bluuebunny/crossref_metadata_2025 huggingface dataset:
An Adenosine 3′:5′-Cyclic Monophosphate-Binding Protein That Acts on the Transcription Process
Authors: Eron L. , Arditti R. , Zubay G. , Connaway S. , Beckwith J. R.
Published: May 2006

An assay system for the
in vitro
transcription of the
lac
operon is described. A protein factor (CAP) and cyclic AMP, which are essential for the
lac
expression
in vivo
, also stimulate
lac
transcription
in vitro
.
A Series of Hybrid Cells Containing Different Ratios of Parental Chromosomes Formed by Two Steps of Artificial Fusion
Authors: Murayama-Okabayashi Fumiko , Okada Yoshio , Tachibana Takehiko
Published: May 2006

Double hybridization of Ehrlich ascites tumor cells (ETC) and L cells was performed. In the first step, a hybrid (LE) of ETC and L
AG
(a mutant of L cells, resistant to 10 μg/ml of 8-azaguanine) and a hybrid (LL) of L
AG
and L
BrdU
(a mutant of L cells, resistant to 100 μg/ml of 5-bromodeoxyuridine) were prepared by the use of artificial fusion by UV-irradiated HVJ (Sendai virus). In the second step the LE hybrid and ETC, or the LL hybrid and ETC, were fused again by UV-HVJ. The hybrids (LEE and LLE) were segregated during culture. Thus, the series of hybrids L, LLE, LE, LEE, and ETC was obtained. The morphological feature and karyological characters of these hybrids and the distribution of antigens corresponding to each parent on their cell surfaces supported the above identification of the series of hybrids obtained by double hybridization.

All three hybrids acquired new characters, such as the ability to form large colonies in soft agar and large tumors on the chorioallantoic membrane of chicken eggs, unlike either parent. The tumor-forming capacity of the series was ETC > LEE > LE > LLE; L cells formed no tumor in mouse abdomen under the test conditions.
Chemical Modifications of Transfer RNA Species. Desulfurization with Raney Nickel
Authors: Hecht Sidney M. , Kirkegaard Leslie H. , Bock Robert M.
Published: May 2006

A single, modified nucleoside in
Escherichia coli
tRNA, 6-(3-methyl-2-butenylamino)-2-methyl-thio-9-β-D-ribofuranosylpurine, has been desulfurized with Raney nickel to afford its probable biosynthetic precursor. The limitations of the reaction at the nucleoside and tRNA levels and its lack of inhibition of the amino acid acceptor activity of tRNA are described.
Extrinsic Cotton Effects Characteristic of Specific Hapten-Antibody Interactions
Authors: Glaser Michael , Singer S. J.
Published: May 2006

The reversible binding of the haptens 2,4-dinitrophenyllysine (DNP-lysine) and 2,4,6-trinitrophenyllysine (TNP-lysine) to either the nitrophenyl-binding myeloma protein MOPC-315 or to pooled mouse anti-DNP or anti-TNP antibodies produces large and characteristic extrinsic Cotton effects (in the circular dichroic spectra). Despite the similarities in binding characteristics of the three proteins, the circular dichroic spectra produced by the haptens bound to the active sites of these proteins were markedly different. Extrinsic Cotton effects, therefore, provide a powerful new probe of the structure of the reversible complex formed between a hapten and an antibody active site.
Comparative Properties of RNA and DNA Templates for the DNA Polymerase of Rous Sarcoma Virus
Authors: Duesberg Peter , Helm Klaus V. D. , Canaani Eli
Published: May 2006

Several natural RNAs were compared with respect to their template activities for the DNA polymerase of Rous Sarcoma Virus during a 2-hr incubation period. 60-70S viral RNA was found to be a 5- to 10-fold better template than heat-dissociated Rous viral RNA, influenza virus RNA, tobacco mosaic virus RNA, or ribosomal RNA. Denatured salmon DNA is a little better, and poly(dAT) is 2-4 times better as a template for the enzyme than is 60-70S Rous viral RNA. The 60-70S RNAs of different strains of avian tumor viruses have very similar template activities for a given avian tumor virus DNA polymerase. Oligo(dT) or oligo(dC) were found to enhance the template activity of heat-dissociated Rous viral RNA 20- to 30-fold, and that of other natural RNAs tested one- to several-fold. DNA syntheses of 1-24% were obtained during a 2-hour incubation of the enzyme with the above RNA templates. The results suggest that the enzyme prefers partially doublestranded or hybrid regions of RNAs for optimal DNA synthesis, but certain regions of single-stranded RNA can also serve as templates.

Poly(dAT) competes with viral RNA for purified DNA polymerase during DNA synthesis, as would be expected if RNA- and DNA-dependent DNA synthesis was performed by at least one common active site of the same enzyme.
Uridine Diphosphate-4-Keto-Glucose, an Intermediate in the Uridine Diphosphate-Galactose-4-Epimerase Reaction
Authors: Maitra Utpalendu S. , Ankel Helmut
Published: May 2006

When UDP-galactose 4-epimerase (EC 5.1.3.2) from
Escherichia coli
is incubated with UDP-galactose, then reduced with NaB
3
H
4
, label is found in UDP-glucose and UDP-galactose. Enzymatic and chemical degradation demonstrates that the label is bound to carbon 4 of the glycosyl moieties. These results provide direct evidence for the existence of UDP-4-keto-glucose as an enzyme-bound intermediate in the epimerization reaction, and they exclude the formation of a 3-keto intermediate.
Assignment of Four Linkage Groups to Chromosomes in
Mus musculus
and a Cytogenetic Method for Locating Their Centromeric Ends
Authors: Miller D. A. , Kouri R. E. , Dev V. G. , Grewal M. S. , Hutton J. J. , Miller O. J.
Published: May 2006

