bluuebunny/crossref_metadata_2025 huggingface dataset:
New Small Polypeptides Associated with DNA-Dependent RNA Polymerase of
Escherichia coli
after Infection with Bacteriophage T4
Authors: Stevens Audrey
Published: May 2006

Four new small polypeptides are associated with DNA-dependent RNA polymerase from
E. coli
after infection with T4 phage. The new polypeptides are easily detected in RNA polymerase from
E. coli
cells labeled with amino acids after phage infection. Their molecular weights range from 10,000 to 22,000, as detected by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. All four polypeptides are found after infection with either wild-type T4 phage or T4 early amber mutants in genes 44, 42, 47, and 46. None of the polypeptides is labeled significantly before 5 min after infection at 30°. When two maturation-defective amber mutants in gene 55 of T4 phage are used for infection, a polypeptide with a molecular weight of 22,000 is absent. When a maturation-defective amber mutant in gene 33 of T4 phage is used, another small protein is absent.
Allergic Encephalomyelitis in Monkeys Induced by a Peptide from the A1 Protein
Authors: Eylar E. H. , Brostoff S. , Jackson J. , Carter H.
Published: May 2006

A major disease-inducing site for induction of experimental allergic encephalomyelitis in monkeys exists in Peptide P 14, the 37-residue segment of the A1 protein comprising its COOH-terminus. The peptide appears to contain the dominant encephalitogenic determinant, since it was as active as the A1 protein on a molar basis. By contrast, the 9-residue tryptophan region and the Peptide R region, active in guinea pigs and rabbits, respectively, were comparatively inactive in monkeys. The clinical and histologic expression of the disease produced by Peptide P 14 appeared identical to that induced by the intact A1 protein.
Neuronal Dynamics and Axonal Flow, V. The Semisolid State of the Moving Axonal Column
Authors: Weiss Paul A.
Published: May 2006

Evidence assembled since the first comprehensive description of “axonal flow”, by deformation analysis, electron microscopy, cinemicrography, and microrheology, has confirmed that the axon of the mature neuron is (
a
) a semisolid column; (
b
) in cellulifugal motion at about 1 μm/min (1 mm per day); (
c
) continuously reproduced at its perikaryal base; (
d
) propelled by a microperistaltic pulse wave in its surface; and (
e
) undergoing internal dissolution at the nerve ending. The axon thus “flows” as a structural entity (“axonal flow”), in contradistinction to fast “intraaxonal transport” of molecules and molecular assemblies along internal routes and by mechanisms that are still unknown.
Approximations to Self-Consistent Field Molecular Wavefunctions
Authors: Halgren Thomas A. , Lipscomb William N.
Published: May 2006

Unparameterized and parameterized versions are outlined of a new method for approximating self-consistent field wavefunctions from first principles at the minimum basis set level for complex molecules containing hydrogen and first-row atoms. The Hartree-Fock self-consistent field equations for closed-shell molecules are solved, retaining all one-electron integrals, and approximating the two-electron Coulomb integrals, hybrid integrals, and exchange integrals of the form (

i
A
j
A

[unk]

i
A
j
A

) and (

i
A
j
B

[unk]

i
A
j
B

) for centers
A
and
B
. A symmetrically orthogonalized basis set is used and rotational invariance is achieved by transformation to local axes that are unique for atoms in anisotropic environments. Parameterization based upon first-principle self-consistent field wavefunctions for a large number of molecules yields
F
-matrix elements to 0.007 atomic units (au), density matrix elements to 0.007 electrons, orbital populations and atomic charges to 0.01-0.02 electrons, orbital energies to 0.01 au, and total energies to 0.02 au (all standard deviations), in computational times only a few times larger than those required for complete neglect of differential overlap calculations.
Transpeptidase Activity of
Streptomyces
D-Alanyl-D Carboxypeptidases
Authors: Pollock J. J. , Ghuysen J. M. , Linder R. , Salton M. R. J. , Perkins H. R. , Nieto M. , Leyh-Bouille M. , Frere J. M. , Johnson K.
Published: May 2006

In the presence of
N
α
,
N
ε
-diacetyl-L-Lys-D-Ala-D-Ala as donor, and either D-[
14
C]alanine, [
14
C]-glycine, or
meso
-[
3
H]diaminopimelic acid as acceptor, the DD carboxypeptidases from
Streptomyces
R61 and R39 catalyze a transpeptidation reaction with the release of terminal D-alanine from the donor and the formation of either
N
α
,
N
ε
-diacetyl-L-Lys-D-Ala-D-[
14
C]Ala,
N
α
,
N
ε
-diacetyl-L-Lys-D-Ala-[
14
C] Gly, or
N
α
,
N
ε
-diacetyl-L-Lys-D-Ala-D-
meso
- [
3
H]diaminopimelic acid. The reaction appears to be a true transpeptidation, and is not simply a “reversal of hydrolysis”. Transpeptidation is inhibited by pencillin at concentrations that inhibit hydrolysis (carboxypeptidase action) of the donor peptide. There are differences in the specificity profiles of the
Streptomyces
enzymes for acceptor molecules:only the R61 enzyme used [
14
C]Gly-Gly as acceptor; transfer of
N
α
,
N
ε
-diacetyl-L-Lys-D-Ala to this acceptor resulted in the formation of
N
α
,
N
ε
-diacetyl-Lys-D-Ala-[
14
C] Gly-Gly, with the synthesis of a (D-Ala-Gly) peptide bond in an endoposition.
Characterization of Messenger Ribonucleoprotein and Messenger RNA from KB Cells
Authors: Kumar Ajit , Lindberg Uno
Published: May 2006

