bluuebunny/crossref_metadata_2025 huggingface dataset:
Malignant Transformation of BHK
21
Clone 13 Cells by BK Virus—A Human Papovavirus
Authors: Major Eugene O. , Mayorca Giampiero Di
Published: May 2006

BK virus, a widespread human papovavirus, is shown to cause malignant transformation of BHK
21
clone 13 cells. The transformed cells grow as tumors upon inoculation in adult hamsters. The question of the possible role of this virus in human neoplasia is raised.
The Mode of Action of Vitamin K. Isolation of a Peptide Containing the Vitamin K-Dependent Portion of Prothrombin
Authors: Nelsestuen Gary L. , Suttie John W.
Published: May 2006

Previous evidence has indicated that vitamin K functions in a metabolic step that specifically alters a precursor protein and converts it to biologically active prothrombin. This alteration appears to be related to the biosynthesis or attachment of a noncarbohydrate prosthetic group [Nelsestuen and Suttie (1972)
J. Biol. Chem.
247, 8176]. We report the isolation of a peptide from bovine prothrombin that contains the vitamin K-dependent region of the molecule. The properties of the isolated peptide would appear to account for the major differences observed between prothrombin and its biologically inactive form produced by animals administered Dicumarol orally. These differences are quantitative absorption onto insoluble barium salts and the ability to bind calcium ions. The observed properties of this peptide provide direct evidence for the presence of a covalently bound noncarbohydrate prosthetic group(s) on the prothrombin molecule.
Nuclear Binding of Steroid Receptors: Comparison in Intact Cells and Cell-Free Systems
Authors: Higgins Stephen J. , Rousseau Guy G. , Baxter John D. , Tomkins Gordon M.
Published: May 2006

In regulating gene expression in mammalian tissues, steroid hormones bind to cytoplasmic receptors and the resulting complex associates with the nucleus. In an attempt to study this nuclear association under more precisely controlled conditions, we examined the binding of receptor-[
3
H]steroid complexes to isolated nuclei. Two systems were used: the glucocorticoid-responsive hepatoma cell and the estrogen-sensitive immature rat uterus. Cell-free nuclear binding resembles that observed in the intact cell; it requires the receptor-steroid complex in the appropriate form (“active” complex); it is of high affinity; and it appears to involve about 4000 nuclear acceptor sites per haploid genome. Furthermore, whether binding occurs in intact cells or in cell-free extracts, complexes dissociate from nuclei at similar rates, and the ability of NaCl to extract either type of nuclear-bound complex and the sedimentation velocities of the extracted complexes are identical. Despite these similarities, acceptor sites detected in isolated nuclei differ from those of intact cells, since in neither hepatoma cells nor in the uterus do complexes bound to the nuclei of intact cells prevent further cell-free binding. We conclude that receptor-steroid complexes bind to acceptor sites in isolated nuclei that are chemically similar to, but topographically different from, those of the intact cell.
Synaptic Rearrangement in the Dentate Gyrus: Histochemical Evidence of Adjustments after Lesions in Immature and Adult Rats
Authors: Cotman Carl W. , Matthews Dee Ann , Taylor Dwan , Lynch Gary
Published: May 2006

In immature animals, ablation of the entorhinal cortex elicited a rapid intensification of acetylcholinesterase (EC 3.1.1.7) staining in the outer one-quarter of the molecular layer of the dentate gyrus. Subsequent lesions of the septum eliminated this acetylcholinesterase intensification. Electron-microscopic histochemical analysis demonstrated a 30-fold increase in the number of acetylcholinesterase-positive synaptic endings in the intensification zone. The acetylcholinesterase augmentation thus appears attributable, in part at least, to an increase in the number of acetylcholinesterase-rich synaptic endings established by septo-hippocampal fibers. Observations in a comparative study of immature and adult rats point to the animal's developmental state as a major determinant of differences in these lesion-induced neuronal adjustments.
Relatedness of Mouse Satellite Deoxyribonucleic Acid to Deoxyribonucleic Acid of Various
Mus
Species
Authors: Rice Nancy Reed , Straus Neil A.
Published: May 2006

Mouse (
Mus musculus musculus
) satellite DNA is able to reassociate with repeated DNA sequences of
Mus caroli
and
Mus cervicolor
, but low thermal stability of the products indicates significant differences between satellite and related DNAs of these two
Mus
species. There appear to be several satellite-related populations in
M
.
caroli
DNA, each of which forms hybrids of low thermal stability with repeated sequences of
M
.
cervicolor
DNA. DNAs from the subspecies
Mus musculus molossinus
and
Mus musculus castaneus
reassociate with mouse satellite to form hybrids of very high thermal stability, but the satellite content of
M
.
m
.
musculus
DNA is only about 60% that of
M
.
m
.
musculus
DNA. Reassociation of
M
.
m
.
musculus
nonrepeated DNA with
M. m. molossinus
DNA reveals no detectable differences between them; reassociation with
M. caroli
(or
M. cervicolor
) DNA yields a product whose melting temperature depression relative to homologous DNA is about 5°.
Asymptotics of Some Relativistic Markov Processes
Authors: Dudley R. M.
Published: May 2006

Markov processes in special-relativistic position-velocity phase space are proved to have converging velocities as
t
→ + ∞ under some mild assumptions on transition probabilities. This offers a possible mechanism to explain the recession of galaxies.
Electron Transport-Linked Compared with Proton-Induced ATP Generation in
Thiobacillus novellus
Authors: Cole J. S. , Aleem M. I. H.
Published: May 2006

