bluuebunny/crossref_metadata_2025 huggingface dataset:
The 3′-Terminal Nucleosides of the High Molecular Weight RNA of C-Type Viruses
Authors: Maruyama H. B. , Hatanaka M. , Gilden R. V.
Published: May 2006

Tumor virus RNAs from several mammalian and one reptilian species were purified; their 3′-terminal nucleoside was identified by separation of the trialcohols produced by periodate oxidation followed by reduction and tritiation with NaB
3
H
4
. Each virus contained uridine as the predominant terminal nucleoside. Molecular weight estimations based on the tritiation reactions were consistent with a structure consisting of four subunits.
Localization of Two Additional Hypervariable Regions in Immunoglobulin Heavy Chains
Authors: Kehoe J. Michael , Capra J. Donald
Published: May 2006

Cyanogen bromide fragments were isolated from the heavy chains of three human IgG myeloma proteins of the V
H
III subgroup, sequenced by an automated method, and localized to the variable region. Inspection of these sequences, together with corresponding stretches from both human and animal proteins (studied in other laboratories) led to the detection of two additional hypervariable regions characteristic of the V
H
segment of immunoglobulin heavy chains. These areas of hypervariability, involving heavy-chain residues 86-91 and 101-109, were separated by a region of relative constancy. The close relationship of these two hypervariable regions, and the previously described first heavy-chain hypervariable region (residues 31-37), to the first heavy-chain disulphide bridge implies that the three hypervariable areas might be in close steric approximation in native immunoglobulin molecules.

Examination of the sequences of the terminal portion of V
H
of all these proteins (the segment from residue 95 to the beginning of homology region C
H
l) revealed that no subgroup-specific residues could be identified in this area. Thus, heavy-chain subgroup distinctions may not extend through the entire variable region.
Conditions Leading to Enhanced Response to Glucagon, Epinephrine, or Prostaglandins by Adenylate Cyclase of Normal and Malignant Cultured Cells
Authors: Makman Maynard H.
Published: May 2006

HeLa S3 cells, a clonal strain adapted for growth in suspension culture, contain adenylate cyclase activity that is stimulated by glucagon, prostaglandin E
1
, and epinephrine. Total enzymatic activity and response to hormones is increased as a result of these cells being in stationary culture for several days. The parental strain of HeLa cells normally grown in stationary culture shows even greater adenylate cyclase activity. Hepatoma (HTC) cells grown in suspension culture have no detectable adenylate cyclase activity, but when grown in stationary culture they contain low, but detectable, amounts of adenylate cyclase, which is stimulated by glucagon, epinephrine, or prostaglandins. Chang's liver cells, both suspension and stationary culture, contain relatively high levels of adenylate cyclase that is stimulated by epinephrine or prostaglandin E
1
, with differences in activity depending upon culture conditions. Adenylate cyclase of 3T3 and L929 mouse fibroblasts respond to catecholamines, as well as to prostaglandin E
1
, but not to glucagon. Characteristic increases in basal activity of adenylate cyclase and in activity in the presence of hormone occurred as cell density increased during stationary culture of certain cell lines, but do not occur with fluoride ion present. In addition to the influence of growth conditions and rate or phase of cell growth on cyclase activity and hormonal response, the cultured cell lines frequently showed marked differences in activity from one another; malignant cells generally exhibited less activity. It is postulated that adenylate cyclase activity may be enhanced by cell to surface contact or cell to cell interaction and that this phenomenon may represent a form of self regulation or modulation of hormonal response by a tissue.
A Soluble Mitochondrial ATP Synthetase Complex Catalyzing ATP-Phosphate and ATP-ADP Exchange
Authors: Fisher Robert J. , Chen Jenn C. , Sani B. P. , Kaplay Suresh S. , Sanadi D. Rao
Published: May 2006

The highly purified soluble ATP synthetase complex from mitochondria, containing energy-transfer Factor A (the terminal ADP phosphorylation enzyme of oxidative phosphorylation) and Factor D, catalyzes ATP-P
i
and ATP-ADP exchange reactions. The ATP-P
i
exchange activity is inhibited by low concentrations of the uncouplers of oxidative phosphorylation, oligomycin and
p
-chloromercnriphenylsulfonate. It is stimulated threefold by dithiothreitol and is Mg
++
dependent. Antiserum to coupling factor 1 (F
1
) also inhibits the ATP-P
i
exchange. The ATP-ADP exchange activity appears to be greater than the ATP-P
i
exchange activity. The results suggest that the nonphosphorylated high-energy intermediate (X∼C), and possibly the phosphorylated intermediate (X∼P), are formed on the synthetase. Sites of uncoupler and oligomycin action reside in the terminal ATP synthetase.
Inhibition of the DNA Polymerase of Rauscher Leukemia Virus by Single-Stranded Polyribonucleotides
Authors: Tuominen F. William , Kenney Francis T.
Published: May 2006

The DNA polymerase of Rauscher murine leukemia virus is strongly and specifically inhibited by nontemplate, single-stranded polyribonucleotides with either the resident viral RNA, native calf-thymus DNA, or poly[d(A-T)] as templates. These inhibitory homopolymers are apparently bound to the template site of the polymerase, since they interact competitively with the template. The strength of the inhibition depends on the particular homopolymer used: poly(U) > poly(G) » poly(A) > poly(C). The

K
i

for poly(U) was 0.08 μg/ml, which represents an apparent affinity six times greater than that observed for viral RNA. No such inhibition was observed with a highly purified DNA polymerase from mouse embryos or the
Escherichia coli
enzyme.
Distinguishing Reverse Transcriptase of an RNA Tumor Virus from Other Known DNA Polymerases
Authors: Goodman N. C. , Spiegelman S.
Published: May 2006

Assays are described that permit one to distinguish the reverse transcriptase of RNA tumor viruses from known normal cellular DNA-instructed DNA polymerases. Template responses of purified reverse transcriptase were compared with those of similar preparations of the DNA polymerase I of
Escherichia coli
and of calf-thymus polymerase. All three enzymes responded well to the synthetic duplexes poly(dT)·poly(A), poly(U)·poly(A), and poly(dT)·poly(dA). Hence, these duplexes can detect, but cannot distinguish reverse, transcriptase from the known normal DNA polymerases. However, certain oligomer-homopolymer complexes serve as excellent distinguishing agents. The reverse transcriptase responds very well to (dT)
10
·poly(A) and very poorly to (dT)
10
·poly(dA), whereas both cellular DNA polymerases do not exhibit this behavior.

