bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction of Acetyl-α-Chymotrypsin and Other Esters with an Ionizable Nucleophile, Monoisonitrosoacetone
Authors: Wedler F. C. , Killian F. L. , Bender M. L.
Published: May 2006

The rate of deacylation of acetyl-α-chymotrypsin is accelerated by the addition of an ionizable nucleophile, monoisonitrosoacetone (pK
a
8.3) in a linear, first-order fashion at all pH's. The pH dependence of the rate enhancement is a bell-shaped curve with true pK
a
's at 7.3 and 8.3, corresponding to ionization of an enzyme active site group and of nucleophile, respectively. Extrakinetic evidence and model ester reactions suggest that the most likely mechanism involves neutral imidazole acting as a general base toward protonated monoisonitrosoacetone, rather than protonated imidazole acting as a general acid to assist the attack of monoisonitrosoacetone anion.
Simplifying Intersections of Surfaces
Authors: Griffith H. C. , Harrold O. G.
Published: May 2006

Suppose μ and
v
are arcs whose union is an arc α and whose intersection is an arc β. Suppose further that μ and
v
, respectively, lie in the boundaries of the disks
M
and
N
. It is shown that either α lies on the boundary of a disk or μ and
v
, respectively, lie in the boundaries of disks
M
′ and
N
′ which meet only in the arc β. The construction is basic to recent results exploring new questions formerly considered only in the piecewise linear category.
A Mechanism for Penicillinase Secretion in
Bacillus licheniformis
Authors: Sargent M. G. , Lampen J. O.
Published: May 2006

Cell-bound isozymes of penicillinase are distinguished from extracellular enzyme by their capacity to bind deoxycholate and to elute with an apparent molecular weight of 45,000 on gel filtration in its presence. By methods that are unlikely to involve changes in primary structure, the cell-bound forms (both from the plasma membrane and from the periplasmic vesicles) can be converted to forms that are very similar if not identical to the exo-form (i.e., eluting with a molecular weight of 24,000 in the presence and absence of deoxycholate). In the case of plasma membrane penicillinase, addition of 25 per cent potassium phosphate at pH 9.0 leads to a 65 per cent conversion in 20 minutes at 30°. Vesicle fraction penicillinase can be converted by pH 9.0 treatment alone. We suggest that the conversion involves a change from a hydrophobic to a hydrophilic conformational type, and that this is the crucial step for enzyme secretion in microorganisms. A model is presented to account for existing data in which we postulate that monomers of the newly synthesized penicillinase in an extended hydrophobic conformation are inserted into the membrane at special growing points where they may change to a hydrophilic exoform, or polymerize to the major plasma membrane type of penicillinase.
Complementarity of RNA Produced by Enzymic Transcription of Native and Denatured
B. subtilis
DNA
Authors: Cassuto Era , Stein Marshall , Chargaff Erwin
Published: May 2006

This paper describes the preparation and some of the properties of the RNA specimens synthesized with the aid of the RNA polymerase of
E. coli
by transcription of the following DNA templates: (
a
) undenatured
B. subtilis
DNA (yielding N-RNA); (
b
) separated strand fractions L and H isolated by chromatography of the denatured DNA on methylated albumin (yielding L-RNA and H-RNA, respectively). The study of the hybridization behavior of the various RNA products showed that N-RNA, though able to form hybrids with either strand, hybridized with H-DNA to twice as great an extent as with L-DNA. The transcripts of the separated L and H fractions exhibited complete specificity with respect to complexing: L-RNA hybridized only with L-DNA, H-RNA only with H-DNA.
An Electromagnetic Catheter Blood Flow Meter of Minimal Lateral Dimensions
Authors: Kolin Alexander
Published: May 2006

A method is described to reduce the lateral dimensions of an electromagnetic catheter blood flow meter to the maximum possible extent. To achieve this, the magnetic field is generated by a magnet placed outside the subject. Thus, only the electrodes and a minimal supporting structure have to be introduced into the blood vessel to pick up the electromotive force induced in the blood streaming at right angles to the magnetic field. To suppress induction of a transformer electromotive force in the electrode leads, the latter form a co-axial lead system of small gauge. One electrode is at the tip of the insulated external tube of this lead system (a gauge no. 28 hypodermic tube) and is insulated from it. The other electrode is a bare section of the external tube about 2 cm from its tip. The tube is bent at an angle of about 30° just below the second electrode. Thus, this bent section places the two electrodes near two diametrically opposite wall sections of the blood vessels after insertion of the fine catheter via a hollow catheter through a branch blood vessel into the main vessel. The catheter is rotated until the plane containing the bent section is perpendicular to the magnetic field. The potential difference between the two electrodes measures the volume rate of flow through the blood vessel. This principle can be used to monitor the flow in the major blood vessels as well as in their branches. Catheter flow meters down to about 0.5 mm in external diameter have thus been made and much smaller ones can be made without excessive difficulty.
Premeiotic DNA Synthesis and the Time of Chromosome Pairing in
Locusta migratoria
Authors: Moens Peter B.
Published: May 2006

Labeled spermatocytes from locusts killed 0, 1, 2, 3, 4, and 6 days after exposure to tritiated thymidine were examined with the electron microscope to determine their meiotic stage. It was found that tritiated thymidine uptake in young spermatocyte nuclei is completed some 24 hours before synaptinemal complexes are formed. It is concluded that in the locust, premeiotic DNA synthesis is completed well in advance of pairing of homologous chromosomes as marked by the formation of synaptinemal complexes. The G-1 and the S-phase are in the order of 24 hours each, while meiotic prophase lasts four to five days under the conditions used.
Theory of a Class of Locally Convex Vector Lattices Which Include the Lebesgue Spaces
Authors: Bogdanowicz Witold M.
Published: May 2006

In this paper is presented the theory of a class of locally convex lattices (
L
-lattices) of real functions which generalize the classical Lebesgue spaces. The monotone and dominated convergence theorems for convergence almost everywhere and sequential and order completeness of such lattices are established. These results are obtained through characterization of linear lattices of functions closed under pointwise or dominated convergence everywhere and closed under Stone's operation
f
→
f
[unk]1. Such lattices are characterized in terms of measurability with respect to sigma or delta rings.