The mitotic chromosomes in primary cultured cells from mouse embryos of the translocation stocks,
T(5;18)26H, T(5;11)7Ca
, and
T(14;17)264Ca
, have been identified by their distinctive fluorescent-banding patterns after staining with quinacrine mustard. In this way, linkage group (LG) V has been assigned to chromosome 2, LGXVIII to chromosome 9, and LGXIV and LGXVII to either of chromosomes 3 or 13. The assignment of LGXI to chromosome 6 has been confirmed. The centromeres of chromosomes 1 (LGXIII), 2 (LGV), 9 (LGXVIII), and 16 (LGIX) have been located at the ends nearest the genes fuzzy (
fz
), Danforth's short tail (
Sd
), nervous (
nr
), and
T
of their respective linkage groups by a cytogenetic method. The centromere of the X (LGXX) has been tentatively assigned to the end nearest to the scurfy (
sf
) locus.
Translation of Exogenous Messenger RNA for Hemoglobin on Reticulocyte and Liver Ribosomes
Authors: Prichard P. M. , Picciano D. J. , Laycock D. G. , Anderson W. F.
Published: May 2006

The ribosome and initiation factor requirements for translation of rabbit-reticulocyte hemoglobin mRNA on rabbit reticulocyte ribosomes, reticulocyte ribosomal subunits, and liver ribosomes have been studied. Excellent synthesis of globin chains from exogenous mRNA in the fractionated cell-free system has been achieved. There is a near absolute requirement for each of the initiation factors, M
1
, M
2
, and M
3
(as well as for the supernatant proteins) for the translation of exogenous mRNA. Liver microsomal wash will partially replace reticulocyte factors M
1
and M
2
, but will not replace the requirement for reticulocyte factor M
3
. Rabbit liver ribosomes and rabbit reticulocyte ribosomes are equally active in their ability to support the translation of exogenous hemoglobin mRNA.
Migration of Mouse 3T3 Fibroblasts in Response to a Serum Factor
Authors: Lipton Allan , Klinger Ingrid , Paul Dieter , Holley Robert W.
Published: May 2006

A serum factor that promotes migration of (mouse) 3T3 fibroblast cells is shown to be distinct from the growth-promoting and cell-survival factors of serum. The factor promotes migration of cells from the edge of a wound in confluent 3T3 cells, but cell migration under these conditions does not lead to the initiation of DNA synthesis. Subsequent addition of serum initiates DNA synthesis in the migrating cells. The results establish that breaking contacts between quiescent 3T3 cells is not sufficient to initiate DNA synthesis. The DNA synthesis observed in migrating 3T3 cells in the typical “woundhealing” experiment presumably results because the migrating cells have an increased ability to use serum factors. Serum-factor requirements for “wound healing” in cultured 3T3 cells are discussed.
Association Factor of Ribosomal Subunits from
Bacillus stearothermophilus
Authors: García-Patrone M. , González N. S. , Algranati I. D.
Published: May 2006

The isolation of a new factor, which can cause the
in vitro
association of 30S and 50S ribosomal subunits at low Mg
++
concentration, is described. The association factor is eluted together with the dissociation protein when ribosomes of
Bacillus stearothermophilus
are washed with salt solutions of high concentration. The association activity is heat-stable, whereas dissociation factor is inactivated after 10 min at 80°C. This treatment allows the separation of both factors. Several properties rule out the possibility that uncharged, amino-acyl-, or peptidyl-tRNA are responsible for the association process described in this report. Digestion with trypsin shows that the association factor contains at least two components, one of which is a protein.
Isolation of Catenated and Replicating DNA Molecules of Colicin Factor E1 from Minicells
Authors: Inselburg Joseph , Fuke Motohiro
Published: May 2006

Various catenated and replicating molecules of colicin E1 isolated from minicells have been identified in regions of neutral sucrose density gradients or cesium chloride-ethidium bromide density gradients. These colicin molecules have been found in those regions of the gradient where pulse-labeled DNA accumulates.
Karyological Properties of Human-Mouse Somatic Hybrids
Authors: Jami Jacques , Grandchamp Simone
Published: May 2006

Karyological examinations performed 24 hr to 11 days after Sendai virus-induced fusion of mouse cells of the permanent line 3T3 and human diploid cells, suggest that hybrids with extensive loss of human chromosomes derive from fusion involving all the chromosomes of both parental cells. Examination of 39 independent clones isolated from two different crosses between L mouse cells and cells of two permanent human lines, D98/AH2 and VA2, show that the karyotypes of human-mouse hybrids are a function of the interaction between the parental cells: the mouse chromosomal complement may be doubled or not. For the first time, viable hybrids that have retained almost all of the human chromosomes have been isolated.
A Note on the Ground State Energy of an Assembly of Interacting Electrons
Authors: Isihara Akira , Montroll Elliott W.
Published: May 2006

The ground state energy of an assembly of charged particles of density ρ imbedded in a continuum of charge of the other sign in an electrically neutral system is considered. Asymptotic formulae for the ground state energy of such systems are known in the high- and low-density regimes. An interpolation formula covering the entire density range is derived using the method of two-point Padé approximants. A phase transition from an electron lettice to an electron gas seems to occur at
r
3
≅ 14,
r
3
being the radius of a sphere which, on the average, contains a single charge, in units of the Bohr radius of the electron in a hydrogen atom.
Persistence of a Repressed Epstein-Barr Virus Genome in Burkitt Lymphoma Cells Made Resistant to 5-Bromodeoxyuridine
Authors: Hampar Berge , Derge Jeffery G. , Martos Lidia M. , Walker John L.
Published: May 2006

The P3HR-1 line of human lymphoblastoid cells that is Epstein-Barr virus positive was made resistant to 5-bromodeoxyuridine. Epstein-Barr virus-associated antigens, but not virus particles, were produced in P3HR-1(BU) cells maintained on 5-bromodeoxyuridine. However, virus particles did appear within 4 days after removal of the drug. Thymidine kinase activity was limited to P3HR-1(BU) cells producing viral antigen, whereas all control P3HR-1 cells showed thymidine kinase activity regardless of viral antigen synthesis.

