

Simple models are presented that describe the rules for almost all the packing that occurs between and among alpha-helices and pleated sheets. These packing rules, together with the primary and secondary structures, are the major determinants of the three-dimensional structure of proteins.
Restrictions on the coefficients of hyperbolic systems of partial differential equations
Authors: John Fritz
Published: May 2006

The paper deals with hyperbolic homogeneous systems [Formula: see text] of partial differential equations with constant coefficients for an
N
-vector
u
(
t,x
1
,...,

x
n

). Here,
P
is a matrix form of order
N
and degree
m
. In the scalar case (
N
= 1), every hyperbolic
P
is limit of strictly hyperbolic ones. This does not hold for systems as is shown here for the special case
N
=
n
= 3,
m
= 2. Assuming
P
(1,0,...,0) to be the unit matrix, we represent
P
by a point in R
81
. The hyperbolic
P
form a closed set
H
in R
81
, the strictly hyperbolic ones an open subset

H
s

of
H
. An example is given for a
P
in
H
which is not in the closure of

H
s

. Moreover, it is shown that near that
P
the set
H
coincides with an algebraic manifold of codimension 4.
5′-Terminal nucleotide sequence of
Escherichia coli
lactose repressor mRNA: Features of translational initiation and reinitiation sites
Authors: Steege Deborah A.
Published: May 2006

In a sequence of 214 nucleotides at the 5′ terminus of the
I
gene mRNA, which codes for the lactose repressor protein of
Escherichia coli
, (
i
) an untranslated leader sequence of 28 residues precedes the repressor coding region; (
ii
) a GUG initiates synthesis of the wild-type repressor; (
iii
) GUG and AUG are the functional initiators for the synthesis of restart polypeptides activated by early
I
gene amber mutations, confirming previous assignments for these residues based on protein sequencing data; and (
iv
) sequences complementary to 16S ribosomal RNA provide stronger potential mRNA·16S rRNA interaction at the wild-type initiation site than at the restart sites. When
I
mRNA is used to direct the formation of initiation complexes
in vitro
, ribosomes bind only to the wild-type initiator region.

A striking feature of the
I
mRNA sequence is the presence of a number of in-phase GUGs that have not been observed to serve as initiation signals
in vivo
in the nonsense mutant strains examined. The selective use of potential initiator triplets in the
I
mRNA leads to the following conclusions. First, when presented with several neighboring initiator triplets at the wild-type initiator region, ribosomes select the one preceded by the strongest appropriately positioned complementarity to the 16S 3′ end. Second, ribosomes do not restart after termination simply by moving to the next available initiator codon. Third, the formation of stable secondary structures predicted for the untranslated
I
mRNA beyond chain-terminating nonsense mutations may prevent ribosome access to some potential reinitiation sites.
31P nuclear magnetic relaxation studies of phosphocreatine in intact muscle: determination of intracellular free magnesium.
Authors: Cohen S M , Burt C T
Published: May 2006

31P nuclear magnetic relaxation rates for phosphocreatine in intact frog gastrocnemius were compared with those observed in model solutions at 4 degrees, a temperature at which muscle maintains its physiological state for at least 5 hr. Both nuclear Overhauser effect and spin-lattice relaxation rate (1/T1) experiments indicate that dipole-dipole interactions from the dominant relaxation path for 31P in intact muscle and model solutions, independent of phosphocreatine and Mg concentrations. Spin-spin relaxation rates (1/T2) measured by modified Carr-Purcell-Melboom-Gill spin-echo experiments suggest the importance of scalar coupling modulated by chemical exchange with free Mg. From these results, we estimate the free intracellular Mg in intact muscle as 4.4 mM and demonstrate that 31P T2 experiments can be used as a tool for studying free Mg levels with minimum disturbance of the intact cell.
Reovirus mRNA can be covalently crosslinked via the 5' cap to proteins in initiation complexes.
Authors: Sonenberg N , Shatkin A J
Published: May 2006

