bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation of the
gal
Repressor
Authors: Parks J. S. , Gottesman M. , Shimada K. , Weisberg R. A. , Perlman R. L. , Pastan I.
Published: May 2006

The repressor of the galactose operon of
Escherichia coli
has been partially purified and identified as a protein. Induction of a lysogen in which λ was linked to the bacterial
gal
R and lysine genes resulted in a large increase in the production of the
gal
repressor. Single-step purification by affinity chromatography, using the ligand
p
-aminophenyl-β-D-thiogalactoside linked to beaded agarose, provided a convenient method of separating the
gal
repressor from other DNA-binding proteins. Binding of
gal
repressor to λp
gal
[
32
P]DNA was studied by assay of binding to a nitrocellulose filter. Interaction between
gal
repressor and λp
gal
DNA showed a high degree of specificity; the dissociation constant of the complex was estimated to be 1.0 × 10
-12
M. Unlabeled λp
gal
DNA competed for binding to
gal
repressor, but λDNA and λh80d
lac
DNA did not. Fucose and galactose, which function as inducers of the galactose operon
in vivo
, produced one-half maximal inhibition of
gal
repressor-λp
gal
DNA binding at concentrations of 5 × 10
-5
M.
Preparation of a “Chemical Vaccine” Against Tumor Progression
Authors: Shier W. Thomas
Published: May 2006

A synthetic antigen containing the presumed receptor site for wheat-germ agglutinin (a lectin capable of specifically agglutinating tumor cells) elicits an immune response in mice capable of cross-reacting with receptor sites for wheat-germ agglutinin on tumor-cell surfaces. Mice immunized against the antigen in complete Freund's adjuvant are able to reject five times as many transplanted myeloma tumor cells as are rejected by otherwise identically treated control mice. Methylcholanthrene-induced tumors appear later in mice immunized against the antigen than in controls. The protection of mice against tumor transplants can be transferred to unimmunized mice with spleen cells, but not with serum from immunized donors. Immunization of mice against the wheat-germ agglutinin receptor seemed to have no marked deleterious effect on biological processes in normal dividing cells.
The Absolute Configuration of Natural (-)-Stercobilin and Other Urobilinoid Compounds
Authors: Brockmann Hans , Knobloch Gerrit , Plieninger Hans , Ehl K. , Ruppert J. , Moscowitz Albert , Watson C. J.
Published: May 2006

Chromic acid degradation of natural (-)-stercobilin (1) yields 2(R)-methyl-3(R)-ethylsuccinimide (+2), whereby the absolute configuration of 1 at the chiral centers C-1, C-2, C-7, and C-8 is established. The substituted oxo-tetrahydrodipyrromethane precursor, 5, for the total synthesis of (-)-stercobilins 3 and 4, in which the relative configuration between the asymmetric centers is known, yields 2(S)-methyl-3(S)-ethylsuccinimide (-2) under the same conditions of degradation. Nuclear magnetic resonance studies of 1 and 3 show that in 1 the hydrogen atoms at C-2 and C-2′, as well as those at C-7 and C-7′, are
trans
relative to one another. Accordingly, natural (-)-stercobilin possesses the 2′(S), 7′(S) configuration, and has the configuration formula 6(1 (R), 2(R), 2′(S), 7′(S), 7(R), 8(R)). These results, coupled with those of earlier studies, also establish the absolute configuration of the (+)-urobilin 7 and of the phycobilin 8 at C-7′.
pH-Dependent Conformational Changes of Concanavalin A
Authors: Zand R. , Agrawal B. B. L. , Goldstein I. J.
Published: May 2006

The pH dependence of the conformation of concanavalin A has been studied by means of optical rotatory dispersion and circular dichroism spectroscopy. At pH 2.9, 5.0, and 7.0, the major contribution to organized structure appears to be the β conformation. At pH 9.1, the conformation of concanavalin A approaches the random coil or unordered form. No evidence could be found for the presence of any significant amount of α helix. The pH of maximum precipitin-like activity of concanavalin A is paralleled by the pH dependence of the parameter b
0
in the Moffitt equation.
DNA-Directed Cell-Free Synthesis of Biologically Active Transfer RNA:
su
+
III
Tyrosyl-tRNA
Authors: Zubay Geoffrey , Cheong Loretta , Gefter Malcolm
Published: May 2006

Biologically active
su
+
III
tyrosyl-tRNA has been synthesized in a DNA-directed cell-free system from
Escerichia coli
. Such a system should be most useful for studying the mechanism of tRNA synthesis. This tRNA is capable of suppressing amber mutations in the gene coding for β-galactosidase (EC 3.2.1.23) and, therefore, must be capable of being charged and transferring amino acids. A 4-fold stimulation in the activity of the tRNA formed
de novo
is obtained with isopentenyl pyrophosphate, a compound involved in the post-transcriptional acylation of an adenine base adjacent to the anticodon. It has been suggested elsewhere that formation of RNA subject to stringent control may be inhibited by guanosine tetraphosphate (ppGpp). However, guanosine tetraphosphate did not affect the synthesis of su
+
III tyrosyl-tRNA, even though the synthesis of this tRNA is subject to stringent control.
Carbon Dioxide Hydration Activity of Carbonic Anhydrase: Kinetics of Alkylated Anhydrases B and C from Humans
Authors: Khalifah Raja G. , Edsall John T.
Published: May 2006