Cellular DNA in most P3HR-1(BU) cells was made via pathways that did not involve thymidine kinase. In cells having a pathway that involved thymidine kinase, a second DNA of density 1.71 g/cm
3
, corresponding to Epstein-Barr virus, was detected.

It was concluded that: (
a
) a repressed Epstein-Barr virus genome persists in P3HR-1(BU) cells that do not contain thymidine kinase, with activation of the viral genome being accompanied by productive infection and the appearance of enzyme, and (
b
) thymidine kinase activity in P3HR-1(BU) cells could be used as a marker for viral genome expression.
Host-Gene Control of C-Type RNA Tumor Virus: Inheritance of the Group-Specific Antigen of Murine Leukemia Virus
Authors: Taylor B. A. , Meier H. , Myers D. D.
Published: May 2006

Genetic studies were aimed at elucidation of the mechanism of inheritance of the group-specific antigen of the murine leukemia virus. Two approaches have been used. First, a classical Mendelian hybridization experiment was performed with mice of the high-leukemia AKR strain and the low-leukemia C57L strain; the first filial (F
1
) generation hybrids, the second filial (F
2
) generation hybrids, and the backcrosses to the two parental strains. Second, a number of partially inbred lines derived from the F
2
generation of the same cross were used. The results of these studies demonstrate a specific genetic regulation of expression of group-specific antigens. Genes permissive to the expression of the antigen are dominant or semidominant to their nonpermissive alleles. It appears that two dominant genes carried by the AKR strain, but not by the C57L strain, are necessary for the presence of a complete virus; one of these controls the expression of group-specific antigen.
Isolation of
Saccharomyces cerevisiae
Mitochondrial Formyltetrahydrofolic Acid:Methionyl-tRNA Transformylase and the Hybridization of Mitochondrial fMet-tRNA with Mitochondrial DNA
Authors: Halbreich A. , Rabinowitz M.
Published: May 2006

Formyltetrahydrofolic acid:methionyl-tRNA transformylase was isolated from
Saccharomyces cerevisiae
mitochondria and used to prepare yeast mitochondrial [
3
H]formylmethionyl-tRNA. This fMet-tRNA hybridizes with mitochondrial DNA but not with yeast nuclear or
E. coli
DNA. Unlabeled mitochondrial, but not extramitochondrial, tRNA competes in this reaction. tRNA was eluted from the hybrid and found to contain the label almost exclusively in fMet-tRNA. Yeast cytoplasmic fMet-tRNA formylated with
Escherichia coli
enzyme, and
E. coli
fMet-tRNA, do not hybridize with mitochondrial DNA. It is concluded that yeast mitochondrial tRNA
fMet
is a gene product of the mitochondrial genome.
Cellular Site of
Escherichia coli
Ribosomal RNA Synthesis
Authors: Haywood Anne M.
Published: May 2006

Escherichia coli
, grown for a generation after the addition of [
14
C]uracil and for one minute after a pulse of [
3
H]uracil, were lysed in the presence of 6 mM Mg
++
, and divided into a 30,000 ×
g
“supernatant” and sediment. The sediment was resuspended in buffer containing no divalent cations, and again centrifuged to give the “Mg
++
sediment” and the remaining “sediment”. The ratio of
3
H (one-minute pulse RNA) to
14
C (Stable RNA) in the supernatant is 1/6 to 1/10 that of the sediment RNA, and the ratio of
3
H:
14
C in the Mg
++
sediment is 1/2 to 1/6 that in the sediment RNA. Gel electrophoresis of RNA from the different fractions shows that ribosomal RNA precursors first appear in the sediment. It is concluded that the site of ribosomal RNA synthesis is associated with a sedimentable structure, which is probably cell membrane.
Chick Embryo Ribosome Crystals: Analysis of Bonding and Functional Activity
In Vitro
Authors: Byers Breck
Published: May 2006

The intracellular ribosome crystals from chick embryos incubated at 5°C have been isolated; stable products of their dissociation were shown to include single ribosomes, tetramers of ribosomes, and tetramers of large subunits. Conditions were found for the formation
in vitro
not only of the
p4
crystals from ribosomal tetramers but also of the tetramers themselves from free ribosomes. The polypeptide synthesizing activity of these ribosomes was found to be unimpaired by their constraint in the tetrameric configuration.
Zoospore Germination in
Blastocladiella emersonii:
Cell Differentiation without Protein Synthesis?
Authors: Soll D. R. , Sonneborn D. R.
Published: May 2006

Evidence is presented to suggest that several early events of zoospore germination in the water mold,
Blastocladiella emersonii
, are not dependent upon concomitant protein synthesis. The events involve abrupt, dramatic changes in cell architecture. On account of this evidence, as well as evidence available from other sources, we question whether differential protein synthesis provides an exclusive and sufficient mechanism for phenotypic change (i.e., cell differentiation). Rather, we argue that mechanisms for bringing about structural alterations in the preformed machinery of the cell should also be given attention.
Reinitiation of RNA Synthesis on Transcription of Chromatin DNA by
Escherichia coli
RNA Polymerase
Authors: Morris Margaret E. , Gould Hannah
Published: May 2006

The transcription of DNA in chromatin by
Escherichia coli
RNA polymerase resembles that of isolated DNA in two important respects: the release of nascent RNA and reinitiation of RNA synthesis is dependent on the salt concentration, and RNA synthesis is markedly stimulated by the addition of ribosomes.
Pathogenicity Resulting from Mutation at the
b
Locus of
Ustilago maydis
Authors: Day P. R. , Anagnostakis S. L. , Puhalla J. E.
Published: May 2006

