bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Degradation of Liver Acetyl Coenzyme A Carboxylase in Genetically Obese Mice
Authors: Nakanishi Shigetada , Numa Shosaku
Published: May 2006

The total cytosol activity of acetyl-CoA carboxylase (acetyl-CoA:CO
2
ligase (ADP), EC 6.4.1.2) in the liver is known to be 6- to 10-fold higher in genetically obese hyperglycemic mice (C57BL/6J-
ob
) than in nonobese mice. The results of immunochemical titrations, Ouchterlony double-diffusion analysis, and kinetic and heat inactivation studies indicated that this rise in the level of carboxylase activity in liver extracts from obese mice was ascribed to an increase in the quantity of the enzyme protein, which was indistinguishable from that derived from nonobese mice. Combined immunochemical and isotopic techniques showed that the rate of synthesis of the carboxylase per liver was 7.7-fold higher in obese than in nonobese mice. The rate of degradation of the carboxylase was found to be 1.7-fold lower in obese than in nonobese mice, the half-life being 115 and 67 hr, respectively. These results indicate that the increase in the acetyl-CoA carboxylase content of the liver in obese mice is due mainly to a rise in the rate of enzyme synthesis, and in a minor degree, to a decrease in the rate of enzyme degradation.
Nucleoside Diphosphokinase Activity Associated with DNA Polymerases
Authors: Miller Lois K. , Wells Robert D.
Published: May 2006

Nucleoside diphosphokinase activity is present in highly purified preparations of DNA polymerase from
Micrococcus luteus
and
Escherichia coli
, and in a partially purified DNA polymerase from avian myeloblastosis virus. The activity is also observed in the protein fragment of molecular weight 76,000 that is produced by subtilisin cleavage of DNA polymerase I from
E. coli.
The NDP kinase activity in DNA polymerase preparations from
M. luteus
uses various ribo- and deoxyribonucleoside di- and triphosphates as substrates. The presence of this activity in preparations of DNA polymerase results in the apparent use of deoxyribonucleoside diphosphates as substrates for DNA synthesis, provided that some triphosphate is present to serve as a phosphate donor.
Protein Synthesis Directed by Encephalomyocarditis Virus RNA: Properties of a Transfer RNA-Dependent System
Authors: Aviv H. , Boime I. , Leder P.
Published: May 2006

Small amounts of encephalomyocarditis virus RNA direct a 50-fold increase in amino acid incorporation, in appropriately supplemented ascites tumor cell extracts, under conditions that give rise to authentic viral polypeptides. Incorporation in these crude extracts has a novel characteristic, namely, that it is almost entirely dependent upon the addition of exogenous tRNA. Further, this incorporation is restricted in that tRNA derived from ascites tumor cells or from rat liver permits translation of viral RNA, whereas tRNA from yeast or
Escherichia coli
does not. These translational barriers are due, at least in part, to an incompatibility between the tRNA of yeast and
E. coli
and the aminoacyl-tRNA synthetases of the ascites tumor cell. A more extensive basis for this incompatibility is suggested, however, by the failure of the
E. coli
aminoacyl-tRNA synthetases to restore viral RNA-directed protein synthesis in the presence of tRNA from
E. coli
, although the
coli
synthetases fully restore the poly(U)-directed synthesis of polyphenyl-alanine. The possible role that unique or favored codon classes might play in this restriction is considered, together with the implications of the observed requirement for tRNA.
Enzymic Removal and Re-expression of a Histocompatibility Antigen, HL-A 2, at the Surface of Human Peripheral Lymphocytes
Authors: Turner M. J. , Strominger J. L. , Sanderson A. R.
Published: May 2006

The removal by papain of a histocompatibility antigen, HL-A 2, from the surface of intact peripheral blood lymphocytes has been examined. Up to 80% of the antigenic determinant can be removed within 90 minutes. If the cells are reincubated in nutritive medium, re-expression of HL-A 2 is complete within 6 hours. Re-expression is reversibly inhibited by puromycin (50 μg/ml), but actinomycin D (6 μg/ml) only partially inhibited re-expression after 2 hours of prior incubation with the drug.
Teichoic Acid Hydrolase Activity in Soil Bacteria
Authors: Wise Edmund M. , Glickman Rhona S. , Teimer Ellen
Published: May 2006

Bacterial phosphodiesterases have been found that are capable of cleaving the backbone of teichoic acid. Such enzymes have not been reported previously. An aerobic, gram-negative, rod-shaped bacterium producing this activity was detected and isolated by autoradiography of soil suspensions growing on minimal medium containing
32
P-labeled
Bacillus subtilis
ATCC 6051 cell walls as the sole phosphorus source. Broken-cell preparations are capable of depolymerizing teichoic acids in media of low ionic strength at near-neutral pH values. An active teichoicase is also present in
B. subtilis
, ATCC 6051 (the Marburg strain), especially in sporulating cultures.
Cytochalasin B: Effects on Cell Morphology, Cell Adhesion, and Mucopolysaccharide Synthesis
Authors: Sanger J. W. , Holtzer H.
Published: May 2006

Cytochalasin B reversibly causes extensive branching of myoblasts, fibroblasts, and nonencapsulated chondroblasts; it does not induce the formation of similar processes in myotubes, erythrocytes, amnion cells, encapsulated chondroblasts, or HeLa cells. The drug has no effect on the spontaneous contractions of isolated skeletal, cardiac, or smooth-muscle cells. Within 60 min, it depresses the incorporation of [
14
C]glucosamine into total mucopolysaccharide and glycoproteins by over 50%. The drug interferes with adhesion and sorting-out of dissociated embryonic cells. Cytochalasin B is likely to produce changes in components of the cell surface whose function is not readily or solely related to a system of “primitive contractile microfilaments.”
Initiation, Release, and Reinitiation of RNA Chains by Bacteriophage-T3-Induced Polymerase from T3 DNA Templates
Authors: Maitra Umadas , Huang Henry H.
Published: May 2006