Purified single-stranded RNA also serves as a diagnostic device, since only reverse transcriptase gives a detectable response. To be definitive, a positive response to RNA must be accompanied by a demonstration via molecular hybridization that the DNA product is complementary to the RNA and not to some minor DNA contaminant.
The Isolation and Characterization of a Photochemically Active Complex from
Chloropseudomonas ethylica
Authors: Fowler C. F. , Nugent N. A. , Fuller R. C.
Published: May 2006

A photochemically active subcellular fraction has been isolated from the green bacterium
Chloropseudomonas ethylica
. It is enriched in bacteriochlorophyll
a
and contains only a small amount of Chlorobium chlorophyll. Both a reaction-center bleaching (P840) and a cytochrome oxidation (C553) are observed to occur in the fraction. Particles that are contained in the fraction are larger than 1.5 × 10
6
daltons and exhibit a range of sizes consistent with some form of polymeric association of similar subunits. Around 80 bacteriochlorophyll
a
molecules are present per P840. In an intact photosynthetic apparatus there are about 1000-1500 total chlorophylls (including Chlorobium chlorophyll) per reaction center.

The redox potentials of the reaction center P840 and C553 were found to be 0.24 and 0.17 V, respectively, in one-electron reactions. The potentials of these components are around 0.2 V lower than comparable components found in other photosynthetic organisms.
Mutation Causing Temperature-Sensitive Expression of Cell Transformation by a Tumor Virus
Authors: Renger Hartmut C. , Basilico Claudio
Published: May 2006

A procedure has been devised to isolate 3T3 mouse fibroblasts transformed by simian virus 40 (SV40) that express their transformed phenotype at low (32°C) but not at high (39°C) temperature. Three parameters typical of malignant growth
in vitro:
(
a
) high saturation density in culture, (
b
) ability to form colonies on monolayers of normal 3T3 cells, and (
c
) lack of contact inhibition of DNA synthesis, are temperature sensitive. These phenotypic changes are fully reversible. The serum requirement for growth appears to be largely unchanged by temperature. These cells seem to owe their behavior to a cellular, rather than to a viral, alteration since after fusion of the temperature-sensitive transformed cells with permissive monkey cells, a procedure that leads to rescue (i.e., multiplication of the virus), wild-type SV40 virus is produced.
Molecular Orbital Studies of Ethylenediamine Conformations
Authors: Jhon Mu Shik , Cho Ung-Ln , Kier Lemont B. , Eyring Henry
Published: May 2006

Semiempirical quantum mechanical treatments are applied to the ethylenediamine di-cation, mono-action, and neutral molecule by the use of the extended Huckel theory.

The minimum energies of conformations of molecules for rotation about the CH
2
-CH
2
axis is found. The theoretical predictions for the conformation with minimum values. The importance of the ethylenediamine conformations are discussed.
Binding of α-Bungarotoxin to Acetylcholine Receptors In Mammalian Muscle
Authors: Berg Darwin K. , Kelly Regis B. , Sargent Peter B. , Williamson Patrick , Hall Zach W.
Published: May 2006

Experiments were performed to determine the specificity of [
125
I]α-bungarotoxin binding to skeletal muscle. In adult rat diaphragm, [
125
I]α-bungarotoxin was found to bind almost exclusively to those regions of the muscle that contain endplates and are known to be sensitive to acetylcholine. In contrast, chronically denervated adult muscle and muscle from neonatal rats, both of which are sensitive along their entire lengths, bound substantial amounts of toxin in all regions. Toxin binding to all muscles was inhibited by
d
-tubocurarine and by carbamylcholine, but not by atropine. The bound [
125
I]toxin was solubilized by homogenization of the tissue in 1% Triton X-100 and was recovered as a single band, distinct from free toxin, after zone sedimentation. Treatment of the solubilized, toxin-bound complex with 2-mercaptoethanol and sodium dodecyl sulfate resulted in the recovery of free toxin. A toxin-bound complex was also obtained when toxin was incubated directly with extracts of muscle endplate regions prepared by homogenization in Triton X-100. No such complex was observed with extracts prepared from muscle lacking endplates. These results are consistent with the interpretation that α-bungarotoxin binds specifically to the acetylcholine receptor of mammalian skeletal muscle.
An Inhibitory Protein of
Escherichia coli
RNA Polymerase in Bacteriophage T3-Infected Cells
Authors: Mahadik S. P. , Dharmgrongartama B. , Srinivasan P. R.
Published: May 2006

A partially purified protein isolated from bacteriophage T3-infected cells of
Escherichia coli
B markedly inhibits the activity of
E. coli
RNA polymerase, slightly inhibits the activity of purified T3 polymerase, and does not inhibit the activity of either core polymerase or the ribosome-bound T3 polymerase. The properties of this protein and its mechanism of action have been studied. It appears to antagonize the action of the sigma factor component of RNA polymerase.
Transformation of
Agrobacterium tumefaciens
into a Non-oncogenic Species by an
Escherichia coli
RNA
Authors: Beljanski Mirko , Beljanski Monique , Manigault Pierre , Bourgarel Pierre
Published: May 2006