The apparently soluble electron-transport system, that does not sediment when centrifuged at 144,000 ×
g
or 300,000 ×
g
for 3 hr, catalyzes oxidative phosphorylation with an efficiency comparable to that of an intact mitochondrial system. While the proton-induced phosphorylation occurs in whole cells, crude cell-free extracts, and supernatants from low-speed centrifugation, it does not occur in either the 144,000 or 300,000 ×
g
supernatant fractions. The data show that oxidative energy can be conserved as ATP under conditions that are incompatible with the basic postulate of the chemiosmotic hypothesis.
The Nucleotide Sequence of the Lactose Messenger Ribonucleic Acid Transcribed from the UV5 Promoter Mutant of
Escherichia coli
Authors: Maizels Nancy M.
Published: May 2006

I have sequenced the first 63 bases of mRNA transcribed
in vitro
from the UV5 promoter mutant of the
E. coli
lactose operon. Sonic fragments of DNA, 1000 base pairs long and purified to contain only the
lac
operator-promoter region, were used as template. The UV5 promoter mutation allows transcription of the
lac
operon in the absence of catabolite activator protein and cAMP;
lac
repressor controls the synthesis of this RNA. I find that during synthesis, RNA polymerase pauses at particular sites along the DNA, naturally generating several discrete sizes of RNA that provide overlaps useful for sequencing. The UV5
lac
mRNA initiates within the
lac
operator and copies the operator sequence. The AUG initiator codon for β-galactosidase occurs at position 39 of the message. The sequence is: pppA-A-U-U-G-U-G-A-G-C-G-G-A-U-A-A-C-A-A-U-U-U- C-A-C-A-C-A-G-G-A-A-A-C-A-G-C-U-A-U-G-A-C-C-A-U- G-A-U-U-A-C-G-G-A-U-U-C-A-C-U-G-G.
Cell-Free Translation of the Globin Message within Polydisperse High-Molecular-Weight Ribonucleic Acid of Avian Erythrocytes
Authors: Ruiz-Carrillo A. , Beato M. , Schutz G. , Feigelson P. , Allfrey V. G.
Published: May 2006

Polydisperse high-molecular-weight RNA of nucleated avian erythrocytes includes sequences coding for globin chains. The RNA was extracted from immature erythrocytes of ducks and fractionated under denaturing conditions by sucrose density gradient centrifugation in 99% dimethylsulfoxide. The RNA sedimenting faster than 45 S was able to direct the synthesis of duck globins in the Krebs II ascites cell-free protein-synthesizing system. The newly synthesized globin molecules have been identified by their characteristic electrophoretic properties in polyacrylamide gels containing either urea or sodium dodecyl sulfate, and by immunoprecipitation of the released globin chains by rabbit antibodies against duck hemoglobin. In order to rule out the possibility of a contamination of the high-molecular-weight RNA with duck-globin messenger RNA tailing from the 9-10S region, rabbit-globin messenger RNA was added to duck RNA as an internal control. No rabbit-globin messenger RNA activity could be detected in the RNA fractions sedimenting faster than 45 S. It is concluded that high-molecular-weight RNAs in the nucleated erythroid cell contain sequences of globin messenger RNAs covalently attached to larger polynucleotide chains. These results support the view that polydisperse nuclear RNA is the precursor of the cytoplasmic messenger RNA fraction.
Mitogenic Properties of Pea Lectin and Its Chemical Derivatives
Authors: Trowbridge Ian S.
Published: May 2006

A mitogenic lectin that has a carbohydrate-binding specificity similar to that of concanavalin A (Con A) can be isolated from pea seeds. Chemical modification (succinylation, acetylation, or treatment with the diazonium salt of sulfanilic acid), changes its biological properties. In mitogenic stimulation of mouse spleen cells and in hemagglutination, the differences between the chemically modified pea lectin and the native molecule are similar to those observed between succinyl-Con A and native Con A. However, whereas chemical modification converts tetrameric Con A to a dimeric molecule, similar treatments of the pea lectin do not change its quaternary structure. The results of binding studies of the pea lectin and its derivatives to mouse spleen cells suggest that the differences in biological activities may be explained by a reduction in binding affinity of the pea lectin for glycoproteins on the spleen cell surface after chemical modification.
Manipulation of Fatty Acid Composition in Animal Cells Grown in Culture
Authors: Wisnieski Bernadine J. , Williams Robert E. , Fox C. Fred
Published: May 2006

The fatty acid composition of animal cells cultured in serum-free medium can be manipulated when the synthesis of endogenous fatty acids is inhibited by a biotin analog and fatty acids are supplied in the medium as detergent esters of Tween. When mouse LM cells were grown in medium supplemented with Tween-19:0 (an ester of Tween and nonadecanoic acid), odd chain fatty acid content of cellular phospholipids and neutral lipids increased from 1% to 75%. Concurrently, the saturated fatty acid content increased from 27% to 85%. Similar alterations in fatty acid content have been observed when BHK
21
cells are subjected to the same enrichment regime. The ability to control the fatty acid composition of cultured animal cells is a prerequisite to investigations into the role of the membrane lipid physical state in processes unique to these cells.
Binding Properties
In Vitro
of Phytochrome to a Membrane Fraction
Authors: Marmé D. , Boisard J. , Briggs W. R.
Published: May 2006

