bluuebunny/crossref_metadata_2025 huggingface dataset:
Esterification of Low Density Lipoprotein Cholesterol in Human Fibroblasts and Its Absence in Homozygous Familial Hypercholesterolemia
Authors: Goldstein Joseph L. , Dana Suzanna E. , Brown Michael S.
Published: May 2006

A new mechanism is described for the cellular esterification of cholesterol derived from extra-cellular lipoproteins. Incubation of monolayers of cultured fibroblasts from normal human subjects with low density lipoproteins led to a 30- to 40-fold increase in the rate of incorporation of either [
14
C]acetate or [
14
C]oleate into the fatty acid fraction of cholesteryl [
14
C]esters. This stimulation of cholesteryl ester formation by low density lipoproteins occurred despite the fact that endogenous synthesis of free cholesterol was completely suppressed by the lipoprotein. Thus, exogenous cholesterol contained in low density lipoproteins, rather than endogenously synthesized sterol, appeared to provide the cholesterol substrate for this cellular esterfication process. High density lipoproteins and the lipoprotein-deficient fraction of serum neither stimulated cholesteryl ester formation nor inhibited cholesterol synthesis. Both the low density lipoprotein-dependent increase in cholesterol esterification and decrease in free cholesterol synthesis required the interaction of the lipoprotein with its recently described cell surface receptor. Cells from homozygotes with familial hypercholesterolemia, which lack specific low density lipoprotein receptors, showed neither lipoprotein-dependent cholesterol esterification nor suppression of cholesterol synthesis. The reciprocal changes in free cholesterol synthesis and cholesteryl ester formation produced by low density lipoprotein-receptor interactions may play an important role in the regulation of the cholesterol content of mammalian cells.
Effects of Inducers and Epoxide Hydrase on the Metabolism of Benzo[
a
]pyrene by Liver Microsomes and a Reconstituted System: Analysis by High Pressure Liquid Chromatography
Authors: Holder Gerald , Yagi Haruhiko , Dansette Patrick , Jerina Donald M. , Levin W. , Lu Anthony Y. H. , Conney A. H.
Published: May 2006

The mobilities of 24 potential metabolites of benzo[
a
]pyrene were examined with high pressure liquid chromatography. Twelve phenols, five quinones, four dihydrodiols, and three oxides were studied. The chromatographic procedure employed allowed the separation and quantitation of benzopyrene metabolites into three major groups consisting of phenols, quinones, and dihydrodiols. Two of the benzopyrene oxides were unstable during chromatography, whereas the third oxide was more stable and chromatographed in the quinone fraction.

Treatment of rats with phenobarbital or 3-methylcholanthrene enhanced the metabolism of benzopyrene by liver microsomes and altered the relative amounts of the various metabolites formed. In the absence of epoxide hydrase (EC 4.2.1.63), benzopyrene was metabolized primarily to phenols and quinones but was not appreciably metabolized to dihydrodiols by a solubilized, reconstituted cytochrome
P
-448 monooxygenase system. Addition of partially purified epoxide hydrase resulted in the formation of benzopyrene dihydrodiols with a concomitant decrease in the formation of phenolic metabolites, indicating that benzopyrene undergoes metabolism via arene oxides that are precursors for dihydrodiols and phenols.
Significance of Plasma Dopamine β-Hydroxylase Activity as an Index of Sympathetic Neuronal Function
Authors: Reid John L. , Kopin Irwin J.
Published: May 2006

Plasma norepinephrine and dopamine β-hydroxylase (EC 1.14.17.1) activity were measured in rats. Adrenergic neuron blockade with bretylium for 4 hr and ganglion blockade with chlorisondamine for 72 hr lowered plasma norepinephrine. Neither treatment altered plasma dopamine β-hydroxylase activity. Phenoxybenzamine for up to 48 hr markedly raised plasma norepinephrine and transiently lowered plasma dopamine β-hydroxylase at 24 hr. Prolonged pharmacological modification of sympathetic nervous activity and plasma norepinephrine were not attended by parallel changes in circulating dopamine β-hydroxylase activity. Plasma dopamine β-hydroxylase activity does not appear to be a sensitive index of prolonged alterations in sympathetic neural activity. Norepinephrine in plasma, however, appears to reflect sensitively and accurately the rate of release of the neurotransmitter.
Sarcoma-Virus-Related RNA Sequences in Normal Rat Cells
Authors: Tsuchida Nobuo , Gilden Raymond V. , Hatanaka Masakazu
Published: May 2006

A rat type C virus spontaneously activated from the NRK (normal rat kidney) cell line was found to have two major size classes of viral RNA subunits sedimenting at 35 and 30 S. Virus-producing cells contained both RNA species, while normal “virus-free” rat cells contained primarily virus-specific 30S RNA species. A DNA transcript, specific for Kirsten sarcoma virus, prepared from virus activated in nonproducer BALB/c cells originally transformed by Kirsten sarcoma virus and rendered specific for the virus by absorption of sequences related to mouse helper virus hybridized only with the 30S RNA species of virus-producing rat cells and normal rat cells. These findings are consistent with the hypothesis that sarcoma-specific nucleic acid sequences in kirsten sarcoma virus emerged through a process that incorporated some portions of 30S RNA species from rat cells (either normal or virus-producing) into the Kirsten leukemia virus during passage
in vivo
of that virus. The virus designated M-MSV(RaLV), which originally derived from tumor induced by Moloney sarcoma virus (M-MSV) in rats, contained 35S RNA species of rat type C viruses and 30S RNA species specific for both rat and mouse viruses. It appears striking that for these two animal species, sarcoma-virus-specific information resides on a 30S subunit.
The Chemical and Biological Effects of
cis
-Dichlorodiammineplatinum (II), an Antitumor Agent, on DNA
Authors: Munchausen Linda L.
Published: May 2006