This paper explores the genetic basis of the ability of the fungus,
Ustilago maydis
, to induce neoplastic galls in the corn plant (
Zea mays
). Pathogenic mutants of
U. maydis
were produced by ultraviolet irradiation of cultures of nonpathogenic diploids homozygous at the
b
locus. The mutants formed smaller neoplasms, produced fewer teliospores, and showed higher frequencies of meiotic failure and lower rates of basidiospore survival than did the wild-type fungus.
Kinetics of Insulin Release from the Perfused Rat Pancreas Caused by Glucose, Glucosamine, and Galactose
Authors: Landgraf Rüdiger , Kotler-Brajtburg Janina , Matschinsky Franz M.
Published: May 2006

Under appropriate conditions, not only glucose but also glucosamine and galactose can serve as potent stimulants for insulin release from the isolated, perfused rat pancreas. Since galactose and, probably, glucosamine are not metabolized in the islets, and since these three compounds have in all likelihood common sites of action, it is postulated that a glucoreceptor of broad specificity is involved in the mechanism of insulin release, and that metabolism of glucose is not an essential part of the releasing action of this sugar.
Specific Transformylation of One Methionyl-tRNA from Cotton Seeding Chloroplasts by Endogenous and
Escherichia coli
Transformylases
Authors: Merrick William C. , Dure III L. S.
Published: May 2006

Two isoaccepting chloroplastic and one cytoplasmic tRNA
Met
species have been separated from germinating cotton cotyledons. The methionylated form of one of the chloroplastic species (but none of the other or of the cytoplasmic tRNA
Met
) can be formylated either by an endogenous transformylase or by
Escherichia coli
transformylase.
Radioresistance of the Enhancing Effect of Cells from Carrier-Immunized Mice in an
In Vitro
Primary Immune Response
Authors: Kettman J. , Dutton R. W.
Published: May 2006

The
in vitro
primary response of mouse spleen cell suspensions to 2,4,6-trinitrophenyl(Tnp)-erythrocytes has been studied. The number of anti-Tnp plaque-forming cells that arise after antigenic stimulation
in vitro
is greatly enhanced by prior immunization
in vivo
with the carrier erythrocyte. The enhancement is antigen specific. The priming for an enhanced response can be elicited with very low antigen doses and is often apparent 24 hr after immunization. It is marked from day 3 to day 14. Spleen cells from carrier-primed mice will enhance the anti-Tnp response of normal cells when mixed cultures of the two cell populations are challenged with Tnp-erythrocytes
in vitro
. The carrier-primed cells mediating this enhancing effect are thymus derived.

The development of the thymus-derived, carrier-specific cell population has been generally assumed to involve the antigenic stimulation of cell proliferation. It was, therefore, somewhat surprising to find that the enhancing effect of the carrier-primed cells, once they had been generated, is not inhibited by x-irradiation.
Interconversion of Cyclic Nucleotide-Activated and Cyclic Nucleotide-Independent Forms of a Protein Kinase from Beef Heart
Authors: Erlichman Jack , Hirsch Allen H. , Rosen Ora M.
Published: May 2006

A protein kinase activated by cyclic nucleotides was purified from beef heart. Upon exposure to adenosine 3′:5′-cyclic monophosphate (cyclic AMP) during gel filtration on Sephadex G-200, the protein kinase dissociated into a cyclic nucleotide-independent protein kinase and a cyclic nucleotide-binding protein. A similar or identical cyclic nucleotide-independent protein kinase could be obtained in highly purified form by clution from a DEAE-cellulose column with 10
-6
M cyclic AMP; the cyclic AMP-binding protein was apparently retained by the resin. The addition of cyclic nucleotide-binding protein to cyclic nucleotide-independent protein kinase resulted in the reappearance of cyclic nucleotide-dependent protein kinase, which could be isolated by filtration on Sephadex G-200 in the absence of cyclic AMP. These results confirm and extend previous suggestions that cyclic nucleotides activate protein kinases by dissociating them from inhibitory, cyclic nucleotide-binding proteins.
The Influence of Neighboring Base Pairs upon Base-Pair Substitution Mutation Rates
Authors: Koch Robert E.
Published: May 2006

The 2-aminopurine-induced transition, A·T → G·C, was studied at particular sites in bacteriophage T4 as a function of the nearby base-pair composition of the DNA. Changing a base pair changed the transition rate at the adjacent base pair up to 23-fold, and at the next base pair by a lesser amount. Destabilization was achieved by replacing an A·T base pair by a G·C base pair.
Role of the Receptor in the Mechanism of Action of Adenosine 3′:5′-Cyclic Monophosphate
Authors: Gill Gordon N. , Garren Leonard D.
Published: May 2006

Highly purified cAMP-dependent protein phosphokinase from adrenal-cortical tissue contains cAMP-receptor activity. In activating the kinase, cAMP binds to the receptor and causes it to dissociate from its complex with the kinase. The kinase, freed of receptor, is fully activated and no longer stimulable by cAMP. Kinase can be similarly activated by differentially denaturing the receptor with heat. Addition of receptor suppresses kinase activity; this suppression can be overcome by cAMP. After dissociation of receptor, two molecular forms of the activated kinase exist. The cAMP receptor thus functions as a repressor of the protein kinase; binding of cAMP to receptor causes it to dissociate from the kinase, which is then fully activated.
Conformational Changes in Ribosomes during Protein Synthesis
Authors: Schreier Max H. , Noll Hans
Published: May 2006