Transforming RNA excreted by showdomycin-resistant
Escherichia coli
induces a persistent, heritable, and spectacular change in
Agrobacterium tumefaciens
B
6
, a bacterium that carries the oncogenic principle for tumor induction in plants. Transformants possessing new physiological and biochemical properties have completely or partially lost the capacity for tumor induction. They synthetize new ribosomes whose components are profoundly modified. On the basis of biological and biochemical characteristics, one is inclined to consider the completely transformed
Agrobacterium tumefaciens
as a “new species”.
Homogeneous Antibody Elicited with Dinitrophenyl-Gramicidin-S
Authors: Montgomery Paul C. , Rockey John H. , Williamson Alan R.
Published: May 2006

Rabbit antibody to dinitrophenyl hapten has been elicited by hyperimmunization with a bifunctional cyclic decapeptide antigen, di-dinitrophenyl-gramicidin-S. Examination of the induced antibody by isoelectric focusing, and Sipsian analysis of the haptenbinding data, demonstrated that di-dinitrophenyl-gramicidin-S was capable of stimulating and maintaining the production of a biosynthetically homogeneous antibody in the adult animal.
Nucleotide Sequencing of DNA: Preliminary Characterization of the Products of Specific Cleavages at Guanine, Cytosine, or Adenine Residues
Authors: Salser Winston , Fry Kirk , Brunk Clifford , Poon Raymond
Published: May 2006

DNA synthesized
in vitro
from a phage M13 template has been cleaved at either guanine, adenine, or cytosine residues by ribosubstitution techniques. Fingerprints of the fragments obtained suggest that DNA sequencing will be possible with this technique.
Electron Microscopic Studies of Replicating and Catenated Colicin Factor E1 DNA Isolated from Minicells
Authors: Fuke Motohiro , Inselburg Joseph
Published: May 2006

Replicating and catenated DNA molecules of colicin factor E1 that were isolated from minicells were observed by electron microscopy. Two new replicating structures that have been found include: molecules that contain two untwisted replicated branches of the same length and a twisted unreplicated branch, and a twisted circular molecule with a long tail. Other molecular forms identified include circular dimers, three types of catenated dimers (open-open, open-twisted, and twisted-twisted), catenated dimers in which one of the linked molecules is replicating, catenated trimers, and a tetamer.
A Genetic Locus for Inducibility of C-Type Virus in BALB/c Cells: The Effect of a Nonlinked Regulatory Gene on Detection of Virus after Chemical Activation
Authors: Stephenson John R. , Aaronson Stuart A.
Published: May 2006

Previous studies have shown that chemicals can transiently activate endogenous C-type viruses from embryo cells of the BALB/c mouse strain, but not from cells of another mouse strain, NIH Swiss. The number of genetic loci for inducibility of endogenous virus in BALB/c cells was investigated with cell lines derived from appropriate, F
1
, F
2
-hybrid, and backcross generation embryos of these strains. A single genetic locus responsible for inducibility of virus in BALB/c cells was detected, and tentatively designated
Ind
. A second locus, previously described in studies of mouse-cell susceptibility to exogenous virus infection,
Fv-1
, was found to be genetically nonlinked to
Ind
. This regulatory gene plays an important role in determining whether the induced viruses of BALB/c cells can persist after chemical activation.
In Vitro
Aggregation of Cytoplasmic Microtubule Subunits
Authors: Borisy Gary G. , Olmsted J. B. , Klugman R. A.
Published: May 2006

The colchicine-binding protein in procine-brain tissue is a dimer of molecular weight 110,000 that is believed to be the subunit of neuronal microtubules. Conditions are established under which the dimers aggregate with reproducible kinetics. This aggregation reaction, which is monitored by development of turbidity, has the following characteristics: (
a
) Colchicine inhibits development of turbidity; (
b
) the reaction inhibited by colchicine is reversed by long-wave ultraviolet irradiation; (
c
) the aggregation is temperature-dependent; (
d
) the reaction is nucleotide triphosphate-specific, being stimulated by 1 mM GTP; (
e
) the reaction appears to be specific for microtubule subunits since in the presence of other added proteins and in curde cell extracts, only microtubule subunits aggregate. On the basis of these criteria, we conclude that we have established an
in vitro
system for the aggregation of microtubule subunits that shares some of the properties characteristic of the
in vivo
assembly of cytoplasmic and spindle microtubules.
A Replicating RNA Molecule Suitable for a Detailed Analysis of Extracellular Evolution and Replication
Authors: Kacian D. L. , Mills D. R. , Kramer F. R. , Spiegelman S.
Published: May 2006

The aim of the present study is to make available a replicating molecule of known sequence. Accordingly, we sought a molecule that has the following properties: (
a
) replicates
in vitro
in a manner similar to phage Qβ RNA; (
b
) produces antiparallel complementary strands that can be separated from one another; and (
c
) is small enough to yield its sequence with reasonable effort.

