bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro
Synthesis of Procollagen on Polysomes
Authors: Kerwar S. S. , Kohn Leonard D. , Lapiere Charles M. , Weissbach Herbert
Published: May 2006

The major collagenous products synthesized in a cell-free polysome preparation are pro-α1 and pro-α2, formed in a ratio of 2:1. They are the precursor forms of α1 and α2 chains of normal connective-tissue collagen that are also formed in small amounts. A procollagen peptidase activity has been demonstrated in the supernatant fraction that can account for the formation of α1 and α2 chains from their precursors. The polysomal system is activated by a salt extract of reticulocyte ribosomes and is inhibited by aurintricarboxylic acid, suggesting that the polysomes are able to initiate protein synthesis.
Methadone Plasma Level: Sustained by a Reservoir of Drug in Tissue
Authors: Dole Vincent P. , Kreek Mary Jeanne
Published: May 2006

Binding of methadone in body tissues limits the rise in plasma concentration and prolongs the pharmacological action in patients receiving a daily maintenance dose. An opiate with equal intrinsic activity but greater binding affinity would, therefore, be a better drug than methadone for maintenance treatment; it would be safer when taken in a single dose and longer in its duration of action when taken on a regular schedule.
A Frequency-Dependent Natural Selection Model for the Evolution of Social Cooperation Networks
Authors: Boorman Scott A. , Levitt Paul R.
Published: May 2006

A model is presented for the evolution of several aspects of sociality based on reciprocal ties of social cooperation, modeling especially cooperative hunting behavior in carnivores. This model captures the possibility of a critical threshold in gene frequency, which, if reached, will lead to an explosion toward fixation of the “social” trait. This threshold phenomenon might be restated as follows: the precondition for evolution favorable to the specific form of social behavior considered is hard to satisfy, but—once this condition is satisfied—the tendency toward sociality is effectively irreversible. The simple model proposed appears to be highly robust, with most realistic changes additionally favoring the social gene.
Genetic Transformation in
Escherichia coli
K12
Authors: Cosloy Sharon D. , Oishi Michio
Published: May 2006

An auxotrophic strain of
E. coli
K12 treated with CaCl
2
was transformed for several markers at a frequency of up to 10
-6
per recipient cell by a DNA preparation isolated from a prototrophic strain. The transforming activity of the DNA preparation was eliminated by treatment with DNase, heat, or sonication, whereas RNase or Pronase treatment had little effect. Two closely linked genetic markers (
leu
and
ara
) showed a high degree of cotransformation linkage when high molecular weight DNA was used, but the linkage was almost completely eliminated when sheared, smaller molecular weight DNA was used. There is genetic evidence that the transformation is a result of the replacement of the preexisting genetic marker on the chromosome by that of the donor DNA.
Stimulation of Steroid Secretion in Adrenal Tumor Cells by Choleragen
Authors: Wolff J. , Temple R. , Cook G. Hope
Published: May 2006

Choleragen, the pure protein from cholera toxin, stimulates steroid secretion by Y-1 adrenal tumor cells in culture. The secreted steroids are the same as seen after addition of adrenocorticotropic hormone. Half-maximal stimulation occurs at 15 pM; stimulation is essentially irreversible by washing and partially reversible (for about 1 hr) by antibody, and there is a latent period of about 60 min before stimulation is seen. Stimulation of adenylate cyclase occurs at about 30-fold higher choleragen concentrations. Gangliosides inhibit choleragen stimulation when added before but not after the toxin. Lipopolysaccharides from
Escherichia coli, Salmonella typhosa
, and
Serratia marcescens
also stimulate steroid secretion, but are less potent than choleragen.
Sodium Dynamics in a Northern Ecosystem
Authors: Botkin D. B. , Jordan P. A. , Dominski A. S. , Lowendorf H. S. , Hutchinson G. E.
Published: May 2006

Analyses of terrestrial sources of sodium and estimates of the sodium requirement of moose (
Alces alces
) on Isle Royale, Lake Superior, suggest that availability of the element controls the moose population. The terrestrial vegetation is very poor in the element, but, as elsewhere, submerged and floating leaved water-plants are relatively rich. Consumption of such plants in summer would provide an adequate source, if the animal can store the element. The fairly high sodium contents of freshwater vegetation have been little appreciated. In general, sodium concentration in water-plants, unlike that of potassium, is not correlated with chloride but the latter is ordinarily in excess of the sodium, so that uptake of the latter implies an equivalent supply of NaCl.
Prediction of the Amount of Secondary Structure in a Globular Protein from Its Aminoacid Composition
Authors: Krigbaum W. R. , Knutton Sara Parkey
Published: May 2006