Messenger ribonucleoprotein and mRNA from KB-cells were isolated under conditions designed to minimize nonspecific RNA-protein interaction and to minimize degradation by contaminating ribonucleases. A large fraction, 60-70%, of the messenger ribonucleoprotein from polysomes dissociated
in vitro
by either EDTA or puromycin sedimented faster than the large ribosome subunit. Messenger ribonucleoprotein particles with sedimentation coefficients up to 200 S were observed. Released mRNA was also large, with maximal molecular weights around 5 × 10
6
.
The Viral Oncogene Hypothesis: New Evidence
Authors: Todaro George J. , Huebner Robert J.
Published: May 2006

Recent studies, primarily with mouse, rat, and chicken cells, have provided evidence to support the concept that vertebrates contain the genetic information for producing a type-C RNA tumor virus in an unexpressed form in their somatic cells as well as in their germ cells. This information, which our associates and we postulated has been part of the genetic makeup of vertebrates since early in evolution, can persist for hundreds of generations in cell culture without overt production of virus. It is proposed that the endogenous virogenes (the genes for the production of type-C viruses) and the oncogenes (that portion of the virogene responsible for transforming a normal cell into a tumor cell) are maintained in an unexpressed form by repressors in normal cells. Various agents, including radiation, chemical carcinogens, and, perhaps, exogenously added viruses, may transform cells by “switching on” the endogenous oncogenic information. Some other implications of the viral oncogene theory are presented.
A New Proof of the Interior Gradient Bound for the Minimal Surface Equation in
n
Dimensions
Authors: Trudinger Neil S.
Published: May 2006

An interior gradient bound for classical solutions of the minimal surface equation in
n
variables was established by Bombieri, De Giorgi, and Miranda in 1968. We provide a new and simpler derivation of this estimate and partly develop in the process some new techniques applicable to the study of hypersurfaces in general.
Neoplastic Transformation
In Vitro
of a Clone of Adult Liver Epithelial Cells into Differentiated Hepatoma-Like Cells Under Conditions of Nutritional Stress
Authors: Borek Carmia
Published: May 2006

Differentiated epithelial cells in contact-inhibited monolayers derived from adult rat liver have been transformed
in vitro
into epithelioid neoplastic cells under conditions of nutritional stress. The transformed cells maintain their differentiated quality and manufacture serum proteins. They differ from control cultures in the following properties: They are aneuploid, can be agglutinated by wheat-germ agglutinin and concanavalin A, can grow in suspension, and are able to form colonies in semisoft agar. There is no intercellular communication at permeable junctions between the cells; this is demonstrable by electrical measurement or by injection of fluorescein. The cells show invasiveness in culture, and are not inhibited by contact with normal cells. The characteristics of the hepatocytes after transformation
in vitro
resemble those of epithelioid cells derived from a transplantable hepatoma.
Construction of a Three-Dimensional Model of the Polypeptide Backbone of the Variable Region of Kappa Immunoglobulin Light Chains
Authors: Kabat Elvin A. , Wu Tai Te
Published: May 2006

From (ϕ,Ψ) data for the middle amino acid,
n
, in the series of tripeptides (
n
- 1)(
n
)(
n
+ 1) in six proteins whose three-dimensional structure is known from x-ray studies, (ϕ,Ψ) values for the residues 2-107 of kappa Bence Jones proteins and immunoglobulin light chains were computed. It was assumed that all residues except those in the hypervariable regions 24-34, 50-56, and 89-97, were involved essentially in three-dimensional structure, and hence, their (ϕ,Ψ) angles would mostly be those best satisfying all kappa tri- and constituent di-peptides that occur at those positions. A set of criteria for selecting and averaging (ϕ,Ψ) angles is given. In the hypervariable regions, which are presumed to be involved in site complementarity, the (ϕ,Ψ) angles were selected for a single Bence Jones protein Ag. The three-dimensional models, constructed from the computed (ϕ,Ψ) values by hand and by display computer were very similar, and residues 23 and 88 were sufficiently close for the disulfide bond to form.
Study of Adrenocorticotropic Hormone Conformation by Evaluation of Intramolecular Resonance Energy Transfer in
N
ε
-Dansyllysine
21
-ACTH-(1-24)-Tetrakosipeptide
Authors: Schiller Peter W.
Published: May 2006

The solution conformation of ACTH was studied by intramolecular resonance energy transfer and fluorescence depolarization with the synthetic, biologically active, derivative
N
ε
-dansyllysine
21
-ACTH-(1-24)-tetrakosipeptide. The Förster parameters involved in energy transfer from the donor Trp
9
to the dansyl acceptor attached to the side chain of Lys
21
were determined from measurements with ACTH fragments containing either the donor or the acceptor alone. From determinations of the fluorescence quantum yields of the donor in the derivative and in the native ACTH-(1-24)-tetrakosipeptide, it was shown that besides energy transfer no additional quenching of the donor fluorescence is introduced by the presence of the acceptor. The short measured rotational relaxation time of the dansyl chromophore reflects the flexibility of the lysine side chain and justifies the use of an average value for the orientation factor in the distance calculations. The calculated intramolecular distance is remarkably independent of solvent, indicating a “random coil” situation with regard to residues 9-21.
Allozymes as Diagnostic Characters of Sibling Species of
Drosophila
Authors: Ayala Francisco J. , Powell Jeffrey R.
Published: May 2006

Considerable enzyme variation that is genetically controlled exists within and between natural populations of
Drosophila
. Our studies of two groups of sibling species show that allozyme differences can be used as species-diagnostic characters. A locus is defined as diagnostic if an individual can be correctly assigned to one of two species with a probability of 99% or higher. Between 15 and 32% of the loci studied are diagnostic for any two of the sibling species. If several diagnostic loci are used, the species of any individual can be diagnosed with virtual certainty.
Niche Overlap as a Function of Environmental Variability
Authors: May Robert M. , Arthur Robert H. Mac
Published: May 2006

