bluuebunny/crossref_metadata_2025 huggingface dataset:
Picosecond photodissociation and subsequent recombination processes in carbon monoxide hemoglobin.
Authors: Noe L J , Eisert W G , Rentzepis P M
Published: May 2006

Excitation of HbCO by a single 6-psec 530-nm pulse results in photodissociation with a first-order constant of 0.89 X 10(11) sec-1. The kinetics of photodissociation, monitored by following absorbance changes in the Soret band at 440 nm, are interpreted as corresponding to predissociation followed by a corssing into a dissociative state. Subsequent recombination of CO with the porphyrin system and protein structural transformations were monitored by use of a continuous He-Cd laser beam spatially coincident with the photolysis and Soret interrogation beams at the sample. We find that the latter events take place in three distinct time regions, depending on exciation pulse energy and repetition rate. Exictation of HbCO with a single pulse (0.8--5 mJ) results in a relaxation to the ground state with an associative first-order constant of 5 X 10(3) sec-1. With a 100-pulse train (approximately 7.5 mJ), a new decay grows with a rate constant of 63 sec-1. For a pulse-train energy of 12 mJ or higher, a delay occurs at the onset of the second (slower) recombination.
On localization for double Fourier series
Authors: Goffman Casper , Waterman Daniel
Published: May 2006

The localization theorems for Fourier series of functions of a single variable are classical and easy to prove. The situation is different for Fourier series of functions of several variables, even if one restricts consideration to rectangular, in particular square, partial sums. We show that the answer to the problem can be obtained by considering the notion of
generalized bounded variation
, which we introduced. Given a nondecreasing sequence {λ

n

} of positive numbers such that Σ 1/λ

n

diverges, a function
g
defined on an interval
I
of
R
1
is said to be of Λ-
bounded variation
(ΛBV) if Σ|
g
(

a
n

) —
g
(

b
n

)|/λ

n

converges for every sequence of nonoverlapping intervals (

a
n

,

b
n

) [unk]
I
. If λ

n

=
n
, we say that
g
is of
harmonic bounded variation
(HBV). The definition suitably modified can be extended to functions of several variables. We show that in the case of two variables the localization principle holds for rectangular partial sums if ΛBV = HBV, and that if ΛBV is not contained in HBV, then the localization principle does not hold for ΛBV even in the case of square partial sums.
A new class of pseudo-differential operators
Authors: Nagel Alexander , Stein E. M.
Published: May 2006

We describe a class of pseudo-differential operators and their singular integral realizations and show how these may be used to give precise estimates in various function spaces. Application will be given in particular to several situations in which subelliptic estimates arise for partial differential equations.
On the physical basis for ambiguity in genetic coding interactions.
Authors: Grosjean H J , de Henau S , Crothers D M
Published: May 2006

We report the relative stabilities, in the form of complex lifetimes, of complexes between the tRNAs complementary, or nearly so, in their anticodons. The results show striking parallels with the genetic coding rules, including the wobble interaction and the role of modified nucleotides S2U and V (a 5-oxyacetic acid derivative of U). One important difference between the genetic code and the pairing rules in the tRNA-tRNA interaction is the stability in the latter of the short wobble pairs, which the wobble hypothesis excludes. We stress the potential of U for translational errors, and suggest a simple stereochemical basis for ribosome-mediated discrimination against short wobble pairs. Surprisingly, the stability of anticodon-anticodon complexes does not vary systematically on base sequence. Because of the close similarity to the genetic coding rules, it is tempting to speculate that the interaction between two RNA loops may have been part of the physical basis for the evolutionary origin of the genetic code, and that this mechanism may still be utilized by folding the mRNA on the ribosome into a loop similar to the anticodon loop.
How many base-pairs per turn does DNA have in solution and in chromatin? Some theoretical calculations.
Authors: Levitt M
Published: May 2006

Calculations on a 20-base pair segment of DNA double helix using empirical energy functions show that DNA can be bent smoothly and uniformly into a superhelix with a small enough radius (45 A) to fit the dimensions of chromatin. The variation of energy with the twist of the base pairs about the helix axis shows the straight DNA free in solution is most stable with about 10 1/2 base pairs per turn rather than 10 as observed in the solid state, whereas superhelical DNA in chromatin is most stable with about 10 base pairs per turn. This result, which has a simple physical interpretation, explains the pattern of nuclease cuts and the linkage number changes observed for DNA arranged in chromatin.
Triphosphate residues at the 5' ends of rRNA precursor and 5S RNA from Dictyostelium discoideum.
Authors: Batts-Young B , Lodish H F
Published: May 2006

We present here direct evidence for the preservation of a transcriptional initiation sequence in a eukaryotic rRNA precursor: the 5'-end group for precursor to 17S rRNA (p17S RNA) from Dictyostelium discoideum is identified as the triphosphate residue pppA-. We also show that mature 5S RNA form Dictyostelium bears a different triphosphate residue, pppG-. In contrast, we find no evidence for more than one phosphate at the 5' end of the 25S rRNA precursor (p25S RNA). These observations indicate that synthesis of the large ribosomal RNAs of Dictyostelium begins with the 5'-terminal sequence of the p17S RNA, and that 5S RNA transcription must be initiated independently, despite the close association of the 5S and rRNA coding segments.
Construction and characterization of an Escherichia coli plasmid bearing a functional gene G of bacteriophage phiX174.
Authors: Humayun M Z , Chambers R W
Published: May 2006