In a purified system containing poly(U) and ribosomal subunits from
Escherichia coli
, and purified transfer factors T and G, the active ribosomal complex passes through a cycle of contraction and expansion with the addition of each amino acid; aminoacyl-tRNA binding catalyzed by T produces the stable compact state, corresponding to the 70S conformation, whereas translocation with G expands the ribosome to a less stable 60S form. It is also shown that formation of the first peptide bond must be preceded by translocation with G. These findings are consistent with a model of chain initiation in the absence of initiation factors in which deacylated tRNA
Phe
bound to the P site signals translocation by G and GTP as soon as the 60S initiation complex has been converted to the 70S form by the enzymatic binding of Phe-tRNA.
Genetic Recombination in
Escherichia coli:
The Role of Exonuclease I
Authors: Kushner Sidney R. , Nagaishi Haruko , Templin Ann , Clark Alvin J.
Published: May 2006

The indirect suppression of
recB
-
and
recB
-
recC
-
mutations by the
sbcB
-
allele is caused by the loss of a nuclease active on denatured DNA. Results from enzyme purifications and studies with a specific antiserum demonstrate that the activity present in
sbcB
+
strains, and lost in
sbcB
-
strains, is exonuclease I. It is likely that
sbcB
is the structural gene for exonuclease I. The loss of exonuclease I activity restores the recombination proficiency of
Escherichia coli
cells that has been lost by mutations in the
recB
and/or
recC
genes. This indicates that in the absence of the
recB-recC
-determined enzyme, exonuclease I prevents recombination. Hypothetical pathways illustrating this conclusion are presented.
Binding Sites for Cholinergic Ligands in a Particulate Fraction of
Electrophorus
Electroplax
Authors: Eldefrawi M. E. , Eldefrawi A. T. , O'brien R. D.
Published: May 2006

The binding of four radioactive cholinergic ligands to a particulate fraction of
Electrophorus electricus
electroplax was investigated by equilibrium dialysis and found to be reversible. A single site (concentration, 0.02-0.03 nmol/g electroplax) that bound muscarone and nicotine was found to be on a phospholipoprotein; it is suggested that this is the acetylcholine receptor. Four binding sites for decamethonium were found; the highest-affinity site (0.03 nmol/g) may be the same one that binds muscarone and nicotine, both because of the chemical nature of the binding macromolecule and because decamethonium competes with muscarone and nicotine in binding. Dimethylcurare bound to three sites. The lower-affinity sites appeared to be on different macromolecules.

When binding of the four cholinergic ligands (at 0.01 μM) to 28 arbitrarily selected proteins was determined, it was concluded that muscarone would be the most specific for the acetylcholine receptor, in that it bound to none of the 28 proteins tested; nicotine bound to one, dimethylcurare to two, and decamethonium to ten of the proteins. Nicotine or muscarone appear to be the ligands of choice in studying binding to the acetylcholine receptor; decamethonium appears to have inadequate specificity.
Quantitative
In Vitro
Measurement of Simian Virus 40 Tumor-Specific Antigens
Authors: Wright Peter W. , Law Lloyd W.
Published: May 2006

Humoral antibodies, specific for the SV40 tumor-specific transplantation antigen, can be detected by an
in vitro
cytotoxic assay.
51
Cr-labeled SV40-transformed target cells are selectively killed in the presence of specific antibody and rabbit complement. Inhibition of cytotoxicity can be used to measure the antigen concentration and specific activity on different SV40-transformed cell lines. The assay described has several advantages when compared to other methods currently available to detect the specific SV40 antigen: it is simple, rapid, objective, reproducible, and quantitative.
Unusual Fragments in the Subunit Structure of Concanavalin A
Authors: Wang John L. , Cunningham Bruce A. , Edelman Gerald M.
Published: May 2006

Gel electrophoresis in sodium dodecyl sulfate and gel filtration in guanidine. HCl indicate that native concanavalin A contains several molecular species. An intact subunit of molecular weight 27,000 has been purified from this mixture. In addition, three fragments of the intact subunit have been isolated and characterized. A working model of the concanavalin A molecule has been constructed based on pairings of the intact subunit and of subunits consisting of fragments.
Differential Effect of 5-Bromodeoxyuridine on the Concentrations of Specific Enzymes in Hepatoma Cells in Culture
Authors: Stellwagen Robert H. , Tomkins Gordon M.
Published: May 2006

Growth of cultured rat hepatoma cells in the presence of 5-bromodeoxyuridine results in a rapid inhibition of the synthesis of adrenal steroid-inducible tyrosine aminotransferase (EC 2.6.1.5) and slower decreases in the concentrations of lactate dehydrogenase (EC 1.1.1.27), alcohol dehydrogenase (EC.1.1.1.1), and glucose-6-phosphate dehydrogenase (EC 1.1.1.49). During the same period, neither overall cell growth nor the concentrations of malate dehydrogenase (EC 1.1.1.37), acid phosphatase (EC 3.1.3.2), or alanine aminotransferase (EC 2.6.1.2) were significantly decreased by the base analog. Addition of thymidine to the growth medium rapidly counteracts the inhibition of tyrosine aminotransferase synthesis but restores the normal concentrations of lactate-, alcohol-, and glucose-6-phosphate dehydrogenases much more slowly. Growth of the cells for only one generation in the presence of bromodeoxyuridine, followed by the addition of thymidine, produces transient decreases in the concentrations of the three “late-responding“ dehydrogenases, beginning 2-3 generations after exposure to the analog.