Proteins that are located adjacent to the 5' end of mRNA in initiation complexes have been detected by chemical crosslinking. Reovirus mRNA containing radioactivity exclusively in the [3H]methyl-labeled "cap," m7G(5')ppp(5')-Gm, was oxidized with sodium periodate to convert the 2',3'-cis-diol of the 5'-terminal m7G to a reactive dialdehyde. Oxidized mRNA was incubated in cell-free protein-synthesizing systems derived from wheat germ or mammalian cells, and the resulting mRNA-ribosome initiation complexes were reduced with NaBH3CN. By this chemical procedure, putative Schiff bases between mRNA 5'termini and amino groups of neighboring proteins were stabilized by reduction, yielding covalently linked protein-RNA conjugates. Under conditions of ribosome binding, a limited number of polypeptides associated with the mRNA-ribosome complexes were crosslinked, suggesting that these proteins are positioned near and may interact with the 5' end of mRNA during initiation. This method should also be useful for studying the spatial relationships between molecules in other similar nucleoprotein complexes.
Glycerophospholipid synthesis: improved general method and new analogs containing photoactivable groups.
Authors: Gupta C M , Radhakrishnan R , Khorana H G
Published: May 2006

Current methods for phospholipid synthesis involving acylation of sn-glycero-3-phosphorylcholine, lysolecithins, and related glycerophosphate esters are not satisfactory. With N,N-dimethyl-4-aminopyridine as a catalyst and moderate amounts of fatty acid anhydrides (1.2-1.5 mol equiv per OH group), diacyl or 1,2-mixed diacylphosphatidylcholines, N-protected phosphatidylethanolamines, and phosphatide acids now can be conveniently prepared in high yields (75-90%). New phospholipids containing photoactivable groups, such as trifluorodiazopropionyl, diazirinophenoxy, 2-nitro-4-azidophenoxy, m-azidophenoxy, and alpha, beta-unsaturated keto groups, in the fatty acyl chains have been prepared. These phospholipids are of interest in studies of lipid-lipid and lipid-protein interactions in biological membranes.
The RNA of avian acute leukemia virus MC29.
Authors: Duesberg P H , Bister K , Vogt P K
Published: May 2006

The RNA of myelocytoma virus MC29, a replication-defective avian acute leukemia virus, was investigated. Sedimentation and electrophoretic analyses indicated that the virus contains a distinct 28S RNA with about 5700 nucleotides. It is the smallest avian tumor virus RNA detected to date. The small size of the RNA suggests that the defectiveness of the virus is due to deletions in replicative genes. The RNA shared 3 to 5 of 30 large RNase T
1
-resistant oligonucleotides with the RNA of other avian leukosis and sarcoma viruses. Hybridization indicated that 61% of the viral RNA contains sequences in common with other avian sarcoma and leukosis viruses. At least 32% of the RNA (about 1800 nucleotides) appear to be MC29-specific and may represent the transforming information of the virus. Sequences of the conserved transforming gene of avian sarcoma viruses were not detected in MC29 RNA. It was concluded that the transforming sequences of MC29 RNA define a new class of avian tumor viral transforming genes.
Use of molecular hybridization to purify and analyze albumin messenger RNA from rat liver
Authors: Strair Roger K. , Yap Sing Hiem , Shafritz David A.
Published: May 2006

A new procedure is described for purification of rat liver albumin mRNA. First a population of RNA molecules is enriched for albumin mRNA by immunoprecipitation of polysomes containing albumin nascent chains. Polyadenylylated RNA is prepared from immunoprecipitates, transcribed into complementary DNA, and shown to be enriched severalfold for a particular RNA frequency component. This enriched RNA component is then purified by molecular hybridization to a limited R
0
t value (product of RNA concentration and incubation time), under conditions in which only the most abundant sequence component is annealed. Potentially, this procedure can be employed for the purification of a wide variety of mRNAs present in lesser amounts in the cell.