In order to study the mutagenic effects of site-specific, covalent modifications of biologically active DNA, we need host cells that are permissive for any type of mutation that might be produced in vivo from the modified DNA. Specifically, we require a general, in vivo complementation system for the bacteriophage phiX174 gene G, an essential gene that we have chosen for our initial studies of chemical mutagenesis. Toward this end, we have constructed a plasmid (pphiXG) that carries a functional copy of phiX174 gene G. Three different bacterial strains that are nonpermissive for am9, a gene G amber mutant, have been transformed with pphiXG. The transformants are now permissive for this gene G mutant, but not for the gene A or E mutants that have been tested. This paper describes the construction and the biochemical characterization of this plasmid, pphiXG, and describes some of the biological properties exhibited by the pphiXG-bearing strains.
Role of anions in parathyroid hormone release from dispersed bovine parathyroid cells.
Authors: Brown E M , Pazoles C J , Creutz C E , Aurbach G D , Pollard H B
Published: May 2006

It is known that permeant anions are required for the release of epinephrine from isolated chromaffin granules and of serotonin from intact platelets. We have now investigated the role of anions in the release of a polypeptide hormone, parathyroid hormone, from dispersed bovine parathyroid cells. The release is inhibited 60%-80% by decreasing either [Cl-] or [OH-] and 60%-70% by replacement of NaCl with the impermeant anion isethionate. By contrast, substitution of various monovalent cations in the medium had no effect on the release. Disodium 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate (SITS) and probenecid, which are known to block anion transport in the erythrocyte, also cause a dose-dependent 90%-100% inhibition of release. Moreover, kinetic analysis of inhibition by probenecid suggests that it is competitive with respect to either OH- or Cl-. These results suggest that anions and the anion transport system may play a role in exocytosis of a polypeptide hormone. The proton ionophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone was was also found to block hormone release, and the possibility is discussed of a "chemosmotic" mechanism for exocytosis in this system similar to that previously postulated for chromaffin granules and platelets.
Egg surface glycoprotein receptor for sea urchin sperm bindin.
Authors: Glabe C G , Vacquier V D
Published: May 2006

Bindin is an insoluble protein coating the sperm acrosome process and mediating the adhesion of sperm to sea urchin eggs. Milligrams of bindin have been isolated. Here we report the identification, isolation, and partial characterization of a high molecular weight, trypsin-sensitive glycoprotein fraction from the sea urchin egg surface having species-specific affinity for bindin. This glycoprotein may be the egg surface receptor for bindin. The bindin receptor was released from 125-I-labeled eggs by parthenogenetic activation of eggs with ionophore A23187 in the presence of soybean trypsin inhibitor. The receptor has an isoelectric point of 4.02 and a molecular weight in sea water greater than or equal to 5 X 10(6), suggesting that it is an aggregate. It contains 34% neutral sugars, which are galactose and mannose.
Lucibufagins: Defensive steroids from the fireflies
Photinus ignitus
and
P. marginellus
(Coleoptera: Lampyridae)
Authors: Eisner Thomas , Wiemer David F. , Haynes LeRoy W. , Meinwald Jerrold
Published: May 2006

Feeding tests with thrushes (
Hylocichla
spp.) led to the isolation of three novel steroid pyrones from fireflies (
Photinus ignitus
and
P. marginellus
) responsible, in part at least, for the unpalatability of these insects to the birds. The term
lucibufagin
is coined for these steroidal pyrones. The closest known relatives of lucibufagins are the familiar cardiotonic bufadienolides, found in certain toads and plants.
Intramolecular energy transfer in molecules with a large number of conformations
Authors: Englert A. , Leclerc M.
Published: May 2006

The equations representing the decay kinetics of fluorescence of a donor luminophore in the presence of an acceptor in the same flexible molecule are discussed. The assumption that distances between luminophores attached to chain ends are not correlated with the relative orientations of luminophores is tested by theoretical calculations for the unperturbed chains Tyr-(Ala)

n

-Tyr with
n
equal to 4 and 9. It appears that for these chains, in which the conformation is dominated by entropic factors, the above assumption is satisfactory even for chains with a small number of repeating units (
n
= 4).
Purification of ADP-ribosylated nuclear proteins by covalent chromatography on dihydroxyboryl polyacrylamide beads and their characterization.
Authors: Okayama H , Ueda K , Hayaishi O
Published: May 2006

Nuclear proteins modified by mono or poly ADP-ribosylation were selectively isolated and purified by covalent chromatography on a dihydroxyboryl polyacrylamide bead column that specifically interacts with cis-diol-containing compounds. From rat liver nuclei that had been incubated with NAD+, histones and some nonhistone proteins were extracted with 0.25 M HCl. Approximately 60% of the ADP-ribose incorporated into 20% trichloroacetic acid-precipitable material was recovered in this extract. The ADP-ribosylated material was then isolated from the extract by covalent chromatography on a borate gel column and further purified by carboxymethylcellulose column chromatography. As judged by electrophoretic mobilities in various gel systems and by amino acid compositions, approximately 50% of the ADP-ribose recovered in the carboxymethylcellulose fractions was associated with several nonhistone proteins with molecular weights of 2-6 x 10(4), while 35% aand 15% were associated with histones H2B and H1, respectively. Since the average chain length of the polymer bound to any of these proteins was less than two ADP-ribos-l units, the percentage distribution reflects the number of ADP-ribosylated sites rather than the chain length.
Regulation of protein synthesis: Activation by double-stranded RNA of a protein kinase that phosphorylates eukaryotic initiation factor 2
Authors: Levin Daniel , London Irving M.
Published: May 2006