Application to the theory of Lebesgue integrals is given, permitting one to obtain the classical theory of the integral and of the

L
p

spaces directly from the axioms of the integral. Representations of
L
-lattices in terms of Lebesgue integrals and extensions of
L
-lattices through addition of null functions are given.
Excitation of Metastable Levels in Low Density Nebular Plasmas: [SII] and [ArIV]
Authors: Czyzak S. J. , Krueger T. K. , Aller L. H.
Published: May 2006

Diagnostics of low density nebular plasma by means of its forbidden line spectrum require not only a knowledge of certain intensity ratios as a function of its density and temperature but also a knowledge of the occupation numbers of relevant ionic levels. We present the necessary data for important levels of ionized sulfur and triply ionized argon.
Effects of Cytochalasin B upon Microfilaments Involved in Morphogenesis of Salivary Epithelium
Authors: Spooner Brian S. , Wessels Norman K.
Published: May 2006

Cytochalasin B causes cultured mouse salivary gland epithelium to lose its characteristic shape and to cease undergoing morphogenesis. The drug causes disorganization of the 50 Å microfilaments in epithelial cells that are thought to control cell shape because of contractile properties. Upon removal of cytochalasin, epithelia regain normal shape and resume morphogenesis. Exceptionally large bundles of microfilaments appear in such recovered epithelial cells at points where their contractile activity could account for the changes in cell and tissue shape.
Temporal Phenotypic Heterogeneity as a Substrate for Selection
Authors: Kerster Harold W. , Levin Donald A.
Published: May 2006

The interaction of temporal phenotypic heterogeneity with a population level fitness function was explored through the use of a simple model. The model, based upon experimental data, assumes that the exploitation of pollinators, and seed-set within plant populations are dependent upon the frequency of a pink flower morph in populations composed of pink and white morphs. An increase in pink frequency is accompanied by an increase in seed-set for both morphs. The model also assumes that seed-set within a population is the same for pink and white individuals. In perennials and annuals with long-lived seeds, fluctuations in morph balance from one season to another may lead to reproductive pulses or drags, depending upon which morph was in excess. The reproductive differential which stems from different levels of pollinator service leads to an increase in pink frequency and an attendant fitness gain. The perennial habit and long-lived seeds provide a population with a memory which permits the current population image to compete with images of previous years. As a consequence, fitness gains may be achieved in the absence of interplant or interpopulation selection.
Relationship of a Membrane-Bound D-(-)-Lactic Dehydrogenase to Amino Acid Transport in Isolated Bacterial Membrane Preparations
Authors: Kaback H. R. , Milner L. S.
Published: May 2006

The conversion of D-lactate to pyruvate in isolated membrane preparations of
E. coli
ML 308-225 markedly stimulates the transport of proline, glutamic acid, aspartic acid, aspargine, tryptophan, lysine, serine, alanine, and glycine. The uptake of histidine, phenylalanine, tyrosine, leucine, isoleucine, and valine by the membranes is also markedly stimulated by this conversion, although these amino acids are taken up much less effectively than those mentioned previously. The uptake of arginine, methionine, cystine, and cysteine is enhanced only about twofold in the presence of D-(-)-lactate, and these amino acids are not concentrated well by the membranes. With the exception of glutamate, asparate, asparagine, and methionine, which are converted to other metabolites to varying extents in the intramembranal pool, each of the other amino acids was recovered from the membranes as the unchanged amino acid. Succinate, L-(+)-lactate, D,L-α-hydroxybutyrate, and DPNH partially replace D-(-)-lactate but are less effective.
Influx of Calcium into Rabbit Myocardium in Relation to Its Ionic Environment
Authors: Lee Y. C. P. , Visscher Maurice B.
Published: May 2006

In the first 150 seconds after contracture of rabbit myocardium has been induced by shifting from perfusion with zero [Ca
2+
] and low [K
+
] to solutions with normal levels of those cations, there is a large influx of Ca
2+
as measured both by isotopic tracer flux and by total tissue [Ca]. Tracer studies indicate that the influx is 90 per cent complete in 90 seconds. Contracture due to substitution of either Li
+
or K
+
for Na
+
in perfusion fluids is also associated with an increased influx, but of lesser magnitude. The latter types of contracture are reversible while the former is not. It seems probable that the irreversible contracture is induced by the large Ca
2+
influx.
Influence of Spermine and Reduced Temperature on the Ability of Transplanted Nuclei to Promote Normal Development in Eggs of
Rana pipiens
Authors: Hennen Sally
Published: May 2006