A stop-flow kinetic study was performed on the carbon dioxide hydration activity of the human carbonic anhydrase B isoenzyme carboxymethylated at its histidine
200
, and of the human C isoenzyme carboxyketoethylated at its histidine
63
. The Michaelis-Menten parameters determined between pH 5.6 and 8.7 showed striking differences between the native and the alkylated enzymes, as well as between the modified enzymes themselves. The alkylations caused: (
i
) a decrease in the
k
cat
values, particularly marked for the carboxymethylated B isoenzyme, (
ii
) a change in the apparent pK of the
k
cat
curves, and (
iii
) a dependence of
K
m
on pH, for the alkylated enzymes, in contrast to the pH-independent
K
m
values of the native enzymes. The CO
2
hydration and esterase activities of the carboxymethyl B isoenzyme differ markedly in their pH dependence. A kinetic mechanism, which is found to be compatible with all the present observations, is proposed. The results indicate that the modifiable histidine residues do not play an essential role in the catalytic mechanism of the native carbonic anhydrases, but they may well influence the enzyme activity in a secondary role.
Molecular Events Responsible for Modulation of Neoantigenic Expression: The Cleavage-Associated Neoantigen of Fibrinogen
Authors: Plow Edward , Edgington Thomas S.
Published: May 2006

Molecular events responsible for modulation of neoantigenic expressions of a defined molecule have been explored in relation to three hypothetical molecular models (see below). Fibrinogen and its cleavage-associated neoantigen have been used as a prototype system. Physicochemical and enzymatic factors influencing neoantigenic expression were evaluated. The cleavage-associated neoantigen was not only exposed by plasmin and enzymes of similar specificity, but also in a qualitatively and quantitatively deficient fashion by enzymes of differing specificities. Denaturation of fibrinogen via reduction or pH alteration did not induce the neoantigen, but oxidation of the native fibrinogen molecule did elicit this neoantigenic expression. The neoantigen, once exposed on the D-fragment, was relatively stable to physical and chemical denaturation. These results are inconsistent with proposed
cleavage site specific
and
neoconformational
determinant models and are consistent with a
steric
model, which postulates that the cleavage-associated neoantigenic determinant is buried in native fibrinogen but is exposed in certain altered molecular species. The importance of molecular conformation in the exposure of antigenic expressions of a molecule and in modulation of the binding affinity of a neoantigen for specific antibody is demonstrated.
Cytogenetic Analysis of the First Cleavage Division in Mouse Embryos
Authors: Donahue Roger P.
Published: May 2006

Chromosome counts of 338 mouse zygotes at late prophase and metaphase of the first cleavage division revealed 96.4% diploidy, 1.8% hypodiploidy, 1.2% triploidy, and 0.3% tetraploidy. One additional anomaly might have given rise to an embryo mosaic for maternal but not paternal genes. In zygotes collected without colchicine administration to the mother, one of ten anaphases had a lagging chromosome. Reciprocal crosses with the translation T163H as a marker chromosome at late prophase, when the male- and female-derived chromosome groups have not yet combined, demonstrate that the group derived from the larger pronucleus and having less condensed chromosomes is of paternal origin. T163H undergoes Mendelian segregation in female heterozygotes.
An Osmotically Fragile Mutant of
Bacillus subtilis
with an Active Membrane-Associated Phospholipase A
1
Authors: Kent Claudia , Lennarz W. J.
Published: May 2006

By use of a newly developed procedure for the isolation of mutants with osmotically fragile protoplasts, a mutant of
Bacillus subtilis
was isolated that has a very active enzyme system for the catabolism of phospholipids via the sequential action of a phospholipase A
1
(EC 3.1.1.4) and a lysophospholipase (EC 3.1.1.5). The wild-type bacteria contain no detectable phospholipase A
1
activity, but do contain a protein that specifically inhibits the phospholipase A
1
in the mutant. This protein may play an important role in the control of phospholipid catabolism.
A Unifying Hypothesis Concerning the Nature of Malignant Growth
Authors: Holley Robert W.
Published: May 2006

It is suggested that the crucial change in a malignant cell is an alteration in the cell surface membrane that results in increased internal concentrations of nutrients that regulate cell growth.
Curing of a Killer Factor in
Saccharomyces cerevisiae
Authors: Fink Gerald R. , Styles Cora Ann
Published: May 2006

Many standard laboratory stocks of yeast are able to kill other yeast strains. This property has not been generally recognized because killing is observed only at low pH and not at the pH of standard media. In all strains examined, the genetic determinant for the killer trait shows non-Mendelian inheritance. The segregation patterns of our killer strains indicate that this killer determinant may be different from the killer previously described. Treatment of a killer strain with cycloheximide, but not with ethidium bromide, converts it into a sensitive nonkiller.
Activation of Membrane-Bound Adenylate Cyclase by Glucagon in
Neurospora crassa
Authors: Flawiá Mirtha M. , Torres Héctor N.
Published: May 2006

Membrane-bound adenylate cyclase in
Neurospora crassa
is activated by glucagon. Half-maximal effect is observed at hormone concentrations of about 10 nM. After solubilization of the enzyme with Lubrol-PX, the glucagon effect is lost. Incubation of
neurospora
cells with glucagon leads to a decrease in the activity of glycogen synthetase (EC 2.4.1.11) and to an increase in the activity of glycogen phosphorylase (EC 2.4.1.1) and in the rate of glycogenolysis.
Inactivator of the Third Component of Complement as an Inhibitor in the Properdin Pathway
Authors: Alper Chester A. , Rosen Fred S. , Lachmann Peter J.
Published: May 2006