The relationship between environmental variability and niche overlap is studied for a class of model biological communities in which several species compete on a one-dimensional continuum of resources, e.g., food size. In a strictly unvarying (deterministic) environment, there is in general no limit to the degree of overlap, short of complete congruence. However, in a fluctuating (stochastic) environment, the average food sizes for species adjacent on the resource spectrum must differ by an amount roughly equal to the standard deviation in the food size taken by either individual species. This mathematical result emerges in a nonobvious yet robust way for environmental fluctuations whose variance relative to their mean ranges from around 0.01% to around 30%. In short, there is an effective limit to niche overlap in the real world, and this limit is insensitive to the degree of environmental fluctuation, unless it be very severe. Recent field work, particularly on bird guilds, seems in harmony with the model's conclusion.
Ovalbumin Messenger RNA of Chick Oviduct: Partial Characterization, Estrogen Dependence, and Translation
In Vitro
Authors: Means A. R. , Comstock J. P. , Rosenfeld G. C. , O'Malley B. W.
Published: May 2006

A rapidly-labeled RNA fraction can be isolated from hen oviduct polysomes that has characteristics of the messenger RNA (mRNA) for the cell-specific protein, ovalbumin. This RNA, which sediments in the 8-17S region of sucrose gradients, possesses properties suggestive of the presence of a polyadenylic acid sequence and can be translated with fidelity in a cell-free protein synthesizing system derived from rabbit reticulocytes. The identity of the protein product as ovalbumin is confirmed by three methods, and translation of ovalbumin mRNA is shown to be dependent both on amount of exogenous mRNA and incubation time. Both rate and extent of ovalbumin synthesis is enhanced by the addition of a protein extract from ribosomes that contains peptide chain initiation factors. Finally, the presence of this specific mRNA is shown to be estrogen-dependent: it is induced by estrogen administration to immature chicks, disappears upon cessation of estrogen treatment, and can be reinduced by a single injection of estrogen to chicks that have been pretreated with estrogen and then withdrawn from the hormone.
Fluorescence of Lysozyme: Emissions from Tryptophan Residues 62 and 108 and Energy Migration
Authors: Imoto T. , Forster Leslie S. , Rupley J. A. , Tanaka Fumio
Published: May 2006

The bulk of the fluorescence of lysozyme is located in Trp 62 and Trp 108. By examination of the fluorescence of derivatives in which Trp 62 and/or Trp 108 are specifically oxidized, it has been possible to detect a pH-dependent interaction between tryptophan residues. This interaction is interpreted as energy transfer from Trp 108 to Trp 62.
Simplified Method in Polynucleotide Helix-Coil Transition Theory Including Binding of Complementary Monomer
Authors: Hill Terrell L.
Published: May 2006

The grand partition function for a long linear system of alternating α and β sequences with the restraint of a fixed number,
N
αβ
, of αβ boundaries depends in an extremely simple way on the α-sequence and β-sequence grand partition functions, ξ
α
and ξ
β
. When the restraint is removed, we have μαβ = 0, where μαβ is the chemical potential conjugate to
N
αβ
. The grand partition function and the condition μαβ = 0 lead to the fundamental relation 1 = ξ
α
ξ

β
z
2

, where
z
= e
-ω
αβ

/κ
T

and ωαβ = boundary free energy. This is a generalization of an earlier equation of Hill, and is equivalent to a result due to Lifson. Binding of a substrate does not affect the argument: the new component is simply included in ξα and ξβ. A model for the binding of adenosine on poly(U) is used as an example.
Activation of the Viral Genome in Simian Virus 4-Transformed Nonpermissive Cells by Permissive Cell Extracts
Authors: Suarez H. G. , Sonenshein G. E. , Estrade S. , Bourali M.-F. , Cassingena R. , Tournier P.
Published: May 2006

Simian virus 40-transformed nonpermissive cells in which neither infectious viral DNA nor virions had previously been detected reproducibly yield low levels of infectious simian virus-40 DNA after treatment with extracts of normal permissive cells. Virions were obtained in one out of 37 experiments. Activation of the viral genome is detected only with normal permissive cell extracts and only in simian virus 40-transformed cell lines that are rescuable by heterokaryon formation or by treatment with chemicals. The activating factor(s) is insensitive to deoxyribonuclease and ribonuclease, but is sensitive to heat at 56° and to proteolytic enzymes.
Bacteriophage Qβ Replicase Contains the Protein Biosynthesis Elongation Factors EF Tu and EF Ts
Authors: Blumenthal Thomas , Landers Terry A. , Weber Klaus
Published: May 2006

The enzyme, Qβ replicase, responsible for the replication of the RNA of
Escherichia coli
pahge Qβ, is composed of four nonidentical subunits, three of which, I, III, and IV, are coded for by the bacterial genome, while subunit II is phage-specific.