Bacteriophage T3-induced RNA polymerase, upon copying its specific template, native T3 DNA, initiates RNA chains only with GTP. Denaturation of the DNA results in loss of template specificity for the polymerase. With denatured T3 DNA as template, T3 polymerase initiates RNA chains with both ATP and GTP, and the average length of the resulting RNA chains is markedly reduced. Studies of the polymerase reaction with native T3 DNA
in vitro
show that T3 polymerase is able to terminate RNA synthesis with the release of RNA chains from the template DNA. Polymerase is also released in the process and, acting catalytically, reinitiates new RNA chains. Many moles of RNA chains are thus formed per mole of polymerase added to the reaction mixture.
A Transport Form of Collagen from Embryonic Tendon: Electron Microscopic Demonstration of an NH
2
-Terminal Extension and Evidence Suggesting the Presence of Cystine in the Molecule
Authors: Dehm Peter , Jimenez Sergio A. , Olsen Bjørn R. , Prockop Darwin J.
Published: May 2006

When cells were isolated from chickembryo tendons and incubated
in vitro
for 2-6 hr, essentially all the newly-synthesized collagen was recovered from the incubation medium as a transport form larger than tropocollagen. Experiments in which cells were incubated with [
14
C]cystine suggested that the transport form contained cystine and that it was, in part, stabilized by disulfide bonds. Electron microscopy of segment-long-spacing aggregates prepared from the transport form of collagen showed that the native molecule differed from tropocollagen in that it had an extension of about 13 nm (130 Å) at the NH
2
-terminal end.
Stochastic Model of Unimolecular Reactions and the RRKM Theory
Authors: Lin S. H. , Lau K. H. , Richardson W. , Volk L. , Eyring H.
Published: May 2006

A stochastic model of unimolecular reactions has been adopted for investigation of the validity and limitation of the RRKM theory. The error caused by the steady-state approximation for distribution of energized molecules is small, while the assumption of the internal energy equilibration of energized molecules might cause serious errors for reactions of low activation energies.
Origin of Leg Musculature during
Drosophila
Metamorphosis
Authors: Ursprung H. , Conscience-Egli M. , Fox D. J. , Wallimann T.
Published: May 2006

Pro- and mesothoracic leg imaginal disks of late third-instar larvae of genotypes affecting the electrophoretic mobilities of α-glycerolphosphate dehydrogenase (EC 1.1.1.8) and arginine kinase (EC 2.7.3.3) were transplanted into host larvae of different genotypes. The metamorphosed implants were analyzed microscopically for the presence of musculature, histochemically for the distribution of enzyme activity, and electrophoretically for determination of the phenotypes of the two muscle-marker enzymes. The results permit the conclusion that leg imaginal disks contain muscle stem-cells.
A New Element in the Control of DNA Initiation in
Escherichia coli
Authors: Blau Susan , Mordoh Jose
Published: May 2006

When a thermosensitive mutant of
E. coli
affected in DNA initiation is heated to 41°, a protein needed for DNA initiation is irreversibly denatured. When these bacteria are incubated at 30° in the presence of several concentrations of chloramphenicol, DNA synthesis is greatly stimulated at a chloramphenicol, DNA synthesis is greatly stimulated at a chloramphenicol concentration of 2.5 μg/ml, and then sharply decreases. This stimulation of DNA synthesis appears to be caused by an increased frequency of initiation. The existence of an “anti-initiator” protein controlling the frequency of chromosomal initiation is proposed.
Role of Nonhistone Chomosomal Proteins in the Restriction of Mitotic Chromatin Template Activity
Authors: Stein Gary , Farber John
Published: May 2006

RNA synthesis virtually ceases during mitosis in eukaryotic cells. This phenomenon is explainable, at least in part, by the reduced template activity for RNA synthesis of mitotic chromatin. The restriction in template activity can be accounted for by the presence in the chromatin of mitotic-specific nonhistone proteins. Chromatin reconstituted by gradient dialysis from the pooled histones of S-phase and mitotic chromatin and the nonhistone proteins of mitotic chromatin had a template activity similar to that of native mitotic chromatin, and lower than native S-phase chromatin or chromatin reconstituted with the pooled histones and the S-phase and nonhistone proteins. The template activity was identical for chromatin reconstituted from the pooled nonhistone proteins and either the histones from S-phase or mitotic chromatin. These results are supported with data showing that the procedure of reconstitution produces a chromatin indistinguishable in its protein composition both qualitatively and quantitatively from its native counterpart.
Mechanism of Cytolysis by Complement
Authors: Mayer Manfred M.
Published: May 2006

The attack of complement is directed against the lipid moiety of the cell membrane; a single lesion at the site of fixation of complement proteins C5-C9 is responsible for lysis of a cell. There are two hypothetical models for the generation of this membrane lesion. The first of these, designated the
leaky-patch model
, postulates either direct enzymatic attack or enzymatic generation of a lytic substance by C5-C9. As a result, the phospholipid bilayer of the membrane would be disrupted and a leaky patch permitting passage of water and salt would appear. However, this hole would persist only as long as enzymatic action continues. Thus, the leaky-patch model would not produce a stable hole, and for this reason it is considered an unlikely mechanism.