Incubation of reticulocyte lysates or isolated crude ribosomes with low levels of double-stranded RNA (0.1-10 ng/ml) induces the formation of an inhibitor of protein synthesis initiation similar to that observed in heme deficiency. The inhibitor is associated with a cyclic AMP-independent protein kinase activity (ATP:protein phosphotransferase, EC 2.7.1.37) that phosphorylates the small polypeptide (38,000 daltons) of the eukaryotic initiation factor eIF-2. Activation of the inhibitor requires ATP in addition to double-stranded RNA and is accompanied by the phosphorylation of a 67,000-dalton polypeptide of unknown function. The inhibitor remains associated with the ribosomes during high-speed sedimentation. Once formed, the ribosome-associated inhibitor phosphorylates eIF-2 and inhibits protein synthesis in the absence of double-stranded RNA. Inhibition is prevented by exogenous eIF-2. The bound inhibitor can be solubilized by extraction with 0.5 M KCl. The soluble inhibitor preparation retains the ability to phosphorylate the small polypeptide of eIF-2 and to inhibit protein synthesis. Untreated crude ribosomes also contain cyclic AMP-independent protein kinase activities that phosphorylate the middle polypeptide (49,000 daltons) of eIF-2 and several polypeptide subunits of eIF-3 (160,000, 125,000, and 65,000 daltons); these kinase activities are not affected by double-stranded RNA and do not inhibit protein synthesis.
Translational control by hemin is due to binding to cyclic AMP-dependent protein kinase.
Authors: Datta A , de Haro C , Ochoa S
Published: May 2006

Our previous work [Proc. Natl, Acad. Sci. USA (1977) 74, 1463-1467, 3326-3329] is consistent with the view that (a) the hemin-controlled inhibitor of protein synthesis in reticulocyte lysates (active eIF-2 kinase) is formed by phosphorylation of proinhibitor (inactive eIF-2 kinase) catalyzed by cyclic AMP-dependent protein kinase (ATP-protein phosphotransferase; EC 2.7.1.37), and (b) hemin prevents this conversion by blocking the interaction of cyclic AMP with the kinase's regulation subunit, thereby rendering the enzyme inactive. We now show that hemin blocks cyclic AMP binding because it itself binds specifically to the regulatory subunit. This binding is noncompetitive with respect to cyclic AMP. Whereas unlabeled hemin can displace bound [3H]hemin as well as cyclic [3H]AMP, unlabeled cyclic AMP can displace bound cyclic [3H]AMP but not [3H]hemin. This suggests that cyclic AMP and hemin bind to different sites on the protein and that hemin binding affects cyclic AMP binding in an allosteric manner.
Transcription of cloned tRNA gene fragments and subfragments injected into the oocyte nucleus of Xenopus laevis.
Authors: Kressmann A , Clarkson S G , Pirrotta V , Birnstiel M L
Published: May 2006

Cloned 3.18 kilobase fragments of Xenopus laevis DNA containing genes for tRNAMet1 and for at least one other 4S RNA species are transcribed rapidly after their injection into the nucleus of X. laevis oocytes. The newly synthesized RNA can be resolved by gel electrophoresis into a few predominant 4S RNA species and a series of slower migrating components. One of the 4S RNA species appears to be identical, by fingerprint analysis, to the tRNAMet1 isolated by hybridization of somatic cell RNA to this cloned tRNA gene fragment (tDNA). Thus, the tRNAMet1 produced after injection can be both fully processed and modified. Its rate of synthesis is estimated to be about 6 x 10(9) molecules/hr in each oocyte injected with 2 ng of tDNA. When the tDNA fragment is cleaved into two halves with restriction endonuclease Sst I, each injected half gives rise to a subset of the RNAs produced after injection of the intact fragment. This experiment thus suggests the presence of at least two transcriptional units on this cloned tDNA. This simple way of biologically testing defined restriction fragments may be of value for analyzing the functional organization of other cloned eukaryotic DNA units.
Aspartic acid racemization in heavy molecular weight crystallins and water insoluble protein from normal human lenses and cataracts.
Authors: Masters P M , Bada J L , Zigler J S
Published: May 2006

High D/L aspartic acid ratios are observed in heavy molecular weight aggregates and in water-insoluble protein extracted from whole lenses and nuclear and cortical regions. Purified alpha-, beta-, and gamma-crystallins have low D/L ratios. Fractionation of urea-solubilized material from the water-insoluble protein yields four molecular weight classes of proteins. Fractions representing crosslinked material or apparently degraded products have high D/L ratios. Racemization within lens proteins may contribute to formation of the water-insoluble fraction seen in aging lenses and cataracts.
Precursors of three exported proteins in Escherichia coli.
Authors: Randall L L , Hardy S J , Josefsson L G
Published: May 2006

Arabinose-binding protein, maltose-binding protein, and lambda receptor are synthesized in vitro on membrane-bound polysomes from Escherichia coli. All three proteins are exported from the cytoplasm of E. coli and all three are made in vitro in a form a few thousand daltons larger than the authentic protein. The larger form of arabinose-binding protein is also detected in vivo by pulse labeling. It is concluded that the larger forms of the exported proteins are precursors containing an extra sequence. In contrast to the above, when the intracellular protein elongation factor Tu is synthesized in vitro on free polysomes, it is not detectably larger than the authentic form.
Cell-cell interactions in conjugating Escherichia coli: purification of F pili with biological activity.
Authors: Helmuth R , Achtman M
Published: May 2006

A mutant of the F sex factor has been isolated that produces more F pili per cell than does the wild-type F factor. F pili have been purified in milligram amounts from cells carrying either the mutant or the wild-type sex factor. The technique described yields F pili of up to 99% purity that can specifically bind to Escherichia coli cells and that bind to and reversibly inactivate male-specific bacteriophages. The F pilin subunit has a molecular weight of 10,750 and purified F pili have a buoyant density of 1,200 g/cm3.
Amphibian oocyte maturation and protein synthesis: Related inhibition by cyclic AMP, theophylline, and papaverine
Authors: Bravo Rodrigo , Otero Carlos , Allende Catherine C. , Allende Jorge E.
Published: May 2006