The isolated RNA appears to be a single frequency component by hybridization to complementary DNA transcribed from itself. This RNA is a 17S species and represents 5-8% of total cytoplasmic polyadenylylated RNA.
In vitro
translation of the purified RNA has shown that it codes for a single polypeptide that can be identified immunologically as albumin and migrates with rat serum albumin on sodium dodecyl sulfate/polyacrylamide gels. This albumin mRNA was determined to be essentially pure by comparing its kinetics of hybridization to those obtained with rabbit α + β globin mRNA and its DNA complement. The sequence complexity of purified rat albumin mRNA corresponds to 5.9 × 10
5
daltons.
Bioelectricity and regeneration: large currents leave the stumps of regenerating newt limbs.
Authors: Borgens R B , Vanable J W , Jaffe L F
Published: May 2006

Electrical currents near regenerating newt limbs were measured with a recently developed vibrating probe. Steady currents with local surface densities of 10 to 100 muA/cm2 or more leave the end of the stump during the first 5-10 days after amputation and are balanced by currents with densities of only 1-3 muA/cm2 that enter the intact skin around the stump. They are immediately dependent upon the entry of sodium ions into this skin and are therefore inferred to be skin-driven. The outward currents are comparable in direction, density, duration, and position to artificially imposed currents previously found sufficient to induce significant regeneration of amputated adult frog limbs. This comparison suggests that the endogenous stump currents play some causal role in initiating regeneration.
Evidence for an immunoglobulin-dependent antigen-specific helper T cell.
Authors: Janeway C A , Murgita R A , Weinbaum F I , Asofsky R , Wigzell H
Published: May 2006

Evidence from various systems suggests that thymus-derived lymphocytes can affect the quality of antibody responses by recognizing various portions of the immunoglobulin receptor of bone-marrow-derived thymus-independent lymphocytes. A model for this process is proposed involving two antigen-specific mature T helper cells, one of which also is specific for immunoglobulin determinants. These two cells act synergistically. Evidence from adoptive secondary antibody responses demonstrates that both cells are antigen-specific T cells and that the immunoglobulin-recognizing T helper cell is absent from experimentally agammaglobulinemic mice. This cell is termed an "immunoglobulin-dependent T cell" because its activation requires the presence of immunoglobulin.
Antigen-specific purification of blocking factors from sera of mice with chemically induced tumors.
Authors: Nepom J T , Hellström I , Hellström K E
Published: May 2006

Serum from mice with growing tumors can prevent ("block") the destruction of tumor cells by immune lymphocytes, as measured in a microcytotoxicity assay. Factors responsible for this blocking activity were purified by binding to immune adsorbents that had been prepared from antibodies obtained by immunizing BALB/c mice to the homologous tumors. Two transplantable BALB/c sarcoma lines with individually different tumor-specific transplantation antigens were studied in parallel. The original tumor-specific blocking activity was recovered by elution of the immune adsorbents; that is, (i) eluates blocked the reduction of surviving tumor cell targets by immune lymphocytes only if the tumor specificity, and (ii) immune adsorbent columns prepared from tumor-immune sera recognized the purified blocking fractions in a tumor-specific fashion, indicating that a portion of the humoral response in the immune mice was directed against a factor that was individually distinct for each tumor. Absorption of eluates with the homologous tumor cells removed their blocking activity, indicating that the blocking factors have antigen-binding properties. Blocking activity in the purified fractions resided in molecules presumptively identified as glycoproteins by affinity chromatography on concanavalin A-Sepharose.
Translation of 35S and of subgenomic regions of avian sarcoma virus RNA.
Authors: Purchio A F , Erikson E , Erikson R L
Published: May 2006

Rabbit antiserum monospecific for an internal structural protein, p27, of avian sarcoma viruses (ASV) was found to immunoprecipitate polypeptides with molecular weights (Mr) of 180,000 and 76,000 from cell-free reticulocyte lysates programmed by ASV 35S RNA and also from lysates of ASV-infected cells. In addition, the Mr 180,000 protein was also precipitated by antiserum raised against virion DNA polymerase, suggesting that is a product of the two genes nearest the 5' end of virion 35S RNA. We have also investigated the ability of subgenomic portions of virion RNA to program cell-free protein synthesis. A 10-12S poly(A)-containing fragment of RNA from both nondefective and transformation-defective ASV directed the synthesis of a polypeptide of Mr 29,000 immunologically unrelated to the gs antigens; 20-24S poly(A)-containing RNA from nondefective ASV directed the synthesis of a polypeptide of Mr 60,000 not found when a similar RNA preparation from transformation-defective ASV was translated, suggesting that it is the product of the ASV src gene. These results indicate that internal initiation sites for protein synthesis exist on the 35S RNA genome.
Nerve growth factor increases activity of ornithine decarboxylase in superior cervical ganglia of young rats.
Authors: MacDonnell P C , Nagaiah K , Lakshmanan J , Guroff G
Published: May 2006