cis
-Dichlorodiammineplatinum (II) binds irreversibly to the bases in DNA; the amount of platinum complex bound can be determined from changes in the ultraviolet absorption spectrum. As the ratio of platinum to phosphate is increased, an increasing inactivation of bacterial transforming DNA is observed. At a ratio that corresponds to spectrometric saturation, transforming activity is inactivated >10
5
-fold. The
trans
isomer of the platinum complex, which is not effective against tumors, induces a similar inactivation of transforming DNA but with half the efficiency, indicating a different mode of binding. The sensitivity to inactivation by
cis
isomer varies slightly with the genetic marker assayed but is not dependent on the excision repair system. Uptake of DNA by competent cells is unaffected by bound platinum complex; however, integration of platinum-bound transforming DNA into the host genome decreases as the mole fraction of platinum increases. This loss of integration parallels the decreased transforming activity of the DNA. Although the drug induces interstrand crosslinks in DNA
in vitro
, these crosslinks are relatively rare events and cannot account for the observed inactivation.
Intra
molecular Hydrogen Bonding in Flavin Adenine Dinucleotide
Authors: Raszka Matthew , Kaplan Nathan O.
Published: May 2006

Data obtained by means of proton magnetic resonance spectroscopy indicate that specific association of FMN occurs with AMP in aqueous solution, because much weaker interaction is observed with FMN of either GMP or CMP. A comparison of FAD with a 1:1 mixture of FMN and AMP suggests that the flavin is involved in an
intra
molecular hydrogen bonding with the adenine moiety of FAD. The temperature dependence of chemical shifts would seem to indicate that the pyrophosphate linkage acts to reinforce stacking interactions as well as hydrogen bonding in the coenzyme. The linkage also limits the number of cyclic hydrogen bonding configurations, and a model is proposed to describe a fraction of unstacked FAD in aqueous solution.

A parallel study was made of NAD
+
and its analogues; in contrast to FAD, no clear evidence of cyclic hydrogen bonding was obtained with the pyridine coenzymes.
Antibody to Myosin: The Specific Visualization of Myosin-Containing Filaments in Nonmuscle Cells
Authors: Weber Klaus , Groeschel-Stewart Ute
Published: May 2006

Myosin in human, rat, mouse, and chicken fibroblasts was localized by indirect immunofluorescence microscopy using antibodies prepared in rabbits against highly purified chicken gizzard myosin. Filaments containing myosin span the interior of the cells and are often parallel to each other. The majority of the fibers are concentrated toward the adhesive side of the cell. Most of the myosin-containing filaments show “interruptions” or “striations.” From a comparison of these fibers in fluorescence and phase microscopy and from previous results on actin-containing fibers, we conclude that at least some of the cytoplasmic myosin can be found in the actin-containing fibers, which themselves have been shown to be very similar or identical to the microfilament bundles. The occurrence of both myosin and actin in the microfilament bundles provides a basis for the motility and contractility of the cell.
Viable Molecular Hybrids of Bacteriophage Lambda and Eukaryotic DNA
Authors: Thomas Marjorie , Cameron John R. , Davis Ronald W.
Published: May 2006

A bacteriophage λ strain has been constructed and a method developed by which DNA from potentially any source can be covalently inserted through
Eco
RI cohesive ends into the middle of the λ DNA. These hybrid DNAs can infect nonrestricting
Escherichia coli
cells and can then propagate as plaque-forming phage. A unique feature of this λ strain is that extra DNA in the middle of its genome is required for plaque formation. A large number of such phages have been produced with
E. coli
DNA and
Drosophila melanogaster
DNA.
Selective Degradation of Abnormal Proteins in Mammalian Tissue Culture Cells
Authors: Capecchi Mario R. , Capecchi Nancy E. , Hughes Stephen H. , Wahl Geoffrey M.
Published: May 2006

The degradation rates of several missense mutants of hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8) in mouse L cells are compared to those of the wild-type enzyme. Although the rates of total protein breakdown in the mutant cell lines are identical to that of the parental L cell line, defective molecules of hypoxanthine-guanine phosphoribosyltransferase present in the mutant cell lines are degraded much faster than the wild-type enzyme. The level of defective phosphoribosyltransferase molecules present in the mutant cell lines is inversely proportional to the breakdown rate. This observation indicates that the major factor determining the concentrations of the defective phosphoribosyltransferases is their specific degradation rate. These results strongly support the hypothesis that abnormal proteins are selectively degraded in mammalian cells.
Hormonal Control of Messenger Ribonucleic Acid Metabolism in Barley Aleurone Layers
Authors: Ho David Tuan-Hua , Varner J. E.
Published: May 2006

Ribonucleic acid containing poly(adenylic acid) [poly(A)-RNA] is present in barley aleurone layers. This poly(A)-RNA becomes labeled with radioactive precursors of RNA during the incubation of isolated aleurone layers with or without gibberellic acid. However, the rate of synthesis of poly(A)-RNA is enhanced by gibberellic acid. This enhancement begins within 3-4 hr of addition of the hormone and reaches a maximum, which is about 50-60% over the control, 10-12 hr after addition of the hormone. Cordycepin inhibits total RNA as well as poly(A)-RNA synthesis in barley aleurone layers. However, cordycepin inhibits the hormone-controlled synthesis of α-amylase (EC 3.2.1.1) only if it is added 12 hr or less after gibberellic acid. The insensitivity of α-amylase production to cordycepin after 12 hr of gibberellic acid treatment suggests that α-amylase is translated from stable messenger RNA.
Gene Frequency Comparisons Between Taxa: Support for the Natural Selection of Protein Polymorphisms
Authors: Ayala Francisco J. , Gilpin Michael E.
Published: May 2006