Two inhibitors of cyclic AMP phosphodiesterase (3′:5′-cyclic-AMP 5′-nucleotidohydrolase, EC 3.1.4.17), theophylline and papaverine, inhibit the maturation of
Xenopus laevis
oocytes induced by four different stimuli: human chorionic gonadotropin, progesterone, testosterone, and lanthanum ions. Addition of 1 mM cyclic AMP to the medium delays maturation by approximately 2 hr. Papaverine, theophylline, and cyclic AMP inhibit amino acid incorporation into oocyte proteins by 50% or more but do not inhibit amino acid uptake. The capacity of theophylline to block maturation and protein synthesis is reversed in a parallel fashion by addition of 1-5 mM calcium ion to the medium. Addition of papaverine, theophylline, and cycloheximide to oocytes at different times after hormonal treatment shows that the step sensitive to blockage by the three drugs is coincident and precedes germinal vesicle breakdown by about 1.5 hr. Theophylline and papaverine do not increase endogenous cyclic AMP levels in oocytes but do block the decrease of cyclic AMP levels observed 3 hr after progesterone treatment. Both drugs inhibit oocyte cyclic AMP phosphodiesterase measured
in vivo
and severely inhibit the stimulus of calcium uptake caused by progesterone and human chorionic gonadotropin. These results suggest that cyclic AMP, theophylline, and papaverine may block oocyte maturation by inhibiting protein synthesis, possibly via a cyclic AMP-dependent protein kinase as shown in reticulocytes [Datta, A., De Haro, C., Sierra, J. & Ochoa, S. (1977)
Proc. Natl. Acad. Sci., USA
74, 1463-1467].
Detection and kinetic behavior of preproinsulin in pancreatic islets.
Authors: Patzelt C , Labrecque A D , Duguid J R , Carroll R J , Keim P S , Heinrikson R L , Steiner D F
Published: May 2006

Newly synthesized rat islet proteins have been analyzed by polyacrylamide slab gel electrophoresis and fluorography. A minor component having an apparent molecular weight of 11,100 was identified as preproinsulin by the sensitivity of its synthesis to glucose, the pattern of NH2-terminal leucine residues, and the rapidity of its appearance and disappearance during incubation of islets or islet cell tumors. A small amount of labeled peptide material which may represent the excised NH2-terminal extension of preproinsulin or its fragment was also detected. The kinetics of formation and processing of the preproinsulin fraction were complex, consisting of a rapidly turning over component having a half-life of about 1 min and a slower minor fraction that may have bypassed the normal cleavage process. The electrophoretic resolution of the preproinsulin and proinsulin fractions into two bands each is consistent with the presence of two closely related gene products in rat islets rather than intermediate stages in the processing of these peptides.
Ligands containing heavy atoms: Perturbation of phosphorescence of a tryptophan residue in the binding site of wheat germ agglutinin
Authors: Monsigny Michel , Delmotte Francis , Hélène Claude
Published: May 2006

Information on the structure of binding sites of wheat germ agglutinin was obtained on the basis of fluorescence and phosphorescence changes of tryptophan residues induced by the binding of several thiomercuribenzoate derivatives of glycosides. The thiomercuribenzoate derivatives bind selectively to wheat germ agglutinin in the same way as the corresponding sugars. Using the thiomercuribenzoate of di-
N
-acetyl-β-chitobiose, it was found that: (
i
) the fluorescence of tryptophan residues was drastically quenched at both 298 and 77 K; (
ii
) the phosphorescence intensity was strongly enhanced at 77 K; (
iii
) the phosphorescence lifetime was markedly decreased. A similar effect was observed with the thiomercuribenzoate of
N
-acetyl-β-D-glucosamine. These changes were completely reversed upon addition of 1-
O
-methyl-di-
N
-acetyl-β-chitobioside. The thiomercuribenzoate of β-D-glucose had no effect at all, and the thiomercuribenzoate of tri-
N
-acetyl-β-chitotriose had a limited effect. These results are interpreted as a specific heavy atom effect due to a close contact between one tryptophan residue of the protein and the heavy atom of the bound ligand. They are consistent with the view that: (
i
) binding sites of wheat germ agglutinin may be divided in three subsites, A, B, and C; (
ii
) a tryptophan residue is in the binding site at subsite C; and (
iii
) this residue and the ligand are in close contact. This new method, using the enhancement of spin-orbit coupling due to the selective perturbation induced in a tryptophan residue by a ligand containing a heavy atom, has proved to be suitable for locating the tryptophan residue in the binding site of wheat germ agglutinin and can probably be extended to other sugar-binding proteins.
Entrapment of metaphase chromosomes into phospholipid vesicles (lipochromosomes): Carrier potential in gene transfer
Authors: Mukherjee Anil B. , Orloff Sheldon , Butler Jean DeB. , Triche Timothy , Lalley Peter , Schulman Joseph D.
Published: May 2006