Brief irradiation of a buffer extract of dark-grown zucchini squash seedlings with red light results in the binding of the far-red-absorbing form of phytochrome to a particulate fraction. A low concentration of magnesium (0.1 mM) permits partial far-red reversal of the binding. A higher concentration (10 mM) yields actually enhanced binding after the far-red treatment. Both magnesium and calcium have a strong effect on the vesicularization of the phytochrome-binding particles and on their aggregation into readily sedimentable complexes. At concentrations above 10 mM, binding of the far-red-absorbing form of phytochrome is inhibited. These effects were not observed with sodium or potassium. Increasing the H
+
concentration led to increased binding of the far-red-absorbing form. This form of phytochrome bound at pH 6.5 and 10 mM magnesium is released if either the pH is raised to 8.0 or the magnesium concentration is raised to 50 mM. These properties suggest a new method for phytochrome purification.
Immunological Function of Lymphocytes Fractionated with Antigen-Derivatized Fibers
Authors: Rutishauser U. , D'Eustachio P. , Edelman G. M.
Published: May 2006

Specific antigen-binding cells from spleens of immune and nonimmune mice were isolated by the method of fiber fractionation. After removal from the fibers, these cells were assayed for their viability, their ability to rebind to fibers of the same specificity, and their
in vivo
response to the antigen after transfer to syngeneic irradiated recipients. These experiments indicate that the fiber method yields highly enriched populations of specific antigen-binding cells that are viable and include antigen-sensitive bone marrow-derived cells capable of undergoing mitosis and differentiating into antibody-secreting cells.
Mutations Affecting the Structure of Hypoxanthine: Guanine Phosphoribosyltransferase in Cultured Chinese Hamster Cells
Authors: Beaudet A. L. , Roufa D. J. , Caskey C. T.
Published: May 2006

14 Clones resistant to 8-azaguanine, isolated from mutagenically treated cultured cells from Chinese hamsters, were tested for loss of enzymic and immunological activities of hypoxanthine: guanine phosphoribosyltransferase. Three of the clones had no enzymic activity but reacted strongly with antiserum prepared against the enzyme (CRM
+
), indicating the presence of a defective enzyme protein, probably caused by a mutation in its structural gene. The other 11 mutants had little or no enzymic or immunologic activity. Revertant clones with positive enzymic and crossreacting immunologic activities were derived from both classes of mutants. The antiserum has been used for rapid purification of the phosphoribosyltransferase from Chinese hamster cells by immunoadsorbant affinity chromatography.
Cycloheximide and Acetoxycycloheximide: Inhibition of Tyrosine Hydroxylase Activity and Amnestic Effects
Authors: Flexner Louis B. , Serota Roger G. , Goodman Richard H.
Published: May 2006

Mice and rats trained after treatment with cycloheximide or acetoxycycloheximide in a conditioned avoidance response develop an amnesia of their training experience. This amnesia has been attributed to the profound inhibition of protein synthesis caused by the two antibiotics. Evidence is presented that additionally the antibiotics inhibit the activity of tyrosine hydroxylase, a finding that suggests that their amnestic effect may be due in part to reduction of the functional pool of norepinephrine.
Secretion and Extracellular Processing of Procollagen by Cultured Human Fibroblasts
Authors: Goldberg Burton , Sherr Charles J.
Published: May 2006

Cultures of human diploid fibroblasts were labeled with radioactive proline and glycine, and the precursor of collagen (procollagen) in cells and medium was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A covalently assembled molecule with the composition (pro α1)
2
·pro α2 (approximate molecular weight, 360,000) appeared intracellularly soon after synthesis of the constituent chains, and could be detected in the medium after 60 min of labeling. The molecule was stabilized by disulfide bonds between cysteine residues in the amino-terminal procollagen peptide sequences of the three chains. Collagenase digested the molecule to peptides of 30,000 molecular weight or less. Limited digestion with pepsin excised nonhelical procollagen peptides, yielding native, triple-helical tropocollagen. Pulse-chase experiments indicated that a peptidase in the medium sequentially excised the nonhelical peptides from the molecule, generating tropocollagen molecules that aggregated as fibers in the cell layer. The excised, nonhelical procollagen peptides contained little or no proline or glycine. Intramolecular bonds of the lysyl aldehyde type were not detected in the secreted molecule, as reduction of the medium always resulted in quantitative recovery of free pro α chains in dodecyl sulfate-urea. Lysyl-derived, covalent bonds appeared to form between tropocollagen molecules aggregating in the cell layer. We suggest the term “pro-tropocollagen” for the assembled, secreted precursor of collagen.
Phosphorylation of Ribosomal Proteins by Substrate-Specific Protein Kinases from Rabbit Reticulocytes
Authors: Traugh Jolinda A. , Mumby Marc , Traut Robert R.
Published: May 2006

Three protein kinase activities have been identified in ribosome-free supernatant from rabbit reticulocytes by DEAE-chromatography. Two of the protein kinase activities have similar substrate specificities, but differ in respect to dependency on cAMP for activation. These kinases preferentially phosphorylate histone, and also phosphorylate identical ribosomal proteins. One protein band in the 40S ribosomal subunit and six protein bands in the 60S subunit are phosphorylated, as demonstrated by Na dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The third kinase activity preferentially phosphorylates casein, instead of histone, and can use both [γ-
32
P]ATP and [γ-
32
P]GTP as phosphate donors. This protein kinase activity phosphorylates one protein band in the 40S subunit different from that phosphorylated by the other two kinases and four bands in the 60S subunit, only one of which is coincident with the proteins phosphorylated by the histone-specific activities.
Cystic Fibrosis: Fractionation of Fibroblast Media Demonstrating Ciliary Inhibition
Authors: Bowman Barbara H. , Barnett Don R. , Matalon Reuben , Danes B. Shannon , Bearn Alexander G.
Published: May 2006

A chromatographic fraction has been identified in media from fibroblast cultures derived from 15 of 18 cystic fibrosis patients and 8 of 10 heterozygotes that inhibits ciliary activity, as judged by the oyster gill assay. The analogous fraction of media from cultures of fibroblasts derived from 11 normal individuals did not inhibit ciliary activity under the experimental conditions used. The chromatographic fractions containing the ciliary inhibitory activity from both fibroblast media and sera of cystic fibrosis patients and heterozygotes eluted in the same position from diethylaminoethyl-cellulose at pH 8.5.