The hypothesis has been advanced that the pervasive protein variation found in natural populations of many organisms is adaptively neutral, and thus not subject to natural selection. This neutrality hypothesis predicts that at polymorphic gene loci different configurations of allelic frequencies will occur in different species. Results of an extensive study of protein variation in several species of
Drosophila
show that any two species have very similar allelic frequencies at a substantial proportion of all gene loci, while at many other loci the species have very different sets of alleles. Genetic distances have been calculated between pairs of subspecies, morphologically similar species, and morphologically different species. The distribution of genetic distances is strikingly different from the predictions of the neutrality theory. Protein variation appears to be maintained by natural selection.
Spontaneous Current Pulses Through Developing Fucoid Eggs
Authors: Nuccitelli Richard , Jaffe Lionel F.
Published: May 2006

Using a newly developed, extracellular vibrating electrode, we can now measure the electrical currents that traverse a single developing cell. We have studied the eggs of the common seaweed,
Pelvetia
, during their first 2 days of development and find that the endogenous electrical current through them includes a pulse component as well as a relatively steady component. Both of these enter the egg's growing tip and leave the rest of the embryo. The current pulses first appear a few hours after growth begins and have a characteristic shape that is independent of amplitude. They have a duration of about 100 sec, an average frequency of 1-5 per hr, and enter with peak surface intensities of 3-10 (and rarely up to 30) μA/cm
2
. By the two-cell stage they account for about a fourth of the total transembryonic current. Since they may overlap to any degree and (as is documented elsewhere) are generally accompanied by peak membrane depolarizations of only 2-6 mV, their course does not seem to be voltage-controlled. Thus, they seem essentially different from action potentials. We also find that the rate at which the egg grows in length is roughly proportional to the size of the steady current traversing it.
Isolation and Characterization of the Carboxypeptidase Y Inhibitor from Yeast
Authors: Matern Heidrun , Hoffmann Marion , Holzer Helmut
Published: May 2006

Rapid acetone fractionation of crude yeast extract at low temperature separates carboxypeptidase Y inhibitor from the carboxypeptidase Y-inhibitor complex. On a protein basis the inhibitor has been purified 890-fold, resulting in homogeneity as determined by disc electrophoresis and filtration on Sephadex G-75. The molecular weight was calculated to be about 25,000. The inhibitor is heat-labile in crude extracts, whereas in the purified form it loses only 11% of its activity when it is heated at 100° for 5 min. The inhibitor is inactivated by the yeast proteinases A (EC 3.4.23.8) and B (EC 3.4.22.9), respectively, but not by carboxypeptidase Y (EC 3.4.12.8). The inhibitor inhibits carboxypeptidase Y at a 1.5:1.0 protein-based weight ratio by 80%. At the same concentration ratios, proteinases A and B from yeast, as well as bovine pancreas carboxypeptidases A and B, are not inhibited.
Viable Deletion Mutants of Simian Virus 40: Selective Isolation by Means of a Restriction Endonuclease from
Hemophilus parainfluenzae
Authors: Mertz Janet E. , Berg Paul
Published: May 2006

Resistance of simian virus 40 (SV40) DNA to cleavage by
Hemophilus parainfluenzae
II (
Hpa
II) restriction endonuclease has been used as a positive,
in vitro
selection for mutants lacking the one
Hpa
II endonuclease-cleavage site of wild-type SV40 DNA. Each of 10 viable mutants isolated by this procedure multiplies significantly more slowly than wild-type virus and contains a small deletion (80 to 190 base pairs in size) of the region of the genome that includes the
Hpa
II endonuclease-recognition sequence. These well-defined mutants, having a selective disadvantage for growth, would not have been readily obtained by conventional methods used to screen for viral mutants. Therefore, in certain circumstances, restriction endonucleases are effective reagents for the selection of new classes of mutants. Because these small deletions can be visualized in heteroduplexes, these mutants provide internal markers for mapping other alterations or features of the simian virus 40 genome.
Synthesis of Complementary RNA Sequences During Productive Adenovirus Infection
Authors: Pettersson Ulf , Philipson Lennart
Published: May 2006

Liquid RNA·DNA hybridization with separated strands of adenovirus type 2 DNA revealed that late nuclear RNA can hybridize to about 85% of the 1-strand and 10-15% of the h-strand, whereas late cytoplasmic RNA hybridizes to 65-70% and 25% of the l- and h-strand, respectively. With separated strands from the six
Eco
RI fragments of adenovirus type 2 DNA as probes, it was shown that late nuclear RNA hydridizes to 85-90% of the l-strand from all six
Eco
RI fragments. Since late cytoplasmic RNA hybridizes to 40-50% of the h-strand from both fragments
Eco
RI-B and
Eco
RI-C, complementary viral RNA sequences are synthesized during adenovirus infection. Complementarity between nuclear and cytoplasmic RNA could also be demonstrated by showing that late cytoplasmic RNA which had been preincubated with late nuclear RNA hybridized to a smaller fraction of the h-strand of fragment
Eco
RI-C than without preincubation. Double-stranded RNA which contains sequences that correspond to at least 60% of the viral genome was isolated from infected cells. However, less than 2% of the newly synthesized late RNA became double-stranded after incubation under annealing conditions, which suggests that RNA derived from one of the strands is present at a low concentration. Accordingly, it was shown that nearly all viral cytoplasmic RNA which is synthesized late after infection is derived from the l-strand.
Reverse Transcriptase: Correlation of Zinc Content with Activity
Authors: Poiesz Bernard J. , Seal Gita , Loeb Lawrence A.
Published: May 2006