Transfer of genes from one type of cultured mammalian cell to another by using isolated metaphase chromosomes has been reported with a frequency of one per 10
6
-10
8
cells. Very recently a rate of 16/10
6
has been reported with Chinese hamster ovary cells [Spandidos, D. A. & Siminovitch, L. (1977)
Proc. Natl. Acad. Sci. USA
74, 3480-3484]. To increase the frequency of gene transfer, we isolated metaphase chromosomes from hypoxanthine guanine phosphoribosyltransferase (HGPRT) positive cells, entrapped them in liposomes, and fused the lipochromosomes with HGPRT-negative cells. Lipochromosomes were prepared with cholesterol and egg lecithin, using isolated metaphase chromosomes from a mouse-human somatic hybrid cell line (A9/HRBC2); the entire X chromosome, including the HGPRT, glucose-6-phosphate dehydrogenase, and phosphoglycerate kinase genes, is the only recognizable human genetic material retained by the hybrids. Enclosure of the chromosomes in the lipid envelope was confirmed by electron and fluorescence microscopy and differential centrifugation. These lipochromosomes were fused with HGPRT
-
mouse cells (A9) in the presence or absence of polyethylene glycol and transferents were selected in hypoxanthine/aminopterin/thymidine (HAT) medium. The frequency of transfer was at least once per 10
5
cells, a minimum 10-fold improvement over previous methods. The selected cells contained HGPRT activity similar to the amount found in the A9/HRBC2 cells. Starch gel electrophoresis verified that the observed HGPRT activity in the transferents is due to the human enzyme. Human glucose-6-phosphate dehydrogenase and phosphoglycerate kinase were also identified electrophoretically in the transferents. Karyotyping with C and Q banding did not reveal the presence of the whole human X chromosome or a visible extra fragment of a human chromosome associated with the mouse genome. The biochemical data strongly suggest, however, that transfer of a portion of the human X chromosome has occurred in these transferents. Thus, at least three X-linked genes have been transferred from one cell to another with high frequency, using metaphase chromosomes.
Isolation and characterization of enterotoxin-deficient mutants of Escherichia coli.
Authors: Silva M L , Maas W K , Gyles C L
Published: May 2006

The genes controlling the production of two types of enterotoxin of Escherichia coli, one heat-labile (LT) and the other heat-stable (ST), are found on plasmids. The absence of a direct selection procedure has made it difficult to isolate mutants affecting toxin production. However, the availability of a naturally occurring "recombinant" plasmid, carrying genes for LT and ST formation and also for resistance to tetracycline, streptomycin, and sulfonamides, made it possible to use comutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine to enrich for such mutants. We have isolated and characterized 58 LT- mutants and 7 ST- mutants. Among the LT- group we found amber mutants, temperature-sensitive mutants (most of which produce unusually heat-labile LT), and "leaky" mutants with reduced LT activity. The majority of the tested LT- mutants produced immunologically crossreacting material, in most cases in wild-type amounts. Among all 17 of the LT- mutants that could be transferred, the mutation was found to be on the plasmid. In contrast, only one of four transferrable ST- mutants appeared to be a plasmid mutant.
Transfection of Fv-1 permissive and restrictive mouse cells with integrated DNA of murine leukemia viruses.
Authors: Hsu I C , Yang W K , Tennant R W , Brown A
Published: May 2006

Whole-cell DNA preparations isolated from SC-1 cells chronically infected with N- or B-tropic murine leukemia viruses (MuLV) were tested for infectious activity in an Fv-1n (NIH-3T3) and two Fv-Ib (C57BL/6 and SV-A31) cell cultures. Efficiency of transfection for all DNAs was better in the NIH-3T3 cells than in C57BL/6 or SV-A31 cells; and an [N-tropic MuLV]SC-1 cell DNA preparation was slightly more infectious than a [B-tropic MuLV]SC-1 cell DNA preparation in all three cell cultures, regardless of their Fv-1 genotypes. Progeny viruses from the transfection showed N- or B-tropism corresponding to that of the parent viruses produced by the infected SC-1 cells that were used for the DNA preparation. DNA dose-response studies in NIH-3T3 cells revealed a one-hit mechanism for both the [B-tropic MuLV]SC-1 cell DNA and the [N-tropic MuLV]SC-1 cell DNA preparation. These results demonstrate that, in contrast to virion infection, transfection of N- and B-tropic MuLV with DNA preparations from chronically infected cells is not affected by the Fv-1 gene.
Specific antibody-dependent binding of complement component C1q to hapten-sensitized lipid vesicles.
Authors: Parce J W , Henry N , McConnell H M
Published: May 2006

The binding of a component of human complement (C1q) to membrane-bound specific anti-nitroxide antibodies was studied as a function of the physical properties (fluid vs. solid) of vesicle lipids. The antibodies were bound to spin-label lipid haptens in the vesicle membrane. The binding of C1q to the sensitized vesicles shows a maximum as a function of specific IgG concentration. The binding of antibodies and of C1q to the vesicle membrane does not depend strongly on the physical state of the membrane lipids. even at low hapten (0.05 mol%) concentrations. These results are of significance for the understanding of the previously reported effect of lipid physical states on complement depletion.
Characterization of two types of human papillomaviruses in lesions of epidermodysplasia verruciformis
Authors: Orth Gérard , Jablonska Stefania , Favre Michel , Croissant Odile , Jarzabek-Chorzelska Maria , Rzesa Genowefa
Published: May 2006