Nerve growth factor produces a rapid increase in the activity of ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) in superior cervical ganglia of young rats in vivo and in vitro. Maximum activity occurs 6-7 hr after the addition of nerve growth factor. The nerve growth factor-mediated increase in ornithine decarboxylase activity in vitro can be prevented by the addition of cycloheximide, actinomycin D, or antibody to nerve growth factor. A number of other agents were tested for their ability to increase ornithine decarboxylase were tested for their ability to increase ornithine decarboxylase activity in the ganglia; only nerve growth factor, and, to a slight extent, insulin were able to raise the activity of the enzyme. High concentrations of dibutyryl cyclic AMP (10 mM) were able to mimic the effect of nerve growth factor.
Calcitonin: Its hormonal action on the gill
Authors: Milhaud Gérard , Rankin John Clifford , Bolis L. , Benson A. A.
Published: May 2006

When isolated salmon gills were perfused under simulated
in vivo
conditions, norepinephrine increased and calcitonin decreased the rate of flow of perfusate and the influx of calcium and phosphate through the gill. Only the increased water flow was mediated by β-adrenergic receptors. Differences in sensitivity to both hormones were observed with gills from prespawning and postspawning salmon; gills from freshwater-adapted fish were less sensitive to norepinephrine and more sensitive to calcitonin, suggesting a decreased production of this hormone in the late stage of the life cycle. The antagonistic effects of calcitonin and norepinephrine on the gill strongly implicate their regulatory role for calcium homeostasis
in vivo;
the major process being regulated is the influx of calcium into the gill. In fish, calcitonin performs an important role in regulating gill function.
Role of ecdysone, pupariation factors, and cyclic AMP in formation and tanning of the puparium of the fleshfly
Sarcophaga bullata
Authors: Seligman Morris , Blechl Ann , Blechl James , Herman Paul , Fraenkel G.
Published: May 2006

Two pupariation factors, anterior retraction factor (ARF) and puparium tanning factor (PTF), are absent from the hemolymph of larvae at the time of tanning accelerated by ARF/PTF, cyclic AMP, or dopamine. ARF and PTF are not involved in derepression of dopa decarboxylase (aromatic L-amino-acid decarboxylase, aromatic L-amino-acid carboxy-lyase, EC 4.1.1.28) synthesis initiated by ecdysone. Tanning is entirely inhibited by injection of two transcriptional inhibitors, actinomycin and BrdUrd, and two translational inhibitors, puromycin and cycloheximide. Retraction activity is more severely inhibited by the transcriptional than by the translational inhibitors. A tanning response is initiated by cyclic AMP in the presence of the transcriptional but not the translational inhibitors. Dihydric tanning substances (dopa, dopamine) initiate tanning in the presence of both types of inhibitors. Release of ARF and PTF from the central nervous system is inhibited by the four inhibitors. ARF totally reverses the inhibitory effects on retraction, whereas PTF does not reverse inhibition of tanning. These data are interpreted to mean that PTF is concerned with the regulation of two components of the tanning response: (
i
) acceleration of synthesis of a particular protein (associated with the tyrosine hydroxylation complex), and (
ii
) activation via cyclic AMP of a component of the tyrosine hydroxylating system.
A valid model for the mechanism of oxidation of tryptophan to formylkynurenine—25 years later
Authors: Nakagawa Masako , Watanabe Hideyuki , Kodato Shinichi , Okajima Haruo , Hino Tohru , Flippen Judith L. , Witkop Bernhard
Published: May 2006