Subunit IV is shown to be identical to the protein synthesis elongation factor EF Ts by the following criteria: coelectrophoresis on polyacrylamide gels in sodium dodecyl sulfate and in urea buffers, identity of the first seven amino acids at the amino-terminus, precipitation of sub-unit IV by anti-EF T-factor serum, and stimulation of EF Tu-GDP exchange by subunit IV. Subunit III is shown to be identical to the protein synthesis elongation factor EF Tu by the following criteria: coelectrophoresis on sodium dodecyl sulfate gels, precipitation of EF Tu by anti-Qβ replicase serum, binding of guanine nucleotides, and binding of phenylalanyl-tRNA. In addition, Qβ replicase activity can be reconstituted from subunits I and II with EF Tu and EF Ts.
Purification of Erythropoietin-Responsive Cells by Immune Hemolysis
Authors: Cantor Linda N. , Morris Allan J. , Marks Paul A. , Rifkind Richard A.
Published: May 2006

Immature erythroid cell precursors from 12- and 13-day fetal mouse livers were concentrated by differential antibody-mediated hemolysis. The effect of erythropoietin on these purified erythroid cell precursors was studied
in vitro
. Addition of erythropoietin stimulates erythroid cells to proliferate, and to differentiate to cells that actively synthesize hemoglobin. This erythropoietin-induced erythropoiesis is sustained in culture for at least 48 hr.
Indirect Suppression of
recB
and
recC
Mutations by Exonuclease I Deficiency
Authors: Kushner Sidney R. , Nagaishi Haruko , Clark Alvin J.
Published: May 2006

recB
-
and recC
-
strains of
Escherichia coli
K12 are recombination deficient and sensitive to ultraviolet light and the drug, mitomycin C. We have reported that
sbcB
mutations indirectly suppress all three phenotypes and result in the loss of exonuclease I. In this publication we report the occurrence of other mutations that lead to loss of exonuclease I and indirectly suppress mitomycin and UV sensitivity but not recombination deficiency. These mutations (called
xonA
) are cotransducible with
his
and closely linked with
sbcB
. Both
sbcB
and
xonA
mutant strains appear to have identical residual amounts of nuclease activity on single-stranded DNA. It is hypothesized that exonuclease I possesses a second activity other than its known ability to degrade single-stranded DNA from a 3′-OH terminus. Accordingly,
sbcB
mutations would alter the second activity while
xonA
mutations would not.
Environmental Stimuli in the Progression of BHK/21 Cells Through the Cell Cycle
Authors: Shodell M.
Published: May 2006

An L-cell line adapted to grow in protein-free medium is a source of material that stimulates the proliferation of serum-dependent BHK cells under otherwise protein-free conditions. The material produced by the L-cells is resolvable into separate DNA-synthetic and mitotic stimulatory activities. The stimulation of mitosis is dependent upon the presence of one or more heat-labile macromolecules, which can be concentrated by ultrafiltration, and at least one dialyzable component is essential for the initiation of DNA synthesis.
RNA-Primed DNA Synthesis
In Vitro
Authors: Keller Walter
Published: May 2006

In vitro
DNA synthesis on single-stranded circular DNA can be initiated by RNA primers. RNA chains are covalently extended by DNA polymerase II from KB cells and DNA polymerase I from
Micrococcus luteus
, but not by an RNA-dependent DNA polymerase from avian myeloblastosis virus. The reaction product consists of DNA chains with a piece of RNA at their 5′-ends, hydrogen bonded to the template DNA. The primer RNA is linked to the product DNA via a 3′:5′-phosphodiester bond, and can be specifically removed by ribonuclease H. The possible role of ribonuclease H in RNA-primed DNA synthesis
in vivo
is discussed.
Sequential Degradation of Insulin by Rat Liver Homogenates
Authors: Varandani P. T. , Shroyer Lois A. , Nafz Mary Ann
Published: May 2006

Insulin was incubated with rat liver homogenate in the presence of glutathione. The products formed were examined by chromatography on a Sephadex G-75 column, with 50% acetic acid as eluent. The results show that insulin is degraded by rat liver homogenates in sequential order: first, a splitting of insulin into A and B chains by glutathione-insulin transhydrogenase, followed by proteolysis of the resulting polypeptides to small molecular weight components.
Transcription in Yeast: Separation and Properties of Multiple RNA Polymerases
Authors: Adman Ray , Schultz Loren D. , Hall Benjamin D.
Published: May 2006

Four peaks of DNA-directed RNA polymerase activity are resolved by salt gradient elution of a sonicated yeast cell extract on DEAE-Sephadex. The enzymes, which are named IA, IB, II, and III in order of elution, all appear to come from cell nuclei. Only enzyme II is sensitive to α-amanitin. All enzymes are more active with Mn
++
than with Mg
++
as divalent ion. Enzymes IB and II have salt optima in the range 0.05-0.10 M (NH
4
)
2
SO
4
, whereas enzyme III is maximally active at 0.20-0.25 M (NH
4
)
2
SO
4
. With optimal salt concentration and saturating DNA, the template preference ratio, activity on native calfthymus DNA divided by activity on denatured calf-thymus DNA, is 2.2 for IB, 0.4 for II, and 3.5 for III. None of the yeast polymerases was inhibited by rifamycin SV. Rifamycin AF/013 effectively inhibited polymerases IB, II, and III.
Quantitative Abnormalities of Allotypic Genes in Families with Primary Immune Deficiencies
Authors: Litwin Stephen D. , Fudenberg H. Hugh
Published: May 2006

Genetic antigens of human immunoglobulin G (Gm factors) were measured in members of the families of selected patients with primary immunodeficiency. The sera of seven out of 27 heterozygous relatives had either deficient concentrations of one Gm allotype or an unbalanced ratio of Gm(f)/Gm(a). Since these markers for allelic IgG1 genes are found in almost equal amounts in normal heterozygous persons, the results suggested that there was a quantitative deficiency in the expression in serum of one Gm gene. In several families allotype abnormalities were found in three successive generations; in one instance the quantitative defect appeared to segregate independently of the Gm genes. The experimental data failed to support a recessive gene hypothesis, in that too few of the close relatives had evidence indicating that they were carriers of defective Gm genes. The results were interpreted as consistent with an inherited regulatory defect in certain families with this disorder.
3′:5′-Cyclic Adenosine Monophosphate Phosphodiesterase: Negative Cooperativity
Authors: Russell T. R. , Thompson W. J. , Schneider F. W. , Appleman M. M.
Published: May 2006