Human papillomaviruses (HPVs) found in lesions of 11 patients suffering from epidermodysplasia verruciformis were compared to HPV type 1 (HPV-1) and HPV type 2 (HPV-2) previously characterized in plantar and common warts, respectively. Complementary RNAs (cRNAs) to HPV-1, HPV-2, and viruses obtained from two patients with epidermodysplasia verruciformis (J.D. HPV and J.K. HPV) were used in cRNA·DNA filter hybridization experiments. No sequence homology was detected between HPV-1 or HPV-2 DNAs and DNAs obtained from the 11 epidermodysplasia verruciformis HPV isolates. Furthermore, with J.D. and J.K. HPV cRNAs, epidermodysplasia verruciformis HPV DNAs fell into two groups showing little, if any, sequence homology. A lower extent of annealing was observed for the DNAs of some isolates showing a genetic heterogeneity within each of the two groups. Almost no antigenic crossreaction was detected by immunodiffusion and indirect immunofluorescence tests, either between epidermodysplasia verruciformis HPVs and HPV-1 or HPV-2 or between J.D. and J.K. HPVs. Viruses belonging to the same group have common antigenic properties, but antigenic differences were observed when two of the viruses sharing only partial DNA sequence homology were compared. Viruses related to J.D. HPV were preferentially associated with flat wart-like lesions of epidermodysplasia verruciformis and were further found in the lesions of five patients bearing multiple flat warts. Viruses related to J.K. HPV were found in morphologically distinct lesions (red spots) present in some patients with epidermodysplasia verruciformis. Thus, we propose to distinguish two other types of HPVs designated provisionally as HPV type 3 (HPV-3) and HPV type 4 (HPV-4), with J.D. and J.K. HPVs as prototypes, respectively. Malignant conversion of some epidermodysplasia verruciformis lesions is more frequently associated with HPV-4 than with HPV-3 infection.
Identification of a polypeptide encoded by the avian sarcoma virus src gene.
Authors: Purchio A F , Erikson E , Brugge J S , Erikson R L
Published: May 2006

Two techniques were used to search for the polypeptide encoded by the avian sarcoma virus (ASV) src gene. First, antiserum from rabbits bearing ASV-induced fibrosarcomas was used to immunoprecipitate a transformation-specific antigen from ASV-transformed chick embryo fibroblasts. This antigen has an apparent molecular weight (Mr) of 60,000. Second, the 3' one-third of the ASV genome, selected by oligo(dT)-cellulose chromatography and sucrose gradient sedimentation, was translated in a mRNA-dependent reticulocyte cell-free lysate. This RNA species programmed the synthesis of a polypeptide that comigrated with the transformation-specific antigen of Mr 60,000 immunoprecipitated from transformed cells. The methionine-containing tryptic peptides from the polypeptides of Mr 60,000 obtained from translation in vitro and from immunoprecipitation were found to be identical upon two-dimensional fractionation.
Amino acid sequence of the beta chain of human fibrinogen: homology with the gamma chain.
Authors: Watt K W , Takagi T , Doolittle R F
Published: May 2006

The beta chain of human fibrinogen is composed of 452 +/- 5 amino acid residues, 14 of which are methionines. Consistent with these findings we have isolated and characterized 15 fragments after cyanogen bromide digestion of carboxymethylated beta chains. The arrangement of several of these peptides was deduced on the basis of overlapping peptides isolated from the fragments D and E produced by the plasmic digestion of fibrinogen and/or from a tryptic digest of citraconylated beta chains. Most of the other cyanogen bromide fragments can be aligned by homology with the alpha and/or gamma chains from human fibrinogen, although the positioning of a few of the smallest peptides is still ambiguous. The homology of the beta chain with the gamma chain is especially strong in certain regions of the domain that includes fragment D.
Excision of DNA segments introduced into cloning vectors by the poly(dA-dT) joining method.
Authors: Goff S P , Berg P
Published: May 2006

A method is described for excising cloned DNA segments that have been inserted into their vectors by poly(dA-dT) joins. The recombinant DNA is cleaved within the vector DNA portion by one or more restriction endonucleases to generate a linear DNA molecule with the insert DNA sequence flanked by the poly(dA-dT) joins. After denaturation, the single strands "snap back" because of the intrastrand poly(dA) and poly(dT) sequences to form circular structures with "tails" of vector DNA. The vector portion of the DNA is then digested by Escherichia coli exonuclease VII, while the insert portion remains resistant to attack. The resistant strands are annealed and purified by electrophoresis in agarose. The insert DNA segment free of contaminating vector sequences can be used as a hybridization probe and for insertion into a new vector since suitable cohesive termini are generated from the retained poly(dA) and poly(dT) tails by an appropriate exonuclease.
High-resolution 31P nuclear magnetic resonance study of rat liver mitochondria.
Authors: Ogawa S , Rottenberg H , Brown T R , Shulman R G , Castillo C L , Glynn P
Published: May 2006

Intact mitochondria were studied by high-resolution 31P nuclear magnetic resonance. Observable internal phosphate compounds included inorganic phosphate (Pi), ADP, and ATP. The internal pH was determined by the chemical shift of the internal Pi, the pK2 (6.7) of which was measured in uncoupled mitochondria. The observed equilibrium relation between the internal and the external Pi was consistent with the exchange equilibrium through the H2PO4-/OH- carrier. The internal ATP and ADP were essentially Mg2+ bound and their resonances were distinguishable from those of the external ATP and ADP by the chemical shift differences due to the Mg2+ concentration gradient and deltapH. Oxidative phosphorylation was followed by the separate resonances of Pi and adenine nucleotides both internal and external to mitochondria. From these resonances the internal and external phosphate potentials could be estimated.
Dexamethasone modulates binding and action of epidermal growth factor in serum-free cell culture
Authors: Baker Joffre B. , Barsh Gregory S. , Carney Darrell H. , Cunningham Dennis D.
Published: May 2006

Experiments probing the mechanism by which glucocorticoids modulate cell proliferation were carried out on serum-free cell cultures of quiescent human diploid foreskin (HF) cells. Added alone, the synthetic glucocorticoid dexamethasone had no effect on cell number. However, dexamethasone enhanced the mitogenic response of HF cells to epidermal growth factor (EGF) by 50% at all EGF concentrations. The mitogenic action of EGF was maximally promoted by a dexamethasone concentration of 100 ng/ml (0.25 μM).