Evidence has been obtained that a single protein, known to modulate classical complement activation, also acts as an inhibitor in the properdin or alternate complement pathway. A highly purified inactivator of the third component of complement (C3) from human serum inhibited the proteolysis of Factor B in the properdin system (glycine-rich β-glycoprotein) by glycine-rich β-glycoproteinase. The inhibition was by the enzymatic destruction of glycine-rich β-glycoproteinase activity. The major fragment of C3, C3b, which is the only known substrate of the C3 inactivator, blocked the destruction of glycine-rich β-glycoproteinase by the C3 inactivator. Thus, in its inhibition of the porperdin pathway, the C3 inactivator destroys both the active form of glycine-rich β-glycoproteinase and a protein involved in the conversion of the zymogen form of this enzyme (proglycine-rich β-glycoproteinase) to its active form. The increased susceptibility to infections in a patient homozygous for deficiency of the C3 inactivator demonstrates the biologic significance of this protein.
Competition, Competitive Repulsion, and Coexistence
Authors: Darlington P. J.
Published: May 2006

This manuscript is concerned with concepts rather than abstruse details or mathematics. Discussed are: competition; extended competition, proposed for competition in the strict sense, extended and modified by all related interactions including predation, parasitism, disease, and even cooperation, all of which can be “weapons of competition”; competitive repulsion, proposed for the sum of forces that determine spacings, including ecologic spacings, of individuals and populations; Darwin (biotic) equilibriums; competitive extinction, Gause's principle, limited and limiting resources, and single-resource competition; de facto coexistence of competing species, exemplified by green plants competing for sunlight; niche competition; the two concepts of competitive exclusion; devision of resources and of their utilizers; cause and effect in real situations; and niches, niche overlap, and coexistence. Stressed is the complexity of the real world, and the confusion that can and does arise from modeling it too simply.
Genetic Control of α-Glycerolphosphate Dehydrogenase in Mouse Brain
Authors: Kozak Leslie P.
Published: May 2006

Activity of α-glycerolphosphate dehydrogenase (EC 1.1.1.8), linked to cytoplasmic nicotinamide adenine dinucleotide, is higher in brains of BALB/cJ mice than in brains of C57BL/6J mice. The magnitude of the difference is dependent on both the age and brain region of the mice. Maximal differences are observed at 20 days of age and are detected in the cerebellum, with only marginal differences occurring in other brain regions. Kidney and liver of BALB/cJ mice have higher enzyme activity than those of C57BL/6J mice, whereas muscle-enzyme activity is lower in BALB/cJ mice than in C57BL/6J mice.

In addition to differences in activity, α-glycerolphosphate dehydrogenase in BALB/cJ mice is more sensitive to heat denaturation. The half-life for the enzyme at 50° in BALB/cJ, (BALB/cJ x C57BL/6J)F
1
hybrid, and C57BL/6J mice is 1, 1.7, and 3 min, respectively. Genetic analysis of the mode of inheritance of the heat-sensitive enzyme reveals that the trait is determined by a single autosomal gene. Genetic analysis of the activity of α-glycerolphosphate dehydrogenase in the cerebellum indicates that the mechanism of inheritance for this trait involves two or more genes and that one of these genes also confers heat sensitivity on the enzyme. The affect of these genes on enzyme activity is codominant and additive.
Purification of Insulin-Specific Protease by Affinity Chromatography
Authors: Duckworth William C. , Heinemann Martha A. , Kitabchi Abbas E.
Published: May 2006

A single enzyme that proteolytically degrades insulin was isolated from rat skeletal muscle. This enzyme was purified 1000-fold by a series of steps, including affinity chromatography on insulin bound to agarose at the NH
2
-terminal phenylalanine of the B chain. Insulin linked to agarose at the B-29 lysine residue did not bind the enzyme and, therefore, was not suitable for purification procedures. Insulin linked at the phenylalanine residue was a substrate for the enzyme and was degraded by it; insulin attached to agarose at the lysine residue was not degraded by the enzyme. The purified enzyme preparation yielded one major band on polyacrylamide gel electrophoresis, and elution of this area of the gel yielded insulin-degrading activity. The purified enzyme degraded insulin but not proinsulin, with a

K
m

for insulin of 22 nM and a

K
i

for proinsulin of 40 nM. The enzyme is sulfhydryl-dependent, with a physiological pH optimum.
Synthesis of Plastoquinone Analogs and Inhibition of Photosynthetic and Mammalian Enzyme Systems
Authors: Bøler Jan , Pardini Ronald , Mustafa Hanna T. , Folkers Karl , Dilley Richard A. , Crane Frederick L.
Published: May 2006

New 5-hydroxy- and 5-chloro-6-alkyl-1,4-benzoquinones with one or two methyl groups on the nucleus were synthesized as potential antimetabolites of plastoquinones for biological research on photosynthetic and mammalian enzyme systems; the primary emphasis was on photosynthesis.

2,3-Dimethyl-5-hydroxy-6-phytyl-1,4-benzoquinone completely inhibited in chloroplasts the water-dependent electron transport, but photosystem I was insensitive to this analog. The data are consistent with the interpretation that this analog inhibits electron transport in the chain prior to the site of electron donation from the ascorbate-dichlorophenolindophenol couple. Concentrations of 70 μM and 120 μM of this analog caused about 50 and 100% inhibition, respectively, of cyclic photophosphorylation.

2,3-Dimethyl-5-hydroxy-6-phytyl-1,4-benzoquinone is a new type of inhibitor of photosynthetic electron transport that specifically inhibits the rate-limiting step between photosystems I and II. Structurally related analogs caused inhibitions in the range of 50-100% in chloroplasts.