Evidence is presented that DNA polymerase of avian myeloblastosis virus has an obligatory zinc requirement for activity. Previous studies indicate that the purified polymerase contains zinc in a stoichiometry of about 1 g-atom/mole. We now find that the enzyme-bound zinc is exchangeable with radioactive
65
Zn; after isoelectric focusing, the radioactive
65
Zn is coincident with polymerase activity. Dialysis of the
65
Zn-labeled polymerase against the chelator, 1,10-phenanthroline, results in a progressive loss of radioactive
65
Zn and polymerase activity. Thereupon, incubation of the inactivated enzyme with Zn
2+
fully restores activity. Thus, the DNA polymerase present in an oncogenic RNA virus, like animal DNA polymerases, can be rigorously classified as a zinc metalloenzyme. DNA polymerase of avian myeloblastosis virus is inactivated by 1,10-phenanthroline at a much faster rate than the bacterial and animal DNA polymerases that have been tested. It may, therefore, be possible to inactivate selectively DNA polymerases from animal tumor viruses by brief exposure to appropriate metal chelators.
Initiator RNA in Discontinuous Polyoma DNA Synthesis
Authors: Reichard Peter , Eliasson Rolf , Söderman Gunilla
Published: May 2006

During replication of polyoma DNA in isolated nuclei, RNA was found attached to the 5′ ends of growing progeny strands. This RNA starts with either ATP or GTP and can be labeled at its 5′ end with
32
P from β-labeled nucleotides. Digestion of progeny strands with pancreatic DNase released
32
P-labeled RNA that, on gel electrophoresis, gave a distinct peak in the position expected for a decanucleotide. We believe that this short RNA is involved in the initiation of the discontinuous synthesis of DNA and propose the name “initiator RNA” for it. The covalent linkage of initiator RNA to 5′ ends of growing DNA chains was substantiated by the finding that
32
P was transferred to ribonucleotides by alkaline hydrolysis of purified initiator RNA obtained by DNase digestion of polyoma progeny strands synthesized from [α-
32
P]dTTP. While initiator RNA was quite homogeneous in size, it had no unique base sequence since digestion with pancreatic RNase of initiator RNA labeled at its 5′ end with
32
P released a variety of different [
32
P]oligonucleotides. The switch from RNA to DNA synthesis during strand elongation may thus depend on the size of initiator RNA rather than on a specific base sequence.
Studies on the Reverse Transcriptase of RNA Tumor Viruses. Structural Relatedness of Two Subunits of Avian RNA Tumor Viruses
Authors: Gibson Wade , Verma Inder M.
Published: May 2006

The structural relationship of the small (α) and large (β) subunits of reverse transcriptase isolated from two avian RNA tumor viruses has been examined by tryptic peptide analysis. Comparison of the tryptic hydrolysates of the isolated subunits by two-dimensional separation on thin-layer cellulose plates indicates that (
i
) the α subunit of reverse transcriptase of avian myeloblastosis virus is structurally related to the β subunit; (
ii
) the α and β subunits of the enzyme of Rous sarcoma virus also appear to be related; and (
iii
) there appears to be an extensive amino-acid sequence homology between reverse transcriptases of avian myeloblastosis virus and Rous sarcoma virus. Evidence is also presented that both α and β subunits can be identified in purified avian myeloblastosis virions.
Proton-Enhanced
13
C Nuclear Magnetic Resonance of Lipids and Biomembranes
Authors: Urbina Julio , Waugh J. S.
Published: May 2006

A recently developed nuclear double resonance technique which permits sensitive detection, together with high resolution, of rare spins in solids or other dipolar-coupled nuclear systems [Pines, Gibby, and Waugh (1973)
J. Chem. Phys.
59, 569] has been applied to the study of natural abundance
13
C-nuclear magnetic resonance in lipid mesophases and of selectively labeled carbon sites in bacterial membranes.

Detailed microscopic information on the molecular organization and phase transitions of the lipid phases and their interaction with ions and other molecules can be obtained from the study of the chemical shift anisotropies and dynamical aspects of the
13
C NMR spectra of
unsonicated
lipid dispersions (liposomes). Experiments are reported which demonstrated the feasibility of quantitatively observing the
13
C-nuclear magnetic resonance of specifically labeled sites in unperturbed
Escherichia coli
membrane vesicles for the study of the physical state of the lipids with the aim of relating it to the known lipid-dependent functional properties of the membranes.
Electron Diffraction of Wet Phospholipid Bilayers
Authors: Hui S. W. , Parsons D. F. , Cowden M.
Published: May 2006

The structure of fully hydrated dipalmitoyl lecithin single bilayers, and monolayers deposited on Formvar substrates are studied by electron diffraction, using a hydration stage fitted to an electron microscope. Selective area diffraction patterns of these films indicate that there are domains consisting of mosaics of crystallites of hexagonally packed lipid chains. The size of these domains are typically several μm in diameter. The diffraction intensity agrees with that calculated from the electron scattering factor of the hydrocarbon chains of the lipid molecule.
Transformation by Simian Virus 40 of Spleen Cells from a Hyperimmune Rabbit: Demonstration of Production of Specific Antibody to the Immunizing Antigen
Authors: Strosberg A. D. , Collins J. J. , Black P. H. , Malamud D. , Wilbert S. , Bloch K. J. , Haber E.
Published: May 2006