The second hypothesis, termed the
doughnut model
, describes a structural concept for creating a hydrophilic passage through the hydrophobic phospholipid bilayer of the membrane. In essence, this would be a rigid and hollow structure, like a doughnut, with a hydrophobic exterior, which is inserted into the phospholipid bilayer of the cell membrane in such a way that its hollow hydrophilic core becomes a channel through which salt and water can exchange freely between the interior of the cell and the extracellular environment. The late-acting complement proteins C5-C9 are the most probable source of the structural components of the doughnut. A combination of the leaky-patch and doughnut models may represent the most likely mechanism.
Karyotypic, Virologic, and Immunologic Analyses of Two Continuous Lymphocyte Lines Established from New Zealand Black Mice: Possible Relationship of Chromosomal Mosaicism to Autoimmunity
Authors: Lerner Richard A. , Jensen Fred , Kennel Stephen J. , Dixon Frank J. , Roches Ginger Des , Francke Uta
Published: May 2006

Two continuous-suspension lymphocyte lines were isolated from the spleen and fibrosarcoma of a New Zealand Black female mouse. A C-type virus with a density of 1.16 g × cm
-3
, 70S RNA, and RNA-directed DNA polymerase activity was isolated. The virus was infectious for NRK, NZB, (NZB x NZW)F
1
, and (NZW x NZW)F
1
embryos, and for BALB/c 3T3 cells, but not for NIH Swiss cells. All cells from established lymphocyte cultures, as well as some embryo cells from New Zealand Black mice, showed karyotypic abnormalities. The possibility of chromosomal mosaicism is suggested.
An Adenosine Triphosphate-Phosphate Exchange Catalyzed by a Soluble Enzyme Couple Inhibited by Uncouplers of Oxidative Phosphorylation
Authors: Allison William S. , Benitez Lita V.
Published: May 2006

The sulfenic acid form of glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12), which is an acyl phosphatase, will catalyze an acetyl phosphate-Pi exchange reaction. This exchange reaction is reversibly inhibited by the uncouplers of oxidative phosphorylation, 2,4-dinitrophenol,
m
-Cl carbonylcyanide-phenylhydrazone, pentachlorophenol, and 5-chloro-3-tert-butyl-2′-chloro-4′-nitrosalicylanalide, and is irreversibly inhibited by cyanide and dicumarol. An ATP-Pi exchange reaction similar to that catalyzed by mitochondria can be simulated by a system composed of oxidized glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase (EC 2.7.1.28), 3-phosphoglycerate, ATP,
32
Pi, and appropriate cofactors. The ATP-Pi exchange is inhibited by uncouplers of oxidative phosphorylation. Higher concentrations of uncouplers will also inhibit the ATPase reaction catalyzed by the coupled enzyme system. The exchange reactions catalyzed by the sulfenic acid form of glyceraldehyde-3-phosphate are consistent with a sulfenyl carboxylate intermediate. On the basis of these observations, a reaction scheme has been postulated for covalent coupling in oxidative phosphorylation that includes a sulfenyl carboxylate as a nonphosphorylated, high energy intermediate and an acyl phosphate as a phosphorylated, high energy intermediate.
Glucocorticoid Action on Hybrid Clones Derived from Cultured Myeloma and Lymphoma Cell Lines
Authors: Gehring Ulrich , Mohit Behzad , Tomkins Gordon M.
Published: May 2006

Cells of a cloned myeloma line from a Balb/c mouse contain specific cytoplasmic glucocorticoid receptors and are killed by dexamethasone. Cells of a lymphoma line (from mouse strain C57BL) also contain specific glucocorticoid receptors but are resistant to the steroid. Cells of two hybrid clones with widely differing chromosome numbers, derived by fusion between the resistant lymphoma and the sensitive myeloma, contain specific glucocorticoid receptors with similar binding properties as the parental receptors and are killed by dexamethasone. Since the lethal effect of the steroid is expressed in the hybrid cells, failure of the parent lymphoma line to be affected by dexamethasone is probably not due to an inhibitor of the lethal reaction.
In Vivo
Production of an RNA-DNA Copolymer after Infection of
Escherichia coli
by Bacteriophage T4
Authors: Buckley Patrick J. , Kosturko Linda D. , Kozinski Andrzej W.
Published: May 2006

An RNA-DNA copolymer was isolated from
Escherichia coli
infected with bacteriophage T4. The RNA and DNA are covalently linked, and in the same polynucleotide strand. The DNA of the copolymer hybridizes specifically to the left strand of phage T4 DNA. The copolymer is produced in cells infected with amber mutants of phage T4 deficient in DNA replication and is not inhibited by the addition of chloramphenicol.
A Mutant of
Escherichia coli
Defective in DNA Polymerase II Activity
Authors: Hirota Yukinori , Gefter Malcolm , Mindich Leonard
Published: May 2006

A mutant of
E. coli
defective in DNA polymerase II activity was isolated. Extracts had about 0.1% of the normal activity of the DNA polymerase. The effect of the mutation on the ability of cells to replicate DNA of various sources was analyzed. Mutant bacteria grow normally, at 41° as well as at 30°. All bacteriophages, F factors, and R factors examined so far grow normally in the mutant. Sensitivity of the mutant to ultraviolet radiation and alkylating reagents in growth media was the same as that of the wild type.