These analogs showed marginal inhibition in mitochondrial coenzyme Q
10
-oxidase systems from beef heart.
Perturbed Angular Correlation Study of a Haptenic Molecule
Authors: Meares Claude F. , Sundberg Michael W. , Baldeschwieler John D.
Published: May 2006

The angular correlation of the 173-247 keV gamma-ray cascade after the electron-capture decay of
111
In is strongly perturbed when the 1-
p
-nitrophenyl-ethylenediaminetetraacetate chelate of
111
In
8+
is added to a solution containing rabbit antibody to dinitrophenyl groups. The radioactive chelate can be displaced by the addition of dinitrophenyllysine or unlabeled chelate. The average association constant between the antibody and the labeled chelate has been estimated from perturbed angular correlation measurements; this value is compared to the results of equilibrium dialysis. These experiments provide good evidence that information concerning macromolecular behavior can be obtained from perturbed angular correlation experiments that use chemically specific labels.
The Sensitivity of Developing Cardiac Myofibrils to Cytochalasin-B
Authors: Manasek Francis J. , Burnside Beth , Stroman John
Published: May 2006

Developing cardiac muscle cells of 11- to 13-somite chick embryos are sensitive to cytochalasin-B. In cultured chick embryos, ranging in development from 11 to 13 somites, hearts stop beating in the presence of this agent. Both polarized light and electron microscopic examination show that cytochalasin-B disrupts existing myofibrils and inhibits the formation of new ones. Discrete Z-bands are not present in treated heart cells and thick, presumably myosin, filaments are found in disarray. These effects are reversible; after cytochalasin-B is removed from the medium, heartbeat recovers and myofibrils with discrete Z-bands reappear. Fibrillar sensitivity appears to be a function of age since fibrils in hearts of embryos having from 22 to 28 pairs of somites are more resistant.
Affinity Chromatography of RNA-Dependent DNA Polymerase from RNA Tumor Viruses on a Solid Phase Immunoadsorbent
Authors: Livingston David M. , Scolnick Edward M. , Parks Wade P. , Todaro George J.
Published: May 2006

A solid phase immunoadsorbent specific for RNA-dependent DNA polymerase from murine and feline RNA tumor viruses has been prepared. The enzymes from murine and feline virus but not from avian virus bind to columns of this material. Bound enzymes can be eluted in active form. This method has permitted selective purification of viral enzyme from crude extracts of virus-transformed cells, since the immunoadsorbent has no affinity for cellular DNA polymerases.
In Vitro
Synthesis of Ribosomal RNA by
Bacillus subtilis
RNA Polymerase
Authors: Hussey Caroline , Pero Janice , Shorenstein Rosalind G. , Losick Richard
Published: May 2006

Two kinds of hybridization competition experiments show that
Bacillus subtilis
RNA polymerase synthesizes ribosomal RNA (rRNA)
in vitro
with
B. subtilis
DNA as a template. First, RNA synthesized
in vitro
competes with the hybridization of [
32
P]rRNA synthesized
in vivo
to the heavy strand of
B. subtilis
DNA. Second, unlabeled rRNA synthesized
in vivo
competes with the hybridization of [
3
H]RNA synthesized
in vitro
to denatured DNA or heavy-strand DNA, but not to light-strand DNA. The ability of RNA polymerase holoenzyme to synthesize rRNA
in vitro
is not lost after extensive purification. RNA polymerase core enzyme, however, which is missing the σ factor, synthesizes little rRNA
in vitro
.

RNA polymerase purified from wild-type sporulating cells synthesizes little rRNA
in vitro
, while the
in vitro
synthesis of rRNA by RNA polymerase from stationary phase cells of the sporulation-defective mutant
rfr
10 is apparently unimpaired.
The Mechanism of Viral Carcinogenesis by DNA Mammalian Viruses: RNA Transcripts Containing Viral and Highly Reiterated Cellular Base Sequences in Adenovirus-Transformed Cells
Authors: Tsuei Deane , Fujinaga Kei , Green Maurice
Published: May 2006

Virus-specific RNA was isolated from cells transformed by human adenovirus 2 and 7 by multiple hybridizations with and elutions from homologous viral DNA; RNA molecules purified by this selection procedure hybridized efficiently with both viral DNA (24-50%) and DNA from untransformed cells (12-27%). Virus-specific RNA isolated in the same manner from cells productively infected with adenoviruses did not hybridize significantly with cellular DNA. These findings suggest that RNA molecules containing covalently-linked viral and cellular sequences are transcribed in cells transformed by human adenoviruses. The high efficiency of hybridization with DNA from untransformed cells implies that viral DNA is integrated adjacent to highly reiterated cellular DNA sequences.
Regulation of Adenosine 3′:5′-Cyclic Monophosphate Phosphodiesterase Activity in Fibroblasts by Intracellular Concentrations of Cyclic Adenosine Monophosphate
Authors: D'Armiento Massimo , Johnson George S. , Pastan Ira
Published: May 2006

Cyclic AMP-phosphodiesterase is present in various mouse fibroblasts. Contact-inhibited 3T3 cells contain two forms of the enzyme, one with a

K
m

of 2.5 μM and the second with a

K
m

of 71 μM. As 3T3 cells grow to confluency and cAMP concentrations rise, the activity of the first enzyme increases, whereas that of the second is unchanged. A line of SV40-transformed 3T3 cells with low cAMP concentration also has low levels of the cAMP-phosphodiesterase with a

K
m

of 2.5 μM. Treatment of 3T3 and SV40-transformed 3T3 cells with dibutyryl cAMP and theophylline increases cAMP-phosphodiesterase accumulation. This accumulation is blocked by cycloheximide and actinomycin D. The newly formed enzyme resembles the higher affinity enzyme present in unstimulated cells, since it has a

K
m

of 1.2-2.0 μM, and is stimulated by snake venom. In L cells in which cAMP concentrations are elevated by treatment with prostaglandin E
1
, cAMP phosphodiesterase also accumulates. We conclude that intracellular concentrations of cAMP regulate the synthesis of cAMP-phosphodiesterase, and that cAMP functions as an inducer of the enzyme.
Epinephrine Binding to the Catecholamine Receptor and Activation of the Adenylate Cyclase in Erythrocyte Membranes
Authors: Schramm M. , Feinstein H. , Naim E. , Lang M. , Lasser M.
Published: May 2006