Binding studies with
125
I-labeled EGF (
125
I-EGF) suggested that dexamethasone caused this “permissive” effect by modulating cell surface receptors for EGF. Paralleling their increased responsiveness to EGF growth stimulation, dexamethasone-treated cells exhibited a 50-100% increased ability to bind physiological concentrations of
125
I-EGF. A binding increase was apparent after a 4-hr dexamethasone treatment. The dexamethasone-treated cells maintained an increased ability to bind
125
I-EGF during the prolonged exposure to EGF that was required to stimulate cell division. Moreover, the increase in
125
I-EGF binding exhibited a dexamethasone dose-dependence similar to that for the enhancement of EGF mitogenesis, suggesting a relationship between the dexamethasone effects on binding and growth.

An investigation of the binding increase showed that it was specific for glucocorticoids, and required protein synthesis. The enhancement of
125
I-EGF binding diminished with increasing concentrations of
125
I-EGF, indicating that dexamethasone caused a qualitative change in the EGF receptors (possibly a change in receptor affinity or cooperativity). The alteration in
125
I-EGF binding may occur as part of a far-reaching dexamethasone-mediated change in the cell surface, because dexamethasone treatment slightly increased the ability of HF cells to bind
125
I-insulin, and decreased by half their ability to bind
125
I-thrombin.
Protein kinase activity associated with the avian sarcoma virus src gene product.
Authors: Collett M S , Erikson R L
Published: May 2006

Incorporation of phosphorus from [gamma-32P]ATP into protein was catalyzed by specific immunoprecipitates from avian sarcoma virus (ASV)-transformed avian and mammalian cells. This incorporation was observed only when antiserum from tumor-bearing rabbits able to specifically precipitate the ASV sarcoma gene product, p60src, was used to immunoprecipitate antigens from transformed cell lysates. Immunoprecipitates of extracts from normal cells or cells infected with a transformation-defective ASV mutant showed no activity in this assay, nor did any immune complexes formed with normal rabbit serum and any of the cell extracts tested. The expression of the protein kinase activity (ATP:protein phosphotransferase, EC 2.7.1.37) was growth temperature-dependent in cells infected with an ASV mutant temperature-sensitive for the transformation. These results on an enzymatic activity associated with the ASV transforming protein are discussed in terms of protein phosphorylation as a mechanism for viral transformation.
Adrenergic differentiation of cells of the cholinergic ciliary and Remak ganglia in avian embryo after in vivo transplantation.
Authors: Le Douarin N M , Teillet M A , Ziller C , Smith J
Published: May 2006

We have previously shown that the neural crest is regionalized early into "adrenergic" and "cholinergic" areas from which arise, respectively, the sympathetic and parasympathetic ganglioblasts of the autonomic nervous system. This regionalization does not correspond, however, to an irreversible determination of the neural crest cells since, under certain experimental conditions, cholinergic cells can arise from the adrenergic region of the crest and vice versa. The phenotypic expression of the presumptive ganglion cells appears to be responsive to the environmental conditions they encounter during and/or after their migration. In the present study we show that the developmental behavior of parasympathetic ganglion cells which have stopped migrating and at least some of which have started to differentiate into cholinergic neurons can be profoundly modified if they are transplanted into a younger embryo at the trunk neural crest level. The crest level. The grafted ganglion cells start migrating and stop in the same sites as the host neural crest cells. Their further differentiation depends on their localization. When situated in the adrenergic ganglia and in the suprarenal gland they synthesize catehcolamines, whereas they differentiate into nonfluorescent, silver-staining ganglion cells if they migrate in the gut wall. Thus, the differentiation of autonomic neurons is dependent on tissue interactions even after the neural crest cells have grouped to form ganglionic structures in which biochemical differentiation is already in progress.
Homologous nucleotide sequences between prokaryotic and eukaryotic mRNAs: the 5'-end sequence of the mRNA of the lipoprotein of the Escherichia coli outer membrane.
Authors: Pirtle R M , Pirtle I L , Inouye M
Published: May 2006

The sequence of the first 89 nucleotides at the 5' end of the mRNA for the lipoprotein of the Escherichia coli outer membrane is: GCUACAUGGAGAUUAACUCAAUCU-AGAGGGUAUUAAUAAUGAAAGCUACUAAACUGGUACU-GGGCGCGGUAAUCCUGGGUUCUACUCUG. The sequence of the first 72 nucleotides was established by direct sequencing methods and was extended to 89 residues on the basis of the known sequences of oligonucleotides obtained from complete digestion of the mRNA by ribonuclease T1 or A and the known amino acid sequence of the prolipoprotein. The mRNA has an untranslated region of 38 residues before the initiation codon, AUG. A unique feature of the 5'-end sequence of the mRNA is that the sequence of 12 nucleotides (GUAUUAAUAAUG) prior to, and including, the initiation codon is the same as that found at the ribosome-binding site for 80S ribosomes in brome mosaic virus RNA4, a eukaryotic mRNA [Dasgupta, R., Shih, D., Saris, C. & Kaesberg, P. (1975) Nature 256, 624-628].
Effect of calcium on structure and function of a hyaluronic acid matrix: Carbon-13 nuclear magnetic resonance analysis and the diffusional behavior of small solutes
Authors: Napier Mary A. , Hadler Nortin M.
Published: May 2006

Natural-abundance
13
C NMR at 25.16 MHz has been used to study a 2.5% matrix of hyaluronic acid at various degrees of polymerization and at various ionic strengths. Peak assignment is facilitated by comparing proton-decoupled and off-resonance-decoupled spectra of a hyaluronidase-depolymerized matrix with spectra from relevant monosaccharides. In contrast to the spectrum following depolymerization, the spectrum for intact matrix has considerable broadening, particularly for peaks assigned to the
N
-acetylglucosamine moiety. This is most dramatic for the hydroxymethylene carbon. With the addition of Ca
2+
above 5 mM these broadened peaks narrow and approach the sharpness observed for the hyaluronidase digest. There is no shift in resonance peak positions. These changes are quantitatively less impressive if Na
+
is substituted for Ca
2+
.