Multiple regression is used to obtain relationships for predicting the amount of secondary structure in a protein molecule from a knowledge of its aminoacid composition. We tested these relations using 18 proteins of known structure, but omitting the protein to be predicted. Independent predictions were made for the two subchains of hemoglobin and insulin. The average errors for these 20 chains or subchains are: helix ± 7.1%, β-sheet ± 6.9%, turn ± 4.2%, and coil ± 5.7%. A second set of relations yielding somewhat inferior predictions is given for the case in which Asp and Asn, and Glu and Gln, are not differentiated. Predictions are also listed for 15 proteins for which the aminoacid sequence or tertiary structure is unknown.
Altered Enzymes in Drug-Resistant Variants of Mammalian Tissue Culture Cells
Authors: Sharp J. D. , Capecchi N. E. , Capecchi M. R.
Published: May 2006

Two selective procedures are compared in an effort to isolate variants of mouse L cells containing structural gene mutations. Among the resulting variant cloned cell lines are found two types of alterations in the enzyme hypoxanthine phosphoribosyl transferase (EC 2.4.2.8) (
1
): enzyme with altered kinetic constants causing
in vivo
and
in vitro
resistance to 8-azaguanine; and (
2
) enzyme with altered heat sensitivity
in vitro
. These results support the view that tissue culture cell variants can arise from structural gene mutations.
Synthesis of a Large Precursor to Ribosomal RNA in a Mutant of
Escherichia coli
Authors: Nikolaev N. , Silengo L. , Schlessinger D.
Published: May 2006

A mutant of
E. coli
, isolated by Kindler and Hofschneider as a strain defective in RNase III activity, forms a 30S precursor of ribosomal RNA (“30S pre-rRNA”). The half-life of the 30S pre-rRNA in growing cells at 30°, estimated by the rate of specific
3
[H]uridine incorporation, is about 1 min. In rifampicin-treated cells, the RNA is metabolized to mature rRNA with a half-life of about 2 min.

The 30S pre-rRNA has been highly purified. DNA-RNA hybridization tests demonstrate that it contains both 16S and 23S rRNA sequences. Also, in cultures treated with rifampicin, the cleavage products of radioactive 30S pre-rRNA include 25S and 17.5S RNA species, destined to becomes 23S and 16S rRNA. Thus, each 30S chain probably contains one 16S and one 23S RNA sequence, as well as additional sequences. Two independent techniques indicate that the additional portions account for about 27% of the total lenght: (
1
) By comparison to the sedimentation rate and electrophoretic mobility of marker RNAs, the 30S pre-RNA has an apparent molecular weight of 2.3 × 10
6
± 5%, or 28% more than the sum of 16S and 23S rRNA; (
2
) 27% of the 30S pre-rRNA is not competed away from hybridization by mature 16S and 23S rRNA.

Thus, bacteria appear to make a pre-rRNA similar in some respects to that observed in eukaryotes; though in normal
E. coli
cells, the pre-rRNA is ordinarily cleaved endonucleolytically during its formation.
Transcription of Simian Virus 40. III. Mapping of “Early” and “Late” Species of RNA
Authors: Sambrook Joe , Sugden Bill , Keller Walter , Sharp Phillip A.
Published: May 2006

To determine the orientation of transcription of the E and L strands of DNA from simian virus 40 (SV40), we used linear DNA prepared by cleavage of superhelical viral DNA by endonuclease R·R
1
from
Escherichia coli
as a primer·template for DNA polymerase. The resulting molecules, which were labeled only at the 3′ end of each DNA strand, were then cleaved with
Hemophilus parainfluenzae
endonuclease
Hpa
I. The ensuing four DNA fragments, whose locations on the viral genome are known, were separated by electrophoresis, denatured, and hybridized to asymmetric SV40 complementary RNA. From the pattern of hybridization of the fragments containing the labeled 3′ ends, we conclude that transcription of SV40 proceeds in a clockwise direction on the L strand and in a counterclockwise direction on the E strand as drawn on the conventional SV40 map.

To map the “early” and “late” regions of the viral genome, we extracted RNA from lytically infected cells and hybridized it to the separated strands of the four fragments of
32
P-labeled SV40 DNA. Early after infection, RNA complementary to part of the E strand of the contiguous fragments A and C was detected. Late polysomal RNA was complementary to part of the L strand sequences of fragments A and C and to the total L strand sequence of fragments B and D.
300-MHz Nuclear Magnetic Resonance Study of Oxytocin in Aqueous Solution: Conformational Implications
Authors: Brewster A. I. Richard , Hruby V. J.
Published: May 2006

The 300-MHz nuclear magnetic resonance spectrum of the peptide hormone, oxytocin, in water, was obtained. Extensive nuclear magnetic resonance spindecoupling experiments, including those involving irradiation of the α-proton resonance under the water peak, studies using partially deuterated hormone derivatives, and nuclear magnetic resonance studies of some precursor peptides to oxytocin, permitted us to assign most of the proton resonance of the hormone unambiguously. The JNα values and temperature dependence of the chemical shift of the peptide amide and carboxamide protons of oxytocin were also obtained. These studies indicate that, in aqueous solution, oxytocin is a flexible molecule possessing several different conformations. Corresponding studies of [4-leucine]oxytocin were also made, with similar results and conclusions.
Structure of Hemoglobin M Boston, a Variant with a Five-Coordinated Ferric Heme
Authors: Pulsinelli P. D. , Perutz M. F. , Nagel R. L.
Published: May 2006