It is concluded that the selective inhibitory effects of the analog could result from a mechanism in which bromodeoxyuridine is uniformly incorporated into cellular DNA, but inhibits the transcription of only certain genes into messenger RNA. A mathematical model is derived to account for the observed differences in the kinetics of the inhibition of synthesis of the gene products that are sensitive to the analog.
Circular Chloroplast DNA from
Euglena gracilis
Authors: Manning Jerry E. , Wolstenholme David R. , Ryan Robert S. , Hunter Janice A. , Richards Oliver C.
Published: May 2006

Chloroplast DNA of the protozoan flagellate,
Euglena gracilis
, exists as circular molecules, 40 μm in contour length, as shown by electron microscopy and buoyant density analyses.
Isolation of a Calcium-Sequestering Protein from Sarcoplasmic Reticulum
Authors: MacLennan David H. , Wong P. T. S.
Published: May 2006

An acidic protein has been extracted from sarcoplasmic reticulum with KCl and deoxycholate. The protein, which remains soluble after extraction, has been highly purified by fractionation on DEAE-cellulose, Sephadex, and hydroxylaptite. It has a molecular weight of 44,000 and contains 392 amino acid residues per molecule, of which 146 are either glutamic or aspartic acid. No phosphorus, sialic acid, or lipid has been detected in the preparation. The protein has been shown to bind up to 970 nmol of Ca
++
per mg (43 mol/mol) at pH 7.5, with an apparent dissociation constant of 4 × 10
-5
M. Preliminary data indicate that the protein is unique to sarcoplasmic reticulum and that it is hydrophobically bonded on the interior of these vesicles. The protein is believed to play a role in sequestering calcium within sarcoplasmic reticulum. The name Calsequestrin is suggested for the protein.
Magnetic Anisotropy and the Orientation of Retinal Rods in a Homogeneous Magnetic Field
Authors: Hong Felix T. , Mauzerall David , Mauro Alexander
Published: May 2006

The reported orientation of retinal rods in a homogeneous magnetic field can be explained by the magnetic anisotropy of oriented molecules in the disc membranes of the rods.

The energy of a single rod as a function of orientation in the magnetic field, the time required for alingment of the rod in a viscous medium, and the fluctuations of orientation are calculated. Arguments that rhodopsin is the constituent responsible for the effect are given. The possibility of orientation due to inhomogeneity of the magnetic field is ruled out. The application of magnetic anisotropy as an experimental tool in biology is indicated.
Mechanism of Action of 1,25-Dihydroxycholecalciferol on Intestinal Calcium Transport
Authors: Tanaka Y. , DeLuca H. F. , Omdahl J. , Holick M. F.
Published: May 2006

The prior administration of actinomycin D prevents the metabolism of [
3
H]25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol, a metabolite of vitamin D
3
that is effective in the stimulation of intestinal calcium transport. In this paper, the question of whether the response of intestinal calcium transport to 1,25-dihydroxycholecalciferol is sensitive to actinomycin D was examined. While the response of intestinal transport to physiological amounts of 25-hydroxycholecalciferol is blocked by actinomycin D, the response of intestinal calcium transport to 1,25-dihydroxycholecalciferol is insensitive to the antibiotic. These results suggest that 1,25-dihydroxycholecalciferol, or a further metabolite thereof, is the metabolically active form of vitamin D in the intestine, that it functions by a process not involving transcription of DNA, and that the step sensitive to actinomycin D in the action of vitamin D on the intestine does not occur in the intestine, but is the conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol in the kidney.
Practical, Stereoselective Synthesis of
Cecropia
Juvenile Hormone
Authors: Tamelen E. E. Van , McCurry P. , Huber U.
Published: May 2006

The high-yield, stereoselective conversion of geraniol (3,7-dimethyl-
trans
-2,6-octadien-1-ol) to the insect juvenile hormone, methyl 12,14-dihomojuvenate (methyl
cis
-10-epoxy-3,11-dimethyl-7-ethyl-
trans, trans
-2,6-tridecadienoate), has been performed by means of a nine-step route that avoids chromatography of intermediates.
Adenosine Triphosphate-Dependent Synthesis of Biologically Active DNA by Azide-Poisoned Bacteria
Authors: Ganesan A. T.
Published: May 2006

Nonviable cells of
Bacillus subtilis
, when made permeable by treatment under controlled conditions with nonionic detergent, can be shown to replicate DNA normally and to repair certain regions of the chromosome. The former process is stimulated by ATP in the presence of dATP, dCTP, dGTP, and dTTP. The product, a result of semiconservative replication, is biologically active; synthesis of the newly-formed regions of the chromosome appears to be sequential.
An Alternate Complement Pathway: C-3 Cleaving Activity, Not Due to [unk], on Endotoxic Lipopolysaccharide after Treatment with Guinea Pig Serum; Relation to Properdin
Authors: Marcus Robert L. , Shin Hyun S. , Mayer Manfred M.
Published: May 2006

The reaction between endotoxic lipopolysaccharide (LPS) and the guinea pig complement system was shown to proceed by way of an intermediate complex, LPS-X, which contains at least six guinea pig serum proteins. LPS-X, like [unk] (sheep erythrocytes carrying antibody molecules and [unk] complexes), destroys the C3 molecule by cleavage. On incubation at 37°C, LPS-X loses its capacity to destroy C3 at about the same rate as the decay of [unk], so that it has been assumed that LPS-X carries [unk] sites that are responsible for the destruction of C3.

We have now shown that monospecific rabbit antiguinea pig C2, which effectively inhibits C3 cleavage by [unk], does not interfere with the destruction of C3 by LPS-X. Furthermore, not more than a trace of C2a
d
is released from LPS-X on incubation at 37°C. These results indicate that LPS-X does not carry a significant quantity of [unk] and, hence, that its capacity to destroy C3 is due to another factor which is presumably a component of the properdin system.
Site-Directed Cross-Linking: A New Approach to Mapping Antibody Combining Sites
Authors: Hadler Nortin M. , Metzger Henry
Published: May 2006

The γA myeloma protein 315 from the mouse was affinity-labeled with
m
-nitrobenzene diazonium fluoroborate which, as shown previously, leads to selective modification of the tyrosine at position 34 in the light chains of this protein. The azotyrosine bond was reduced with dithionite to form 3-aminotyrosine. The aryl amino group of the aminotyrosine was selectively reacted with the bifunctional reagent 1,5-difluoro-2,4-dinitrobenzene. Cross-links were formed between the aminotyrosine and at least two residues—one on the same light chain and one in the Fd region of the heavy chain. Since affinity labeling of various antibodies with diazonium reagents has frequently led to azotyrosine formation, the approach described in this paper should have general applicability.
Purification of IMP:Pyrophosphate Phosphoribosyltransferases, Catalytically Incompetent Enzymes in Lesch-Nyhan Disease
Authors: Rubin Charles S. , Dancis Joseph , Yip Lily C. , Nowinski Robert C. , Balis M. Earl
Published: May 2006