The mutation,
polB1
, is recessive with respect to wild type. The
polB1
mutation can coexist with recombination-defective mutations. Genetic mapping studies show the mutation to be located at about 2 min on the
E. coli
map.
Blocking by Histones of Accessibility to DNA in Chromatin: Addition of Histones
Authors: Mirsky Alfred E. , Silverman Bert , Panda Nimai C.
Published: May 2006

The blocking effect of histones on accessibility of DNA to DNase has been studied by addition of various histones to chromatin in intact or histone-depleted thymus nuclei (those from which all lysine-rich histone was removed and those from which much of the arginine-rich histone was removed) and to deoxyribonucleoprotein (chromatin) extracted from nuclei. In each case lysine-rich histone, weight for weight, blocks accessibility more effectively than does arginine-rich histone. Fractions of the arginine-rich histone differ considerably from each other in their blocking efficacy. Phosphorylation of lysine-rich histone tempers its blocking effectiveness.
Ribosomal RNA Genes of
Neurospora:
Isolation and Characterization
Authors: Chattopadhyay Sisir K. , Kohne David E. , Dutta Sisr K.
Published: May 2006

DNA sequences in
Neurospora crassa
that code for ribosomal RNA have been isolated in a highly purified state by DNA-RNA hybridization. About 100 separate ribosomal RNA genes exist in each nucleus. These genes are composed of repeated sequences that are present about 100 times per nucleus. The individual members of this group of DNA sequences are essentially identical.
Nonhistone Chromosomal Proteins in Synchronized HeLa Cells
Authors: Bhorjee Jaswant S. , Pederson Thoru
Published: May 2006

Chromatin was isolated from synchronized HeLa cells at different stages of the cell division cycle and fractionated into DNA, histones, and nonhistone proteins. Electrophoresis of the nonhistone proteins in sodium dodecyl sulfate-polyacrylamide gels revealed a highly reproducible pattern of 22 bands, having estimated molecular weights of 15,000-180,000, with 85% (by mass) over 40,000. The amounts of some nonhistone proteins varied during the cell cycle by as much as 50%, while others remained at a constant level. One group of nonhistone proteins (molecular weight 75,000) was greatly reduced just before the start of DNA replication (S-phase), then returned to normal levels in the mid-S phase. These results are discussed with regard to the possible role of nonhistone proteins in regulating chromosome structure and function.
Specificity of the
cis
-Isomers of Inhibitors of Uredospore Germination in the Rust Fungi
Authors: Allen Paul J.
Published: May 2006

The
cis
- but not the
trans
-isomers of the natural inhibitors, methyl ferulate and methyl 3,4-dimethoxycinnamate, inhibit germination of the uredospores of wheat-stem rust. Minimum concentrations for 50% inhibition are about 7 and 140 nM, respectively. Ultraviolet radiation activates the
trans
-isomers by partial conversion to the
cis
-forms, and partially inactivates the
cis
-form by the reverse transformation. About 100 molecules of the germination stimulant,
n
-nonyl alcohol, are required per molecule of methyl
cis
-ferulate to overcome inhibition and restore 50% germination. Seasonal and age differences in sensitivity of spores to inhibitor may be related to variations in content of stimulant.
Ammonia Intoxication in Rats: Protection by
N
-Carbamoyl-L-Glutamate Plus L-Arginine
Authors: Kim Sangduk , Paik Woon Ki , Cohen Philip P.
Published: May 2006

Rats given a lethal dose (LD
99.9
) of ammonium acetate (10.8 mmol/kg of body weight) were protected to the extent of 85 and 76% when previously injected with
N
-carbamoyl glutamate or L-arginine, respectively, at a level of 4 mmol/kg of body weight. At a dose of 1 mmol/kg of body weight, L-arginine protected 24%, while
N
-carbamoyl-L-glutamate protected 61% of the animals. When a combination of
N
-carbamoyl-L-glutamate plus L-arginine (1 mmol each per kg of body weight) was injected,
100% of the rats were protected
. The efficacy of
N
-carbamoyl-L-glutamate is related to its role as an activator of mitochondrial carbamoyl phosphate synthetase (EC 2.7.2.5) and its resistance to hydrolysis by tissue acylaminoacid acylase.
N
-Acetyl-L-glutamate, the naturally occurring and most effective activator of mitochondrial carbamoyl phosphate synthetase, was relatively ineffective in protection against lethal dose of ammonium acetate, because of its ready hydrolysis by acylaminoacid acylase.

The findings reported provide a rational basis for the use of
N
-carbamoyl-L-glutamate plus L-arginine in the prevention and treatment of hyperammonemia in clinical conditions of liver disease and parental infusion of amino acids, and in feeding of urea supplements to ruminants.
Initiation of Picornavirus Protein Synthesis in Ascites Cell Extracts
Authors: Öberg Bo F. , Shatkin Aaron J.
Published: May 2006

The current model of picornavirus protein formation implies that initiation of protein synthesis occurs at a single site on the viral RNA, and that the large polypeptide formed is later cleaved. A direct test of this model was made
in vitro
by studying the incorporation of [
35
S]methionine from rabbit liver Met-tRNA
M
Met
and fMet-tRNA
F
Met
into encephalomyocarditis virus RNA-coded proteins in extracts of Ehrlich ascites cells. The incorporation of
N
-formylmethionine was complete within 5 min, while utilization of Met-tRNA
M
Met
continued for 20 min. Tryptic digests of [
35
S]methionine-labeled products from Met-tRNA
M
Met
analyzed by anion-exchange chromatography yielded more than 30 peptides, as compared to about 15 [
35
S]methionine-labeled peptides from purified encephalomyocarditis virus. In contrast, products labeled with fMet-tRNA
F
Met
yielded one major
26
S-labeled tryptic peptide. The N-terminal location of methionine in this peptide was verified by Edman degradation. One predominant N-terminal tryptic peptide was also obtained with fMet-tRNA
F
Met
when mouse Elberfeld and mengo-virus RNAs were used as messengers. On the basis of N-terminal compared with internal labeling of the products, no evidence for
in vitro
post-translational cleavage was found. The results are consistent with a single initiation site for synthesis of picornavirus proteins.
Crystals of Phosphorylcholine-Binding Fab-Fragments from Mouse Myeloma Proteins: Preparation and X-Ray Analysis
Authors: Rudikoff Stuart , Potter Michael , Segal David M. , Padlan Eduardo A. , Davies David R.
Published: May 2006