Turkey erythrocyte membranes showed specific binding of [
3
H]epinephrine. The concentration of hormone required for half-maximal binding (30 μM) was the same as that required for half-maximal activation of the adenylate cyclase located in the same membrane preparation. The binding reaction at 37°C reached completion during the first minute of incubation, which agrees well with the known rapidity of the biological response to catecholamines. Specific binding was abolished by heating the membranes 1 min at 100°C. Chromatography of the bound
3
H, after its extraction from the membranes, indicated that the hormone had fully retained its chemical structure. Epinephrine binding was inhibited by the β-adrenergic blocking agent propranolol, which also inhibited the activation of adenylate cyclase by the hormone. The specificity of phenethylamine derivatives in displacing [
3
H]epinephrine from the binding sites showed that a typical catecholamine receptor was responsible for the binding. Displacement of the bound hormone by analogs lacking the catechol group was more extensive at 37°C than at 0°C. Some of the analogs that displaced epinephrine from the binding site caused only a feeble activation of the adenylate cyclase, but were able to inhibit the activation of the enzyme by epinephrine. Thus, binding to a catecholamine receptor on a membrane preparation is an essential, but insufficient, condition to elicit a response.
A Factor That Can be Used to Regulate an
In Vitro
Primary Immune Response
Authors: Watson James , Thoman Marilyn
Published: May 2006

A factor has been isolated that supports the stimulation of an immune response against heterologous erythrocyte antigens in mouse spleen cells cultured in a medium that contains deficient serum. The factor is secreted by certain spleen cells that are obtained in permanent culture after leukemia virus infection. The factor permits antigen-sensitive cells derived from bone marrow to mature to antibody-forming cells. This factor can be used in controlling the initiation of a primary immune response
in vitro
.
Methylxanthine-Induced Escalation: A Propagated Wave Phenomenon Observed in Skeletal Muscle Developing in Culture
Authors: Coleman Annette W. , Coleman John R. , Griffin James D. , Weltman Joel K. , Chapman K. M.
Published: May 2006

Relatively low concentrations of methylxanthines increase spontaneous twitching in cultured muscle fibers; they also cause a second activity, escalation, which is the initiation and undiminished propagation of visible waves. The effect on twitching is abolished by depolarizing concentrations of K
+
or by tetrodotoxin; the effect on escalation is not. Escalation is prevented by removal of external Ca
++
or by the addition of tetracaine.
Some Implications of the Activation of Murine Leukemia Virus by Halogenated Pyrimidines
Authors: Rowe Wallace P. , Lowy Douglas R. , Teich Natalie , Hartley Janet W.
Published: May 2006

Genetic information of murine leukemia viruses is known to be present in essentially all mice. Delineation of the biological effects of the expression of this genetic information is complicated by the difficulty in determining whether the presence of a viral antigen in a tissue is the result of gene activation that occurs independently in a large number of cells, proliferation of antigen-positive cells, or of spread of infectious virus from a few cells. This problem is further complicated by the difficulty in determining whether activation of virus genetic material is the cause or result of a biological phenomenon, such as malignancy. Further understanding of the activation of virus genes in normal cells is of great importance in answering these questions.

In vitro
techniques were used for the study of induction of virus. Virus-negative cell lines were established from embryos of AKR mice, which
in vivo
produce high titers of infectious murine leukemia virus. It was found that 5-iododeoxyuridine and 5-bromodeoxyuridine were potent inducers of virus synthesis in all clones and subclones of the AKR cells tested. In addition to establishing that the complete viral genome is a heritable component of all cells of the AKR mouse, these studies of virus activation provide novel approaches to a number of important problems in the biology of leukemia viruses.
On the Development of Programs in Cancer Research
Authors: Cohen Seymour S.
Published: May 2006

This paper discusses some problems of the participation of scientists in developing broad, long-range programs of cancer research by national and local medical centers. The 17-year performance of the Scientific Advisory Committee of the National Foundation for Infantile Paralysis in development of polio vaccines is discussed with respect to: (
i
) the formulation of programs and priorities in the absence of much fundamental knowledge; (
ii
) the support of basic research, (
iii
) its attitude on the direction of scientific effort, and (
iv
) the cooperative activities among numerous capable, strongwilled, independent scientists. This historic effort provides an excellent model for scientific participation in the development of comprehensive programs of cancer research.
Current Status of Chemical Carcinogenesis
Authors: Shubik Philippe
Published: May 2006

The prevention of cancer by the elimination of, or decreased contact with, chemical carcinogens is dealt with under three headings. (
a
) Exposure of special groups: occupational cancer, iatronic cancer; (
b
) exposure of whole populations; (
c
) discovery of chemical carcinogens in the course of toxicity studies. It is most important that a major effort be made to interrelate findings in man with those in the laboratory. Combination and organization of the findings from many approaches: clinical and preventive medicine, public health, environmental protection, and laboratory research are required.
Determination of the Backbone Structure of Nucleic Acids and Nucleic Acid Oligomers by Laser Raman Scattering
Authors: Erfurth Stephen C. , Kiser Ernest J. , Peticolas Warner L.
Published: May 2006

Raman spectra of fibers of DNA that have been prepared in the A, B, and C forms are presented and compared with Raman spectra of DNA and RNA in dilute solution. It is shown that the phosphate vibrations in the region 750-850 cm
-1
are very sensitive to the specific conformation of the phosphate group in the backbone chain and are virtually independent of all ohter factors. Thus, a very simple method for the determination of the specific conformation of the backbone chain of nucleic acids, at least so far as the sugar-phosphate chain is concerned, appears available. The method is applied to short oligomers and dimers of ribonucleosides. It is found that at low temperatures, at pH 7, the phosphate group goes into the geometry of the A conformation when the stacking forces between the bases are sufficiently strong.
Detection and Isolation of the Repressor Protein for the Tryptophan Operon of
Escherichia coli
Authors: Zubay G. , Morse Daniel E. , Schrenk W. Jurgen , Miller J. H. M.
Published: May 2006