Extracts of spleen cells obtained from a rabbit hyperimmunized with Type III pneumococcal vaccine and transformed with simian virus 40, were subjected to agarose gel electrophoresis in the presence of an [
125
I]S3 polysaccharide-protein conjugate. Binding of radioactivity in the gamma globulin region was observed. Extracts and media obtained from labeled cell cultures contained a protein that bound to an S3, but not to an S8 or inactivated S3 immunoadsorbent. After elution, the bound protein showed a single band on isoelectric focusing which corresponded in isoelectric point to one of the serum anti-S3 antibodies of the donor rabbit. These observations strongly suggest that a normal committed lymphoid cell may be brought into continuous culture by virus transformation and yet retain its ability to synthesize specific antibody.
A Kinase That Transfers the γ-Phosphoryl Group of GTP to Proteins of Eukaryotic 40S Ribosomal Subunits
Authors: Ventimiglia Frank A. , Wool Ira G.
Published: May 2006

An enzyme in rat-liver cytosol transferred the γ-phosphoryl of GTP to serine and threonine residues of at least four proteins (S6, S10, S14 or S15, and S17) of the small (40S) subunit of rat-liver ribosomes. A number of nonribosomal proteins in the enzyme preparation were also phosphorylated; they were preferentially and tightly bound to the large subunit. The enzyme could be distinguished from protein kinase-ATP (which also phosphorylated ribosomal proteins) by a number of criteria: (
1
) GTP was the phosphoryl donor; (
2
) the pattern of phosphorylation of ribosomal proteins by the two enzymes was different; and (
3
) the protein kinase that used GTP as the phosphoryl donor was not stimulated by cyclic AMP (or by cyclic GMP).
Inhibition of Bacterial Growth by β-Chloro-D-Alanine
Authors: Manning James M. , Merrifield Nancy E. , Jones Wanda M. , Gotschlich Emil C.
Published: May 2006

The D- and L-isomers of β-chloroalanine inhibit the growth of
Diplococcus pneumoniae, Streptococcus pyogenes, Bacillus subtilis
, and
Escherichia coli
. With pneumococcus the inhibition by β-chloro-D-alanine is completely prevented by either D-alanine or D-alanyl-D-alanine, while L-alanine is not effective in preventing the inhibition. The inhibition of growth by β-chloro-L-alanine is not affected by D-alanine and is only partially prevented by high concentrations of L-alanine. The intracellular free alanine in untreated
E. coli
and
B. subtilis
is about 95% in the D-configuration while the free intracellular alanine in both organisms after treatment with β-chloro-D-alanine is predominantly the L-isomer. These results suggested that the β-chloroamino acid inactivates alanine racemase (EC 5.1.1.1). Indeed, when extracts of
E. coli
or
B. subtilis
were treated with β-chloro-D-alanine, the activities of alanine racemase and of D-glutamate-D-alanine transaminase were found to be 90-95% inhibited. Studies with mice have shown that β-chloro-D-alanine is an effective antibacterial agent
in vivo
againt
D. pneumoniae, S. pyogenes
, and
E. coli
.
A Colinear Map Relating the Simian Virus 40 (SV40) DNA Segments of Six Adenovirus-SV40 Hybrids to the DNA Fragments Produced by Restriction Endonuclease Cleavage of SV40 DNA
Authors: Lebowitz Paul , Kelly Thomas J. , Nathans Daniel , Lee T. N. H. , Lewis Andrew M.
Published: May 2006

The simian virus 40 (SV40) DNA segments present in a series of adenovirus-SV40 hybrids have been mapped with respect to the sites of cleavage of SV40 DNA by restriction endonucleases. Two approaches have been used. First, nucleic acid hybridizations were performed between equimolar quantities of the denatured DNAs of SV40 and each hybrid virus and the radiolabeled transcripts of 11 DNA fragments obtained by cleavage of SV40 DNA by restriction endonuclease from
Hemophilus influenzae
. Secondly, selected fragments of SV40 DNA produced by the
H. influenzae
or
H. parainfluenzae
restriction endonucleases were used to form heteroduplex DNA molecules with adenovirus and adenovirus-SV40 hybrid DNA, which were then analyzed by electron microscopy. The two sets of data were consistent and have permitted alignment of the map of the SV40 segments of the hybrid viruses with the
H. influenzae
and
H. parainfluenzae
cleavage maps of SV40. Since cells infected with some of the hybrid viruses contain one or more SV40-specific antigens, the genetic determinants of these antigens could be localized on the cleavage map.
An
Escherichia coli
Mutant with an Altered Elongation Factor Tu
Authors: Lupker J. H. , Verschoor G. J. , De Rooij F. W. M. , Rörsch A. , Bosch L.
Published: May 2006

A thermosensitive mutant of
Escherichia coli
has been isolated that is unable to replicate the bacteriophage MS2 at 42° but permits phage production at 37°. Thermal inactivation studies of the supernatant enzymes show that this mutant contains a factor essential for the polymerization of phenylalanine from phenylalanyl-tRNA that at 50° is more rapidly inactivated than the corresponding wild-type factor. The elongation factor Tu (EF-Tu) was isolated and purified to apparent homogeneity as the EF-Tu·GDP complex, both from mutant and wild-type cells.