We report here the isolation of a replicating RNA molecule that contains 218 nucleotides and possesses the other features desired for a definitive analysis of the replicating mechanism. Despite its small size, this molecule can mutate to previously determined phenotypes. It will, therefore, permit the precise identification of the base changes required to mutate from one phenotype to another in the course of extracellular Darwinian selection experiments.
Functional Modification of 16S Ribosomal RNA by Kethoxal
Authors: Noller Harry F. , Chaires Jonathan B.
Published: May 2006

Kethoxal reacts with 30S ribosomal subunits to give totally inactive particles, as measured by
in vitro
protein synthesis. It is postulated that functional modification occurs at the binding site for transfer RNA since (
a
) loss of specific binding of transfer RNA, but not binding of messenger RNA, is simultaneous with loss of protein synthesis, and (
b
) loss of activity is inhibited by bound transfer RNA. By means of
in vitro
reconstitution and labeling techniques, it is found that loss of transfer RNA-binding activity is correlated with the modification of six or seven guanine residues in 16S RNA.
Carcinogens as Frameshift Mutagens: Metabolites and Derivatives of 2-Acetylaminofluorene and Other Aromatic Amine Carcinogens
Authors: Ames Bruce N. , Gurney E. G. , Miller James A. , Bartsch H.
Published: May 2006

Several carcinogenic metabolites of the carcinogen 2-acetyl-aminofluorene, especially 2-nitrosofluorene and
N
-hydroxy-2-aminofluorene, are potent frameshift mutagens for
Salmonella typhimurium
. 2-Nitrosonaphthalene, 2-nitrosophenanthrene, 4-nitroso-
trans
-stilbene, 4-nitrosobiphenyl, and 4-nitrosoazobenzene, all of which are metabolites or likely metabolites of carcinogenic aromatic amines, are also potent frameshift mutagens. These compounds may be frameshift mutagens of the class that intercalates into DNA and then reacts covalently with the DNA; various ultimate carcinogens may be of this type. The utility of a set of bacterial strains for detecting carcinogens as mutagens is shown.
Nuclear Magnetic Resonance Determination of the Angle Ψ in Peptides
Authors: Karplus S. , Karplus M.
Published: May 2006

A simple theoretical model is used to suggest that the NCCH coupling constant,
Jnh
, has a dihedral angle dependence that can serve for estimating the angle Ψ in peptides. Some experimental comparisons are made to test the model; they include a new measurement of
Jnh
in
N
-acetylglycine.
A Particle Associated with the Polyadenylate Segment in Mammalian Messenger RNA
Authors: Kwan Sau-Wah , Brawerman George
Published: May 2006

A structure consisting of poly(A) complexed with other components is released from polysomes by ribonuclease treatment. The poly(A) complex has a sedimentation value of 12-15, while the corresponding sedimentation value for free poly(A) is 4. The complex does not appear to represent an artifact formed by interaction of free poly(A) with either cytoplasmic or polysomal proteins. The polynucleotide released from the complex by treatment with sodium dodecyl sulfate shows the same electrophoretic mobility as that of poly(A) isolated from deproteinized polysomal RNA. The poly(A) in the complex is partially protected from digestion by T
2
ribonuclease. At least part of the poly(A) is available for base pairing with poly(U). The components associated with the poly(A) cause it to bind to Millipore filters at low ionic strength. These components are removed from the complex by Pronase digestion. The findings indicate that the poly(A) segment in messenger RNA serves as a binding site for a particle. This particle appears to consist of proteins.
Production of Procollagen by Human Fibroblasts in Culture
Authors: Smith Barbara D. , Byers Peter H. , Martin George R.
Published: May 2006

Three hydroxyproline-containing proteins secreted into the medium by human fibroblasts in culture were isolated and characterized. A minor fraction was identical to the collagen monomer. The major fraction was a form of procollagen, which contained, in addition to pro α and α chains, a component estimated to have a molecular weight of 250,000. This component was a dimer of pro α chains joined by disulfide bonds. The third fraction, much lower in hydroxyproline and hydroxylysine content, was of still greater size. Pro α chains were released upon denaturation and reduction, indicating that this fraction may contain pro α chains linked by disulfide bonds to noncollagenous material.
The Possible Role of Aromatic Residues of
Clostridium acidi-urici
Ferredoxin in Electron Transport
Authors: Packer Elliot L. , Sternlicht Himan , Rabinowitz Jesse C.
Published: May 2006

The
13
C-resonances of the 2′,6′-ring carbon atoms of both tyrosyl residues of
Clostridium acidi-urici
ferredoxin are shifted downfield in the oxidized and reduced protein relative to these resonance positions in free tyrosine. These results show that both tyrosyl residues in the oxidized and reduced protein are in magnetically equivalent environments, and suggest that both tyrosyl residues are close to the two iron-sulfur clusters in the reduced and oxidized proteins and that each cluster is equally accessible to one reducing electron.
Mutants of
Salmonella typhimurium
and
Escherichia coli
Pleiotropically Defective in Active Transport
Authors: Hong Jen-Shiang , Kaback H. R.
Published: May 2006

Two classes of mutants isolated from
E. coli
and
Salmonella typhimurium
are altered in respiration-coupled active transport, as studied in whole cells and/or isolated membrane vesicles. Mutant cells defective in D-lactate dehydrogenase (
dld
) transport amino acids and lactose normally. Membrane vesicles prepared from these mutants do not exhibit D-lactate-dependent transport, D-lactate oxidation, or D-lactate: dichlorophenolindophenol reductase activity. However, succinate-dependent transport is markedly enhanced in these mutants, without a corresponding increase in succinic dehydrogenase activity.