X-ray analysis of the natural valency hybrid α
2
+M Boston
β
2
deoxy
shows that the ferric iron atoms in the abnormal α subunits are bonded to the phenolate side chains of the tyrosines that have replaced the distal histidines; the iron atoms are displaced to the distal side of the porphyrin ring and are not bonded to the proximal histidines. The resulting changes in tertiary structure of the α subunits stabilize the hemoglobin tetramer in the quaternary deoxy structure, which lowers the oxygen affinity of the normal β subunits and causes cyanosis. The strength of the bond from the ferric iron to the phenolate oxygen appears to be the main factor responsible for the many abnormal properties of hemoglobin M Boston.
Properties of the β Nerve Growth Factor Receptor of Avian Dorsal Root Ganglia
Authors: Herrup Karl , Shooter E. M.
Published: May 2006

Iodination of the β nerve growth factor protein up to 4.1 iodines per mole of nerve growth factor was achieved with no loss of biological activity. At this level of incorporation no native or monoiodo nerve growth factor remained, the major species being the tri- and tetraiodo derivatives. An
125
I-labeled β nerve growth factor of high specific activity containing 0.5 iodine per mole of β nerve growth factor was used to determine the specific binding of nerve growth factor to dorsal root ganglion cells of 8-day-old embryonic chicks. The specific binding of
125
I-labeled nerve growth factor reached saturation at 30-50 ng/ml and half-saturation at 7-8 ng/ml (0.26 nM). The number of receptors per responsive medio-dorsal cell was calculated to be about 2 × 10
4
. The pattern of displacement of bound
125
I-labeled β nerve growth factor by native β nerve growth factor showed that the two proteins had identical affinities for the receptor. The specificity of the binding for β nerve growth factor was demonstrated by the fact that only native β nerve growth factor displaced the bound
125
I-labeled form. Partially inactivated derivatives of β nerve growth factor retained the same fraction of their specific-binding capacity as of their biological activity. The specificity of the binding for cell type was shown by the lack of any specific component of
125
I-labeled β nerve growth factor binding to liver or brain cells. The rate constant for association of β nerve growth factor with its receptor,
k
1
, was 1.0 × 10
7
mol
-1
sec
-1
and the rate constant for dissociation,
k
-1
, 1.2 × 10
-8
sec
-1
.
The Labyrinthine Sense Organs of the Frog
Authors: Wever Ernest Glen
Published: May 2006

A study of the macula and crista organs of the frog's labyrinth with the use of an improved method of histological preparation has shown these endings to be more complex than heretofore believed. The structure lying over the layer of sensory and supporting cells is not a single “gelatinous” body as commonly described, but consists of two distinct layers with separate functions.

In all these endings—macula sacculi, macula utriculi, macula lagenae, and the cristae of the three semicircular canals—there is a special tectorial structure that lies over the cellular surface and makes the connections to the ciliary tufts of the hair cells. It has the general form of a reticulum, though in the saccule it is somewhat elaborated.

A preliminary study of other vertebrates indicates that this tectorial reticulum is present in all the labyrinthine endings throughout the series from fishes to mammals.

Consideration is given to the possible advantages of this special tectorial structure in the stimulation process.
Influence of Leaving-Group Electronic Effect on α-Chymotrypsin: Catalytic Constants of Specific Substrates
Authors: Philipp Manfred , Pollack Ralph M. , Bender Myron L.
Published: May 2006

Rate constants and binding constants for the α-chymotrypsin-catalyzed hydrolysis of
N
-acetyltyrosine, tryptophan, and phenylalanine anilides are presented. Both
k
cat
and
K
m
are independent of electronic effects in the substrate over a range of 9.8 orders of magnitude (as measured by pK of the leaving group). Similarly,
K
m
is independent of charge and orientation about the α-carbon for various substrates and pseudo-substrates. These results are not consistent with the pretransition state protonation hypothesis; instead, they are discussed in terms of a tetrahedral intermediate that is thermodynamically less stable than the Michaelis complex.
Radioimmunoassay for Human Alpha
1
-Fetoprotein
Authors: Silver Hulbert K. B. , Gold Phil , Feder Stephen , Freedman Samuel O. , Shuster Joseph
Published: May 2006

A method of radioimmunoassay has been developed for the quantitation of alpha
1
-fetoprotein in human serum. The assay requires 20 μl of serum, can be completed in 8 hr, and can reproducibly detect concentrations of 20 ng of alpha
1
-fetoprotein per ml of serum. Hence, the method is about 500-fold more sensitive for the detection of alpha
1
-fetoprotein than the Ouchterlony teohnique currently in general use. The procedure is of potential clinical value as an aid in the diagnosis of cancer and a number of noncancerous hepatic diseases.
Interpretation of the Binding of Carbon Monoxide to Hemoglobin Under Photodissociating Conditions
Authors: Szabo A. , Karplus M.
Published: May 2006