The data suggest the existence of a considerable degree of order in regions of the matrix at physiological concentrations of Ca
2+
. Within such a matrix the translational movement of lysine and glucose is enhanced relative to that in a matrix of agarose. Further addition of Ca
2+
abrogates not only matrix order, but the enhanced diffusivity as well.
Recognition site of
Escherichia coli
B restriction enzyme on ϕXsB1 and simian virus 40 DNAs: An interrupted sequence
Authors: Lautenberger James A. , Kan Nancy Chen , Lackey David , Linn Stuart , Edgell Marshall H. , Hutchison Clyde A.
Published: May 2006

Methyl groups placed on ϕXsB1 replicative form DNA by the
Escherichia coli
B modification enzyme are located in the overlap between fragments
Mbo
II-3 and
Alu
I-2, a 61-base-pair DNA segment. Mutations that led to loss of susceptibility to restriction by
E. coli
B occurred within this segment at three positions spanning 14 nucleotides. A sequence difference between ϕXsB1 and ϕX
am
3
cs
70, a ϕX174 strain not restricted by
E. coli
B, occurs at one of these positions. The site on simian virus 40 DNA methylated by the modification enzyme is located in the 115-base-pair overlap between fragments
Hae
III-I and
Alu
I-G. The sequences of these segments of ϕXsB1 and simian virus 40 DNA and two regions of phage f1 DNA recognized by the
E. coli
B restriction enzyme [Ravetch, J. V., Horiuchi, K. & Zinder, N. D. (1978)
Proc. Natl. Acad. Sci. USA
75, 2266-2270] contain a homology of nine bases in the configuration:

5′-T-G-A... 8N... T-G-C-T... 9N... T-N-N-T-3′.

The sequence 5′-T-G-A... 8N... T-G-C-T-3′ may constitute the restriction enzyme recognition site since it does not occur in ϕX
am
3
cs
70 DNA and occurs only once in simian virus 40 DNA, and since all observed mutations leading to loss of the site occur at one of the bases specified by this sequence. Analysis of the sequence of ϕX
am
3
cs
70 showed that if no other residues are recognized, all seven of these bases are essential for recognition and the interval between the two groups of specified bases must be precisely eight.
Variable region genes for the immunoglobulin framework are assembled from small segments of DNA—A hypothesis
Authors: Kabat Elvin A. , Wu Tai Te , Bilofsky Howard
Published: May 2006

Sequences of each of the four framework segments FR1, FR2, FR3, and FR4 of the variable regions (V-regions) of light and heavy chains of immunoglobulins were grouped into sets with identical sequences. Sets contained from 1 to 18 members. When each V-region was traced from one FR to the next, it was seen that members of the same set in FR1 could be associated with different sets in FR2, FR3, and FR4. This suggests that the framework for the light and heavy chain V-regions is assembled during embryonic development from sets of minigenes for each FR segment. FR4 from three sets of human V

k

I chains also contained members of V

k

II, V

k

III, and V

k

IV subgroups; one FR2 set contained eight rabbit V

k

, one human V

k

IV, and four mouse V

k

and an FR4 set contained two human V
H
III and one mouse V
H
III, indicating substantial evolutionary preservation of these sequences and suggesting that the sets of minigenes are highly conserved in the germ line. The clone of Tonegawa
et al
. [Tonegawa, S., Maxam, A. M., Tizard, R., Bernard, O. & Gilbert, W. (1978)
Proc. Natl. Acad. Sci. USA
75, 1485-1489] could be a hybrid FR1 and FR3 coming from minigenes of MOPC 315 (a V
λ
II) whereas FR2 would come from MOPC 104E (a V
λ
I). That FR4 is not joined to the rest of the V-region in 12-day-old mouse embryo DNA is also in accord with this hypothesis. Mouse sperm DNA should be examined to establish whether the hypothesized minigenes are separated by intervening sequences and whether the complementarity-determining (hypervariable) regions or segments of the V-region are separated from the framework in genomic DNA. Sperm DNA from rabbits or other species could be used to search for minigene segments whose sequences are identical in several species.
Ovarian ornithine decarboxylase regulation in the immature, the pubescent, and the pseudopregnant rat.
Authors: Nureddin A
Published: May 2006

Ovarian ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) regulation was investigated in immature, pubescent, and pseudopregnant rats. After initial induction of the enzyme by injection of lutropin in the immature rat, continued daily injections resulted in a graded decrease in the activity of the enzyme. In the 32-day-old rat, the induction and subsequent decline in enzymic activity after a single injection of lutropin could only be partially reversed by injections of the hormone at 4-hr intervals. This decrease could not be attributed to a decrease in ovarian in vivo uptake of the hormone. In the pseudopregnant rat, ovarian ornithine decarboxylase is highly refractory to induction by either a single injection or repeated injections of lutropin. This refractoriness occurs despite a 2- to 3-fold increase in ovarian in vivo uptake of the hormone compared to that in the 32-day-old rat. It is suggested that the refractoriness observed with all three tissues is a function of cell differentiation.