Although the serum ciliary inhibitor had consistently been detected in a fraction that contained predominantly immunoglobulin G, results of the fractionation of fibroblast media demonstrate that the ciliary inhibitor is present in a protein fraction containing three species of different molecular weight and in which IgG cannot be detected by the techniques used.
RNA Initiation with Dinucleoside Monophosphates during Transcription of Bacteriophage T4 DNA with RNA Polymerase of
Escherichia coli
Authors: Hoffman David J. , Niyogi Salil K.
Published: May 2006

The effects of dinucleoside monophosphates on the transcription of phage T4 DNA by
E. coli
RNA polymerase have been examined at various concentrations of the sigma subunit and extremely low concentration of ribonucleoside triphosphate. The following conclusions were reached: (
i
) Labeled specific dinucleoside monophosphates are incorporated as chain initiators. (
ii
) When the ratio of sigma factor to core enzyme is small, there is a general stimulation by most 5′-guanosyl dinucleoside monophosphates. (
iii
) When the ratio is increased or holoenzyme is present, ApU, CpA, UpA, and GpU are the most effective stimulators. (
iv
) At high concentrations of sigma factor, only certain adenosine-containing dinucleoside monophosphates (ApU, CpA, UpA, and ApA) stimulate the reaction. (
v
) Competition hybridization studies indicate that the RNAs stimulated by dinucleoside monophosphates (ApU, CpA, UpA, and GpU) are of the T4 “early” type. (
vi
) Studies involving both combinations of stimulatory dinucleoside monophosphates and competitive effects of these compounds on chain initiation by ATP and GTP suggest that the stimulatory dinucleoside monophosphates act as chain initiators and may recognize part of a continuous sequence in a promoter region. Studies based on the incorporation of
3
H-labeled stimulatory dinucleoside monophosphates support the above conclusions.
Biological and Molecular Evidence for the Transgenosis of Genes from Bacteria to Plant Cells
Authors: Doy C. H. , Gresshoff P. M. , Rolfe B. G.
Published: May 2006

Specialized transducing phages (λ and ϕ80) have been used as vectors in the transfer of genes (wild type and mutant) from the bacterium
Escherichia coli
to haploid cell lines of the plants
Lycopersicon esculentum
and
Arabidopsis thaliana
. The overall phenomenon of transfer, gene maintenance, transcription, translation, and function has been termed transgenosis. Transgenosis of galactose and lactose operon genes was detected by survival and growth of the plant cells on defined medium with galactose and lactose as sole sources of bulk carbon. Phages carrying a defective operon, unrelated bacterial genes, or no bacterial genes, do not affect the normal result of death on these media, nor do they prevent growth on optimal growth media. Transgenosis of the
E. coli
gene
z
(
lac
operon) was confirmed by a biochemical-immunological test specific for
E. coli
β-galactosidase. Plant cells were unable to effectively suppress an
E. coli
nonsense mutation. The
E. coli
mutant suppressor gene,
supF
+
, specifies insertion of tyrosine at amber (UAG) nonsense codons. Introduction of
supF
+
results in a lethal transgenosis on medium normally optimal for plant cell growth. It is concluded that amber codons are vital to the life of plant cells. Differentiating cells of
A. thaliana
were not affected by
supF
+
.
Role of Medium-Range Interactions in Proteins
Authors: Ponnuswamy P. K. , Warme P. K. , Scheraga Harold A.
Published: May 2006

The energies of oligopeptide segments of lysozyme are minimized with respect to the dihedral angles of the central residue. As the length of the oligopeptide segment increases, up to a nonapeptide, the low-energy conformation becomes that observed in the x-ray structure in most cases. This finding suggests that, while short-range interactions appear to play the dominant role in determining the conformation of an amino-acid residue in a protein, the additional interactions required to stabilize the conformation uniquely may be only of medium range, i.e., those within a nonapeptide, and longer-range interactions may be of considerably less importance.
Carbohydrate Catabolism and the Enhancement of Uptake of Galactose in Hamster Cells Transformed by Polyoma Virus
Authors: Kalckar H. M. , Ullrey D. , Kijomoto S. , Hakomori S.
Published: May 2006

Untransformed as well as polyoma virus-transformed hamster cells can be grown equally well on a slow catabolite like galactose as on a rapid catabolite like glucose. The rate of uptake of galactose is greatly enhanced in the transformed cells as compared with untransformed cells, and this enhancement of entry was as markedly expressed in galactose-grown cultures as in glucose-grown cultures. Since the transformed cultures grown in glucose medium consume practically all of their carbohydrate, contrary to the galactose-grown cultures, problems dealing with regulation of transport by substrate concentrations have to be dealt with also. The galactose captured by the cells accumulates initially as galactose, α-galactose-1-phosphate, and UDP-galactose. However, after a 24-hr growth on a galactose growth medium, the product accumulated was almost exclusively galactitol. In spite of the enhancement of entry of galactose into the transformed cells, the metabolic pathway becomes stalled even before it has reached the stage of glucose-1-phosphate, largely due to a choke of the enzyme UDP-galactose-4-epimerase (EC 5.1.3.2). Among the sparse amounts of catabolic products generated by the transformed cells from galactose, carbon dioxide (allebeit no D-xylose) and lactic acid were found, both of them in much smaller amounts than seen if glucose is the carbohydrate source. Also, growth of transformed cells on a galactose medium gradually tends to become oriented, a phenomenon that could be called “contact promotion.” Subsequent addition of glucose disturbs the oriented growth and interferes with contact promotion.
A Stopped-Flow Apparatus with Light-Scattering Detection and Its Application to Biochemical Reactions
Authors: Riesner Detlev , Buenemann Hans
Published: May 2006