DNA from a transducing bacteriophage carrying a fusion of the tryptophan and lactose operons of
E. coli
(λd
trp-lac
) has been used to direct cell-free synthesis of β-galactosidase (EC 3.2.1.23). Whereas normal
lac
operon (λd
lac
) DNA requires adenosine-3′:5′-cyclic monophosphate (cAMP) for β-galactosidase synthesis,
trp-lac
DNA is unaffected by cAMP. This difference in cAMP dependence verifies the presence of a cAMP-requiring promoter in the
lac
operon that has been removed from the
trp-lac
DNA. Synthesis with
trp-lac
DNA is controlled by the protein product of the tryptophan repressor gene (
trpR
). Synthesis in extracts of
trpR
-
(repressor-negative) cells is progressively reduced by increased additions of extract from
trpR
+
cells. No
trpR
-
product repression is seen when β-galactosidase synthesis is programmed by normal
lac
DNA. This highly sensitive and specific assay has facilitated quantitation and partial purification of the
trp
repressor.
The 3′-Terminal Nucleosides of the High Molecular Weight RNA of Avian Myeloblastosis Virus
Authors: Stephenson Mary L. , Wirthlin Le Roy S. , Scott Jesse F. , Zamecnik Paul C.
Published: May 2006

The RNA isolated from avian myeloblastosis virus was fractionated by sucrose density gradient centrifugation. The 3′-OH terminal nucleosides of various fractions were determined by periodate oxidation followed by tritiated borohydride reduction. The 60-70S fraction and the 35S RNA derived from it by heating both have adenosine as the major terminal nucleoside, with cytidine as the next most frequent terminal. Control samples of tRNA
met

f. coli

and 28S ribosomal RNA from mouse ascites tumor cells gave the expected terminal residues and molecular weights.
Molecular Complexes of Methoxyindoles with 1,3,5-Trinitrobenzene and Tetracyanoethylene
Authors: Sung M. T. , Parker J. A.
Published: May 2006

Association constants for 1:1 molecular complexes formed between 1,3,5-trinitrobenzene and various methoxy-substituted indoles have been determined by chemical-shift measurements in their nuclear magnetic resonance spectra. The values of association constants for the molecular complexes are comparable to those obtained by optical spectroscopy. The effect on the association constants and relative chemical shifts of the acceptor protons of the pure complexes of various donors is considered. The association constants and relative chemical shifts of the complexes determined by different protons on the nidoles in the presence of an excess of 1,3,5-trinitrobenzene are different. The possible structure of the complexes is discussed. The molecular complexes between tetracyanoethylene and various methoxyindoles have also been studied.
Homonuclear Internuclear Double Resonance Spectroscopy as a Basis for Determination of Amino Acid Conformation
Authors: Gibbons W. A. , Alms H. , Sogn J. , Wyssbrod H. R.
Published: May 2006

INDOR (Internuclear Double Resonance) spectroscopy is shown to be superior to conventional (spectra obtained not by
sweeping
, but by
maintaining constant
the decoupling frequency) nuclear single- or double-resonance techniques for conformational studies of amino acids and amino acid residues in the following ways: (
a
) INDOR spectra of amino acids are inherently simpler than conventional proton magnetic resonance spectra of amino acids, and INDOR spectra of individual amino acid residues are slightly, if at all, complicated by overlap with either solvent peaks or the transitions of nuclei in other residues. (
b
) For each amino acid, the side-chain and C
α
proton belong to a particular class of spin system characterized by unique INDOR spectra, the pattern of which aids in the proper assignment of spectral lines. (
c
) For an amino acid with a first-order spin system, INDOR spectra
directly
reveal hidden chemical shifts and coupling constants. For an amino acid with a spin system other than first-order, INDOR spectra
indirectly
reveal values for chemical shifts and coupling constants as follows: INDOR spectra permit construction of a
topological spin energy level diagram
which, in turn, allows division of the PMR spectrum of the spin system into subspectra that easily yield values for chemical shifts and coupling constants.

Although we only report INDOR spectra of free amino acids or amino acid derivatives that resemble amino acid residues in polypeptides,
we, in effect, demonstrate a novel method to obtain total polypeptide conformation based on INDOR spectroscopy
, inasmuch as the total conformation is the sum of the individual residue conformations.
Increased Efficiency of Exogenous Messenger RNA Translation in a Krebs Ascites Cell Lysate
Authors: Metafora S. , Terada M. , Dow L. W. , Marks P. A. , Bank A.
Published: May 2006

Addition of a 0.5 M KCl wash fraction from rabbit reticulocyte ribosomes causes a 3- to 10-fold increase in the extent of translation of natural mRNAs by Krebs-cell lysates. In the presence of the wash fraction, 1 pmol of rabbit or mouse 10S RNA directs the incorporation of 80 pmol of leucine into rabbit globin. The addition of human 10S RNA results in the synthesis of equal amounts of human α and β chains, identified by column chromatography. The stimulation by the wash fraction is almost completely dependent on added mammalian tRNA. In contrast to the wash fraction from rabbit reticulocytes, the wash fraction isolated from Krebs-cell ribosomes is inhibitory to both endogenous and exogenous mRNA translation. The stimulation by the wash fraction from rabbit ribosomes is not specific for globin mRNAs, but also increases endogenous, phage Qβ, and viral RNA-directed protein synthesis.
Inhibition of Glucose-Induced Release of Insulin by Aldose Reductase Inhibitors
Authors: Gabbay Kenneth H. , Tze Wah Jun
Published: May 2006