Previous work has shown that nuclei of young embryos (to gastrula stage) promote normal development when transplanted into enucleated eggs. As development proceeds to later stages, the nuclei become increasingly restricted in their capacity to promote normal cleavage and development, and the majority of the embryos that do develop possess abnormal chromosome complements (see references 1 through 4). Experiments reported in this paper show that a reduction in the temperature at which the transplantation operation is performed (from 20-11°C) improves the capacity of the nuclei to promote cleavage of recipient eggs, but appears not to improve later development. The capacity to promote postgastrula development is significantly improved when the donor cells are exposed to the polyamine, spermine, prior to and during nuclear transfer. This improvement is correlated with a reduction in the incidence of chromosomal abnormalities. The mechanism of this effect of spermine, and its relationship to the nuclear differentiation problem, is considered.
Phosphoglucomutase Mutants of
Neurospora sitophila
and Their Relation to Morphology
Authors: Mishra N. C. , Tatum E. L.
Published: May 2006

Biochemical and genetic evidence is presented that the
rg-1
and
rg-2
genes control the structure of the two isozymes of phosphoglucomutase (Phosphoglucomutase I and II) in
Neurospora silophila
. Results of kinetic and gel filtration studies show that the two phosphoglucomutases may exist
in vitro
either as separate or as a single but complex molecular species depending on the ionic concentration. The complex phosphoglucomutase molecule is suggested to be the physiologically active form of the enzyme. The change in the enzyme structure is discussed in relation to the morphological change in the ragged mutant strains.
Replicative Form II DNA of ϕX174; Resistance to Exonucleolytic Cleavage by
E. coli
DNA Polymerase
Authors: Razin Aharon , Sinsheimer Robert L.
Published: May 2006

The progeny replicative form II DNA isolated from
E. coli
cells infected with ϕX174 is resistant to the exonucleolytic activity associated with
E. coli
DNA polymerase. A limited endonucleolytic cleavage with micrococcal endonuclease renders the replicative form II molecule susceptible to the exonucleolytic activity associated with the
E. coli
DNA polymerase.

These experiments suggest that the resistance of the replicative form II DNA to the exonucleolytic activity is a result of the structure of these molecules at their 5′-terminus.
A Variable Region Subclass of Heavy Chains Common to Immunoglobulins G, A, and M and Characterized by an Unblocked Amino-Terminal Residue
Authors: Wang A. C. , Pink J. R. L. , Fudenberg H. H. , Ohms J.
Published: May 2006

Heavy chains of IgG, IgA, and IgM classes of human immunoglobulins were compared by N-terminal residue determination and partial amino acid sequence analysis. A third subclass of the variable region of heavy chains was observed; an unblocked glutamic acid as the N-terminal residue is characteristic of this subclass. Our results indicated that the heavy chain variable region subclasses are not class specific, and that a given heavy chain variable region may be found in association with constant regions for μ-chains, α-chains, or γ-chains of various subclasses.
The Dynamics of Life, III. Mechanisms of Nonsurvival and the Relation of Dose Size
Authors: Stover Betsy J. , Eyring Henry
Published: May 2006

From the steady-state theory of mutation rates we have the probability,
q
, of the occurrence of a critical change at some site in a cell that leads to genetic alternation, and the probability,
p
= 1 -
q
, that the site either is not changed or that it has been repaired. In this paper the formal theory is extended to include survival of biological systems. Single and multiple mechanisms of nonsurvival, and multiple factors acting on a single mechanism, are considered. The number of sites that must be altered to lead to nonsurvival is examined and found to be greater than one. The effect of independent action on separate sets of sites, and the relationship between dose size and survival time are given.
A T4-Induced Endonuclease Which Attacks T4 DNA
Authors: Altman Sidney , Meselson Matthew
Published: May 2006

A DNA endonucleolytic activity that introduces single-stranded breaks into native T4 DNA is found in T4-infected
E. coli
. This endonuclease attacks other double-stranded, but not single-stranded, DNA. Experiments with ultraviolet-irradiated phages and amber mutants indicate that the enzyme is made beginning about five minutes after infection at 37° C.
Suppression of Chemical Mutagenesis in Bacteriophage T4 by Genetically Modified DNA Polymerases
Authors: Drake John W. , Greening Elaine O.
Published: May 2006

Two antimutagenic DNA polymerases of bacteriophage T4 markedly reduce transition mutagenesis by a variety of chemical mutagens. Spontaneous mutation and mutagenesis by 2-aminopurine, 5-bromodeoxyuridine, and thymine deprivation are strongly suppressed. Mutagenesis at G:C sites by ethyl methanesulfonate, and at A:T sites by nitrous acid, is moderately suppressed. Mutagenesis at G:C sites by hydroxylamine and by nitrous acid is not suppressed. These results support the notion that the indispensable DNA polymerase of bacteriophage T4 plays a crucial role in the selection of the correct base during DNA replication. The data also reveal that mutagenic specificities of chemical agents depend as much upon the characteristics of the enzymatic apparatus of DNA replication as they do upon the chemistry of primary mutational lesions.
Tolerance to Opioid Narcotics, II. Cellular Tolerance to Levorphanol in Mouse Brain
Authors: Richter Judith A. , Goldstein Avram
Published: May 2006

Mice were made tolerant to a large dose of levorphanol, a congener of morphine. Then
3
H-levorphanol was given. The concentration of free, unchanged levorphanol in the brain water (ultrafiltrate) was found to be much higher than required to produce pharmacologic effects in nontolerant animals. The result indicates that tolerance arises from a diminished sensitivity to the drug at cellular or subcellular sites of drug action in the brain.
FLOWS WITH CROSS SECTIONS
Authors: Verjovsky Alberto
Published: May 2006

Let
M
be a compact connected
C
∞
-manifold, of dimension
n
, without boundary. Let

f
t
: M

→
M
be a

C
r

-flow with cross section. Let

D
r

(
M
) be the topological group of diffeomorphisms of
M
with

C
r

-topology (1 ≤
r
≤ ∞) and let
D
o

r

(
M
) be its connected component of the identity. Let [unk](
M
) be the group of
I
-cobordism classes in

D
r

(
M
) generated by orientation-preserving diffeomorphisms. For
f
ε

D
r

(
M
) denote by [
f
] its
I
-cobordism class. Theorem 1 deals with the dependence of
M
(
f
) on [
f
]. Theorem 2:
S
6
×
S
1
has at least 28 distinct differentiable structures.