The second class of mutants is defective in the coupling of electron transfer to active transport. Whole cells and membrane vesicles prepared from these
etc
mutants exhibit markedly reduced ability to transport amino acids, despite the ability of the vesicles to oxidize D-lactate, succinate, and NADH. Vectorial phosphorylation of α-methylglucoside by these mutants is normal. Electrontransfer coupling mutants are similar phenotypically to mutants uncoupled for oxidative phosphorylation (
uncA
), but have normal ATPase activity. Moreover,
uncA
mutants catalyze active transport as well as does the wild type. These experiments indicate that the
ETC
component is essential for the coupling of respiratory energy to active transport, and provide further evidence that the generation or utilization of ATP is not involved in these transport mechanisms.
Evidence for a Transcription-Control Region of Simian Virus 40 in the Adenovirus 2—Simian Virus 40 Hybrid, Ad2
+
ND
1
Authors: Patch Cephas T. , Lewis Andrew M. , Levine Arthur S.
Published: May 2006

The complementary DNA strands of the nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid virus, Ad2
+
ND
1
, were separated by isopycnic banding in a CsCl density gradient in the presence of synthetic polyribonucleotides. Separated strands were used in DNA-RNA hybridization reactions with RNA from cells productively infected by Ad2 or SV40, and with complementary SV40 RNA transcribed asymmetrically
in vitro
. About five times as much Ad2 RNA hybridized to the light stand of Ad2
+
ND
1
as to the heavy strand. Complementary RNA and early SV40 RNA (RNA synthesized before viral DNA replication) had significant homology only with the light strand. Only half as much of a preparation of RNA synthesized before and after viral DNA replication (early-plus-late SV40 RNA) hybridized to the light strand as to the heavy strand. These results indicate that templates for both late and early SV40 RNA are present in Ad2
+
ND
1
. Therefore, the small SV40 segment within this virus (10-18% of the SV40 genome) must contain a transcription-control region. Ad2
+
ND
1
should thus be useful in the selective study of transcription as it occurs in cells infected by the oncogenic virus SV40.
Enzymatic Oligomerization of Bacteriophage P22 DNA and of Linear Simian Virus 40 DNA
Authors: Sgaramella Vittorio
Published: May 2006

Linear double-stranded molecules of the circularly permuted and terminally redundant DNA of
Salmonella
bacteriophage P22 have been converted to oligomeric products in the presence of polynucleotide ligase coded for by the coliphage T4. The reaction has been monitored by sucrose density-gradient centrifugation and electron microscopy. It goes slowly and gives yields of 30-40%. The products are mainly dimers and trimers, but higher oligomers are also present.

DNA ligase extracted from uninfected
Escherichia coli
seems unable to perform a similar reaction, which is concluded to involve the fully base-paired termini.

Linear double-stranded molecules of simian virus(SV) 40 DNA, produced by the action of the bacterial restriction endonuclease R
1
, are oligomerized by either ligase; therefore, this reaction seems to involve single-stranded cohesive ends. No mixed products could be found when P22 DNA and linear SV 40 DNA were exposed together to the T4 ligase.
Radioresistance of Carrier-Specific Helper Thymus-Derived Lymphocytes in Mice
Authors: Hamaoka Toshiyuki , Katz David H. , Benacerraf Baruj
Published: May 2006

The effect of x-irradiation on the capacity of carrier-specific mouse T (thymus-derived) lymphocytes to exert a helper function for hapten-specific B (bone marrow-derived) lymphocytes
in vivo
has been investigated again. Helper function is abolished by exposure of such cells to x-irradiation before, or immediately after, transfer to adoptive hosts. On the other hand, when exposure to x-irradiation occurs under circumstances in which the carrier-primed cells are well-localized in the appropriate lymphoid organs, i.e., either in the carrier-primed animal or 24 hr after adoptive transfer to syngeneic recipients, the capacity of T lymphocytes to serve as specific helper cells is clearly radioresistant. Evidence indicates that x-irradiation results in undefined, and subtle, changes in the migratory capacity of mouse T lymphocytes, but not in abrogation of T-cell helper function.
Resolution and Reconstitution of the Phosphatidate-Synthesizing System of Rat-Liver Microsomes
Authors: Yamashita Satoshi , Hosaka Kohei , Numa Shosaku
Published: May 2006

The phosphatidate-synthesizing system of rat-liver microsomes was resolved into two component enzymes, glycerolphosphate acyltransferase and 1-acylglycerolphosphate acyltransferase. The resolution is effected by sucrose density gradient centrifugation in the presence of a nonionic detergent, Triton X-100. Combination of both enzymes results in reconstitution of the phosphatidate-synthesizing system. These results establish that two distinct enzymes, glycerolphosphate acyltransferase and 1-acylglycerolphosphate acyltransferase, are required for synthesis of phosphatidic acid from
sn
-glycerol 3-phosphate.

Furthermore, the 1-acylglycerolphosphate acyltransferase preparation efficiently uses unsaturated (or saturated) fatty acyl-CoA as acyl donor. Our previous studies showed that the glycerolphosphate acyltransferase preparation catalyzes formation of 1-acylglycerol 3-phosphate, using preferentially saturated fatty acyl-CoA as acyl donor. These findings indicate that the reconstituted system is capable of yielding phosphatidic acid with an asymmetric fatty acid distribution.
Sulfhydryl Group Catalysis of Charge Transfer
Authors: Szent-Györgyi Albert , McLaughlin Jane
Published: May 2006

Sulfhydryl compounds, like cysteine and glutathione, catalyze charge transfer between aldehydes and amines.
A DNA-Unwinding Protein Isolated from
Escherichia coli:
Its Interaction with DNA and with DNA Polymerases
Authors: Sigal Nolan , Delius Hajo , Kornberg Thomas , Gefter Malcolm L. , Alberts Bruce
Published: May 2006

A DNA-unwinding protein has been purified to homogeneity from
E. coli
. This protein has a molecular weight of about 22,000, as judged by its electrophoretic mobility on polyacrylamide gels containing sodium dodecylsulfate, and it appears to be present in about 800 copies per log-phase cell. It binds tightly and cooperatively to single-stranded DNA, and much less tightly, if at all, to RNA or double-stranded DNA.