Aldose reductase (alditol: NADP oxidoreductase, EC 1.1.1.21) is the enzyme responsible for the conversion of glucose to its sugar alcohol, sorbitol. In this study, aldose reductase and a closely related enzyme, L-hexonate dehydrogenase (L-gulonate: NADP oxidoreductase, EC 1.1.1.19), were purified from rat pancreas. Glutaric acid, 2,4-dimethyl glutaric acid, 3,3-tetramethylene glutaric acid, and colchicine inhibited both enzymes, albeit with different potencies. These compounds also inhibited both phases of glucose-induced release of insulin by the perfused rat pancreas. The potencies of these inhibitors in depressing the release of insulin correlated with their effectiveness in inhibiting aldose reductase. At higher concentrations of inhibitors, tolbutamide-induced release of insulin was also depressed. The addition of exogenous sorbitol to pancreases treated with glutaric acid restored their ability to respond to glucose and tolbutamide. These findings suggest that the conversion of free intracellular glucose to sorbitol in the beta cell is an essential step in the glucose-induced release mechanism.
Development of Cellular Immunity in the Human Fetus: Dichotomy of Proliferative and Cytotoxic Responses of Lymphoid Cells to Phytohemagglutinin
Authors: Stites Daniel P. , Carr Martin C. , Fudenberg H. Hugh
Published: May 2006

The reactivity of cells
in vitro
was investigated with specimens from various lymphoid organs of seven human fetuses. Thymocytes responded to stimulation by phytohemagglutinin with significant increases in synthesis of DNA, but failed to produce destruction of xenogeneic target cells. In cells from bone marrow, precisely the converse pattern of reactivity to the mitogen was detected. Lymphocytes from spleen and peripheral blood demonstrated both phytohemagglutinin-dependent functions, while hepatic cells did not respond to phytohemagglutinin. Based on the striking dichotomy of phytohemagglutinin-dependent responses in fetal thymocytes and bone-marrow lymphoid cells, we conclude that phytohemagglutinin-dependent cytotoxicity and DNA synthesis are functions of different populations of lymphoid cells during human embryonic development.
Axonal Sprouts and [
3
H]Norepinephrine Uptake by Superior Cervical Ganglia in Organ Culture
Authors: Silberstein Stephen D. , Johnson David G. , Hanbauer Ingeborg , Bloom Floyd E. , Kopin Irwin J.
Published: May 2006

Superior cervical ganglia from adult rats maintained in organ culture show a progressive increase in the rate of uptake of [
3
H]norepinephrine. The enhanced uptake of norepinephrine is a consequence of the development of axonal sprouts. Formation of axonal sprouts, which appear to have many of the properties of sympathetic nerve endings, is inhibited by colchicine and vinblastine, presumably because of the interaction of these drugs with neurotubular protein.
Measurement of Transmembrane Potentials in Phospholipid Vesicles
Authors: Kornberg Roger D. , McNamee Mark G. , McConnell Harden M.
Published: May 2006

Phosphatidylcholine vesicles are permeable to tempotartrate, a spin-label derivative of tartaric acid. The inside-outside distribution of tempotartrate is coupled to the inside-outside distribution of H
+
, so it must be a measure of the transmembrane electrical potential difference in vesicles permeable to H
+
. This prediction is borne out by the finding that the inside-outside distribution of tempotartrate is the reciprocal of the inside-outside distribution of K
+
in vesicles prepared in the presence of valinomycin.

The inside-outside distribution of tempotartrate is, by contrast, equal to the inside-outside distribution of Cl
-
in vesicles without valinomycin. This is evidence that an inside-outside Cl
-
concentration gradient induces an H
+
gradient, which must be due to HCl permeation.
Correlation of Messenger RNA Function with Adenylate-Rich Segments in the Genomes of Single-Stranded RNA Viruses
Authors: Johnston Robert E. , Bose Henry R.
Published: May 2006

Oligonucleotides enriched in adenylate residues have been demonstrated in the genomes of two positive-strand RNA viruses, Sindbis and Columbia SK. Such oligonucleotides were not found in the genome of vesicular stomatitis virus, a negative-strand virus. The adenylate-rich oligonucleotides from Sindbis and Columbia SK viruses appeared similar when analyzed by zonal sedimentation in sucrose-sodium dodecyl sulfate.
Juvenile Hormone Induction of Esterases: A Mechanism for the Regulation of Juvenile Hormone Titer
Authors: Whitmore Donald , Whitmore Elaine , Gilbert Lawrence I.
Published: May 2006

Within a few hours after injection of juvenile hormone into
Hyalophora gloveri
pupae, several fast-migrating carboxylesterases (EC 3.1.1.1) that are sensitive to di
iso
propylfluorophosphate appear in the hemolymph. Treatment of the pupae with puromycin or actinomycin D prevents the appearance of these hemolymph enzymes, suggesting
de novo
synthesis of the carboxylesterases. Of the several other compounds investigated, only a potent mimic of the juvenile hormone is able to induce these enzymes. When the induced enzymes are incubated
in vitro
with
14
C-labeled juvenile hormone, the hormone is rapidly and efficiently degraded. It is suggested that these induced carboxylesterases play an important role in the regulation of juvenile hormone titer.
Calf Crystallin Synthesis in Frog Cells: The Translation of Lens-Cell 14S RNA in Oocytes
Authors: Berns A. J. M. , Kraaikamp M. Van , Bloemendal H. , Lane C. D.
Published: May 2006

14S RNA isolated from calf-lens polyribosomes was injected into oocytes of the frog
Xenopus laevis
. Oocytes injected with 14S RNA and buffer contained a protein resembling the A2 chain of calf α-crystallin; oocytes injected with buffer alone contained no crystallin-like material. αA2 crystallin polypeptides were identified by various criteria: urea-gel electrophoresis under acidic and basic conditions, gel electrophoresis in sodium dodecyl sulfate, N-terminal analysis, and paper chromatography of methionine-containing tryptic peptides.