Addition of purified wild-type EF-Tu·GDP to reaction mixtures fully restored the activity of thermally inactivated mutant supernatants. These experiments excluded EF-Ts as the thermolabile factor involved. Similar inactivation studies, dealing with the purified factors and performed in reaction mixtures that were not supplemented with GDP, revealed that the half-life of mutant EF-Tu·GDP at 50° was 1.5 min, that of the wild-type factor 6 min. Addition of GDP (10μM) to the medium reduced the inactivation rate of both wild-type and mutant factor and also the difference in inactivation kinetics. Besides the altered elongation factor Tu, the mutant skill contains a second mutation affecting the glutaminyl-tRNA synthetase.
Multiple Regulation of Galactose Operon—Genetic Evidence for a Distinct Site in the Galactose Operon that Responds to
capR
Gene Regulation in
Escherichia coli
K-12
Authors: Hua Sui-Sheng , Markovitz Alvin
Published: May 2006

Previous results demonstrated that the
capR
(
lon
) locus, which is not linked to the
gal
operon, independently controls the synthesis of the
gal
operon enzymes and
gal
mRNA, i.e.,
galO
+
capR9
strains are derepressed 4- to 6-fold as compared to
galO
+
capR
+
strains. A mutation has been isolated and localized in the galactose operator region that defines a new and distinct site of control. Mutation in this site, designated

galO

capR
+

, causes a 4-fold increase in the galactose enzymes, galactokinase (EC 2.7.1.6) and UDP-galactose-4-epimerase (EC 5.1.3.2), in a
capR
+
background. These mutants exhibit a reduced response to regulation by the unlinked regulator gene
capR
(
lon
). However, the

galO

capR
+

mutants are still subject to control by the
galR
repressor, since they can be further derepressed by growth in the presence of D-fucose. They also synthesize more galactokinase when grown in glycerol as compared to glucose. Thus there are now at least three, and probably four, sites for control of mRNA synthesis in the operator-promoter regions of the
gal
operon, making it one of the most complex control systems to date for a single operon in bacteria. The complexity is sufficient to accommodate models for differentiation in higher organisms that require more than one “switch” to control a single group of genes.
The Molecular Basis of Self-Association of Antibodies to IgG (Rheumatoid Factors) in Rheumatoid Arthritis
Authors: Pope Richard M. , Teller David C. , Mannik Mart
Published: May 2006

The serum and synovial fluid of many patients with rheumatoid arthritis contain immune complexes composed of immunoglobulin G (IgG). In this study such complexes from one patient are shown to be formed by self-association of IgG-antibodies to IgG (IgG-rheumatoid factors), so that each molecule serves as an antibody as well as an antigen. All F(ab′)
2
and Fab′ fragments derived from these complexes have antibody binding sites for normal IgG. Due to a high association constant in the formation of a cyclic complex by these antibodies, normal IgG is excluded as an antigen. These studies serve as a model for further elucidation of presence of similar immune complexes in the serum and synovial fluid of patients with rheumatoid arthritis.
Beginnings of Village-Farming Communities in Southeastern Turkey−1972
Authors: Braidwood Robert J. , Cambel Halet , Lawrence Barbara , Redman Charles L. , Stewart Robert B.
Published: May 2006

The mound known as Çayönü Tepesi (38° 16′ N; 39° 43′ E) in southeastern Turkey is one of the increasing number of early village sites which, since World War II, have been excavated archeologically in greater southwestern Asia. The evidence recovered in the autumn 1972 campaign of the Joint Istanbul-Chicago Prehistoric Project is briefly described, with particular attention to Çayönü's architectural remains, which are most remarkable, considering the site's date of about 7000 B.C. There was evidence of domesticated food plants from the beginning but animal domesticates were not present (save the dog) until later in the major prehistoric phase of occupation.
Multiple Forms of DNA Polymerase in Mouse Myeloma
Authors: Matsukage A. , Bohn E. W. , Wilson S. H.
Published: May 2006

Five distinct forms of DNA polymerase (deoxynucleosidetriphosphate: DNA deoxynucleotidyltransferase, EC 2.7.7.7) were separated from extracts of mouse myeloma MOPC-104E using a fractionation procedure based upon sequential ion-exchange column chromatography. The enzymes were characterized according to sedimentation behavior, subcellular localization, chromatographic behavior on hydroxyapatite columns, and reaction properties. The results indicate that myeloma contains two enzymes that appear to correspond to well characterized DNA polymerases found in many other mammalian tissues, a 6S DNA polymerase localized in the cytoplasmic supernatant fraction, and a lower molecular weight (2-3S) DNA polymerase. Also present were a second 6S DNA polymerase localized exclusively in the nuclear fraction and a 6-8S DNA polymerase localized in the cytoplasmic membrane fraction. The enzyme in the cytoplasmic membrane fraction, which accounted for the predominant activity in the myeloma, was active with poly(rA)·(dT)
12-18
as template-primer, but not with activated calf thymus DNA. The detection of this distinct 6-8S membrane-bound DNA polymerase is of particular interest.
Gene Activation in Eukaryotes: Are Nuclear Acidic Proteins the Cause or the Effect?
Authors: Pederson Thoru
Published: May 2006

Nuclear acidic proteins have been implicated in the positive control of gene transcription in eukaryotes. This hypothesis was examined in greater detail by analysis of these proteins during experimental gene activation by a technique for fractionating nuclei into chromatin and the ribonucleoprotein particles that contain heterogeneous nuclear RNA. When synthesis of rat-liver heterogeneous nuclear RNA was stimulated by administration of hydrocortisone, there was a parallel increase in the labeling of acidic proteins in ribonucleoprotein particles. However, there was no detectable effect on the labeling of either acidic chromatin proteins or histones. Thus, the nuclear acidic proteins that respond to the hormone are concerned with a post-transcriptional event, namely the assembly and processing of ribonucleoprotein particles that contain heterogeneous RNA, rather than with direct gene activation. Increases in synthesis of “chromatin” acidic proteins during gene activation observed by others may reflect the presence of these ribonucleoprotein particles in crude chromatin preparations.
Translational Reinitiation: Reinitiation of
lac
Repressor Fragments at Three Internal Sites Early in the
lac i
gene of
Escherichia coli
Authors: Files James G. , Weber Klaus , Miller Jeffrey H.
Published: May 2006