An interpretation is given of recent experiments by Brunori
et al
. on the binding of carbon monoxide by hemoglobin under photodissociating conditions. It is shown that their results follow directly from scalable models for hemoglobin in which the protein-modulated interactions are separable from the ligand binding.
Affinity Binding of Intact Fat Cells and Their Ghosts to Immobilized Insulin
Authors: Soderman Denis D. , Germershausen John , Katzen Howard M.
Published: May 2006

Immobilized insulin, prepared by coupling insulin directly to agarose or through hydrocarbon “connecting arms,” was demonstrated to be capable of firmly binding intact adipocytes and their ghosts. Various lines of evidence indicate that the insulin receptor on the plasma membrane, in addition to the insulin coupled to the agarose, was responsible for the observed binding. This evidence includes: (
a
) the finding that increasing the “arm” length increased the binding capacities of insulin-Sepharose affinity chromatographic columns, (
b
) specific inhibition and reversal by insulin and antiserum to insulin of the binding, as compared to lesser effects by other peptide hormones, (
c
) the indication that only the plasma membrane sacs, not the other cellular contaminants in the crude ghosts, are capable of binding, and (
d
) the impairment and restoration of trypsin-sensitive membrane binding sites that are also required for insulin biosensitivity. These findings support the idea that the insulin receptor is the trypsin-sensitive site. By use of the differential buoyant densities of the various cell-bead complexes that resulted from the interaction of adipocytes with insulin-Sepharose, a new procedure was developed to demonstrate and study the binding. These complexes could also be demonstrated by interference contrast microscopy. Binding readily occurred under conditions favorable for insulin stimulation of the cells. By coupling tracer amounts of [
125
I]insulin to Sepharose or insulin-Sepharose, the effects of anti-insulin antisera, free insulin, and other peptide hormones and supplemental factors on the buoyant-density distribution of the complexes could be measured, as well as the effects of other ligands coupled to Sepharose.
A Nucleic Acid Associated with a Killer Strain of Yeast
Authors: Vodkin Michael H. , Fink Gerald R.
Published: May 2006

A crude membrane fraction was isolated from both killer
M
(k) and isogenic nonkiller
M
(o) strains of yeast labeled with [
3
H]adenine. Nucleic acids were extracted from this fraction and centrifuged to equilibrium in an ethidium bromide-Cs
2
SO
4
solution. A peak of radioactivity coincident with a single fluorescent band was present in the membrane fraction isolated from cells of the killer strain but was absent from that isolated from nonkiller cells. This material has been characterized as double-stranded RNA by treatment with various nucleases and by chromatography on a cellulose CF-11 column. Sedimentation in a sucrose gradient indicates an S value of 8-10.
Nucleotide Sequence Divergence in the α-Chain-Structural Genes of Tryptophan Synthetase from
Escherichia coli, Salmonella typhimurium
, and
Aerobacter aerogenes
Authors: Li S. L. , Denney R. M. , Yanofsky C.
Published: May 2006

Two different estimates were obtained for the extent of nucleotide sequence divergence in the structural genes of the tryptophan synthetase α-chains of
Escherichia coli, Salmonella typhimurium
, and
Aerobacter aerogenes
. One estimate was based on comparisons of the amino acid sequences of the respective α chains. The other was derived from measurements of the thermal stability of RNA-DNA hybrids formed with phage DNA carrying the α-chain structural gene of
E. coli
and labeled messenger RNA from the three bacterial species. Comparison of the two estimates suggests that during the course of evolution synonymous codon changes have accumulated in the α-chain-structural genes.
Metabolism of Membrane Phospholipids and Its Relation to a Novel Class of Oligosaccharides in
Escherichia coli
Authors: Golde Lambert M. G. Van , Schulman Howard , Kennedy Eugene P.
Published: May 2006

Phosphatidylethanolamine is metabolically stable in exponentially growing cells of
Escherichia coli
, whereas phosphatidylglycerol and cardiolipin (diphosphatidylglycerol), labeled by growth in the presence of
sn
-[
2
-
3
H]glycero-3-
32
P, lose their radioactivity during subsequent growth on unlabeled medium. We have found that the loss of label from the lipid fraction is accompanied by its appearance in a novel type of cell constituent of
E. coli
, a closely related group of oligosaccharides, each containing glycerol and phosphoric acid in equimolar proportions, probably derived as intact glycerophosphate units from phosphatidylglycerol and/or cardiolipin. Glucose is the sole detectable sugar. The glycerophosphate-containing oligosaccharides may be fractionated by ion-exchange chromatography into several subfractions, some of which contain succinic acid in ester linkage. Although apparently derived from membrane phospholipids, the newly discovered substances contain no fatty acids, are soluble in water, and are insoluble in organic solvents such as chloroform. They comprise about 0.5-1% of the dry weight of growing cells.
Host-Gene Control of Type-C RNA Tumor Virus Expression and Tumorigenesis in Inbred Mice
Authors: Meier Hans , Taylor Benjamin A. , Cherry Marianna , Huebner Robert J.
Published: May 2006