IMP:pyrophosphate phosphoribosyltransferase (IPPase) (EC 2.4.2.8) has been purified over 7000-fold from human erythrocytes. The purified enzyme moved as a single band on disc electrophoresis. Antisera prepared in rabbits and rats against the purified enzyme precipitated and neutralized the enzyme, but had no effect on AMP-pyrophosphate phosphoribosyltransferase (EC 2.4.2.7) activity. Evidence was found for isozymes (enzyme variants) of IPPase in normal erythrocytes.

Erythrocyte lysates of five patients with Lesch-Nyhan disease reacted with antisera against normal IPPase. Lysates from LN erythrocytes blocked the inactivation of normal enzyme by the antibody. LN erythrocytes had about the same concentration of enzyme protein as normal erythrocytes.

The genetic defect in LN results in the production of essentially normal amounts of an immunologically identifiable but catalytically incompetent enzyme. Thus LN is apparently the result of a mutation in a structural gene and is not due to deletion of a structural gene or defect in a regulatory gene.
Hypoxanthine-Guanine Phosphoribosyltransferase Deficiency: Chemical Agents Selective for Mutant or Normal Cultured Fibroblasts in Mixed and Heterozygote Cultures
Authors: Fujimoto Wilfred Y. , Subak-Sharpe John H. , Seegmiller J. Edwin
Published: May 2006

Cultured fibroblasts established from skin biopsies from patients with the Lesch-Nyhan syndrome are deficient in hypoxanthine-guanine phosphoribosyl-transferase (EC 2.4.2.8) activity. This deficiency makes possible the use of chemicals that select either for or against deficient variants in cultured fibroblasts. Two-way selection has been achieved by the use of 6-thioguanine, which selects for the deficient mutant, and azaserine, which selects to some extent for the normal allele in mixed cultures, as well as in cultures from heterozygotes. Theoretical considerations predict that the phenomenon of metabolic cooperation would tend to reinforce the former and to weaken the latter type of selection, and this is in accordance with the experimental findings.
Induction of Colonies of Hemoglobin-Synthesizing Cells by Erythropoietin
In Vitro
Authors: Stephenson John R. , Axelrad Arthur A. , McLeod David L. , Shreeve Mona M.
Published: May 2006

A culture method has been developed in which erythroid colonies are produced
in vitro
from hemopoietic cells from the livers of 13-day fetuses of C3H
f
/Bi mice. Heme synthesis by the cultures was correlated with the presence of these colonies, and the hemoglobin produced was shown to be electrophoretically normal. The individual colonies were identified as erythroid since they were erythropoietin-dependent, positively stained by the histochemical “Lepehne” procedure for hemoglobin, and labeled by
59
Fe radioautography. Evidence is presented that the development of these colonies is under separate control from that of granulocytic colonies found in the same cultures.
Serological and Structural Properties of Mason-Pfizer Monkey Virus Isolated from the Mammary Tumor of a Rhesus Monkey
Authors: Nowinski Robert C. , Edynak Eugene , Sarkar Nurul H.
Published: May 2006

We describe here serological and structural properties of a virus, Mason-Pfizer Monkey Virus (M-PMV), isolated from a simian mammary tumor. This virus is morphologically similar to the known oncogenic RNA viruses (oncornaviruses). It has a 60-70S RNA, and its replication is inhibited by actinomycin. Antisera prepared against the virus isolated by density-gradient centrifugation identify at least two viral structural antigens. Immunodiffusion studies show that this virus is serologically unrelated to three types of simian foamy viruses, visna virus, and the known oncornaviruses. Immunofluorescence reveals that the structural proteins of the virus are synthesized cytoplasmically. Although M-PMV productively infects human cells
in vitro
, serological analysis does not show the presence of M-PMV antigens in human neoplasia.
Hormone-Controlled Synthesis of Endoplasmic Reticulum in Barley Aleurone Cells
Authors: Evins Warren H. , Varner J. E.
Published: May 2006

The rate of synthesis of the endoplasmic reticulum in barley aleurone cells after treatment with gibberellic acid was determined by measurement of [
14
C]-choline incorporation into acid-insoluble material in a semipurified fraction containing the endoplasmic reticulum. 94% of the
14
C incorporated into this fraction is extractable by lipid solvents and only 9% is removed by procedures for nucleic acid extraction. Gibberellic acid increases the rate of synthesis of the endoplasmic reticulum 4- to 8-fold, starting about 4 hr after addition of the hormone (at about the same time as polysome formation). Abscisic acid inhibits this gibberellic acid-enhanced increase in the rate of synthesis of endoplasmic reticulum.
Mechanism of Action of Vitamin K: Evidence for the Conversion of a Precursor Protein to Prothrombin in the Rat
Authors: Shah D. V. , Suttie J. W.
Published: May 2006

Previous studies have shown that the vitamin K-induced synthesis of prothrombin in a vitamin K-deficient rat is only slightly inhibited by cycloheximide treatment. Rat prothrombin has now been purified by disc electrophoresis after BaSO
4
adsorption and citrate elution. When cycloheximide (5 mg/kg) was given to vitamin K-deficient rats 30 min before vitamin K, about 70% of the amount of prothrombin seen in rats not treated with cycloheximide was produced (two-stage assay), and the prothrombin band could be seen on the electrophoretic gels. However, if radioactive amino acids are administered to the rats after cycloheximide treatment, the newly formed prothrombin contains no radioactivity. The isolated prothrombin does contain radioactivity if the vitamin K-deficient rats are treated with vitamin K but no cycloheximide. When radioactive amino acids were given to deficient rats 1 hr before cycloheximide and vitamin K, radioactivity was found in prothrombin. These data suggest that, in the intact rat, the action of vitamin K is to convert a protein precursor with a short biological half life to prothrombin.
The Prematurely Evoked Synthesis of Liver Tryptophan Oxygenase
Authors: Greengard Olga , Dewey Henry K.
Published: May 2006