Fab-fragments of several phosphorylcholine-binding mouse-myeloma proteins have been prepared by pepsin digestion; two of these, MOPC 167 and McPC 603, gave large crystals from ammonium sulfate solutions. The Fab-fragment from MOPC 167 crystallizes in a hexagonal space group, but does not diffract to a resolution greater than about 8 Å. In contrast, McPC 603 crystals (space group P6
3
) diffract to about 2.7 Å. An isotopic double-labeling technique was developed that demonstrated that the 603 crystals bind 1 mol of hapten per mol of Fab-fragment, but with a binding constant significantly lower than that observed in solution. The findings indicate that a three-dimensional model of this homogeneous antigen-binding immunoglobulin can be constructed. Accordingly, a search for heavy-atom derivatives and determination of the primary structure are in progress.
A Study of Optimum Population Levels—A Progress Report
Authors: Singer S. Fred
Published: May 2006

The purpose of this study is to explore different approaches and to develop a methodology that will allow a calculation of “optimum levels of population.” The discussion is specialized to the United States, but the methodology should be broad enough to handle other countries, including less-developed countries. The study is based on economics, but with major inputs from the areas of technology, natural resources management, environmental effects, and demography.

The general approach will be to develop an
index for quality of life
(IQL or Q-index) and to maximize this index as a function of level and distribution of population. The technique consists of a reshuffling of national income accounts so as to be able to go from the Gross National Product (GNP) to the index for quality of life, plus a careful discussion of what is and what is not to be included. The initial part of the study consists of a projection of the index for quality of life as population level increases and as population distribution changes, under the assumption of various technologies, particularly as these relate to the consumption of minerals, energy, and other natural resources. One would expect that as economic growth continues, an increasing fraction of expenditures would be for the diseconomics produced by population growth and economic growth.

This study should be useful by providing a rational base for governmental policies regarding population, both in the United States and abroad. Another application of the study is to
technology assessment
, by measurement of the impact on economic well-being through the introduction of new technologies. Therefore, one can gauge the necessary and desirable investments in certain new technologies. In general, mathematical models resulting from this study can become useful diagnostic tools to analyze the consequences of various public and private policy decisions.
A Ribosome Dissociation Factor from Rabbit Reticulocytes
Authors: Lubsen Nicolette H. , Davis Bernard D.
Published: May 2006

A ribosome dissociation factor has been detected in an extract of ribosomal particles from rabbit reticulocytes. This factor dissociates free ribosomes from reticulocytes and also from
Escherichia coli
; it does not dissociate ribosomes complexed with peptidyl-tRNA and mRNA. The reaction appears to be stoichiometric rather than catalytic; it reaches completion in one minute at 37°C, but is very slow at 0°C, and it is antagonized and reversed by Mg
++
. Reticulocyte dissociation factor thus closely resembles that from
E. coli
. However, the activity has been found primarily associated with the native large subunits rather than the small subunits in lysates.
Isolation of Circular DNA from a Mitochondrial Fraction from Yeast
Authors: Clark-Walker G. D.
Published: May 2006

Breakage and fractionation of respiratory competent yeast in the presence of ethidium bromide, and subsequent centrifugation of a detergent lysate of the mitochondrial fraction by the dye-buoyant-density technique, results in the isolation of closed-circular DNA. After removal of bound dye, this DNA has two components when analyzed by equilibrium buoyant density in the analytical ultracentrifuge. A minor component has a buoyant density of 1.684 g/cm
3
, which is characteristic of mitochondrial DNA, but the major component has a buoyant density of 1.701 g/cm
3
. This species of DNA is also present in yeast that have been mutagenized to respiratory deficiency in the presence of the highest concentration of ethidium bromide compatible with cell growth. The closed-circular DNA of buoyant density 1.701 g/cm
3
, and free of linear DNA, is associated with the sole particulate band obtained on sucrose gradient centrifugation of a mitochondrial preparation from respiratory-deficient cells. Two particulate bands are obtained on sucrose gradient centrifugation of a mitochondrial preparation from respiratory-competent cells, the upper band containing DNA of buoyant density 1.701 g/cm
3
and the lower band DNA of buoyant density 1.684 g/cm
3
. The suggestion is advanced, in view of the reputed sedimentation behaviour of yeast peroxisomes, that the closed-circular DNA of buoyant density 1.701 g/cm
3
may be located in peroxisomes.
Detection of Polyadenylic Acid Sequences in Viral and Eukaryotic RNA
Authors: Sheldon Robert , Jurale Christine , Kates Joseph
Published: May 2006

A rapid and specific technique to detect polyriboadenylic acid sequences in RNA is described. The method depends upon the ability of RNAs that contain poly(A) sequences to associate specifically with poly(U) that has been immobilized on fiberglass filters by ultraviolet irradiation. A high proportion of the transcripts synthesized
in vivo
and
in vitro
from the vaccinia virus genome contain poly(A) sequences and bind to the poly(U) filters. Similarly, DNA-like RNA from the nucleus and from the cytoplasmic polyribosomes of HeLa cells is rich in species that bind to poly(U) filters. Poly(U) immobilized on cellulose powder is useful to make columns with a high capacity for the binding and purification of poly(A)-containing RNAs.
Membrane Microfilaments of Erythrocytes: Alteration in Intact Cells Reproduces the Hereditary Spherocytosis Syndrome
Authors: Jacob Harry , Amsden Thomas , White James
Published: May 2006