A stopped-flow apparatus utilizing light-scattering for following the progress of a reaction is described. The method is applicable to all reactions that result in a significant change of the average molecular weight. It was possible due to several modifications of a conventional stopped-flow system to obtain a sensitivity comparable to that of commercial instruments for static light-scattering measurements. Experiments on three reactions are reported: association and dissociation of mercury ligands with DNA, dissociation of the dimers of DNA-dependent RNA polymerase, and complex formation of tRNA
Ser
(yeast) with the cognate aminoacyl-tRNA synthetase. The changes in the intensities of the scattered light are calculated and compared with the measured amplitudes.
A Protein of Molecular Weight 78,000 Bound to the Polyadenylate Region of Eukaryotic Messenger RNAs
Authors: Blobel Günter
Published: May 2006

Two distinct proteins were found to be tightly bound to the heterogeneous messenger RNAs associated with polysomes in mouse L cells and rat hepatocytes. The molecular weight (78,000) of the larger of these two proteins is identical to that of the protein previously found associated with rabbit globin messenger RNA. This protein is shown to be bound to the adenylate-rich region of messenger RNA. The molecular weight of the smaller protein associated with messenger RNAs from hepatic and L-cell polysomes is similar to that found in globin messenger ribonucleoprotein.
Regulation by
N
Gene Protein of Phage Lambda of Anthranilate Synthetase Synthesis
In Vitro
Authors: Dottin Robert P. , Pearson Mark L.
Published: May 2006

The
N
protein of bacteriophage lambda is a positive regulator of early λ gene expression. In a λ
trp
transducing phage, λ
trp
46
Nam
, the synthesis of
trp
enzymes
in vivo
is also dependent on the presence of active
N
protein. The DNA of this phage has been used in a protein-synthesizing system
in vitro
to develop a biochemical assay for the activity of the
N
protein. From the following observations it appears that it is the
N
protein itself that stimulates
trp
enzyme synthesis
in vitro
. An activity that stimulates
trp
enzyme synthesis can be made
in vitro
by λ
N
+
DNA but not by λ
Nam
DNA. This activity can also be detected in extracts of induced λ
N
+
lysogens but not of λ
Nam
lysogens. Furthermore, the activity is temperature sensitive in similar extracts of λ
Nts
lysogens. No such activity is detectable in extracts of induced lysogens of λ
imm
21
. This phage makes all λ-coded gene products outside the immunity region, but lacks an
N
protein activity able to substitute for
N
λ
protein
in vivo
. Our experiments also show that the action of
N
protein is inhibited by the
cI
repressor protein
in vivo
as it is
in vivo
.
Adenosine 3′:5′-Cyclic Monophosphate in
Chlamydomonas reinhardtii:
Isolation and Characterization
Authors: Amrhein Nikolaus , Filner Philip
Published: May 2006

Chlamydomonas reinhardtii
contains a factor that can replace adenosine 3′:5′-cyclic monophosphate (cAMP) in the stimulation of rabbit-muscle protein kinase. The factor cochromatographs and coelectrophoreses with authentic cAMP, and is inactivated by beef heart cyclic nucleotide phosphodiesterase. When
C. reinhardtii
is exposed to aminophylline (theophylline
2
ethylenediamine), the concentration of the factor in the cells increases within 1 hr, from about 25 pmol of cAMP equivalents per g dry weight to more than 250 pmol. Cyclic nucleotide phosphodiesterase activity is present in crude extract of
C. reinhardtii
and is inhibited by theophylline. We conclude that cAMP occurs in
C. reinhardtii
and that the endogenous concentration is governed at least in part by a theophylline-sensitive cyclic nucleotide phosphodiesterase. These findings provide a sound basis for attributing the effects of methylxanthines on flagellar function and regeneration in
C. reinhardtii
to the resultant elevation of endogenous cAMP.
Demonstration of Globin Messenger Sequences in Giant Nuclear Precursors of Messenger RNA of Avian Erythroblasts
Authors: Imaizumi Tereza , Diggelmann Heidi , Scherrer Klaus
Published: May 2006

Highly purified globin mRNA from ducks was copied with RNA-directed DNA polymerase from avian myeloblastosis virus into anti-messenger DNA. With excess RNA, more than 90% of this DNA annealed back to its template with a C
o
t/2 value of 7.5 × 10
-4
mol·sec· liter
-1
; the melting temperature of the hybrid was 86°. Giant nuclear RNA fractions with sedimentation coefficients of more than 50 S formed hybrids of almost equal stability at C
o
t/2 values of 0.05-0.42 mol·sec· liter
-1
, indicating amRNA content of 0.3-1.5%. 12S RNA from the same polyribosomes and nuclear giant RNA from HeLa cells did not cross-hybridize. Although a large part of the giant RNA broke down in 99% dimethylsulfoxide gradients, RNA fractions sedimenting faster than 28S rRNA still were found to consist of up to 0.03% globin mRNA sequences. Thus, the mRNA sequences are contained in the covalent structure of giant nuclear precursors, which are termed precursor-mRNA.
Complex Formation Between Mycobacterial Polysaccharides and Fatty Acyl-CoA Derivatives
Authors: Machida Yoshimasa , Bloch Konrad
Published: May 2006