Like the T4 gene-32 protein characterized previously, the
E. coli
DNA-unwinding protein depresses the melting temperature of double-stranded DNAs, with regions rich in A-T base-pairs being preferentially melted. The
E. coli
protein strongly stimulates
in vitro
DNA synthesis by
E. coli
DNA polymerase II on appropriate templates; however, no stimulation is found with purified polymerases I or III of
E. coli
, or with T4 DNA polymerase. In contrast, gene-32 protein stimulates only the T4 DNA polymerase in a parallel assay.
Alteration of Nucleoside Transport of Chinese Hamster Cells by Dibutyryl Adenosine 3′:5′-Cyclic Monophosphate
Authors: Hauschka Peter V. , Everhart Leighton P. , Rubin Robert W.
Published: May 2006

Cultured Chinese hamster ovary cells showed no significant change in generation time or fraction in the S-phase in the presence of 1 mM
N
6
,
O
2′
-dibutyryl adenosine 3′:5′-cyclic monophosphate. Growth continued for at least two generations
after
expression of the morphological transformation induced by this cyclic AMP analog. Despite identical growth rates,
apparent
rates of DNA and RNA synthesis (incorporation of [
3
H]-thymidine or [
3
H]uridine) were reduced up to 15-fold in log phase by 1 mM cyclic nucleotide. [
3
H]Deoxycytidine incorporation was much less sensitive to dibutyryl cyclic AMP. Uptake studies with [
3
H]thymidine demonstrated an inhibition of transport rate dependent on the concentration of dibutyryl cyclic AMP in the growth medium. The rate of thymidine uptake at 1° was decreased 21-fold by 1 mM cyclic nucleotide; half-maximal inhibition occurred at 6 μM. At 37°, the pool size of acid-soluble thymidylate was strongly reduced by 1 mM cyclic nucleotide, and synergistic reduction of the pool size was found with 0.5 mM aminophylline. Phosphorylation of the acid-soluble intracellular label was unaffected by dibutyryl cyclic AMP. Inhibition of thymidine uptake is attributed to an observed decrease in thymidine kinase activity caused by growth in 1 mM dibutyryl cyclic AMP, and possibly to a simultaneous alteration in membrane permeability. Kinase-facilitated uptake of other metabolites may be regulated in a similar fashion by cyclic AMP.
Mutation of a Cytoplasmic Gene in
Chlamydomonas
Alters Chloroplast Ribosome Function
Authors: Schlanger Gladys , Sager Ruth , Ramanis Zenta
Published: May 2006

A mutation,
car
, determining resistance to several macrolide antibiotics, including carbomycin, has been identified in the alga
Chlamydomonas
as cytoplasmic, and mapped in the known cytoplasmic linkage group close to genes determining resistance to other antibiotics, including streptomycin, erythromycin, and spectinomycin. The effect of the
car
mutation on chloroplast ribosome function was demonstrated with an
in vitro
system incorporating amino acids especially developed to assess activity of 70S chloroplast ribosomes. In an S-30 extract containing both 70S chloroplast and 80S cytoplasmic ribosomes, low concentrations of Mg
++
and spermidine favored 80S ribosome activity, and high concentrations activated 70S ribosomes and reversibly inactivated the 80S component. Under conditions favoring chloroplast ribosome activity, carbomycin inhibited incorporation by an S-30 extract, and by purified 70S ribosomes from wild-type but not from
car
cells. These results show that cytoplasmic genes are directly involved in chloroplast ribosome function and they suggest that the
car
gene product is a ribosomal protein; the results further strengthen the evidence that the cytoplasmic linkage group is located in chloroplast DNA.
Globin Messenger RNA Activity in Erythroid Precursor Cells and the Effect of Erythropoietin
Authors: Terada Masaaki , Cantor Linda , Metafora Salvatore , Rifkind Richard A. , Bank Arthur , Marks Paul A.
Published: May 2006

Cell populations enriched for erythroid precursor cells were fractionated from 13-day fetal-mouse livers by a method of immune hemolysis. These preparations of precursors, contaminated by less than 7% hemoglobinized erythroblasts, synthesize globin at a rate less than 6% that of the unfractionated liver erythroid cell population. RNA was isolated from these precursor cells and assayed for globin mRNA activity in a cell-free system from Krebs ascites tumor. The 6-16S RNA fraction from precursor cells has less than 5% of the globin mRNA activity of RNA isolated from unfractionated populations. Precursor cells incubated with erythropoietin show an increment in the rate of synthesis of globin only after 5-10 hr of incubation. After 10 hr of culture with this hormone, precursor cells show a 6- to 10-fold increase in globin mRNA activity. These results suggest that the precursor cells of hepatic erythropoiesis, responsive to erythropoietin, do not contain globin mRNA in a biologically active form. Erythropoietin-induced differentiation of these cells to erythroblasts is associated with an increase in globin mRNA.
Synergistic Effect of Rifamycin Derivatives and Amphotericin B on Viral Transformation of a Murine Cell Line
Authors: Hackett Adeline J. , Sylvester S. S. , Joss Urs R. , Calvin Melvin
Published: May 2006

One of the most potent inhibitors of RNA-dependent DNA polymerase activity so far described (rifazacyclo-16) was not correspondingly as active in focus inhibition. This discrepancy was thought to be due to the inability of the drug to penetrate the cell membrane. It has been found that a very low level of amphotericin B allows this drug, as well as the previously described 2′,6′-dimethyl-
N
(4′)benzyl-
N
(4′)-[desmethyl] rifampicin, to exhibit a very high capability to inhibit focus formation. Since these two drugs are highly lipophilie, their activity may be expected to be dependent upon any lipophilic components in the medium, such as serum or detergents. The use of amphotericin B as well as serum in tissue cultures is common, and could account for some of the variability in focus inhibition reported in the literature.
Computer Simulation of Fluorescence Depolarization Due to Brownian Motion
Authors: Harvey Stephen C. , Cheung Herbert C.
Published: May 2006