The dye-sensitized photooxygenation of DL-tryptophan in aqueous solution leads to the tricyclic compound 2-carboxy-3a-hydroperoxy-1,2,3,3a,8,8a-hexahydropyrrolo[2,3-
b
]indole which, on reduction with dimethyl sulfide, furnishes two diastereoisomeric alcohols separable by fractional crystallization into a higher melting (mp 254°-256°) and a lower melting (mp 228°) diastereoisomer. Each of these alcohols was correlated with one of the analogous pair of isomeric 1,2-dicarbomethoxy analogs by alkaline hydrolysis and by x-ray analysis. In this way, the 3a-hydroxy-1,2-dimethoxycarbonyl- 1,2,3,3a,8,8a-hexahydropyrrolo[2,3-
b
]indole, mp 163°-164°, was shown to have the
trans
configuration with regard to the relative positions of the hydroxyl and carbomethoxy groups and that, on alkaline hydrolysis, it produced the isomer with mp 228°, which therefore also has the
trans
configuration. The mechanism of the smooth thermal rearrangement of the (presumably ring-chain tautomeric) tryptophan hydroperoxy intermediates to formylkynurenine is discussed with its implications for the biological oxidation by tryptophan 2,3-dioxygenase.
Sequence of an oligonucleotide derived from the 3' end of each of the four brome mosaic viral RNAs.
Authors: Dasgupta R , Kaesberg P
Published: May 2006

A 3'-terminal oligonucleotide fragment, 161 bases long, can be obtained from each of the four brome mosaic virus RNAs by means of nuclease digestion. Like the four intact brome mosaic virus RNAs, each fragment accepts tyrosine in a reaction catalyzed by wheat germ aminoacyl-tRNA synthetase. The complete nucleotide sequence of the RNA 4 fragment has been determined by use of standard radiochemical methods. Comparative data for the fragments from RNAs 1, 2, and 3 show that they have nearly the same sequence as the RNA 4 fragment. The eight bases adjacent to the 3' terminus of the RNA 4 fragment are identical in sequence to the eight terminal bases of tyrosine tRNA from Torula utilis and eleven interior bases are identical in sequence to eleven bases encompassing the anticodon region of tyrosine tRNA from Saccharomyces cerevisiae, T. utilis, and Escherichia coli. Nevertheless, reasonable base-pairing schemes yield, at best, a distorted cloverleaf secondary structure.
Chloroplast DNA distribution in parasexual hybrids as shown by polypeptide composition of fraction I protein.
Authors: Chen K , Wildman S G , Smith H H
Published: May 2006

Sixteen different mature interspecific parasexual hybrids, produced by fusing leaf protoplasts of Nicotiana glauca (G) and N. langsdorffii (L), were analyzed for fraction I protein (ribulose-1,5-bisphosphate carboxylase/oxygenase) which consists of large subunit polypeptides coded by chloroplast DNA and small subunit polypeptides coded by nuclear DNA. All the hybrids showed the combined small subunits of both parents, thus confirming the hybridity of each of the fusion products. Fourteen of the hybrids displayed the large subunit electrofocusing pattern characteristic of only one parent (eight L and six G). From one hybrid callus, two plants were regenerated, of which one had exclusively L-type large subunit and the other had exclusively G. A single plant retained a mixture of L ang G chloroplast DNA's; this later yielded six F2 progeny from one branch, all of which were G type, and three asexual progeny from another branch, all of which had the L-type pattern. In all, 46 F2 progeny and 8 different F3s were analyzed and each of these, with few if any exceptions, showed the same single subunit type as the F1 and F2 parent hybrid plants. Reasons for the rapid sorting out of the chloroplast types are discussed.
Solubilization of apolipoprotein B and its specific binding by the cellular receptor for low density lipoprotein
Authors: Shireman Rachel , Kilgore Laura L. , Fisher Waldo R.
Published: May 2006

Low density lipoprotein (LDL) and very low density lipoprotein (VLDL) bind specifically to a receptor on fibroblasts, and it has been postulated that the apoprotein of LDL (apo B) confers the specificity of cellular binding. This hypothesis has been tested in the present study with a watersoluble apo B-bovine serum albumin complex. The binding of
125
I-labeled apo B to cultured fibroblasts was temperature-dependent. Specific binding ranged between 183 and 859 ng/mg of cell protein at a concentration of 5 μg/ml; at 37°, 750-2199 ng/mg was bound and internalized. The binding of apo B greatly exceeded the amount of
125
I-labeled LDL bound at 4° and 37° in the same experiment. Fibroblasts from a subject homozygous for hyper-β-lipoproteinemia showed minimal binding of
125
I-labeled LDL, consistent with the absence of the cellular LDL receptor. Such cells also had depressed binding of
125
I-labeled apo B.