The mycobacterial polysaccharides MMP and MGLP, which contain numerous
O
-methyl-sugar residues, markedly stimulate fatty acid synthesis catalyzed by a multienzyme complex from
Mycobacterium phlei
[Ilton, M.
et al.
(1971)
Proc. Nat. Acad. Sci. USA
68, 87-91]. When aqueous solutions containing MMP or MGLP and palmitoyl-CoA were chromatographed on Sephadex G-75 under conditions that widely separate the individual components, polysaccharide and fatty acyl-CoA were eluted in a single peak, indicating formation of a molecular complex. Similarly, the mycobacterial polysaccharides associate with the CoA derivatives of C
18
, C
20
, and C
22
acids to yield complexes containing maximally 1 mol of fatty acyl-CoA per mol of polysaccharide. The formation of these novel complexes may result from hydrophobic interactions between the paraffin chains of the acyl-CoA derivatives and
O
-methyl-sugar residues of the polysaccharides.
Inhibition of Murine Leukemia Virus Replication by Poly(vinyluracil) and Poly(vinyladenine)
Authors: Pitha Paula M. , Teich Natalie M. , Lowy Douglas R. , Pitha Josef
Published: May 2006

Poly(1-vinyluracil) and poly(9-vinyladenine), as well as the corresponding polynucleotides poly(uridylate) and poly(adenylate), inhibit acute murine leukemia virus infection in mouse-embryo cells, but they do not significantly inhibit the replication of Sindbis and vesicular stomatitis viruses. The polymers were most effective as inhibitors when added during an early stage of virus replication. Effects of vinyl polymers on the RNA-dependent DNA polymerase from the virions of murine leukemia virus were also observed.
“Recommended Daily Allowances” for Vitamin C
Authors: Yew Man-Li S.
Published: May 2006

Although 41 years have elapsed since the identification of vitamin C, the amounts required for human health are far from established. Pauling's suggestion that human needs for this vitamin probably have been underestimated by a factor of 10 or more has frequently been ignored or refuted by rhetoric rather than by sound experimentation.

In the present study young healthy guinea pigs were fed a scrobutic diet supplemented with ascorbic acid at four widely different levels (0.05, 0.5, 5.0, and 50 mg/100 g of body weight per day). Growth rates both before and after surgical stress, recovery times after anesthesia, scab formation, wound healing, and the production of hydroxyproline and hydroxylysine during wound healing all support the conclusion that young guinea pigs ordinarily need about 5.0 mg/100 g of body weight daily. This is far beyond what is needed to prevent scurvy. Under stress the needs are even higher. On a body-weight basis this amount is equivalent to a need on the part of a 30-kg human child of 1500 mg of ascorbic acid daily. While calculations on a body-weight basis are subject to some uncertainty, the enormous discrepancy (nearly 40-fold) between this amount and that recommended by the Food and Nutrition Board calls attention to the extreme uncertainty about human ascorbic-acid needs, and to an important public health problem related to the best development of young people.
RNA-Directed DNA Polymerase and Virus-Induced Leukemia in Mice
Authors: Wu Alan M. , Ting Robert C. Y. , Gallo Robert C.
Published: May 2006

Rifamycin antibiotics, which inhibit RNA-directed DNA polymerase of Rauscher leuckemia virus, prevent the leukemogenic activity of the virus, and the effect of leukemogenesis correlates with the magnitude of inhibition of the purified enzyme. This inhibition of enzyme activity by rifamycin SV derivatives is due to a relatively tight binding between the enzymes and the inhibitors, yet the binding can be reversed by nonionic detergent. The results of this study suggest that RNA-directed DNA polymerase is essential for induction of leukemia by exogenous virus and correlate with the previous observation that the same derivatives block viral transformation
in vitro
.
Accessibility of DNA in Chromatin to DNA Polymerase and RNA Polymerase
Authors: Silverman Bert , Mirsky Alfred E.
Published: May 2006

The accessibility of DNA in chromatin to both exogenous DNA polymerase and RNA polymerase is slight when compared to isolated DNA. DNA in extracted chromatin is somewhat more accessible to these enzymes than is DNA in the chromatin of isolated nuclei; and the DNA template of chromatin is more accessible to DNA polymerase than to RNA polymerase. In these experiments we have given much attention to the technique of scintillation counting, since artifacts arising in this procedure can lead to erroneous conclusions.
125
I-Labeled DNA·RNA Hybrids in Cytological Preparations
Authors: Altenburg L. C. , Getz M. J. , Crain W. R. , Saunders G. F. , Shaw M. W.
Published: May 2006

RNA complementary to bulk humanplacental DNA was synthesized
in vitro
both in the presence and absence of
3
H-labeled ribonucleotides. The
3
H-labeled RNA was used directly for hybridization to the DNA of human metaphase chromosomes, whereas the unlabeled complementary RNA was labeled chemically with
125
I before hybridization. A comparison of autoradiographs produced by either isotope revealed no qualitative differences in the chromosomal annealing sites of the same population of RNA molecules. Since
125
I-labeled nucleic acids give similar, if not identical, results as do
3
H-labeled nucleic acids in
in situ
hybridization experiments, their use should make possible the localization of genetic elements for which tritium labeling methods are either inadequate or not possible.
“Early” Virus-Specific RNA May Contain Information Necessary for Chromosome Replication and Mitosis Induced by Simian Virus 40
Authors: May Evelyne , May Pierre , Weil Roger
Published: May 2006