A computer program has been written to simulate the Brownian motion of rigid fluorescent molecules. The time dependence of the fluorescence polarization anisotropy as generated by this simulation is in agreement with that predicted by the recent theoretical treatment of Belford, Belford, and Weber (
Proc. Nat. Acad. Sci. USA
(1972) 69, 1392-1393). The program thus serves as a verification of their equation. It is being generalized to cover the case of nonrigid molecules.
Hormonal Interactions in the Uterus: Inhibition of Isoproterenol-Induced Accumulation of Adenosine 3′:5′-Cyclic Monophosphate by Oxytocin and Prostaglandins
Authors: Bhalla Ramesh C. , Sanborn Barbara M. , Korenman Stanley G.
Published: May 2006

Interactions of hormones stimulating and inhibiting uterine contraction were studied
in vitro
in uteri from oophorectomized rats. The β-adrenergic effector, isoproterenol, a potent inhibitor of contraction, produced a dose-related increase of adenylate cyclase and accumulation of adenosine 3′:5′-cyclic monophosphate (cAMP) that was inhibitable by propranolol. Oxytocin, which stimulates contraction, effectively inhibited accumulation of uterine cAMP induced by isoproterenol in the presence or absence of theophylline. Prostaglandins E
2
and F
2α
, each at a maximum effective concentration of 0.5 μM, also inhibited accumulation of cAMP induced by isoproterenol, consistent with their effect in stimulation of uterine contraction. Prostaglandin E
2
, but not prostaglandin F
2α
, stimulated cAMP accumulation in a dose-related manner at concentrations in excess of 0.5 μM. Neither propranolol nor oxytocin inhibited that response. Bovine endometrial adenylate cyclase failed to respond to isoproterenol but was stimulated by prostaglandins E
1
and E
2
. When myometrial preparations were studied, isoproterenol stimulation and prostaglandin effects were observed as for whole castrate uterus. The competitive physiological actions of β-adrenergic effectors on the one hand, and oxytocin and prostaglandins on the other hand, are based on their influences on a myometrial adenylate cyclase. Stimulation of uterine cAMP accumulation by prostaglandin E
2
is due to action at a different and unrelated site.
Isolation and Subunit Structure of Polycytidylate-Dependent RNA Polymerase of Encephalomyocarditis Virus
Authors: Rosenberg H. , Diskin B. , Oron L. , Traub A.
Published: May 2006

A polycytidylate-dependent RNA polymerase of encephalomyocarditis virus was isolated from infected BHK 21 cells. The enzyme was associated with a smooth-membrane fraction, from which it was extracted by a mixture of sodium dodecyl sulfate, Triton X-100, and dithiothreitol, and further purified by chromatography on a Dowex-1 column and by glycerol gradient sedimentation. Analysis of a 6S glycerol gradient peak of RNA polymerase activity by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed the presence of five polypeptides, of molecular weights 72,000, 65,000, 57,000, 45,000, and 35,000. The molecular weights of four of the polypeptides (72,000, 65,000, 45,000, and 35,000) are almost identical to the reported molecular weights of the four subunits of Qβ replicase.
How Genetic Background Masks Single-Gene Heterosis in
Drosophila
Authors: Wills Christopher , Nichols Lois
Published: May 2006

Conditional heterosis associated with two isoallelic forms of octanol dehydrogenase in
Drosophila pseudoobscura
has been detected in flies that have been (
a
) inbred for several generations to make the background genotype as homozygous as practicable, and (
b
) grown on a medium containing a small amount of octanol. The heterosis was first found in inbred males. The possibility that the effect in females was masked by X-linked polymorphic genes affecting the same fitness components as the locus for octanol dehydrogenase was shown to be correct when, on further inbreeding, heterosis was found in the females of one of the lines. The implications of this and other findings for the current understanding of the genetic structure of natural populations is discussed.
Genetics of Human-Mouse Somatic Cell Hybrids: Linkage of Human Genes for Lactate Dehydrogenase-
A
and Esterase-A
4
Authors: Shows Thomas B.
Published: May 2006

By use of human-mouse somatic cell hybrids, an autosomal gene linkage has been determined for the human loci controlling the phenotypes of lactate dehydrogenase-
A
(EC 1.1.1.27) and esterase-A
4
(EC 3.1.1.2). These structural loci were not linked to the lactate dehydrogenase-
B
, peptidase-B linkage, the X chromosome, the E
17
chromosome, or to nine other enzyme phenotypes examined.
Solubilization and Partial Purification of Amino Acid-Specific Components of the D-Lactate Dehyrogenase-Coupled Amino Acid-Transport Systems
Authors: Gordon Adrienne S. , Lombardi F. J. , Kaback H. R.
Published: May 2006

A protein-containing fraction has been solubilized from
E. coli
ML 308-225 membrane vesicles that has many of the properties of the amino acid “carrier proteins” of the D-lactate dehydrogenase-coupled amino acid-transport systems. Membrane vesicles were partially solubilized with the nonionic detergent Brij 36-T, and the solubilized material was fractionated by Sephadex G-100 chromatography in the presence of the same detergent. Three fractions possess binding activity for proline: one of relatively low molecular weight with a high specific activity, and two of higher molecular weight with low specific activities. The higher molecular weight fractions exhibit D-lactate dehydrogenase activity; however, there is no corresponding activity associated with the low molecular weight fraction. Moreover, proline-binding activity is highly specific as it is not inhibited by structurally-unrelated amino acids. In addition to proline, the low molecular weight fraction exhibits binding activities for serine, glycine, lysine, and tyrosine.