Kinetic and chromatographic analysis of cyclic nucleotide phosphodiesterase (EC 3.1.4.c) obtained from rat tissue has revealed that this enzyme exists in at least two molecular forms. After chromatographic separation, one form (cyclic AMP phosphodiesterase) still exhibits kinetics suggestive of the action of either two enzymes or one enzyme under negative cooperative regulation. Computer model studies were undertaken to distinguish between these two possibilities. The matrix method was used to generate the partition functions for (
a
) the sum of two independent enzymes and (
b
) one enzyme exhibiting negative cooperative kinetics. The experimental data were fitted to the theoretical models by a nonlinear least-squares computer program. The results show that, while both models can fit the data, the two-enzyme model would require contamination far in excess of what is detectable physically or by activity measurements. Thus, the negative cooperative model seems the more appropriate theoretical explanation of the observed kinetic behavior of this enzyme. The implication of negative cooperativity with respect to the regulation of cyclic AMP concentrations in physiological systems is discussed.
Initiation Factor IF-3-Dependent Binding of
Escherichia coli
Ribosomes and
N
-Formylmethionine Transfer-RNA to Rabbit Globin Messenger
Authors: Noll Markus , Noll Hans , Lingrel Jerry B.
Published: May 2006

An initiation complex has been formed in high yields from
E. coli
ribosomes, 9S messenger RNA for rabbit hemoglobin, and
N
-formylmethionine-tRNA. Initiation factor IF-3 is required for the binding and puromycin is required for the release of fMet. Valyl-tRNA fails to bind to the second codon, whereas a mixture of 15 aminoacyl-tRNAs promotes incorporation. Together with quantitative data, the findings suggest that IF-3 directs the ribosomes to an AUG codon on one of the two globin messengers, at a site that is different from the normal starting point for globin synthesis.
Ultraviolet Chromophore Transitions in the Rhodopsin Spectrum
Authors: Ebrey Thomas G. , Honig Barry
Published: May 2006

Difference spectra measured at -105° show two decreases in the ultraviolet absorption spectrum of rhodopsin upon bleaching that cannot be attributed to changes in protein conformation. These absorbancy decreases in rhodopsin are consistent with a
cis-trans
isomerization of the chromophore.
Cell Cycle Changes and the Ability of Cells to Undergo Virus-Induced Fusion
Authors: Stadler Joan K. , Adelberg Edward A.
Published: May 2006

Synchronized cells of the mouse leukemic cell line, L5178Y, were examined for their ability to undergo virus-induced fusion. Fusion capacity (defined as the percentage of the original unicellular population that is induced by virus to participate in a fusion event) was measured in cells that were (
i
) arrested by colcemid, (
ii
) released from colcemid block, and (
iii
) released from thymidine block. The results show that fusion capacity is minimal during G1 phase (less than 10%), and rises to a maximum (69%) in arrested mitosis. Treatment of nonsynchronized cells with trypsin increased their fusion capacity to the level characteristic of cells arrested in mitosis. Colcemid-arrested cells produced twice as many hybrid clones as nonsynchronized cells after they were plated in selective medium.
Membrane Dynamics in the Action of Dibutyryl Adenosine 3′:5′-Cyclic Monophosphate and Testosterone on Mammalian Cells
Authors: Puck Theodore T. , Waldren Charles A. , Hsie Abraham W.
Published: May 2006

The first manifestation of reverse transformation, in which a permanent epithelial-like cell is reversibly transformed into a fibroblast-like cell by dibutyryl adenosine cyclic 3′:5′-monophosphate, is the disappearance of a set of violently extending and retracting knobbed structures on the cell membrane with consequent tranquilization of the membrane. The cell then elongates to assume a fibroblast-like morphology. Permanently fibroblast-like cells, which have smooth membranes, can be changed into knobbed epithelial-like cells by the addition of either colcemid or cytochalasin B, agents that disorganize one or the other component, respectively, of the microtubular-microfibrillar system. Permanently smoothmembraned, epithelial-like cells also become knobbed by such treatment. All of these knobbed epithelial-like cells can be converted into smooth-membraned fibroblast-like cells by dibutyryl cAMP alone or with the aid of supporting molecules like testosterone. It is proposed that these are general phenomena and that the knobbed epithelial-like forms and the more highly differentiated smooth-membraned fibroblast-like cells represent extreme situations with respect to the degree of organization of the microtubular-microfibrillar system inside the cell.
Protein Changes in Different Brain Areas as a Function of Intermittent Training
Authors: Hydén Holger , Lange Paul W.
Published: May 2006

Incorporation of [
3
H]leucine into protein of eight different brain areas in rats was determined during 1 month of intermittent training for reversal of handedness. The incorporation values of all areas of the trained animals were lower than those of the controls. This finding was corroborated by autoradiography. After initial training the relative specific activities of the sensory-motor and entorhinal cortex and reticular formation were low compared to those of the hippocampus. With more training and time, these values became inversed.
Stages in Colicin K Action, as Revealed by the Action of Trypsin
Authors: Plate C. A. , Luria S. E.
Published: May 2006

The effects of trypsin on
Escherichia coli
cells that have been treated with colicins have been examined. By the use of trypsin, it has been possible to demonstrate that the action of several colicins (E1, E2, and K) proceeds through at least two stages. Stage I is a period after colicin adsorption when trypsin can restore colony-forming ability to a colicin-treated cell. Stage I is followed by a period when trypsin is unable to restore colony-forming ability (stage II). The transition between stage I and stage II follows first-order kinetics, with a rate proportional to the number of killing units of colicin adsorbed.