Membrane microfilaments are found throughout the animal world in situations suggesting that they fulfill a critical role in providing normal cell shape and plasticity. We have hypothesized that hereditary spherocytosis, a congenital hemolytic anemia associated with intrinsically rigid and mishapen erythrocytes, might result from genetically defective microfilaments in erythrocyte membranes. By using three different drugs (vinblastine, colchicine, and strychnine) that share one common attribute—that of potently precipitating purified microfilamentous protein—we have provided support for this hypothesis. Thus, all the known
in vitro
and
in vivo
characteristics of hereditary spherocytes are reproduced in normal erythrocytes briefly exposed to these precipitating agents.
Synthesis of DNA in Toluene-Treated
Chlamydomonas reinhardi
Authors: Howell Stephen H. , Walker Linda L.
Published: May 2006

Toluene-treated
Chlamydomonas reinhardi
incorporate deoxynucleoside triphosphates (dNTPs) into DNA. Incorporation requires all four dNTPs, but requires neither ATP nor added DNA. The incorporation reaction is linear for nearly 20 min. The product of synthesis in treated cells is mainly chloroplast (β-component) DNA. However, a small quantity of nuclear (α-component) DNA is also synthesized. Synchronously grown cells are most efficient in dNTP incorporation at a time in the cell cycle when chloroplast DNA is normally replicated. Toluene treatment disrupts the internal morphology of the cell, but leaves the outer membrane of the chloroplast intact.
Widespread Presence, in Chickens, of DNA Complementary to the RNA Genome of Avian Leukosis Viruses
Authors: Baluda M. A.
Published: May 2006

DNA-RNA hybridization experiments have demonstrated the widespread presence in chickens of DNA complementary to the RNA of avian myeloblastosis virus. All apparently normal chicken embryos, or adult chickens that were tested, contained viral DNA in amounts ranging from 1.7 to 4.6 viral genome equivalents per cell. Embryos that were negative or positive for the group-specific antigen of avian leukosis viruses contained the same amount of viral DNA. Embryos from a strain of chickens free of leukosis viruses of groups A and B that develop 40% fewer spontaneous leukotic tumors than the original strain contained an average of 2.1 viral DNA equivalents per cell, whereas the original strain contained 3.2 viral DNA equivalents. By comparison, leukemic cells and cells infected with avian myeloblastosis virus or Rous sarcoma virus contained between 4 and 13 viral DNA equivalents. This study provides direct biochemical evidence for the presence in normal chicken cells of avian leukosis virus DNA that is inheritable and that represents either complete or incomplete viral genomes.
Proton Nuclear Magnetic Resonance Studies of Ribonuclease A in H
2
O
Authors: Patel Dinshaw J. , Woodward Clare K. , Bovey Frank A.
Published: May 2006

A resonance (designated
a
) due to an exchangeable proton titrates (pK
a
= 6.1) between 11.5 and 13 ppm in the nuclear magnetic resonance spectrum of RNase A-0.2 M NaCl in H
2
O at 20°. Comparison with models has permitted assignment to a ring-nitrogen proton of histidine in slow exchange with solvent H
2
O. The pH and temperature-dependent line-width changes of resonance
a
are analyzed in terms of an exchange between histidine and protonated histidine, without the necessity to invoke any exchange processes associated with protein conformational changes. Several other resonances due to exchangeable protons are observed between 10 and 15 ppm in the nuclear magnetic resonance spectrum of RNase A in H
2
O.
Quinacrine, A Chromosome Stain Specific for Deoxyadenylate-Deoxythymidylate-Rich Regions in DNA
Authors: Weisblum Bernard , De Haseth Pieter L.
Published: May 2006

Fluorescence of quinacrine in the presence of different polynucleotides was studied to attempt to identify the specific nucleotides responsible for the fluorescence of stained chromosome preparations. A marked enhancement of fluorescence was seen in the presence of bihelical polynucleotides, such as poly(dA-dT), poly(dA)·poly(dT), and poly(rA)·poly(rU), but not in the presence of single-stranded polynucleotides, such as poly(dA), poly(dT), poly(rA), or poly(rU) alone. The higher was the GC content of natural DNAs, the more they quenched. Quenching was also seen with poly(dG) or poly(rG) alone, but not with poly(dC) or poly(rC) alone. Native and denatured DNA were both effective in quenching fluorescence. Thus, a bihelical conformation is
not
required for fluorescence quenching. Nearly all of these properties are shared with proflavine. In contrast, acridine orange, which stains most areas of chromosome preparations, shows enhanced fluorescence in the presence of all members of a series of natural DNAs. These data suggest that base-pairs composed of AT (rather than GC) residues are responsible for the observed fluorescence of specific chromosome regions after treatment with quinacrine, and support the proposal of Ellison and Barr (
Chromosoma
, in press) that the highly localized quinacrine fluorescence in their cytological preparations reflects the presence of DNA that has a high (A + T)/(G + C) ratio.
Bioluminescence: Mechanism and Mode of Control of Scintillon Activity
Authors: Fogel Margaret , Hastings J. W.
Published: May 2006