We analyzed the relationship of genetic factors determining the expression of endogenous type-C RNA tumor viruses and other host-gene markers to tumorigenesis. A hybridization experiment was performed with mice of strains AKR/J and C57L, the first filial (F
1
) generation hybrids, the second filial (F
2
) generation hybrids, and the backcrosses to the two parental strains. The results demonstrated a highly significant and predictable association between the expression of complete infectious virus or the viral group-specific (gs) antigen in spleens of young mice and tumorigenesis later in life. Most of the tumors were thymic leukemia and reticulum sarcoma, but other mesenchymal, as well as epithelial, tumors were also observed. Tumors occurred preferentially in gs-antigen- or virus-positive mice of all crosses; in the C57L-backcross and F
2
mice segregating for gs-antigen and virus expression, a few gs-antigen-negative mice developed reticulum cell sarcomas. At the time of their occurrence, the mice were all gs-antigen-positive, and most had virus as well.

A minor effect of the major histocompatibility locus,
H-2
, on leukemogenesis was found in the F
2
mice. Several tumor types were also found that we have never observed in the two parental strains. Our data provide the most direct biological evidence in favor of the viral oncogene theory. Thus, from the presence or absence of expression in early life of splenic gs antigen or virus, we can predict whether or not a tumor is likely to develop later in life. These findings suggest that the genome of endogenous type-C RNA viruses is the major determinant for tumorigenesis although they provide no clues about the factors responsible for the various histological types.
Synthesis of Guanosine Tetra- and Pentaphosphate Requires the Presence of a Codon-Specific, Uncharged Transfer Ribonucleic Acid in the Acceptor Site of Ribosomes
Authors: Haseltine William A. , Block Ricardo
Published: May 2006

The nucleotides ppGpp and pppGpp accumulate when wild-type, but not
rel
-
, strains of
Escherichia coli
are starved for required amino acids. These compounds are synthesized on ribosomes, in the presence of the product of the
rel
gene, from GDP and GTP; ATP is used as the phosphate donor. The signal for making these compounds is the presence of an uncharged tRNA in the ribosomal acceptor site. These compounds are not accumulated if the ribosomes are actively engaged in protein synthesis.
A Bound Form of Silicon in Glycosaminoglycans and Polyuronides
Authors: Schwarz Klaus
Published: May 2006

Silicon was found to be a constituent of certain glycosaminoglycans and polyuronides, where it occurs firmly bound to the polysaccharide matrix. 330-554 ppm of bound Si were detected in purified hyaluronic acid from umbilical cord, chondroitin 4-sulfate, dermatan sulfate, and heparan sulfate. These amounts correspond to 1 atom of Si per 50,000-85,000 molecular weight or 130-280 repeating units. 57-191 ppm occur in chondroitin 6-sulfate, heparin, and keratan sulfate-2 from cartilage, while hyaluronic acids from vitreous humor and keratan sulfate-1 from cornea were Si-free. Large amounts of bound Si are also present in pectin (2580 ppm) and alginic acid (451 ppm). The bound Si is not dialyzable, does not react with ammonium molybdate, is not liberated by autoclaving or 8 M urea, and is stable against weak alkali and acid. Strong alkali and acid hydrolyze the Si-polysaccharide bond. Free, direct-reacting, dialyzable silicate is obtained. Enzymatic hydrolysis of hyaluronic acid or pectin does not liberate silicic acid, but leads to products of low molecular weight still containing Si in bound form. It is concluded that Si is present as a silanolate, i.e., an ether (or esterlike) derivative of silicic acid, and that R
1
—O—Si—O—R
2
or R
1
—O—Si—O—Si—O—R
2
bridges play a role in the structural organization of glycosaminoglycans and polyuronides. Thus, Si may function as a biological crosslinking agent and contribute to architecture and resilience of connective tissue.
Biochemical Basis of the Resistance of Sugarcane to Eyespot Disease
Authors: Strobel Gary A.
Published: May 2006

Helminthosporoside is the host-specific toxin produced by
Helminthosporium sacchari
, the organism causing eyespot disease on sugarcane. Clones of sugarcane susceptible to the toxin posses a membrane protein that binds the toxin. Membranes of resistant clones do not bind the toxin. In this study, a binding protein from a susceptible clone was compared with its counterpart from a resistant clone. The protein from the resistant clone did not bind the toxin unless it was first treated with mild detergent. The two proteins are antigenically identical, have the same molecular weight, and each contains four subunits. They differ slightly in their electrophoretic mobility and vary with respect to four different aminoacid residues. The basis of resistance of clone H50-7209 to eyespot disease is directly associated with the structurally altered membrane-binding protein.
Evidence for a Monoclonal Origin of Human Atherosclerotic Plaques
Authors: Benditt Earl P. , Benditt John M.
Published: May 2006