Three early amber mutations in the
lac i
gene have been shown to arise from the codons corresponding to residues 7, 12, and 17 of the
lac
repressor polypeptide chain. All three mutations allow translational reinitiation at the same two sites, resulting in the synthesis of two
lac
repressor fragments. The amino-terminal sequences of these fragments show that the first site is the triplet coding for valine residue 23, while the second is the first internal in-phase AUG codon corresponding to residue 42.

Translational reinitiation appears to be a common event in
E. coli
, since there are at least three such sites in the first 70 in-phase codons of the
i
-gene messenger RNA, and all amber mutants found in this region show translational reinitiation. Only one of these sites involves an AUG codon; the other two involve an
in vivo
ambiguity of the genetic code, in that the same codon can be translated into two different amino acids depending on whether it is recognized during initiation or elongation of protein biosynthesis. The two non-AUG codons are the codons corresponding to leucine residue 62 and valine residue 23 of the
lac
repressor.
A Preliminary Map of the Major Transcription Units Read by T7 RNA Polymerase on the T7 and T3 Bacteriophage Chromosomes
Authors: Golomb Miriam , Chamberlin Michael
Published: May 2006

Transcription of T7 DNA by T7 RNA polymerase
in vitro
gives rise to six major size classes of RNAs comprising seven major T7 RNA species. These RNAs are all read from the r-strand of T7 DNA and are not derived from the early (leftmost on the conventional genetic map) region of the molecule. When artifically shortened T7 DNA templates are transcribed, four (I, II, IIIb, and VI) of the seven species are found to be truncated or deleted. This indicates that all are terminated near the right end of the T7 DNA molecule, probably at a common termination site near 98.5%. (Map positions are all given in terms of percentage of total length measured from the left end of the molecule.) Since the approximate lengths of the transcripts are known, the promotor sites for T7 RNA species I, II, IIIb, and VI are tentatively mapped at 56, 64, 83, and 97% on the T7 chromosome. Only a single major T3 RNA is transcribed by T7 RNA polymerase; analysis of transcripts directed by shortened T3 DNA templates indicates it is analogous to T7 RNA species IIIb. Hence the promotor and terminator sites for T3 species IIIb are tentatively mapped at 83 and 98.5%, respectively, on the T3 chromosome. The major transcripts read by T7 RNA polymerase from T3-T7 hybrid phage DNAs vary, depending on which regions of the T7 chromosome are present. This provides an alternative method of mapping the strong T7 promotor sites on the T7 chromosome.
Prediction of Secondary Structure of Proteins. A Comparison of the ϕ,Ψ Angles Previously Predicted for Cytochrome
c
with Recent X-Ray Crystallographic Findings
Authors: Kabat Elvin A. , Wu Tai Te
Published: May 2006

Newer data from the x-ray crystallographic studies of tuna heart ferrocytochrome
c
have increased the number of residues in α-helical segments. This provided an objective test of our method of predicting ϕ,Ψ values for cytochrome
c
using the sequences of 18 cytochromes
c
and twenty 20 × 20 tables for the ϕ,Ψ values of tripeptides in 10 other proteins whose three-dimensional structures were known from x-ray crystallographic studies. Of the 32 residues now considered from x-ray data to be in α-helices, 27 had been predicted to be in the α-helical domain.
Incomplete Restoration of the Bursa-Dependent Immune System After Transplantation of Allogeneic Stem Cells into Immunodeficient Chicks
Authors: Toivanen Paavo , Toivanen Auli , Sorvari Tapani
Published: May 2006

Transplantation of allogeneic cells from bursa of Fabricius into cyclophosphamide-treated, immunodeficient chicks resulted in immunological tolerance to donor line skin grafts; graft-versus-host disease did not occur. Allogeneic bursal stem cells taken from 3-day-old donors induced restoration of bursal morphology, of antibody formation to
Brucella abortus
and of occurrence of pyroninophilic cells and immunoglobulin-bearing cells in the peripheral lymphoid tissues. Secondary response to sheep red blood cells and production of germinal centers were not restored. Transplantation of histocompatible bursal stem cells resulted in a complete reconstitution of the bursa-dependent lymphoid system, both in function and in morphology. Allogeneic postbursal stem cells taken from the bursa of 10-week-old donors had a reconstitutive effect only on the production of antibodies to
Brucella
. Transplanted stem cells maintained their functional potential in the allogeneic environment, since, when transferred back to histocompatible hosts, they displayed normal function. These findings indicate that a complete functional and morphological restoration of the bursa-dependent immune system cannot be achieved without identity of the donor and recipient at loci near to or identical with those determining the major histocompatibility antigens, even though graft-versus-host disease is avoided. This identity permits a full cooperation of the donor and host cells.
At Least One-Third of Zeros of Riemann's Zeta-Function are on σ = ½
Authors: Levinson Norman
Published: May 2006

Starting from the derivative of the functional equation of the zeta-function, it is shown that at least one-third of the zeros of the zeta-function are on the line σ = ½.
Genome Construction Between Bacterial Species
In Vitro:
Replication and Expression of
Staphylococcus
Plasmid Genes in
Escherichia coli
Authors: Chang Annie C. Y. , Cohen Stanley N.
Published: May 2006