Subcellular particles, termed scintillons, isolated from the luminescent dinoflagellate
Gonyaulax
, emit light when the pH is lowered from 8 to 5.7. The capacity to emit a second flash is regained by incubation of scintillons with the low molecular weight luciferin from
Gonyaulax
. This compound was previously demonstrated to be the substrate in the bioluminescent reaction catalyzed by a soluble luciferase isolated from the same cell. A model of the scintillon is presented that involves soluble elements structured within a membrane-bound particle.
Inhibition by Elongation Factor EF G of Aminoacyl-tRNA Binding to Ribosomes
Authors: Cabrer Bartolomé , Vázquez David , Modolell Juan
Published: May 2006

Elongation factor G (EF G), bound to ribosomes either with GMPPCP or with fusidic acid and GDP, inhibits elongation factor Tu (EF Tu)-dependent binding of Phe-tRNA on the ribosome-poly(U) complex and binding of Ala-tRNA on the initiation complex formed with RNA from bacteriophage R17; GTP hydrolysis associated with Phe-tRNA binding is also inhibited. Moreover, nonenzymic binding of Phe-tRNA at high Mg
++
concentration is completely blocked by EF G. Thus, EF G appears to bind at a site that overlaps or interacts with the ribosomal A-site.
Relations between Immunity and Malignancy
Authors: Good Robert A.
Published: May 2006

A higher incidence of malignancy as well as greater susceptibility to infection has been found to be associated with primary immunodeficiencies. An increased incidence of leukemia has been associated with X-linked infantile agammaglobulinemia-an isolated defect of humoral immunities. An increased frequency of a wide variety of malignancies have been found to accompany several different forms of primary immunodeficiency. Secondary immunodeficiencies produced by immunosuppressant therapy to facilitate renal transplantation have also been found to have far too much cancer to be explained by chance assocaition. Many experimental associations between immunity and malignancy have also been encountered, indicating that these two adaptive processes have an essential relationship that must be elucidated.
The Genome of RNA Tumor Viruses Contains Polyadenylic Acid Sequences
Authors: Green Maurice , Cartas Maria
Published: May 2006

The 70S genome of two RNA tumor viruses, murine sarcoma virus and avian myeloblastosis virus, binds to Millipore filters in buffer with high salt concentration and to glass fiber filters containing poly(U). These observations suggest that 70S RNA contains adenylic acid-rich sequences. When digested by pancreatic RNase, 70S RNA of murine sarcoma virus yielded poly(A) sequences that contain 91% adenylic acid. These poly(A) sequences sedimented as a relatively homogenous peak in sucrose gradients with a sedimentation coefficient of 4-5 S, but had a mobility during polyacrylamide gel electrophoresis that corresponds to molecules that sediment at 6-7 S. If we estimate a molecular weight for each sequence of 30,000-60,000 (100-200 nucleotides) and a molecular weight for viral 70S RNA of 3-12 million, each viral genome could contain 1-8 poly(A) sequences. Possible functions of poly(A) in the infecting viral RNA may include a role in the initiation of viral DNA or RNA synthesis, in protein maturation, or in the assembly of the viral genome.
The Shape of Immunoglobulin G Molecules in Solution
Authors: Werner T. C. , Bunting James R. , Cathou Renata E.
Published: May 2006

We have studied the shape of rabbit Immunoglobulin G molecules in solution by using singlet-singlet energy transfer to determine the minimum distance between the two hapten binding sites. A hybrid antibody was prepared in which one site specifically bound the energy donor, ε-dansyl-lysine, and the other site bound the energy acceptor, fluorescein. For this donor-acceptor pair,
R
0
was calculated to be 4.8 ± 0.2 nm (48 ± 2 Å). From a comparison of the lifetime of the donor's excited state in the presence or absence of acceptor, it was found that no energy transfer had occurred in the hybrid. Since the maximum distance over which transfer is measurable was 8.2 nm (82 Å; 1.7
R
0
), and since the Fab moieties exhibit segmental flexibility, the average distance between the two hapten-binding sites was estimated to be 9.2-10 nm (92-102 Å). If one assumes that the length of the Fab fragment is 7 nm (70 Å), the corresponding minimum angle between Fab moieties, α

M

, would be 80-95°. The molecules in solution, thus, have an open
Y
- or
T
-shaped configuration in which the hapten binding sites are not more than 2.5 nm (25 Å) from the extreme ends of the Fab fragments. The existence of conformations in which α

M

is less than 80°, as has been observed in some antibody-antigen complexes, must therefore be the result of definite conformational changes.
Glucagon-Stimulated Phosphorylation of Mitochondrial and Lysosomal Membranes of Rat Liver
In Vivo
Authors: Zahlten Rainer N. , Hochberg Abraham A. , Stratman F. W. , Lardy Henry A.
Published: May 2006

The pancreatic hormone, glucagon, stimulates the net uptake of inorganic
32
P
in vivo
into rat liver and its incorporation into proteins of microsomes, mitochondrial membranes, and lysosomes. Incorporation into cytosolic proteins was enhanced only slightly by glucagon. More than 95% of the protein-bound phosphate is present as phosphoserine. Both the radioactivity and the total amount of protein-bound phosphate are increased after injection of glucagon. Glucagon treatment enhanced
32
P incorporation into the alcohol-ether soluble lipids of mitochondria but did not alter the relative distribution of
32
P in various phospholipid species.
Contact Regions for Dinitrophenyl and Menadione Haptens in an Immunoglobulin Binding More Than One Antigen
Authors: Rosenstein Robert W. , Musson Robert A. , Armstrong Martine Y. K. , Konigsberg W. H. , Richards Frank F.
Published: May 2006