The main cellular elements of atherosclerotic plaques are smooth muscle cells. Because these plaques differ from their precursors in the underlying artery wall in several ways, we have asked the question: Are human atherosclerotic plaques polyclonal or monoclonal in their origin? The X-linked glucose-6-phosphate dehydrogenase (EC 1.1.1.49) in heterozygotic females has been used to obtain an answer. 30 Plaques of different degrees of complexity and 59 samples of normal aorta and iliac artery walls from four females, 25-79 years old, were investigated. The data show that fibrous caps even of relatively large atheromatous plaques, 0.5 cm or greater in diameter, are composed of cells that produce solely or predominantly one enzyme type, whereas samples of artery wall media and intima as small as 0.1 mm
3
are regularly composed of a mixture of cell types. If plaques were a response to injury akin to a healing wound, a reaction to a growth stimulant, or formed due to an organization of a mural thrombus, they would be expected to be polyclonal. Hence, the results imply that atherosclerotic plaques in human beings arise by another mechanism. The mechanism compatible with the monoclonal nature of atherosclerotic plaques is mutation, and the likely causes are chemical mutagens or viruses.
Translation of Brome Mosaic Viral Ribonucleic Acid in a Cell-Free System Derived from Wheat Embryo
Authors: Shih D. S. , Kaesberg Paul
Published: May 2006

The four RNAs of brome mosaic virus induce substantial incorporation of amino acids into protein when used as messengers in a cell-free protein-synthesizing system derived from wheat embryo. RNA 4 is highly efficient as a monocistronic messenger for the viral coat protein. Acetate, derived from acetyl coenzyme A, is incorporated into the product made
in vitro.
Although RNA 3 also contains the coat-protein cistron, it induces synthesis mostly of a protein larger than coat protein. RNAs 1 and 2 also induce the synthesis of substantial amounts of protein other than coat protein. However, an equimolar mixture of RNAs 3 and 4 or of 1, 2, 3, and 4 induces synthesis of coat protein almost exclusively. This result suggests that the coat-protein cistron, when present as a monocistronic messenger, inhibits translation of all other viral messages.
Glia-Induced Morphological Differentiation in Neuroblastoma Cells
Authors: Monard Denis , Solomon Frank , Rentsch Magda , Gysin Reinhard
Published: May 2006

Glial cells release a factor into their culture medium that induces a high degree of morphological differentiation in neuroblastoma cells under normal growth conditions. This phenomenon is not correlated with a change in intracellular adenosine 3′:5′-cyclic monophosphate or in the rate of cell growth. Media from other cell lines tested induce less morphological differentiation or have no effect.
Further Evidence for Oncornaviruses in Human Milk: The Production of Cores
Authors: Feldman Stuart P. , Schlom J. , Spiegelman S.
Published: May 2006

Cores, or nucleoids, have been isolated from particles in human milk. The cores have a density of 1.26-1.27 g/ml and contain a 60-70S RNA in association with an RNA-instructed DNA polymerase. The data offer further evidence of similarity between human milk particles and animal RNA tumor viruses. In addition, core isolation provides a new method for detection of these particles by minimizing the difficulties generated by the presence of cell-associated debris often found in the density region (1.16-1.19 g/ml) characteristic of the intact virion. The procedures described now make available preparations of purified subviral components of a putative human RNA tumor virus.
Independent Segregation of Loci for Activation of Biologically Distinguishable RNA C-Type Viruses in Mouse Cells
Authors: Aaronson Stuart A. , Stephenson John R.
Published: May 2006

Two genetic loci for induction of RNA C-type virus in BALB/c mouse embryo cells segregate independently in backcross embryo cell lines. The viruses at these loci are shown to be biologically distinguishable. The first, described previously, codes for activation of a virus that grows preferentially in NIH Swiss embryo cells. The newly detected locus codes for activation of a virus that grows poorly, if at all, in NIH Swiss or BALB/c cells, but replicates well in a rat cell line. Its serologic properties are different from those of viruses of the two major serologic subgroups of murine leukemia virus. The present findings provide support for the hypothesis that the loci for virus induction in BALB/c cells represent genetic information for C-type viruses and that the endogenous viruses are subject to different cellular genetic controls.
Relationship of the Structure of Bacterial Lipopolysaccharides to Its Function in Mitogenesis and Adjuvanticity
Authors: Chiller Jacques M. , Skidmore Barry J. , Morrison David C. , Weigle William O.
Published: May 2006

The ability of bacterial lipopolysaccharides to induce lymphocyte mitogenesis and to act as an adjuvant of antibody formation was attributable to the lipid-A region of the molecule. Measured by induction of DNA synthesis, lipid A was mitogenic for bone marrow-derived lymphocytes obtained from spleens of congenitally athymic mice but not for thymocytes obtained from thymuses of normal mice. Adjuvanticity was demonstrated by the ability of lipid A to convert a tolerogenic regimen of antigen into one eliciting an immune response and by its ability to markedly enhance the antibody response to a weak antigen.
Control of Chondrogenesis in Limb-Bud Cell Cultures by Bromodeoxyuridine
Authors: Levitt Daniel , Doreman Albert
Published: May 2006