Simian Virus 40 (SV40) induces in “contact-inhibited” tissue culture cells of mouse kidney an abortive infection that leads to the appearance of intra-nuclear SV40-specific tumor (T-) antigen, followed by replication of the mouse-cell chromatin and mitosis, while no viral progeny DNA or capsid protein is produced. Synthesis of “early” SV40-specific RNA (“19S RNA”) begins a few hours before the appearance of T-antigen and appears to be switched off after the onset of chromatin replication. As the most simple working hypothesis that can account for the experimental results available, we assume that early SV40 RNA contains information necessary for production of T-antigen and that this antigen (or an unknown early virus-specific function that would simply parallel the appearance of T-antigen) activates or de-inhibits a cellular regulatory element that governs chromosome replication and mitosis. The experimental results agree with the idea that SV40 acts primarily as a mitogen.
Oxygen Equilibrium and Kinetics of Isolated Subunits from Hemoglobin Kansas
Authors: Riggs Austen , Gibson Quentin H.
Published: May 2006

The isolated β subunit of hemoglobin Kansas has an oxygen affinity that is as low relative to the oxygen affinity of the β
A
subunit as the affinity of hemoglobin Kansas is low relative to hemoglobin A. Thus the low affinity properties of hemoglobin Kansas are almost completely reflected in the properties of the isolated subunits. The kinetic results show that the equilibrium affinity difference results both from a much larger oxygen dissocation rate constant in β
Kansas
(
k
= 37 sec
-1
and 18 sec
-1
for β
Kansas
and β
A
, respectively) and from a lower association reaction rate, The properties of the α chains from hemoglobins A and Kansas appear to be identical, as expected.
A Temperature-Sensitive Change in the Energy of Activation of Hormone-Stimulated Hepatic Adenylyl Cyclase
Authors: Kreiner Peter W. , Keirns James J. , Bitensky Mark W.
Published: May 2006

We describe an abrupt increase (at 32°) in the energy of activation for the reaction of hepatic adenylyl cyclase in the presence of glucagon or epinephrine. This increase is not seen in the presence of fluoride, prostaglandin E
1
, or 1-propanol, or in the absence of cyclase stimulators. The change in energy of activation found with hormones is abolished by 1-propanol. This change does not represent differences in hormone or substrate binding at different temperatures, but seems to reflect interactions among elements of the cyclase stimulation sequence. Similar changes in energy of activation were not observed for alkaline phosphatase, cyclic AMP-phosphodiesterase, 5′-nucleotidase, or ouabain-sensitive ATPase. Since the mole fraction of cholesterol in liver membranes is sufficiently high to preclude a phase change in bulk membrane lipids, our observation suggests either that cyclase is restricted to cholesterol-poor membrane regions or that the change in its energy of activation is largely restricted to protein components of the cyclase apparatus. The data are compatible with fundamental differences in the stimulation process(es) for the hormones (glucagon and epinephrine) as compared with those for fluoride and prostaglandin E
1
.
Relative Orientation with Respect to the Centromere of Ribosomal RNA Genes of the X and Y Chromosomes of
Drosophila melanogaster
Authors: Palumbo G. , Caizzi R. , Ritossa F.
Published: May 2006

We tested for recombination within the DNA that codes for ribosomal RNA (rDNA) on the X and Y chromosomes of
Drosophila melanogaster
. The criterion was the appearance of intermediate
bb
alleles on
X-Y
recombinants from wild
bb
+
and lethal
bb
1
loci carried on parental chromosomes. Recombination within the rDNA occurs only when the rDNA of the X chromosome is inverted. We conclude that rDNAs of normal X and Y chromosomes have opposite orientation with respect to the centromere. The implications of this observation are discussed.
Effect of Thiostrepton on Recycling of
Escherichia coli
Initiation Factor 2
Authors: Mazumder Rajarshi
Published: May 2006

The recycling of initiation factor 2, which requires both GTP and the 50S subunit and involves GTP hydrolysis, appears to be blocked by thiostrepton. However, this antibiotic has little or no effect on the AUG-directed ribosomal binding promoted by initiation factor 2 of fMet-tRNA under conditions that do not permit optimal recycling of the factor. Evidence is presented suggesting that the 50S ribosomal proteins L7 or L12, which are required for the function of the chain elongation factors Tu and G and the accompanying hydrolysis of GTP, are also involved in recycling of initiation factor 2. Although both 5′-guanylylmethylene diphosphonate and thiostrepton seem to block recycling of initiation factor 2, fMet-tRNA bound to the ribosomes in the presence of GTP and thiostrepton can react with puromycin, whereas that bound in the presence of 5′-guanylylmethylene diphosphonate and the antibiotic cannot. It is proposed that initiation factor 2 may interact with two nonidentical ribosomal sites during polypeptide chain initiation.
Crossing-Over Between X and Y Chromosomes During Ribosomal DNA Magnification in
Drosophila melanogaster
Authors: Ritossa F.
Published: May 2006

In genetic combinations undergoing ribosomal DNA magnification, the frequency of crossing-over between X and Y chromosomes is increased at least 20-fold above that in similar combinations not undergoing magnification. Such recombination occurs at the ribosomal DNA level. The data are consistent with a model where extra copies of ribosomal DNA are formed which, after circularization, are integrated into the chromosome.
Primary Dysbetalipoproteinemia: Predominance of a Specific Apoprotein Species in Triglyceride-Rich Lipoproteins
Authors: Havel Richard J. , Kane John P.
Published: May 2006