Protein 460 is a mouse myeloma γ A
2
protein that competitively binds two small haptens, 2,4-ε-dinitrophenyl-L-lysine (Dnp-Lys) and 2-methyl-1:4-naphthaquinone thioglycollate (MenTG), to the antibody-combining region. The intact protein has a relatively inaccessible sulfhydryl group on each heavy chain. When it is substituted with a bulky reagent the binding affinity for MenTG decreases, while the binding of Dnp-Lys remains the same. Guanidine·HCl selectively reduces binding of Dnp-Lys; dimethylsulfoxide selectively reduces binding of MenTG. Papain digestion of protein 460 followed by column chromatography gave two fractions: one contained both binding activities and the other contained the sulfhydryl group. The affinity for Dnp-Lys of the first fraction is the same as that of the whole molecule, while affinity for MenTG is decreased. Since selective alteration of one or the other binding activity can occur in different ways, it seems likely that even though the haptens compete with each other, there is some spatial separation between the groups of contact amino-acid residues involved in the binding of these two haptens. These findings do not support the hypothesis that an immunoglobulin molecule carries combining sites complementary only to a single hapten or to a structurally related series of haptens, but rather suggests that the antibody-combining site may be a polyfunctional region capable of binding several structurally dissimilar haptens. We discuss a mechanism whereby polyfunctional combining sites can give rise to an antibody population (immune serum) that has a high degree of specificity to a single hapten.
Optical Versus Thermal Transitions in Solids at High Pressure
Authors: Drickamer H. G. , Frank C. W. , Slichter C. P.
Published: May 2006

Pressure-induced electronic transitions have been observed in a wide variety of materials. In particular, Mössbauer resonance studies under high pressure have revealed changes of oxidation state and spin state of iron as a function of pressure. These processes involve the thermal transfer of an electron to a new ground state of the system. The difference in energy between states is frequently measured by optical absorption. In this paper, we relate the energy of the optical absorption peak and its half-width to the difference in thermal energy between the two states as a function of pressure. We show that the optical peak will broaden with pressure only if there is a difference between the force constants of the ground and excited states. These relationships permit the prediction from optical absorption data of the pressure at which a new ground state will be obtained. We demonstrate that the predictions are qualitatively correct for the reduction of Fe(III) in a series of ferric hydroxamates, and for the low-spin to high-spin transition of Fe(II) in ferrous phenanthroline complexes.
Regeneration of the Surface Glycoproteins of a Transplantable Mouse Tumor Cell After Treatment With Neuraminidase
Authors: Hughes R. C. , Sanford B. , Jeanloz R. W.
Published: May 2006

Strain A mouse ascites tumor cells that were treated with neuraminidase (EC 3.2.1.18) (these cells show decreased tumor-forming ability in allogeneic C3H mice) rapidly regenerate sialoglycoproteins at the cell surface during culture. The incorporation of labeled D-glucosamine into membrane glycoproteins of cells that were treated or untreated with neuraminidase proceeds at similar rates. Surface glycoproteins that contain sialic acid are synthesized
de novo
during culture of neuraminidase-treated cells, and in nondividing cells, synthesis is accompanied by turnover of the membrane glycoproteins. The rate of turnover of membrane glycoproteins that lack sialic acid residues is the same as that occurring in non-dividing cells that are not treated with neuraminidase and that are cultured under identical conditions. Turnover of the surface membrane of nondividing cells leads to the accumulation of glycoproteins in the supernatant medium of cell cultures. The rapid regeneration of cell surfaces that contain sialic acid by TA3 cells that were treated with neuraminidase, makes it unlikely that the rejection of these cells
in vivo
, in C3H mice, is due solely to the induction of a primary immune response to new or to previously concealed antigenic specificities that would be expressed on the surface of the sialic acid-depleted cell.
Activation of Leukemia Viruses by Graft-Versus-Host and Mixed Lymphocyte Reactions
In Vitro
Authors: Hirsch M. S. , Phillips S. M. , Solnik C. , Black P. H. , Schwartz R. S. , Carpenter C. B.
Published: May 2006

Spleen cells from BALB/c or CAF
1
mice released little or no detectable leukemia virus when cultured 2-7 days
in vitro
. In contrast, spleen cells of CAF
1
mice previously inoculated with parental BALB/c spleen cells released leukemia viruses in 10 of 11 cases studied. Cultures of a mixture of spleen cells from normal BALB/c and CAF
1
mice also contained leukemia viruses. Phytohemagglutinin induced the transformation of lymphocytes in cultures of CAF
1
or BALB/c spleen cells, but this transformation did not activate leukemia viruses. It is concluded that mixed lymphocyte cultures
in vitro
, just as graft-versus-host reactions
in vivo
, can activate leukemia viruses that are normally present in a repressed form. This activation is not solely a function of lymphocyte transformation. The activated mouse leukemia virus may subsequently account for the observed high incidence of neoplasia in graft-versus-host disease.
Assembly of Tobacco Mosaic Virus
In Vitro:
Effect of State of Polymerization of the Protein Component
Authors: Richards Kenneth E. , Williams Robley C.
Published: May 2006

The
in vitro
assembly of tobacco mosaic virus from its constituent RNA and protein was followed by methods of electron microscopy. The effect of the state of polymerization of the protein upon the initiation of assembly of tobacco mosaic virus rods, and the subsequent rod elongation, was investigated. Protein in two identifiable states of polymerization was used: the 20S “disc”, consisting of 34 monomers arrayed as a two-ring structure, and the 4S “A-protein”, consisting of polymers in the trimer range of size. It is concluded, in confirmation of results of others, that rod assembly is initiated by the attachment of one end of the RNA chain of tobacco mosaic virus to one (or possibly a few) disc structure. Rod elongation, on the other hand, is found to take place by the sequential addition of structures of the size of A-protein, or smaller, to the previously initiated rods.