Lymphocytes grown in lipoprotein-deficient medium demonstrated specific binding of LDL; however, freshly isolated lymphocytes did not show such binding. The binding of
125
I-labeled apo B to lymphocytes paralleled the binding of
125
I-labeled LDL. Unlabeled LDL and apo B-albumin complex both competitively inhibited the binding of
125
I-labeled apo B and
125
I-labeled LDL to fibroblasts. When labeled LDL was incubated with fibroblasts for 6 hr at 37°, it underwent cellular internalization and degradation, as measured by the release of
125
I-labeled fragments into the medium. This degradation was inhibited by unlabeled apo B. Conversely,
125
I-labeled apo B also was internalized and degraded by fibroblasts, and this process was inhibited by LDL. These findings demonstrate that apo B binds specifically to the LDL receptor and that the cellular binding of LDL is determined by this apoprotein.
Lipoprotein lipase cofactor activity of a carboxyl-terminal peptide of apolipoprotein C-II.
Authors: Musliner T A , Church E C , Herbert P N , Kingston M J , Shulman R S
Published: May 2006

Apolipoprotein C-II (apoC-II) is a small protein found associated with the plasma lipoproteins. It serves a unique function in the activation of the enzyme lipoprotein lipase (triacylglycerol acyl-hydrolase, EC 3.1.1.3). ApoC-II contains a single arginine residue, permitting tryptic cleavage into two peptides after succinylation of the native protein. The succinylated amino-terminal peptide, approximately 50 residues, did not activate lipoprotein lipase. The succinylated carboxyl-terminal peptide, about 29 residues, had significant cofactor activity. Relative to native apoC-II, the maximal activation observed with the succinylated carboxyl-terminal peptide was 50% lower and the concentration required for half-maximal activity was approximately 10 times higher. Mixtures of the carboxyl- and amino-terminal peptides had no more activity than the carboxyl-terminal peptide alone. Localization of functional properties to the carboxyl region is a feature also common to apolipoproteins C-III, A-II, and A-I.
Chemical evidence that proteolytic cleavage causes the heterogeneity present in human ceruloplasmin preparations.
Authors: Kingston I B , Kingston B L , Putnam F W
Published: May 2006

Nine samples of human ceruloplasmin [iron(II):oxygen oxidoreductase; EC 1.16.3.1] prepared by different procedures have been examined for heterogeneity; gel electrophoresis showed that seven contained a number of components with molecular weights ranging from 20,000 to 130,000, and two contained largely a single component of molecular weight 130,000. Digestion of a single-component preparation with plasmin produced fragments with molecular weights similar to those found in the multicomponent preparations. Amino-terminal analysis, peptide mapping, and amino acid analysis showed that plasmin digestion generated a fragment of 20,000 molecular weight, which corresponded to a component present in a multicomponent ceruloplasmin preparation. The 20,000 molecular weight fragment appears to correspond to the so-called alpha-subunit or L-chain of human ceruloplasmin. Chemical evidence is thus provided that ceruloplasmin is a single-chain protein and that the so-called subunits are fragments. The 20,000 molecular weight fragment contains a single cysteine; amino acid sequence studies have shown that the sequence in the vicinity of this residue is similar to that around the single cysteine residue in plant plastocyanins and bacterial azurins, which are small, blue, copper-containing proteins.
Hepatic mitochondrial cytochrome
P
-450: Isolation and functional characterization
Authors: Sato R. , Atsuta Y. , Imai Y. , Taniguchi S. , Okuda K.
Published: May 2006