Genes carried by
Eco
RI endonuclease-generated fragments of
Staphylococcus
plasmid DNA have been covalently joined to the
E. coli
antibiotic-resistance plasmid pSC101, and the resulting hybrid molecules have been introduced into
E. coli
by transformation. The newly constructed plasmids replicate as biologically functional units in
E. coli
, and express genetic information carried by both of the parent DNA molecules. In addition, electron microscope heteroduplex analysis of the recombinant plasmids indicate that they contain DNA sequences derived from
E. coli
and
Staphylococcus aureus
. Recombinant molecules can transform other
E. coli
cells for penicillin-resistance markers originally carried by the staphylococcal plasmid, and can be transferred among
E. coli
strains by conjugally proficient transfer plasmids.
A Simple Proof of Siegel's Theorem
Authors: Goldfeld Dorian M.
Published: May 2006

A brief and simple proof of Siegel's celebrated theorem that
h(d)
»
d
1/2-[unk]
, as
d
→ ∞, is given. Here
h(d)
denotes the class number of the quadratic field
Q
([unk]-
d
). Simple proofs that do not make use of algebraic number theory have been previously given by Estermann and Chowla.
Amino-Acid Sequence of the Variable Region of the Heavy (Alpha) Chain of a Mouse Myeloma Protein with Anti-Hapten Activity
Authors: Francis Sharron H. , Leslie R. Graham Q. , Hood Leroy , Eisen Herman N.
Published: May 2006

Cyanogen bromide cleavage of the heavy (alpha) chain of protein 315 (an immunoglobulin A mouse myeloma protein with anti-dinitrophenyl activity) yielded five fragments of which one (CN2), with 156 residues, contained the chain's entire variable region. Determination of the amino-acid sequence of CN2 showed that: (
1
) the variable region has appreciable homology (about 33% identities) with the variable region of the light chain from the same molecule; and (
2
) the constant-region sequence immediately following the probable transition from variable to constant domains is the same in the protein-315 α as in human γ1 and μ chains (-Val-Ser-Ser-). The sequence of the cyanogen bromide octapeptide (CN5) from the carboxy terminus of the protein-315 heavy chain closely resembles the corresponding segments of human α and μ chains.
Microtubules from Mammalian Brain: Some Properties of Their Depolymerization Products and a Proposed Mechanism of Assembly and Disassembly
Authors: Kirschner Marc W. , Williams Robley C. , Weingarten Murray , Gerhart John C.
Published: May 2006

Depolymerization products of purified microtubules from porcine brain were examined by sedimentation analysis and electron microscopy. The complete depolymerization mixture exhibited 36S and 6S components in concentration-dependent equilibrium, whether depolymerization was caused by low temperature or by calcium ion. These components were recognized by electron microscopy as spirals and rings, and small particles. Agarose column chromatography yielded two major fractions, a leading one comprising mostly 36S and some 6S material and a trailing one of solely 6S material. The latter had high specific colchicine-binding activity and no tendency to polymerize. For the leading peak material these properties were the converse. It is proposed that tubulin molecules (of mass 110,000 daltons) exist in two states, here called X and Y, with those of the X-state equivalent to the material found predominantly in the trailing fraction, and those of the Y-state equated with the material in the leading fraction. Participation of tubulin molecules in microtubule assembly and disassembly is discussed, based on the assumption that those of both states have longitudinal and lateral binding domains whose strengths differentially depend upon temperature and calcium-ion concentration.
Transfer of Newly Synthesized Proteins from Schwann Cells to the Squid Giant Axon
Authors: Lasek R. J. , Gainer H. , Przybylski R. J.
Published: May 2006

The squid giant axon is presented as a model for the study of macromolecular interaction between cells in the nervous system. When the isolated giant axon was incubated in sea water containing [
3
H]leucine for 0.5-5 hr, newly synthesized proteins appeared in the sheath and axoplasm as demonstrated by: (
i
) radioautography, (
ii
) separation of the sheath and axoplasm by extrusion, and (
iii
) perfusion of electrically excitable axons. The absence of ribosomal RNA in the axoplasm [Lasek, R. J.
et al.
(1973)
Nature
244, 162-165] coupled with other evidence indicates that the labeled proteins that are found in the axoplasm originate in the Schwann cells surrounding the axon. Approximately 50% of the newly synthesized Schwann cell proteins are transferred to the giant axon. These transferred proteins are soluble for the most part and range in molecular size from 12,000 to greater than 200,000 daltons. It is suggested that proteins transferred from the Schwann cell to the axon have a regulatory role in neuronal function.
Uterine Estrogen-Induced Protein: Physical and Immunological Comparison with Ovalbumin
Authors: Katzenellenbogen Benita S. , Williams Linda B.
Published: May 2006

The physical and immunological properties of the estrogen-induced protein from rat uterus are compared with those of ovalbumin from chick oviduct. Both proteins are induced by estrogen and are under estrogenic regulation. Electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gels and elution behavior on Sephadex G-100 column chromatography indicate that the uterine protein has a molecular weight of about 42,000, similar to that of ovalbumin, and likewise is composed of only one subunit. On isoelectric focusing in polyacrylamide gels, both proteins focus at a pH of 4.6. The uterine protein, in addition, shows a component with an isoelectric point of 5.1. Despite considerable similarity in the physical properties of the uterine protein and ovalbumin, there is no significant crossreactivity of anti-ovalbumin gamma globulin with the uterine protein, implying that these two estrogen-regulated proteins are immunologically distinct.