Let
x
o
ε
S
1
and let [unk]

r

be the set of

C
r

-flows (
r
≥ 1) in
M
×
S
1
with cross section
M
× {
x
o
} and inducing in it the identity. Theorem 3: Intuitively to a loop in
D
o

r

based at the identity there corresponds a flow in [unk]

r

, and to homotopic loops correspond isotopic flows.

COROLLARY.
complete analysis of
[unk]

r

/ [unk]
for
dim
M
=
2
.

Theorems 4 and 5 refer to Anosov flows for dim
M
>
3
.
Transferase from
Escherichia coli
Effecting Low-Energy Phosphate Transfer to Nucleosides and Nucleotides
Authors: Brunngraber Elinor F. , Chargaff Erwin
Published: May 2006

This communication describes the partial purification of an enzyme in
Escherichia coli
that is capable of a low-energy transfer of organically bound phosphate to nucleosides, nucleoside 5′-phosphates, and deoxyribonucleoside 5′-triphosphates. With the exception of adenosine, the nucleosides give rise almost exclusively to 2′- and 3′-nucleotides. Thymidine and its derivatives are the best acceptors of phosphate groups. Since 5′-nucleotides are converted in high yields to the nucleoside 3′,5′- or 2′,5′-diphosphates, the enzyme may be regarded as a nucleotide phosphotransferase. In the ribonucleotide series, the aglycone affects the relative amounts of 2′ and 3′ derivatives. The noteworthy formation of nucleoside tetraphosphates suggests several regulatory functions of this enzyme which are discussed briefly.
A Class of Neutral Equations with the Fixed Point Property
Authors: Hale Jack K.
Published: May 2006

For a neutral functional differential equation with a stable operator, D, it is shown that the solution operator is the sum of a contraction and a completely continuous operator.
Bilateral Symmetry in Morphogenesis of Embryos
Authors: Jehle Herbert
Published: May 2006

It is suggested that differentiated embryonic cells have a high specificity of molecular constitution as regards the surface layers surrounding their cellular membranes. Correspondingly, specific interface energies may characterize the early contacts between different cell types. The question is raised whether the morphology of the developing embryo may be understood in terms of cellular arrangements which minimize the total interface energy. Bilateral symmetry prevalent in early embryonic development of higher animals might be understood on the basis of the adoption of such a minimum energy principle if, in addition, one assumes that embryonic development is uniquely determined for a particular species.
Specific Assay for Differentiation in the Stalked Bacterium
Caulobacter crescentus
Authors: Shapiro Lucille , Agabian-Keshishian Nina
Published: May 2006

The bacterium
Caulobacter crescentus
carries out a distinct differentiation process during its life cycle. Cultures of the bacterium have been synchronized and an assay has been developed for monitoring the course of morphogenesis by the selective adsorption of radioactive RNA bacteriophage.
Chromosome Structure and Function in Man, III. Pachytene Analysis and Identification of the Supernumerary Chromosome in a Case of Down's Syndrome (Mongolism)
Authors: Hungerford David A. , Mellman William J. , Balaban Gloria B. , LaBadie Gundula U. , Messatzzia Linda R. , Haller Gail
Published: May 2006

Recently developed pachytene maps of the two small acrocentric autosomes (numbers 21 and 22) of man have been applied to a case of Down's syndrome mosaic for normal and trisomic cells (46,XY/47,XY,21+). Trivalents in trisomic spermatocytes, and thus the supernumerary chromosome, were recognized as compatible in length and chromomere pattern with the shorter of these two chromosomes at the pachytene stage. With the exception of the region of the centromere and the short arm, association among constituents of the trivalent appeared complete.
Measure-Theoretic Properties of Arbitrary Point Sets
Authors: Shiffman Max
Published: May 2006

Consider an arbitary point set
S
on the real number line or in Euclidean
n
-space (the limitation to Euclidean space is unessential). The set
S
has an interior Lebesgue measure

m
i

(
S
) and an exterior Lebesgue measure

m
e

(
S
). There are the following well known inequalities for two disjoint sets
S
1
and
S
2
:

m
i

(
S
1
U
S
2
) [unk]

m
i

(
S
1
) +

m
i

(
S
2
),

m
e

(
S
1
U
S
2
) ≤

m
e

(
S
1
) +

m
e

(
S
2
). These state the
superadditivity
of interior measure for disjoint sets, and the
subadditivity
of exterior measure. The question is posed as to what conditions, besides these, are there on the six quantities

m
i

() and

m
e

() for the disjoint sets
S
1
,
S
2
and for their union
S
1
U
S
2
.

The present paper obtains a
complete
set of conditions on these six quantities. These are in the form of
inequalities
. The variability can be expressed in terms of six independent nonnegative quantities, and the six quantities

m
i

() and

m
e

() for the disjoint sets
S
1
,
S
2
and for
S
1
U
S
2
can be expressed as suitable sums of these.