A CO-binding heme protein was solubilized and partially purified from the inner membrane fraction of rat liver mitochondria by a modification of a method [Imai, Y. & Sato, R. (1974)
Biochem. Biophys. Res. Commun.
60, 8-14] developed to purify cytochrome
P
-450 from liver microsomes. The partially purified preparation contained protoheme and its spectral properties are characteristic of the heme proteins of the cytochrome
P
-450 family. The isolated cytochrome
P
-450 preparation could reconstitute a CO-sensitive, NADPH-dependent 26-hydroxylation activity for 5β-cholestane-3α,7α,-12α-triol when supplemented with NADPH-adrenodoxin reductase and adrenodoxin, both purified from bovine adrenocortical mitochondria. Unlike a cytochrome
P
-450 purified from liver microsomes of drug-untreated rats, however, the liver mitochondrial cytochrome
P
-450 could not catalyze NADPH-dependent benzphetamine
N
-demethylation in the presence of adrenodoxin reductase and adrenodoxin or function with the purified microsomal NADPH-cytochrome
c
reductase plus Emulgen 913 as an electron-donating system. It is concluded that the rat liver inner mitochondrial membrane houses a species of cytochrome
P
-450 functional in 5β-cholestane-3α,7α,12α-triol 26-hydroxylation.
Evidence for a long-range conformational change induced by antigen binding to IgM antibody.
Authors: Brown J C , Koshland M E
Published: May 2006

The effects of antigen binding on IgM antibody conformation were investigated by measuring the immunological reactivity of the Fc-bound J polypeptide. For such measurements anti-azophenyl-beta-D-lactoside and anti-azobenzenearsonate IgM antibodies were examined in a J chain radioimmunoassay before and after complexing with various hapten-conjugates. The assays showed that (i) the accessibility of J chain determinants is very limited in uncomplexed IgM and (ii) their accessibility is significantly enhanced in the presence of an excess of specific antigen. In both antibody systems, enhanced J chain exposure was achieved with the homologous multi-hapten-substituted antigen (1.9-fold), with a small multivalent antigen in which three to four hapten groups were coupled to a heterologous carrier (1.55-fold), and with monohapten-substituted antigen (1.4-fold). Because the J chain is located in the terminal CH4 Fc domains, these data provide direct evidence that a change in Fc conformation is induced by the binding of antigen to the distant Fab combining sites. Moreover, the data indicate that the changes in J chain exposure do not depend on crosslinking by antigen, but can be induced by the interaction of antigen at individual IgM combining sites.
Unusual pulmonary vasodilator activity of 13,14-dehydroprostacyclin methyl ester: comparison with endoperoxides and other prostanoids.
Authors: Hyman A L , Chapnick B M , Kadowitz P J , Lands W E , Crawford C G , Fried J , Barton J
Published: May 2006

Microsomes from stomach fundus and blood vessels transform the endoperoxide, PGH2, into a newly discovered unstable substance, PGI2, that relaxes arterial strips and inhibits platelet aggregation. 13,14-Dehydro-PGI2 methyl ester, a newly synthesized, stable PGI2 analog, was found to have potent vasodilator activity in the feline and simian pulmonary vascular bed. The PGI2 analog decreased lobar arterial perfusion pressure in the intact cat and monkey. Because pulmonary blood flow was held constant and left atrial pressure was unchanged, the decrease in perfusion pressure reflects a decrease in pulmonary vascular resistance. The dilator response was unusual in that it persisted for 10-12 min, whereas the response to PGE1, the only other vasodilator prostaglandin in the mature animal, persisted for only 1-2 min. The dilator response to the PGI2 analog was enhanced when pulmonary vascular resistance was increased. This substance had less effect on cardiac output and aortic pressure than PGE1, whereas it was a more potent pulmonary vasodilator. These data demonstrate that prostacyclin-like substances possess novel vasodilator activity in the pulmonary circulation and suggest a therapeutic use in the treatment of pulmonary hypertensive diseases.
Effect of increased potassium concentrations on particle motion within a neurosecretory structure.
Authors: Englert D , Edwards C
Published: May 2006