Livers of normal rats are devoid of catalytically or immunochemically reactive tryptophan oxygenase (EC 1.13.1.12) up to the 10th postnatal day; the enzyme reaches adult concentrations on about the twentieth day. Premature tryptophan oxygenase synthesis can be evoked in 4-day-old rats: if an injection of glucocorticoid is followed, a day later, by an injection of tryptophan, adult levels of tryptophan oxygenase activity and antigen content can be attained within 5 hr. The prematurely evoked tryptophan oxygenase is degraded in about 2 days, but the preparatory action of the glucocorticoid is longlasting. Even 4 days later, an injection of tryptophan can evoke significant enzyme formation. Actinomycin D, injected together with or 12 hr before the tryptophan, is not inhibitory, but if injected with the glucocorticoid it prevents enzyme formation upon later injection of tryptophan. The observations suggest that appearance of the new enzyme in developing tissue results from the sequential action of more than one stimulus and that the potentiality for its transcription may develop long before its actual synthesis.
Opsonic Defect in Patients with Cystic Fibrosis of the Pancreas
Authors: Biggar W. D. , Holmes B. , Good R. A.
Published: May 2006

Cystic fibrosis of the pancreas is one of the most common inborn errors of metabolism. The high incidence of morbidity and mortality in these patients is primarily due to severe and frequent pulmonary infection. To date, no immune deficiency has been found in cystic fibrosis patients. Their sera contain normal quantities of immunoglobulins and hemolytic complement. In an assay of phagocytosis by alveolar macrophage, six out of nine sera from cystic fibrosis patients failed to support normal phagocytosis of
Pseudomonas aeruginosa
. This deficiency could be corrected by increasing the concentration of serum used in the assay. By contrast, their sera supported normal phagocytosis of Pseudomonas by blood polymorphonuclear leukocytes and continued to support normal phagocytosis when serum dilutions were used. Two patients with severe isolated deficiences of serum immunoglobulin A were found to have a similar defect in the alveolar macrophage assay, but normal phagocytosis by polymorphonuclear leukocytes. It is postulated that cystic fibrosis patients may have a quantitative and (or) functional defect of IgA antibodies, specific for Pseudomonas, and possibly of importance in the pathogenesis of their pulmonary disease.
N
-Acetyl-D-Galactosaminyltransferase in Human Serum and Erythrocyte Membranes
Authors: Kim Young S. , Perdomo Jose , Bella Agustin , Nordberg Judith
Published: May 2006

This study demonstrates the presence of an
N
-acetyl-D-galactosaminyltransferase in human serum and in erythrocyte membranes. This enzyme catalyzes the transfer of
N
-acetyl-D-galactosamine from UDP-
N
-acetyl-D-galactosamine to a mucin receptor and 2′-fucosyllactose that have blood group H activity and may be responsible, therefore, for blood group A antigenicity. It was present in the serum of individuals with blood group A or AB but was absent from those with blood group B or O. The activity measured in the erythrocyte membrane was low and did not show clear-cut separation among donors of different blood groups. The specificity of this enzyme in serum was suggested by the ability of 2′-fucosyllactose to act as an acceptor, as well as desialyzed porcine submaxillary mucin, while lactose and desialized fetuin failed to accept
N
-acetyl-D-galactosamine. The catalytic properties of the
N
-acetyl-D-galactosaminyltransferase from serum and from erythrocyte membranes were similar.
Insulin Receptors in the Liver: Specific Binding of [
125
I]Insulin to the Plasma Membrane and Its Relation to Insulin Bioactivity
Authors: Freychet Pierre , Roth Jesse , Neville David M.
Published: May 2006

With [
125
I]insulin at 7 × 10
-10
M, 25% of the radioactivity was bound to plasma membranes purified from rat liver. 20% of the [
125
I]insulin binding was inhibited by unlabeled insulin at 10
-9
M (6 ng/ml), equivalent to insulin concentrations in hepatic portal blood; inhibition of [
125
I]insulin binding was 80% at 10
-7
M and 90% at 10
-5
M. Eight insulins and derivatives with biological potencies that differed over a 100-fold range inhibited the binding of [
125
I]insulin to liver membranes in direct proportion to their ability to stimulate glucose oxidation in isolated fat cells. Inactive insulin chains, as well as glucagon, ACTH, and human growth harmone were without effect. The binding of [
125
I]insulin increased 55-fold as plasma membrane was purified from crude homogenate. Binding was time- and temperature-dependent, and addition of excess insulin produced rapid dissociation of [
125
I]insulin. This study demonstrates directly the binding of insulin to its biologically important receptors.
Structure of the Poly(G) Polymerase Component of the Bacteriophage f2 Replicase
Authors: Fedoroff Nina V. , Zinder Norton D.
Published: May 2006

A rifampicin-resistant poly(G) polymerase has been purified from f2 sus 11-infected cells. The poly(G) polymerase is believed to represent part of the f2 replicase on the basis of several criteria. It is present only in infected cells and shares the characteristic rifampicin resistance of crude f2 replicase activity. Partially purified poly(G) polymerase preparations exhibit replicase activity, synthesizing f2 “lus”strand RNA from denatured, partially double-stranded f2 RNA template. Highly purified poly(G) polymerase preparations, although lacking replicase activity, contain a protein which is electrophoretically identical to the protein product of the viral replicase cistron.