There appears the interesting property that the „average measure”

m
a

(
S
), defined by

m
a

(
S
) = (

m
i

(
S
) +

m
e

(
S
))/2, is
subadditive
. Also, any linear combination α

m
i

(
S
) + β

m
e

(
S
) is discussed.
A Perturbation Series for Cauchy's Problem for Higher-Order Abstract Parabolic Equations
Authors: Donaldson J. A. , Hersh R.
Published: May 2006

The application of Phillips' perturbation theorem to Cauchy's problem for higher-order parabolic equations is justified by an argument from the theory of Fourier transforms of entire functions.
Differentiable Cohomology on Locally Compact Groups
Authors: Whyburn Kenneth
Published: May 2006

In this paper the notions of vector field and differential form are extended to locally compact groups which are the inverse limit of Lie groups. This is done using Bruhat's definition of [unk]

c

∞
functions on such a group. Vector fields are defined as derivations on the [unk]

c

∞
functions. Then tangent vectors at a point are defined as elements of the inverse limit of the tangent spaces of the Lie groups. Tangent vectors then are put together to form vector fields, corresponding to a bundle definition, and the two notions are shown to be equivalent. Differential forms are defined using a bundle type definition from continuous linear functional on the tangent space. An existence and uniqueness theorem is proven for the exterior differential. Then an analog of the Poincaré lemma leads to the de Rham theorem relating the Cech cohomology with real coefficients to the cohomology of the differential forms.
Cyclic Adenosine 3′:5′-Monophosphate-Stimulated Phosphorylation of Isolated Neurotubule Subunits
Authors: Goodman David B. P. , Rasmussen Howard , DiBella Francis , Guthrow C. Earl
Published: May 2006

The possible relationship between cyclic adenosine 3′:5′-monophosphate (cAMP) and neurotubules in synaptic transmission has been explored. The neurotubular subunit protein from bovine cerebral cortex has been prepared. The addition of cAMP to this preparation in the presence of ATP stimulates the phosphorylation of serine residue(s) in the principal component of the preparation. The neurotubule subunit thus serves as a substrate for an intrinsic, cyclic nucleotide-dependent protein kinase closely associated with the neurotubule subunit. The significance of this finding is discussed in terms of a general model for cellular secretion involving microtubules, cyclic AMP, protein kinase, and calcium ion.
Note on Degree of Convergence of Sequences of Rational Functions of Prescribed Type
Authors: Walsh J. L.
Published: May 2006

This note studies the degree of convergence of various sequences of rational functions of given types which are of best approximation to a given function analytic on a given point set and meromorphic on a larger set. The sequences are conveniently represented by the analog of the Padé table.
Effect of Pyridine Nucleotide Precursors on the Permeability of Toad Bladder in the Presence of Vasopressin, Adenosine 3′:5′-cyclic Monophosphate, and Theophylline
Authors: Fong Conrad T. O. , Silver Lawrence , Lankau Grace
Published: May 2006

The increase and prolongation of water movement in the toad bladder in the presence of the pyridine nucleotide precursors adenine and nicotinamide (when stimulated with vasopressin, adenosine 3′:5′-cyclic phosphate, or theophylline) suggests that pyridine nucleotides may be actively involved in membrane permeability.
Overgrowth-Stimulating Activity of Disrupted Chick Embryo Cells and Cells Infected with Rous Sarcoma Virus
Authors: Rubin H.
Published: May 2006

Sonically disrupted chick embryo cells markedly stimulate DNA synthesis and cell multiplication when added to the medium of population density-inhibited cultures of such cells, but have little effect on the growth rate of sparse cultures. Sonicates from density-inhibited chick embryo cultures have as much overgrowth-stimulating activity as do sonicates from actively growing cells. Sonicates from cells infected with Rous sarcoma virus show markedly increased overgrowth-stimulating activity 4 days after infection. The activity in Rous-cell sonicates falls back to near normal amounts at 6 days concurrently with the appearance of a high content of overgrowth-stimulating activity in the medium. The active material is nondialyzable. It seems that growth-inhibited cells contain material in a sequestered location which, when released, can stimulate rapid growth in similarly inhibited cells.
Topography of the
Escherichia coli
30S Ribosomal Subunit and Streptomycin Binding
Authors: Chang F. N. , Flaks Joel G.
Published: May 2006

Treatment of
Escherichia coli
30S ribosomal subunits with trypsin sequentially removes a number of different ribosomal proteins, as revealed by polyacrylamide gel electrophoresis. Proteins that are removed early by trypsin correlate well with those that are added last during reconstitutive assembly of the 30S subunit from 16S ribosomal RNA and the total protein complement. Proteins that are resistant to removal from the subunit by the highest trypsin concentration used correlate with those that are added early during assembly. Six proteins can be removed from the subunit with trypsin without affecting its ability to bind the antibiotic streptomycin. A decline in the ability of the 30S subunit to bind streptomycin is correlated with the removal of either one, or both, of two proteins, neither one of which is the gene product of the streptomycin locus. The implications of these findings for the topography and assembly of the 30S subunit are considered.
Three-Dimensional Organization of the 30S Ribosomal Proteins from
Escherichia coli
, I. Preliminary Classification of the Proteins
Authors: Craven Gary R. , Gupta Vatsala
Published: May 2006

30S ribosomal subunits from
Escherichia coli
were reacted with three protein reagents. After reaction, the ribosomal proteins were extracted and examined; of the 20 proteins known to compose the particle, nine did not react with any of the three reagents. We have tentatively classified these proteins as „internal,” and the remaining eleven as „external.” A strong correlation was found between these results and the sequence of assembly. Those proteins which enter the assembly process early are classed as internal, whereas those proteins found to participate later in the assembly sequence are classed as external.
Circular Dichroism Studies at Variable Temperature: Urobilinoid Conformation
Authors: Lightner David A. , Docks Edward L. , Horwitz Joseph , Moscowitz Albert
Published: May 2006