Intensity fluctuation spectroscopy was used to detect particle motion within the pericardial organ of the crab Carcinus while it was perfused with media with increased potassium concentrations. Replacement of some or all of the sodium ions of the normal medium with potassium ions caused a graded increase in motion. Evidence is presented which indicates that this effect is not a consequence of membrane depolarization or calcium ion influx, but is due to the flux of potassium chloride and water into the cytoplasm of the cells.
Generalizing Fisher's “reproductive value”: Nonlinear, homogeneous, biparental systems
Authors: Samuelson Paul A.
Published: May 2006

Biparental demographic models violate linearity. However, in their early “dilute” stages before limited environment resources bring need for competitive selection, first-degree-homogeneous relations obtain. For them, a reproductive-value function of the
initial coordinates
is defined to recapitulate their contribution to the asymptotically dominating mode of exponential growth: now the generalized Fisher reproductive value of one sex is altered by relative numbers of the other sex. The new reproductive-value function is also derived for general systems of homogeneous-first-degree differential and difference equations, and is shown to grow
from the start
at the asymptotic growth rate.
Surface differentiation antigens of human mammary epithelial cells carried on the human milk fat globule.
Authors: Ceriani R L , Thompson K , Peterson J A , Abraham S
Published: May 2006

Rabbit antibodies against components of the human milk fat globule bind specifically to normal human breast epithelial cells and cell lines derived from breast carcinomas, as well as to the outer surface of the human milk fat globule. Variation in indirect immunofluorescence staining in both intensity per cell and percentage of cells stained is observed for the different brest cell lines. Cells derived from other epithelial and other ectodermal tissues, fetal fibroblasts, cells of the blood buffy coat, and even fibroblasts of the breast itself do not bind the antibodies. This suggests that these antibodies are detecting cell-type-specific antigens. These normal breast epithelial cell antigens are on the cell surface and their expression is stable in long-term cultured cell lines, even after much chromosomal variation in a given line. By affinity chromatography, three distinct antigenic components can be isolated from the milk fat globule, one of which contains carbohydrate. These differentiation antigens of the human breast epithelial cell are not only useful as specific cell-type markers, but also can provide a tool to study the role of the cell surface in normal and neoplastic mammary development.
Cells reconstituted from cell fragments of two different species multiply and form colonies.
Authors: Krondahl U , Bols N , Ege T , Linder S , Ringertz N R
Published: May 2006

Nuclei (minicells) prepared by cytochalasin-induced enucleation of rat myoblasts (L6) were fused with inactivated Sendai virus to preparations of cytoplasms from mouse fibroblasts (A9). Cell colonies arising from such fusion mixtures were examined 5 days after fusion. In the presence of virus a new type of colony was obtained. The cells in these colonies were derived from reconstituted cells capable of undergoing repeated cell divisions.
Mutagenesis in S49 mouse lymphoma cells: induction of resistance to ouabain, 6-thioguanine, and dibutyryl cyclic AMP.
Authors: Friedrich U , Coffino P
Published: May 2006

The effects of mutagens on three genetic markers--resistance to ouabain, 6-thioguanine, and dibutyryl cyclic AMP (Bt2cAMP), were investigated in a mouse lymphoma cell line, S49. Nitrosoguanidine, ethyl methanesulfonate, ICR 191, and x-rays were used. Mutagen-specific responses were seen. Ouabain resistance was induced by nitrosoguanidine, but not by ICR 191. ICR 191 induced resistance to 6-thioguanine more efficiently than did nitrosoguanidine; the converse was true of resistance to Bt2cAMP. The relative frequency of biochemically distinguishable subtypes of mutants resistant to Bt2cAMP was characteristic of the mutagen used to generate them. The results can be interpreted as follows: nitrosoguanidine and ethyl methanesulfonate frequently, but ICR 191 and x-rays rarely, give rise to DNA base sequence changes that result in structurally altered but functional proteins. This type of change is required for induction of mutants resistant to ouabain and of certain classes of mutants resistant to Bt2cAMP. Resistance to 6-thioguanine and other classes of mutants resistant to Bt2cAMP can result from DNA base sequence changes that lead to extensive alteration of protein structure or expression; these changes are induced by ICR 191 or x-rays.