Initial exposure of cultured limb-bud cells (stage 23-24) to 5-bromo-2′-deoxyuridine (BrdU) irreversibly inhibits differentiation to cartilage under three different culture conditions. The inhibition of chondroitin sulfate synthesis is partially reversed by D-xylose in limb-bud cells after treatment with BrdU. The activities of four enzymes involved in chondroitin sulfate production were reduced in BrdU-treated cultures, but the magnitude of decrease was far less than the decrease in glycosaminoglycan synthesis. The slight increase in the turnover rate of sulfated glycosaminoglycans in BrdU-treated mesenchyme was not sufficient to account for the marked decrease in chondroitin sulfate content. The results suggest that BrdU treatment interferes with normal synthesis of chondroitin sulfate core protein in cultured limb-bud cells, but does not greatly diminish enzyme activities or UDP-sugar levels necessary for production of polysaccharide chains.
Nucleotide Sequences from Tryptophan Messenger RNA of
Escherichia coli
: The Sequence Corresponding to the Amino-Terminal Region of the First Polypeptide Specified by the Operon
Authors: Bronson Morley J. , Squires Craig , Yanofsky Charles
Published: May 2006

Mutants with internal deletions that terminate near the operator end of the tryptophan operon of
E. coli
were used in studies on the nucleotide sequence at the 5′ end of the messenger RNA transcribed on this operon. The findings obtained permitted identification of a sequence of 43 nucleotides corresponding to the aminoterminal 11 amino acids of anthranilate synthetase component I, the polypeptide specified by the operator-proximal structural gene of the operon. It was also shown that the translation initiation codon for this polypeptide is preceded on the messenger by a “leader” sequence of unknown function, at least 150 nucleotides in length.
Adrenal Corticosteroids Enhance Production of Type-C Virus Induced by 5-Iodo-2′-Deoxyuridine from Cultured Mouse Fibroblasts
Authors: Paran M. , Gallo R. C. , Richardson L. S. , Wu A. M.
Published: May 2006

Induction of RNA “tumor” viruses by 5-iodo-2′-deoxyuridine in mouse fibroblasts is stimulated 5- to 25-fold by glucogenic adrenal corticosteroids. Enhancement of virus production by the hormones is inhibited by low concentration of cordycepin, an inhibitor of poly(A) synthesis.
Supersensitivity and Subsensitivity of the β-Adrenergic Receptor in Pineal Gland Regulated by Catecholamine Transmitter
Authors: Deguchi Takeo , Axelrod Julius
Published: May 2006

Depletion of neural norepinephrine by reserpine treatment or by denervation resulted in a greater induction of serotonin
N
-acetyltransferase (EC 2.3.1.5) and a higher elevation of cyclic AMP in postsynaptic pineal cell to small amount of isoproterenol. This increase in responsiveness occurs rapidly within 24 hr after treatment with reserpine. Repeated administration of isoproterenol to the denervated or reserpine-treated rats not only suppressed the superinduction, but also caused a decreased response to isoproterenol in cultured pineal cells. Cultured pineal cells from denervated or reserpine-treated rats were about 10 times more responsive to small amounts of isoproterenol. The response of cultured pineal cells of rats which were repeatedly injected with isoproterenol was markedly reduced after exposure to submaximal amounts of catecholamines. The maximal increase in
N
-acetyltransferase was the same in denervated, reserpine-treated, isoproterenol-treated, and untreated pineal cells. Exposure of rats to continuous lighting (a procedure that reduces sympathetic nerve activity) resulted in a superinduction of pineal
N
-acetyltransferase by isoproterenol. These observations indicate that the responsiveness of the postsynaptic β-adrenergic receptor is conditioned by prior exposure to its agonist, norepinephrine. Decreased norepinephrine results in supersensitivity, and repeated exposure to large amounts of catecholamines causes subsensitivity (tolerance).
Malignant Lymphoma in Cottontop Marmosets after Inoculation with Epstein-Barr Virus
Authors: Shope Thomas , Dechairo Douglas , Miller George
Published: May 2006

Neoplasia resembling human malignant lymphoma, reticulum cell sarcoma type, occurred in cottontop marmosets inoculated with materials containing Epstein-Barr virus. One of four monkeys that received autologous cells transformed
in vitro
by Epstein-Barr virus developed lymphoma in mesenteric lymph nodes 7.5 months after inoculation. Three of four marmosets inoculated with cell-free Epstein-Barr virus developed lymphoma. The latent period for detectable tumor formation after addition of virus was 31-46 days. Immunosuppressive drugs given with the virus accelerated the course of disease. Nevertheless, malignant lymphoma occurred in an animal given only cell-free virus. Six of eight marmosets inoculated with the virus demonstrated antibodies to the virus. Four marmosets not exposed to the virus, including two that received immunosuppressive drugs, developed neither tumors nor antibodies to Epstein-Barr virus. Virus antigen detectable by immunofluorescence was found in 5% of cells shed from one tumor maintained in organ culture. These results imply that Epstein-Barr virus is capable of inducing malignant lymphoma in at least one primate species. Additional evidence is required before its oncogenic capacity in this host can be accepted without reservation.
Transformation of Neuraminidase-Treated Lymphocytes by Soybean Agglutinin
Authors: Novogrodsky Abraham , Katchalski Ephraim
Published: May 2006