A quantitative comparison of the effects of colicin K on colony-forming ability and on several cellular processes indicates that colicin damage to these processes occurs in the stage II period of colicin action and is not subject to reversal by the trypsin treatment that restores viability to cell in stage I. The implications of these findings for an understanding of the mode of action of colicins are discussed.
The Defect in the Hurler and Scheie Syndromes: Deficiency of α-L-Iduronidase
Authors: Bach Gideon , Friedman Robert , Weissmann Bernard , Neufeld Elizabeth F.
Published: May 2006

Skin fibroblasts cultured from patients affected with the Hurler or Scheie syndromes (mucopoly-saccharidoses I or V, respectively) have a functional deficiency of a protein required for catabolism of sulfated mucopolysaccharide that has been designated the “Hurler corrective factor.” We now show Hurler factor purified from normal human urine to be associated with α-L-iduronidase activity. Cell lines deficient in Hurler corrective factor have no detectable activity of α-L-iduronidase (less than 3% of that found in cells from individuals of other genotypes). Such correspondence indicates that Hurler corrective factor and α-L-iduronidase are the same entity. Correction of deficient cells is accompanied by an efficient uptake of α-L-iduronidase from the medium.
Three-Dimensional Structure of L-Thyroxin
Authors: Camerman Norman , Camerman Arthur
Published: May 2006

The biological importance of L-thyroxin, the principal hormone secreted by the thyroid gland, is well established, but the mechanisms of thyroid-hormone action are still largely unexplained. We have crystallized L-thyroxin and determined its three-dimensional structure by x-ray crystallography in the hope that comparison of structures of active and inactive thyroid-hormone analogues will shed some light on hormone mechanisms. We compare the conformation of L-thyroxin to that of triiodo-L-thyronine, a thyroid hormone with greater activity.
Anti-Human Immunoglobulin G Activity of Membrane-Bound Monoclonal Immunoglobulin M in Lymphoproliferative Disorders
Authors: Preud'Homme J. L. , Seligmann M.
Published: May 2006

Lymphocytes from a patient with Waldenström's macroglobulinemia and known anti-immunoglobulin IgG activity of serum monoclonal IgM and lymphocytes from selected patients with chronic lymphocytic leukemia were studied by the membrane immunofluorescence procedure. Freshly drawn lymphocytes were shown to bear simultaneously μ, γ, [unk], and λ chain determinants. Experiments combining redistribution induced by antibody and double labeling proved that IgG was bound to surface IgM. After removal of surface immunoglobulins by treatment with trypsin followed by incubation in culture medium, or after redistribution induced by antibody, the exclusive presence of a newly synthetized monoclonal IgM was demonstrated. Several experiments showed that this surface IgM does specifically bind normal human IgG molecules devoid of aggregated material. The IgG molecules could be removed from the cell surface by lowering the pH. In addition to its high incidence among serum monoclonal macroglobulins, anti-IgG activity of membrane-bound monoclonal IgM is not uncommon in patients with chronic lymphocytic leukemia, a disease that provides homogeneous populations of lymphocytes derived from bone marrow, with receptor sites of defined antibody activity.
Regulation of Tyrosine Hydroxylase Activity in Cultured Mouse Neuroblastoma Cells: Elevation Induced by Analogs of Adenosine 3′:5′-Cyclic Monophosphate
Authors: Waymire J. C. , Weiner N. , Prasad K. N.
Published: May 2006

Mouse neuroblastoma cells in culture have been used as a model for the study of the mechanism by which activities of tyrosine hydroxylase (EC 1.14.3.a) are regulated in sympathetic tissue. The activity of tyrosine hydroxylase in cultured cells drops to barely detectable activities after 1 week and remains low for months in culture in the uncloned cell line of neuroblastoma. Activity in an adrenergic clone isolated from the uncloned line has about 20% of the activity of the fresh grated tumor cell.
N
6
,
O
2′
-dibutyryl adenosine 3′:5′-cyclic monophosphate causes a concentration and time-dependent increase in enzyme activity in both the cloned and uncloned cell lines. Enzyme activity is elevated by other stable analogs of adenosine 3′:5′-cyclic monophosphate, notably the
N
6
-monobutyryl, 8-aminomethyl, and 8-methylthio derivatives of the cyclic nucleotide; by the inhibitor of cyclic nucleotide phosphodiesterase, papaverine; and by sodium butyrate. Changes in cell morphology and tyrosine hydroxylase activity are shown not to be necessarily related.
Simultaneous Determination of Viscosity and Density of Protein Solutions by Magnetic Suspension
Authors: Kupke D. W. , Hodgins M. G. , Beams J. W.
Published: May 2006

The first results are reported with a magnetic suspension instrument for determination of the viscosity and density concurrently on small volumes (0.2 ml) of protein solution. Reasonable agreement was obtained with literature values for the intrinsic viscosities and specific volumes (partial or isopotential) of serum albumin and ribonuclease in native solvents, and in 6 M guanidinium chloride with or without 2-mercaptoethanol. Turnip Yellow Mosaic virus and myosin were also studied, the results with the virus being related to hydration and structure data and those with myosin to the dissociative character of the protein. The possibility of using this approach to follow the time course of viscosity and density changes during reactions is shown.
Effects of Nonpolar Environments on the Redox Potentials of Heme Complexes
Authors: Kassner Richard J.
Published: May 2006

A method has been described for measurement of the oxidation-reduction potentials of redox couples in nonaqueous solutions. This method has been applied to a study of the effect of a nonpolar environment on the redox potential of a heme complex. A positive potential difference of some 300 mV is observed for the measured redox potentials by comparison with reported values for the corresponding heme complex in aqueous solution. The proposal is made that the redox potentials of many high-potential cytochromes may be accounted for by a local heme environment of low-dielectric constant, characteristic of nonpolar amino-acid side chains, and that this factor may play a dominant role in the determination of the oxidation-reduction properties of these proteins.
Parasexual Interspecific Plant Hybridization
Authors: Carlson Peter S. , Smith Harold H. , Dearing Rosemarie D.
Published: May 2006