The proline-binding activity of the low molecular weight fraction is not inhibited by electron transfer or by general metabolic inhibitors that inhibit the accumulation of proline by intact membrane vesicles. In contrast, binding activity is inhibited by
p
-chloromercuribenzoate and
N
-ethylmaleimide, and the inhibition observed with
p
-chloromercuribenzoate is reversed by the addition of dithiothreitol. The effect of these sulfhydryl reagents on binding corresponds to the effect of these compounds on proline transport by intact membrane vesicles.
Evidence for the Presence of Hydrogen-Bonded Secondary Structure in Angiotensin II in Aqueous Solution
Authors: Printz Morton P. , Williams Hazel P. , Craig Lyman C.
Published: May 2006

Automated tritium-hydrogen exchange measurements have been made on the linear octapeptide Val
5
-angiotensin II amide. All six amide hydrogens of the peptide backbone are observable, and are resolved into three classes according to their exchange rates. The rate of exchange of the slowest class,
t
1/2
of 300 min at 0°C (pH 2.5), is compared with that of hydrogens that exchange abnormally slowly in other peptides. It is concluded that these slow hydrogens in angiotensin II are involved in secondary structure with either one or both forming stable, intramolecular hydrogen bonds. This finding demonstrates that linear peptides may have hydrogen-bonded conformations in aqueous solutions. Analysis of the pH dependence of the rate of exchange indicates that one peptide amide hydrogen, namely that of the Asn
1
-Arg
2
peptide bond, is not involved in hydrogen bonding and is freely accessible to the solvent. Thus, the finding of internal hydrogen bonding, together with the assignment of the environment of one peptide bond, places major constraints on the number of allowable conformations of this linear polypeptide hormone.
Expression of Adenylate Cyclase, Catecholamine Receptor, and Cyclic Adenosine Monophosphate-Dependent Protein Kinase in Synchronized Culture of Chang's Liver Cells
Authors: Makman Maynard H. , Klein Monroe I.
Published: May 2006

In Chang's liver cells synchronized by exposure to thymidine, both cyclic adenosine monophosphate-dependent and cyclic adenosine monophosphate-dependent and cyclic adenosine monophosphate-independent protein kinase activities increased throughout the cell cycle in a manner that corresponded approximately to the overall increase in cellular protein. Thus, the catalytic and the cyclic adenosine monophosphate-binding regulatory subunits of protein kinase appear to be temporally coexpressed. Adenylate cyclase activity stimulated by catecholamine, as well as basal activity, decreased markedly after release of cells from thymidine blockade during the S phase of the cell cycle; this was followed by recovery and overall net increase to fully expressed activity by the peak of mitosis. After initial decrease early in the S phase, cyclase activity assayed in the presence of fluoride ion began to rise before the rise in basal and catecholamine-stimulated activities, indicating that regulation of membrane receptors for catecholamines and for basal activity may be at least in part separate from that for catalytic activity of adenylate cyclase. The differential expression of membrane receptors for adenylate cyclase during the Chang's liver cell cycle affords a possible mechanism for control of response to hormones during the cell cycle.
Insulin Biosynthesis: Studies of Islet Polyribosomes
Authors: Permutt M. A. , Kipnis D. M.
Published: May 2006

A method is described for separation of polyribosomes from as few as 25 isolated Islets of Langerhans, representing about 250 μg of pancreatic tissue. Islets are labeled with [
3
H]leucine and polysomes are isolated with liver polyribosomes, which serve as carrier and inhibitor of ribonuclease activity. Islets incubated at 37°C for 45 min in 15.5 mM glucose, then pulsed with [
3
H]leucine, incorporated about 2-3 times more label into nascent peptides on islet polysomes than islets incubated in 2.8 mM glucose. Sucrose gradient analysis of the labeled polysomes indicated that raising the glucose concentration preferentially stimulated synthesis of peptides on trisomes and larger polyribosomes. Islets incubated with [
3
H]leucine for 15 min incorporated two-thirds of the label into proteins on membrane-bound polysomes. At least 85% of the proinsulin synthesis during this time occurs on membrane-bound polysomes.
Inactivation of Ribosomes
In Vitro
by Colicin E
3
and Its Mechanism of Action
Authors: Boon Thierry
Published: May 2006

The incubation of purified ribosomes with colicin E
3
results in the cleavage of a terminal fragment from the 16S ribosomal RNA. The cleavage reaction requires three components: colicin E
3
, the 30S ribosomal subunit, and the 50S ribosomal subunit. An immunity factor found in extracts derived from colicinogenic cells prevents the
in vitro
inactivation of ribosomes by colicin E
3
. Evidence is presented suggesting that it does so by binding to the colicin molecule. The mode of action of colicin E
3
in vivo
can be explained by the assumption that a small fraction of the adsorbed colicin penetrates into the cell and catalytically inactivates the ribosomes.
Magnetic Resonance Studies on Membrane and Model Membrane Systems: Proton Magnetic Relaxation Rates in Sonicated Lecithin Dispersions
Authors: Horwitz Alan F. , Horsley William J. , Klein Melvin P.
Published: May 2006

We have used Fourier transform nuclear magnetic resonance methods to measure the spin-lattice and transverse relaxation times at 220 MHz of the choline
N
-methyl and the fatty-acid α-carbonyl, allyl, vinyl, methylene, and methyl protons of sonicated egg-yolk lecithin. Over the temperature range investigated the T
1
values were, in general, similar to, but different from, one another, suggesting that the relaxation rates of all of the fatty-acid protons are not determined solely by spin-diffusion to a heat sink. Arrhenius plots of the T
1
data gave activation energies similar to those for the barriers to internal rotation in alkanes. The values of the transverse relaxation rate, T
2
, showed a relatively large variation among the proton resonances; about 20% of the methylene protons had a T
2
of 56 msec, while the remaining protons relaxed according to a distribution of values all shorter than 20 msec. Such a distribution of relaxation times is envisioned to arise from a distribution of correlation times stemming from complex motions in which extended angular excursions of the fatty acid chain are coupled to
trans→gauche
conformational transitions.