Lipoproteins of very low density that are unusually rich in cholesteryl esters accumulate in blood plasma in a characteristic primary form of human hyperlipoproteinemia. These lipoproteins, which are thought to be products of the initial catabolic step in the metabolism of normal triglyceride-rich lipoproteins, have beta rather than pre-beta mobility on electrophoresis, presumably because they have lost certain protein components from their surface. In this study, we have used polyacrylamide gel electrophoresis of apoprotein components that are soluble in tetramethylurea to show that the very low-density lipoprotein fraction of blood serum from seven patients with hyperlipoproteinemia contains unusually large amounts of an arginine-rich protein. Pre-beta migrating, very low-density lipoproteins separated from serum of post-absorptive patients and chylomicrons obtained after a fat-rich meal contain normal amounts of this arginine-rich protein, but beta-migrating, very low-density lipoproteins and chylomicron-like particles separated from serum of post-absorptive patients contain more than twice as much. These apparently partially degraded lipoproteins also contain more tetramethylurea-insoluble protein and smaller amounts of the other soluble protein components than their normal counterparts.
Predator-Prey Patterns
Authors: Yorke James A. , Anderson William N.
Published: May 2006

A graph-theoretic condition is given for the existence of stable solutions to the Volterra-Lotka equations.
Variation of Type-B DNA X-Ray Fiber Diagrams with Base Composition
Authors: Bram Stanley
Published: May 2006

Eight natural DNAs of widely differing base composition have been studied by x-ray diffraction in fibers at high relative humidity. The resulting type B diffraction diagrams showed that all of the DNAs had a 34-Å pitch and 3.4-Å interbase pair separation. However, the intensity distribution on the inner three layer lines was a strong function of the base content. In diffraction diagrams of very AT-rich DNA, the intensity of the first and third layer line was 2- or 3-times stronger than in the patterns of GC-rich DNA. These high humidity diffraction patterns agree with x-ray scattering from solutions of DNA. The results are interpreted to imply that each AT base pair may have a different cross section than a GC pair. If this is so, it would appreciably alter the currently held ideas concerning DNA recognition.
Biologically and Chemically Pure mRNA Coding for a Mouse Immunoglobulin L-Chain Prepared with the Aid of Antibodies and Immobilized Oligothymidine
Authors: Schechter Israel
Published: May 2006

The mRNA coding for a mouse immunoglobulin L-chain was prepared from MOPC-321 myeloma polysomes specifically precipitated with antibodies directed against L-chains, followed by chemical purification on oligo(dT)-cellulose. Biological purity (capacity to program the synthesis only of L-chain) was calculated to be ≥95%. This value was based on the estimation of contamination by non-L-chain mRNA activities that were present in large abundance in RNA preparations extracted from the total polysome population. A similar degree of purity was calculated from the extent of precipitation of myeloma and nonmyeloma polysomes with anti-L-chain and non-L-chain antibodies. Chemical purity (95%) was determined from the amount of rRNA in the mRNA preparation by scanning of appropriate gels. In a cell-free system, the purified mRNA directed the synthesis of two precursors heavier than L-chain by about 1300 and 4700 daltons. Cell-free products labeled with 10 [
14
C]aminoacids yielded 27 out of 28 expected L-chain tryptic peptides and four additional peptides. Most probably the latter were derived from extra pieces in the precursors, and the apparent loss of one peptide was due to modifications at the N-terminus. The main fraction of L-chain mRNA was composed of two species of about 420,000 and 450,000 daltons. These molecules are much larger than that required to code for a mature L-chain (calculated about 250,000). The additional nucleotide mass can be accounted for in part for the coding of the extra piece (about 50,000) and in part for the polyadenylate moiety.
Detection and Isolation of a New DNA Polymerase from Human Breast Tumor Cell Line HBT-3 by (dT)
12-18
-Cellulose Chromatography
Authors: Gerwin Brenda I. , Bassin Robert H.
Published: May 2006

Column chromatography on (dT)
12-18
-cellulose was used to detect and isolate a novel DNA polymerase activity from human breast tumor cell line HBT-3. The new enzyme is similar to those of mammalian RNA tumor viruses in its molecular size, preference for poly(A)·(dT)
12-18
as compared to either poly(dA)·(dT)
12-18
or poly(A)·poly(dT), and ability to copy poly(C)·(dG)
12-18
. A similar DNA polymerase activity, defined by its binding to (dT)
12-18
-cellulose, is not detectable in several other cell lines of human tumors.
Addition of Histones to Histone-Depleted Nuclei: Effect on Template Activity Toward DNA and RNA Polymerases
Authors: Silverman Bert , Mirsky Alfred E.
Published: May 2006

The ability of histones to block the accessibility of DNA in chromatin to DNA and RNA polymerases was measured by addition of lysine-rich or arginine-rich histones to nuclei selectively depleted of these histones. By this procedure nuclei were obtained in which all of the original lysine-rich histone in the chromatin was replaced by arginine-rich histone. Conversely in other nuclei, additional lysine-rich histone replaced some of the endogenous arginine-rich histone. Lysine-rich histone was much more effective than arginine-rich histone in blocking accessibility to DNA polymerase. Both classes of histone inhibited template activity toward RNA polymerase to a similar extent.

In addition to lysine-rich histone and total arginine-rich histone, phosphorylated lysine-rich histone, two fragments of lysine-rich histone produced by cleavage with
N
-bromosuccinamide, and fractions IIB and IV of arginine-rich histone were added to histone-depleted nuclei. With both DNA and RNA polymerases as probes, no differences in inhibition of template activity were found when native lysine-rich histone was compared to phosphorylated lysine-rich histone. Similarly, fractions IIB and IV were indistinguishable from total arginine-rich histone. On a molar basis, the carboxyl fragment of lysine-rich histone was as effective as intact lysine-rich histone only when the amino fragment was added to it. By itself, the amino portion of lysine-rich histone was without inhibitory effect in the RNA polymerase assay and resulted in only slight inhibition of template activity toward DNA polymerase.