Measurements of the temperature dependence of the circular dichroism spectra of
l
-stercobilin and
d
-urobilin show that the conformations of these optically-active urobilinoids change with temperature between 163 and 297°K. These conformational changes depend critically on the hydrogen bonding characteristics of the solvent. Thus, in methanol-glycerol (9:1), the chiral sense of the helical conformation of the dipyrrylmethene chromophore is reversed on lowering the temperature, whereas in chloroform, reversal does not occur.
Fine Structure of the Motile Cells and Flagella in a Member of the Actinoplanaceae (Actinomycetales)
Authors: Bland Charles E.
Published: May 2006

The motile cells (sporangiospores) of an undescribed member of the Actinoplanaceae are studied by electron microscopy as shadowed, negatively stained, and sectioned preparations. The rod-shaped spores exhibit a typically bacterial internal structure. However, a single tubular structure (rhapidosome) is positioned just inside the site of flagellar attachment of each spore and is oriented perpendicular to the direction of the flagella. Flagella arise from basal dises and pass through the plasma membrane and the two-layered cell wall to become associated with other flagella to function as a posteriorly directed unit. Each flagellum consists of a helical band or ribbon which dissociates into 5 or 6 subfibrils.
Application of the Chloro Ketal Claisen Reaction to the Total Synthesis of Squalene. Experimental Details
Authors: Werthemann Lucius , Johnson William S.
Published: May 2006

The experimental details are reported for a previously described synthesis of squalene.
Cell-Free Hemoglobin Synthesis in Beta-Thalassemia
Authors: Gilbert J. M. , Thornton A. G. , Nienhuis A. W. , Anderson W. F.
Published: May 2006

Human ribosomes obtained from the reticulocytes of patients having either homozygous beta-thalassemia (thalassemia ribosomes) or a hematological disorder unrelated to thalassemia („normal” ribosomes) have been utilized in a cell-free system highly active in the synthesis of intact human globin chains. This system is dependent on the addition of a ribosomal wash fraction from reticulocytes that contains factors necessary for chain initiation. In response to the ribosomal wash fraction, isolated from either thalassemia, normal human, or rabbit reticulocytes, normal human ribosomes synthesize equal amounts of alpha and beta chains. In contrast, in response to all three types of ribosomal wash fractions, thalassemia ribosomes synthesize 8-times more α than β chains, a ratio similar to that produced in the intact cells of these patients. The molecular defect in beta-thalassemia, therefore, does not appear to be associated with initiation factors.
The SV40 Pseudovirus: Its Potential for General Transduction in Animal Cells
Authors: Grady Leo , Axelrod David , Trilling David
Published: May 2006

The rates of reassociation of DNA from a monkey cell line (Vero), from SV40 pseudovirus (consisting of Vero DNA and virus protein coat), and from mature SV40 were measured. The results show that the host DNA in the pseudovirus contains repeated and unique sequences in the same proportions as normal host DNA; hence, no one portion of the host genome is preferentially incorporated in the pseudovirus. It was also shown that the Vero DNA in the pseudoviruses enters the nuclei of mouse embryo cells without loss of its physical integrity.
Neutral Amphiplasty and Regulation of the Cell Cycle in
Crepis
Herbs
Authors: Langridge W. H. R. , O'Malley T. A. , Wallace H.
Published: May 2006

The duration of phases of the cell cycle are measured in five species and one hybrid of the genus
Crepis
(Compositae), after pulse labeling with tritiated thymidine. The results indicate significant variations in the duration of post-synthetic interphase (
G
2
), which affords a possible explanation for the abnormal chromosome morphology first described in
Crepis
hybrids as neutral amphiplasty.
Multiple Molecular Species of
Escherichia coli
DNA Polymerase
Authors: Yoshida Shonen , Cavalieri Liebe F.
Published: May 2006

DNA polymerase activity from
Escherichia coli
can be demonstrated in various sized molecules ranging in molecular weight from about 10,000 to 120,000 or higher. The characterization of the smaller species is difficult because of their pronounced tendency toward aggregation; the smallest apparently aggregates most readily. The results indicate the following molecular weight classes: 10,000-20,000; 40,000-50,000; 75,000-85,000, and 100,000-120,000. The same classes were obtained with several methods of analysis of material that had been purified in a number of ways, one of which is a new DNA-acrylamide gel chromatographic procedure. The lowest molecular weight species shows no exonucleolytic activity. A proteolytic inhibitor, phenylmethyl sulfonylfluoride, did not eliminate the small active molecules, although proteolysis of high molecular weight DNA polymerase (109,000) has been shown by others to produce fragments of about 75,000 molecular weight. Either there is a naturally occurring polymerase protein of about 20,000 molecular weight, capable of aggregation with itself and with certain other molecules (e.g., exonucleases), or there are certain bonds in a large, native polymerase molecule that are especially susceptible to proteolysis without destroying activity.
A New Reduced Human-Mouse Somatic Cell Hybrid Containing the Human Gene for Adenine Phosphoribosyltransferase
Authors: Kusano Toshihisa , Long Cedric , Green Howard
Published: May 2006