It is concluded that when it is injected into a living frog oocyte, the 14S RNA from lens tissue is reasonably stable and has the properties of an αA2 crystallin messenger. The messenger requires no lens cell-specific components for translation within the oocyte, and the translational machinery of the frog cell will accept messenger RNA from a totally different cell type from another species.

The A2 chains of α-crystallin extracted from lens tissue possess an acetylated N-terminal methionine residue; the N-terminal methionine of αA2 chains derived from frog oocytes injected with 14S RNA was also acetylated.
Control of 25-Hydroxycholecalciferol Metabolism by Parathyroid Glands
Authors: Garabedian M. , Holick M. F. , Deluca H. F. , Boyle I. T.
Published: May 2006

Thyroparathyroidectomy of rats on a diet low in calcium reduces production of 1,25-dihydroxycholecalciferol from 25-hydroxycholecalciferol to negligible levels within 40 hr, and increases production of another metabolite, called Va. Parathyroid extract, at a dose of 20 units per day, prevents these changes. When 40 units per day of parathyroid extract is given 48 hr after thyroparathyroidectomy, 1,25-dihydroxycholecalciferol production is restored almost to control levels within 36 hr. The change brought about by parathyroid extract cannot be attributed to resulting changes in serum calcium or phosphorus concentration. It appears that the parathyroid hormone serves as a tropin for production of 1,25-dihydroxycholecalciferol, the hormonal form of vitamin D responsible for calcium mobilization from intestinal contents and bone.
Properties of the Refolding and Unfolding Reactions of Ribonuclease A
Authors: Tsong Tian Y. , Baldwin Robert L. , Elson Elliot L.
Published: May 2006

Both the refolding kinetics and unfolding kinetics of ribonuclease A have been measured at the same final conditions, as a function of temperature at pH 3.9, by stopped-flow (pH-jump) experiments; absorbance changes at 240 and 286.5 nm were measured. Refolding follows first-order kinetics in the upper two-thirds of the thermal transition zone. Under the same conditions, the unfolding kinetics are biphasic; the terminal phase has the same rate constant as refolding. The biphasic kinetics of unfolding demonstrate the presence of intermediate states. Since both the refolding and unfolding kinetics are consistent with a simple sequential model, the intermediates satisfy kinetic criteria for being on the direct pathway of unfolding. At temperatures just above the transition zone, the fast phase of unfolding becomes the major kinetic phase. The rate of the slow unfolding reaction increases rapidly with temperature, and approaches the average rate of the fast phase at temperatures just above the transition zone. The entire set of kinetic results can be reproduced semiquantitatively by assignment of values to four parameters in a cooperative sequential model. However, reasons are given for the belief that this simple model will have to be generalized before it can give a realistic description of the kinetics of the unfolding reaction.
Surface Glycoproteins of Normal and Transformed Cells: A Difference Determined by Sialic Acid and a Growth-Dependent Sialyl Transferase
Authors: Warren L. , Fuhrer J. P. , Buck C. A.
Published: May 2006

The pattern of elution from a column of Sephadex G-50 of a fucose-labeled carbohydrate component derived from the surface glycoproteins of transformed cells can be altered to resemble that from untransformed cells by enzymatic removal of the sialic acid. These results indicate that the consistent differences found between control and virus-transformed cells may depend upon a relatively specific sialyl transferase that is found in greater amounts (2.5- to 11-times) in transformed cells than in control cells, and in dividing cells as compared to nondividing cells.
5-Fluoro-2′-Deoxyuridylate: Covalent Complex with Thymidylate Synthetase
Authors: Santi Daniel V. , McHenry Charles S.
Published: May 2006

5-Fluoro-2′-deoxyuridylate causes a rapid inactivation of thymidylate synthetase that is dependent upon prior complexation of the cofactor 5,10-methylenetetrahydrofolate. The enzyme-5-fluoro-2′-deoxyuridylate complex may be isolated on nitrocellulose membranes and is not disrupted by 6 M urea. Upon reaction of 5-fluoro-2′-deoxyuridylate with the enzyme in the presence of 5,10-methylenetetrahydrofolate a rapid loss of absorbance is observed at 269 nm, the absorption maximum for the pyrimidine chromophore. It is concluded that a covalent bond is formed between the 6-position of 5-fluoro-2′-deoxyuridylate and a nucleophilic group of the enzyme that is involved in catalysis.
Induction of Immunological Tolerance to Soluble Histocompatibility-2 Antigens of Mice
Authors: Law Lloyd W. , Appella Ettore , Strober Samuel , Wright Peter W. , Fischetti Thomas
Published: May 2006

Immunological tolerance to a soluble, partially purified fraction of histocompatibility (H)-2
a
antigen was induced in B10.D2 strain mice. The fraction used was obtained after chromatography on a Sephadex G-150 column. Tolerance of humoral-antibody formation (cytotoxins and hemagglutinins) was observed in mice injected with soluble antigen since birth, but cell-mediated immunity, as measured by skin graft survival, remained intact. Tolerance was shown to be specific for H-2
a
antigens, since treated mice produced a regular humoral-antibody response to H-2
b
antigens. These findings, along with previous observations of the immunogenic and enhancing properties of our partially purified fraction, suggest that the solubilized antigen contains all the major determinants of H-2
a
antigens expressed on lymphoid-cell surfaces.