Interspecific plant hybrids have been produced by parasexual procedures. Protoplasts of
Nicotiana glauca
and
N. langsdorffii
were isolated, fused, and induced to regenerate into plants. The somatic hybrids were recovered from a mixed population of parental and fused protoplasts by a selective screening method that relies on differential growth of the hybrid on defined culture media. The biochemical and morphological characteristics of the somatically produced hybrid were identical to those of the sexually produced amphiploid.
Cell-Bound Myeloma Proteins on the Surface of Myeloma Cells: Potential Targets for the Immune System
Authors: Hannestad Kristian , Kao Ming-Shian , Eisen Herman N.
Published: May 2006

Rosette formation with 2,4,6-trinitrophenylated (Tnp)-sheep erythrocytes was used to demonstrate cell-bound myeloma proteins on cells from each of the eleven mouse plasmacytomas tested. Tnp-erythrocytes were bound directly by cells from two tumors (MOPC-315 and MOPC-460) that formed myeloma proteins with antihapten combining sites; rosette formation with cells from the other tumors required hybrid antibody fragments with one site specific for Tnp and the other specific for an appropriate immunoglobulin on the tumor cell surface. The cell-bound immunoglobulin of MOPC-315 and of MOPC-460 had the same heavy and light chains, idiotypic determinants, and ligand-binding specificities as the respective myeloma proteins secreted by these tumors. A variant tumor (MOC-315 NR) was grown from the small proportion of MOPC-315 cells (5-10%) that did not bind Tnp-erythrocytes directly: this tumor secreted only the light chain of protein 315, carried this chain on the cell surface, and resembled the variant tumors that arose, probably by immunoselection, in BALB/c mice challenged with MOPC-315 cells while making an immune response to the idiotype of protein 315.
Antigen Cap Formation in Cultured Fibroblasts: A Reflection of Membrane Fluidity and of Cell Motility
Authors: Edidin Michael , Weiss Arthur
Published: May 2006

Reaction of antibody to surface Histocompatibility-2 antigens of cultured mouse fibroblasts causes aggregation of the cellular antigens into caps; these appear as areas of high antigen concentration localized away from the cell processes. Cap formation is inhibited when ATP generation by cells is interrupted, when the temperature is lowered, by addition of cycloheximide—especially over long time periods—and by colcemid. The observations are consistent with a role of the locomotor system of cells in the collection of small antigen-antibody aggregates into a large localized cap. Together with observations on the absence of caps in epithelial cells, these findings suggest that only cells, such as fibroblasts and lymphocytes, that bear leading ruffled membranes are capable of driving antigenantibody aggregates to form caps.
Control of Circadian Change of Serotonin
N
-Acetyltransferase Activity in the Pineal Organ by the β-Adrenergic Receptor
Authors: Deguchi Takeo , Axelrod Julius
Published: May 2006

Serotonin
N
-acetyltransferase (EC 2.3.1.5) activity in the rat pineal organ is enhanced 50-fold at night. Rats exposed to light at night or kept in darkness during the daytime do not show any elevation of enzyme activity. Treatment with reserpine, a compound that depletes norepinephrine from nerves, 1-propranolol, a β-adrenergic blocking agent, or cycloheximide, an inhibitor of protein synthesis, abolishes the nocturnal increase in serotonin
N
-acetyltransferase activity, indicating that the enzyme activity is modulated by neural release of norepinephrine from sympathetic nerves via β-adrenergic receptors, and that the increase in enzyme activity is due to synthesis of new enzyme molecules. When rats are exposed to light at night or injected with 1-propranolol, there is a precipitous fall in serotonin
N
-acetyltransferase activity (half-life 5 min). Cycloheximide administered at night results in a slow fall in enzyme activity (half-life 60 min). When rats are kept in darkness and then exposed to light for 10 min, L-isoproterenol rapidly initiates the elevation of serotonin
N
-acetyltransferase activity to the initial level in 60 min. On the other hand, when the rats are kept in continuous light, L-isoproterenol initiates an increase in serotonin
N
-acetyltransferase activity after a lag phase of 60 min. The results indicate that there are two types of changes in serotonin
N
-acetyltransferase activity; a rapid increase and decrease mediated by the β-adrenergic receptor, and a slow increase and decrease in enzyme activity that appears to represent the turnover of the enzyme.
Sequence of Spontaneous Epstein-Barr Virus Activation and Selective DNA Synthesis in Activated Cells in the Presence of Hydroxyurea
Authors: Hampar Berge , Derge Jeffery G. , Martos Lidia M. , Tagamets Malle A. , Burroughs Mary Alice
Published: May 2006

The sequence of spontaneous Epstein-Barr virus activation was studied in P3HR-1 carrier cells and in P3HR-1(BrdU) cells made resistant to 5-bromodeoxyuridine. Virus activation was initiated during the normal cell cycle, and recruitment of additional virus-activated cells was prevented by the DNA inhibitors, 1-β-D-arabinofuranosylcytosine and hydroxyurea. Virus activation was followed by synthesis of the early antigen complex in the absence of additional detectable DNA synthesis. Early antigen synthesis was followed by hydroxyurea-resistant synthesis of new DNA, which in the case of P3HR-1(BrdU) cells was characterized by the appearance of thymidine kinase. The newly synthesized DNA banded in neutral cesium chloride at peaks corresponding to normal human DNA and Epstein-Barr viral DNA. Synthesis of viral antigen was seen only in cells that had undergone hydroxyurea-resistant DNA synthesis.
Resonance Raman Spectra of Hemoglobin and Cytochrome
c:
Inverse Polarization and Vibronic Scattering
Authors: Spiro Thomas G. , Strekas Thomas C.
Published: May 2006