A system that selects for the gene directing synthesis of the enzyme adenine phosphoribosyltransferase (APRT) uses the antibiotic alanosine to prevent endogenous synthesis of adenylic acid. With the aid of this system, a new series of human-mouse hybrids has been prepared between wild type human diploid fibroblasts and an enzyme-deficient mouse line. Survival of the hybrids depended upon the presence of the APRT, which was shown to have the isoelectric pH characteristic of the human enzyme and not that of the mouse. Reduced hybrids containing the enzyme lacked all human biarmed chromosomes, so that unless a rearrangement had occurred, the
aprt
gene must be located on an acrocentric chromosome. The hybrid cells became APRT
-
with a frequency of 2 × 10
-3
, probably by loss of the human
aprt
chromosome. The APRT
-
progeny could be obtained selectively by growth in medium containing fluoroadenine.
DNA in Uninfected and Virus-Infected Cells Complementary to Avian Tumor Virus RNA
Authors: Rosenthal Peter N. , Robinson Harriet L. , Robinson William S. , Hanafusa Teruko , Hanafusa Hidesaburo
Published: May 2006

The 70S RNA component of several avian tumor viruses was hybridized with DNA extracted from avian tumor virus-infected and uninfected chicken and Japanese quail cells. Tritium-labeled 70S RNAs from Rous sarcoma virus (RSV), Rous associated virus-1 (RAV-1), RAV-60, and Schmidt-Ruppin-RSV (SR-RSV) hybridize from 3 to 10 times more with DNA from uninfected chicken cells than with DNA from
Escherichia coli
, calfthymus, or baby hamster kidney cells. After infection of chicken cells with RSV(RAV-1), SR-RSV, or RAV-2, the amount of 70S avian tumor virus [
3
H]RNA hybridized increases by 1.6 times. The specificity of the hybridization reaction was shown by the specific competition of 70S SR-RSV [
3
H]RNA with 70S RNA from RSV(RAV-1), and not with RNA from Sendai virus or chicken cells. There was no difference in the hybridization of 70S RNA from RSV (RAV-1), RAV-1, or RAV-60 with DNA either from chicken cells that contain RAV-60 in a nonreplicating form or from chicken cells that do not appear to contain RAV-60. These results indicate that both types of uninfected chicken cells contain DNA that is complementary to RNA from several avian tumor viruses and that the amount of complementary DNA increases in such cells after infection with an avian tumor virus. The RNAs of genetically different avian tumor viruses appear to have indistinguishable base sequences by this technique.
The Nutritive Value of Single Foods
Authors: Williams Roger J. , Heffley James D. , Bode Charles W.
Published: May 2006

This is an extension of an earlier study in which we found that while commercial “enriched” bread alone would not support the life of weanling rats in a 90-day test, enrichment could be updated at low cost, with the result that rats consuming the improved bread alone lived during the test period and grew seven times as fast. Prominent nutritionists criticized this study on the basis that bread is not eaten alone and that other single foods are likewise deficient. It was stated: “the experiments you performed would have given the same or similar results if you had begun with milk, eggs, meat, or any other food”.

Skepticism regarding this statement led to experimental trials in which milk, meat, eggs, and several other foods, including breakfast cereals, were fed singly to groups of animals. Eggs proved to be a remarkably complete food, and milk exhibited about the same excellence until the iron deficiency became evident after about two months. “Enriched” breakfast foods and macaroni were highly deficient and could be improved greatly by supplementation.

As an outgrowth of this study, we are developing a method of biological testing which is incomparably better for evaluating foods than consulting food composition tables. On the basis of the tabulated data alone one might conclude that “enriched” puffed rice, for example, is only slightly inferior nutritionally to eggs. Our experiments have shown this assumption to be grossly in error.
Interaction of the Subunits of Adenosine 3′:5′-Cyclic Monophosphate-Dependent Protein Kinase of Muscle
Authors: Brostrom C. O. , Corbin J. D. , King C. A. , Krebs E. G.
Published: May 2006

Two cAMP-dependent protein kinases purified from rabbit skeletal muscle were shown to bind the same amount of cAMP per unit of enzyme activity at several concentrations of this nucleotide. A preparation containing both of these kinases was separated into catalytic (C) and regulatory (R) subunit fractions in the presence of cAMP, the regulatory subunit being obtained as an R·cAMP complex. Addition of increasing amounts of the R·cAMP complex to the holoenzyme (RC) increased the concentration of cAMP required for half-maximal activity of the enzyme. cAMP was liberated from the R·cAMP complex in the presence of added catalytic subunit in a reaction that was facilitated by Mg
2+
, ATP, and warming. These findings are presented in support of a model for activation of the protein kinase by cAMP. The possibility that excess regulatory subunit may serve as a sink for intracellular cAMP is also discussed. It is shown that cAMP bound to the R subunit is not a substrate for the cAMP phosphodiesterase.
Pituitary Peptides and the Suppression of Memory by Puromycin
Authors: Flexner Josefa B. , Flexner Louis B.
Published: May 2006

It has previously been shown that the expression of memory of maze-learning in mice is blocked by intracerebrally-injected puromycin one or more days after the training experience, and that bilateral adrenalectomy before training protects memory against this effect of puromycin. Purified cortrophin gel, injected subcutaneously up to 3 days before training, has now been found to give results like those obtained with adrenalectomy and, additionally, to provide a high degree of protection when injected up to 16 hr after training. Several possible explanations for these effects have been considered and found to be inadequate.
Tissue Differences in Rat Chromosomal RNA
Authors: Mayfield John E. , Bonner James
Published: May 2006

Chromosomal RNA was isolated from several rat tissues by a new technique. It is shown by RNA-DNA hybridization that each tissue contains a distinct population of chromosomal RNA sequences. This finding is compatible with the proposal that chromosomal RNA is involved in the process of gene activation.
Host-Gene Control of C-Type Tumor Virus-Expression and Tumorigenesis: Relevance of Studies in Inbred Mice to Cancer in Man and Other Species
Authors: Meier Hans , Huebner Robert J.
Published: May 2006

C-type RNA viruses are tumorigenic in mice and other species. They are widespread and transmitted in an intimate relationship with host-cell genetic material. Tumorigenesis is no doubt a complex biological phenomenon, and involves both genetic and environmental factors. Among the genetic factors, single-locus determination is probably exceptional; yet, a number of genes are known in inbred mice and other species, including man, that can exert a major influence. Clearly, studies with inbred mice apply outside the murine model and justify generalizations on the etiology of cancer.