Resonance Raman spectra of hemoglobin and cytochrome
c
in dilute solution contain prominent bands that exhibit
inverse
polarization, i.e., the polarization vector of the incident radiation is rotated through 90° for 90° scattering, giving infinite depolarization ratios. This phenomenon is shown to require an antisymmetric molecular-scattering tensor. The antisymmetry, which is characteristic of resonance scattering, is associated with the form of a particular class of vibrations, A
20
, of the tetragonal heme chromophores. The dependence of the resonance Raman spectra on the wavelength of the exciting radiation, as well as their polarization properties, demonstrates that the prominent bands correspond to vibronically active modes of the first electronic transition of the heme proteins, and provide confirmation of Albrecht's vibronic theory of Raman intensities.
Regeneration of Cation-Transport Capacity in HeLa Cell Membranes After Specific Blockade by Ouabain
Authors: Vaughan Gerald L. , Cook John S.
Published: May 2006

The cardiac glycoside, ouabain, inhibits alkali-cation transport in HeLa cells. It binds to 0.75 × 10
6
sites per cell, and the half-time for its dissociation is 16 hr. After partial blockade by ouabain, the cell generates new ouabain-binding sites, with total restoration of transport in 10% of a cell cycle(∼3 hr). This recovery requires protein synthesis and appears to be a response to altered cell-electrolyte content, since growth of cells in media with low K
+
concentration enhances the titer of the transport enzyme in a fashion similar to the effect of ouabain. Totally blocked cells do not recover.
Ribonucleic Acid Synthesis in Cells Infected with Herpes Simplex Virus: Controls of Transcription and of RNA Abundance
Authors: Frenkel Niza , Roizman Bernard
Published: May 2006

Analysis of the kinetics of hybridization in liquid of labeled herpes simplex virus-1 DNA and excess viral RNA revealed the following: (
i
) Cells infected by herpes simplex virus-1 for 2 hr (before DNA synthesis) contain two classes of RNA molecules differing 140-fold in molar concentrations. The abundant and scarce RNAs are transcribed from 14 and 30% of the DNA, respectively. RNA extracted at 8 hr after infection (late RNA) also contains abundant and scarce classes differing 40-fold in molar concentrations; these are transcribed from 19 and 28% of viral DNA, respectively. Abundance competition hybridization tests indicate that the abundant RNA at 2 hr is a subset of the 8-hr abundant RNA. (
ii
) The abundant RNAs probably specify structural proteins, as indicated by estimates of DNA template required for structural proteins and by experiments showing that 19 of 24 proteins (corresponding to 68% of genetic information for structural proteins) are already made between 0.5 and 2 hr after infection. We conclude that there are two types of transcriptional controls, i.e., on-off and abundance controls, and that the synthesis of most structural components is an early viral function.
Inhibition of a DNA Polymerase from
Bacillus subtilis
by Hydroxyphenylazopyrimidines
Authors: Gass Kenneth B. , Low Robert L. , Cozzarelli Nicholas R.
Published: May 2006

The antimicrobial agent, 6-(
p
-hydroxyphenylazo)-uracil, specifically inhibits DNA polymerase III of
Bacillus subtilis
with a

K
i

of less than 1 μM. The inhibition requires prior reduction of the drug, is reversible, and is competitive with dGTP. High amounts of dATP prevent inhibition by the closely related drug, 6-(
p
-hydroxyphenylazo)-isocytosine. A model is presented in which the inhibitors base-pair with the template while part of a ternary complex with the enzyme. These results imply that DNA polymerase III of
B. subtilis
is necessary for chromosomal replication.
Thermal Motion and Forced Migration of Colloidal Particles Generate Hydrostatic Pressure in Solvent
Authors: Hammel H. T. , Scholander P. F.
Published: May 2006

A colloidal solution of ferrite particles in an osmometer has been used to demonstrate that the property that propels water across the semipermeable membrane is the decrease in hydrostatic pressure in the water of the solution. A magnetic field gradient directed so as to force the ferrite particles away from the semipermeable membrane of the osmometer and toward the free surface of the solution enhanced the colloidal osmotic pressure. The enhancement of this pressure was always exactly equal to the augmentation of the pressure as measured by the outward force of the particles, against the area of the free surface. Contrariwise, directing the magnetic field gradient so as to force the ferrite particles away from the free surface and toward the semipermeable membrane diminished the colloidal osmotic pressure of the solution. For a sufficiently forceful field gradient, the initial colloidal osmotic pressure could be negative, followed by an equilibrium pressure approaching zero regardless of the force of the particles against the membrane. Thus, the osmotic pressure of a solution is to be attributed to the pressure in the solvent generated in opposition to the pressure of the solute particles caused by their interaction with the free surface (Brownian motion and/or an external field force), or by their viscous shear when they migrate through the solvent, or both.
Bromodeoxyuridine Dependence—A New Mutation in Mammalian Cells
Authors: Davidson Richard L. , Bick Michael D.
Published: May 2006

When cells of a Syrian hamster melanoma were grown in increasing concentrations of bromodeoxyuridine (BrdU), lines of mutant cells able to grow well at high concentrations of BrdU were isolated. The mutant cells were characterized by BrdU dependence. In the absence of BrdU, the cells grew very poorly. The requirement for BrdU was specific for both the bromine and the deoxy sugar. The mutant cells incorporated BrdU into the DNA, replacing about 50% of the thymine residues with bromouracil. The reason for the BrdU dependence is not known.