The types of cancer observed in man are similar to those of inbred strains of mice, and their stochastic and often familial occurrences suggest that genetic factors play important roles in both man and mouse. A number of heritable disorders predipsose to tumorigenesis. Investigations of the relationship between various polymorphic phenotypes and human tumors should be intensified. For instance, a study of high-risk human-tumor groups could aid considerably not only in the recognition of etiological agents but also of underlying host-gene controlled mechanisms. Indeed epidemiological studies have already led to the identification of mutant genes that influence the incidence of human cancer. Such studies may be guided by findings in inbred strains of mice. There is good evidence in inbred mice that mutations in host chromosomes determine whether or not genes coding for RNA oncogene viral “functions” become expressed as cancer. Although an etiological role of C-type RNA virus has not yet been demonstrated in human cancer, studies of the interaction of viral and host-cell genomes in mice and other species, and the visualization of C-type virus in human tumors have provided good reasons for suspecting the presence in man of oncogenic genes (oncogenes) homologous to those of the C-type viral genomes, which are well studied in mice, hamsters, cats, rats, and chickens.
Vitamin B
6
-Responsive Histidine Deficiency in Mutants of
Salmonella typhimurium
Authors: Henderson Gary B. , Snell Esmond E.
Published: May 2006

A mutant of
Salmonella typhimurium
LT-2 that requires either vitamin B
6
or histidine for growth was found to synthesize vitamin B
5
in amounts comparable to the parent strain, but to be deficient in imidazoleacetol phosphate transaminase (L-histidinolphosphate: 2-oxoglutarate aminotransferase, EC 2.6.1.9), an enzyme required for histidine biosynthesis. The mutant apotransaminase required a 50-fold higher concentration of pyridoxal 5′-phosphate for half-maximum activation than the corresponding wild-type enzyme; the fully activated mutant enzyme also displays a much lower maximum rate of catalysis than the enzyme from the parent strain. Such mutational changes in bacteria resemble those in certain vitamin B
6
-responsive genetic diseases in man and provide useful experimental material for the study of factors involved in coenzyme binding and enzymatic catalysis.
On the — 1.9 Volt (Alternating Current) Polarographic Signal of Tissues
Authors: Hata Shun-Ichi , Egyud Laszlo G. , Szent-Györgyi A.
Published: May 2006

A polarographic signal at — 1.9 V (against a saturated-calomel electrode as a reference) is present in extracts of rapidly proliferating animal and plant tissues of normal and cancerous origin. A similar signal was also found in “germ cells”. The possible lack of this signal in human urine may be helpful for the early detection of neoplasias.
Evidence for Hydrogen Abstraction by Classical Radicals in the Norbornenyl-Nortricyclyl System
Authors: Halgren Thomas A. , Firkins John L. , Fujimoto T. A. , Suzukawa H. H. , Roberts John D.
Published: May 2006

Studies of product compositions and deuterium-label rearrangements at various concentrations of tri-
n
-butyltin hydride in the reductions of
exo
-and
endo
-5-bromonorbornene and 2-bromonortricyclcne to mixtures of norbornene and nortricyclene lead to three main conclusions: (
i
) at least two radical intermediates contribute to product formation; (
ii
) each intermediate yields predominantly (80% or more) one product; and (
iii
) nortricyclene is predominantly derived from a symmetrical intermediate. This constitutes strong evidence for hydrogen abstraction by classical (i.e., single-product) norbornenyl and nortricyclyl radicals. It is argued that the norbornenyl-nortricyclyl system is exceptionally well suited for the generation of a nonclassical (dual-product) radical; hence, the existence of a nonclassical radical in any other system is rather unlikely.
Characterization of Mitochondrial Ribosomes from Yeast
Authors: Morimoto H. , Halvorson H. O.
Published: May 2006

A method for the preparation of mitochondrial ribosomes from yeast is presented. Mitochondrial ribosomes differ from their cytoplasmic counterpart in nucleotide composition, electrophoretic mobility of a number of their respective ribosomal proteins, and thermal denaturation profiles. The mitochondrial and cytoplasmic ribosomes have identical sedimentation coefficients (80 S) and dissociate into 60S and 40S subunits. These findings demonstrate that, in yeast, mitochondrial ribosomes are distinct from cytoplasmic ribosomes.
A Role of Aminoacyl-tRNA in the Regulation of Protein Breakdown in
Escherichia coli
Authors: Goldberg Alfred L.
Published: May 2006

The rate of degradation of cell proteins in
Escherichia coli
was studied under various conditions that affect levels of charged tRNA. Protein breakdown increased markedly when the synthesis of valyl-tRNA was prevented in strains containing temperature-sensitive valyl-tRNA synthetase or when the formation of
N
-formylmethionyl-tRNA was inhibited with trimethoprim. Conversely, protein breakdown decreased in a valine auxotroph-administered valine or an analog capable of attachment to the valyl-tRNA. It appears that changes in the levels of aminoacyl-tRNA regulate protein breakdown by mechanisms similar to those controlling the synthesis of ribosomal RNA. These experiments also demonstrate that protein synthesis is not essential for protein degradation and suggest that the inhibition of degradation in starving cells by chloramphenicol is a secondary effect of the accumulation of charged tRNA.