Transformation of mouse-spleen lymphocytes in the presence of soybean agglutinin is markedly enhanced after their treatment with neuraminidase (EC 3.2.1.18). Incubation of the cells with the enzyme also facilitates their agglutination by the lectin. The soybean agglutinin-induced agglutination and transformation is inhibited specifically by
N
-acetyl-D-galactosamine. New specific binding sites for soybean agglutinin were shown to appear after neuraminidase treatment. It is postulated that the transformation of neuraminidase-treated mouse-spleen lymphocytes induced by soybean agglutinin is caused by the binding of the lectin to galactosyl residues exposed by the action of neuraminidase on the cell membrane.
Some Binding Parameters of Chromatin Acidic Proteins with High Affinity for Deoxyribonucleic Acid
Authors: Patel Gordhan L. , Thomas Terry L.
Published: May 2006

A fraction of chromatin acidic protein from rat liver, predominantly comprised of low-molecular-weight species, showed highest
in vitro
affinity for DNA when compared with other fractions of nuclear acidic protein. Maximum binding of this protein fraction was observed at physiological ionic strength of 0.14 M NaCl and DNA/protein ratio > 1. Comparison of their binding to homologous and heterologous DNAs showed partial species specificity. All molecular species of this protein fraction appear to bind to DNA.
Disulfide Bond Dihedral Angles from Raman Spectroscopy
Authors: Van Wart Harold E. , Lewis Aaron , Scheraga Harold A. , Saeva Frank D.
Published: May 2006

Raman spectra of several compounds containing the CS-SC moiety were obtained (in the solid phase) from 450-800 cm
-1
to investigate the S-S and C-S stretching behavior. The S-S stretching frequency varied linearly with the CS-SC dihedral angle (obtained from either x-ray or neutron diffraction or ultraviolet absorption) for compounds whose CC-SS dihedral angles were not very different. The ratio of the intensities of the S-S and C-S stretching bands exhibited no recognizable correlation with either the CS-SC dihedral angle or the CSS bond angle, probably because this ratio is sensitive to the crystalline environment. The linear dependence of the S-S stretching frequency on dihedral angle leads to a dihedral angle for the plant hormone, malformin A, that is in excellent agreement with that estimated from the longest wavelength CS-SC ultraviolet absorption band.
Synthesis of the Myoglobin Active Site
Authors: Chang C. K. , Traylor T. G.
Published: May 2006

A simple heme-imidazole compound, having the same geometry as the heme-imidazole complex in myoglobin, has been synthesized. This compound, ferropyrroporphyrin-
N
-[3-(1-imidazolyl)propyl]amide, reversibly binds oxygen in the solid state or when dissolved in a polystyrene film. These results suggest that the principal factors governing reversible oxygen binding are the electronic nature of the base (imidazole), neighboring-group effects of the basic group, and immobilization of the heme group.
Scanning Transmission Electron Microscopy at High Resolution
Authors: Wall J. , Langmore J. , Isaacson M. , Crewe A. V.
Published: May 2006

We have shown that a scanning transmission electron microscope with a high brightness field emission source is capable of obtaining better than 3 Å resolution using 30 to 40 keV electrons. Elastic dark field images of single atoms of uranium and mercury are shown which demonstrate this fact as determined by a modified Rayleigh criterion. Point-to-point micrograph resolution between 2.5 and 3.0 Å is found in dark field images of micro-crystallites of uranium and thorium compounds. Furthermore, adequate contrast is available to observe single atoms as light as silver.
Study of the Franck-Condon and Herzberg-Teller Approximations
Authors: Lin S. H. , Eyring H.
Published: May 2006

Using the Born-Oppenheimer parameter λ = (
m/M
)
1/4
as a perturbation parameter, we find that for allowed transitions, the zeroth order approximation of the spectral intensity gives rise to the Condon approximation, the first order vibronic coupling and anharmonic effect appear in the first order approximation of the spectral intensity, which gives us the non-Condon scheme, and only the intensity of the transitions of totally-symmetric modes with nonvanishing normal coordinate displacements is affected by the inclusion of the first order vibronic coupling and anharmonic effect. For symmetry-forbidden but vibronic-allowed transitions, the first nonvanishing term of the spectral intensity is second order with respect to λ and the B-O couplings do not appear in the calculation of the spectral intensity until the fourth order approximation with respect to λ; in this case, other high order vibronic couplings and anharmonic effect are competing with the B-O couplings.
The Identity of Glutathione
S
-Transferase B with Ligandin, a Major Binding Protein of Liver
Authors: Habig William H. , Pabst Michael J. , Fleischner Gerald , Gatmaitan Zenaida , Arias Irwin M. , Jakoby William B.
Published: May 2006

Evidence is presented that ligandin, an intracellular protein involved in the binding of such anions as bilirubin, indocyanine green, and penicillin, is identical to glutathione
S
-transferase B (EC 2.5.1.18), an enzyme catalyzing the conjugation of glutathione with such electrophiles as 1-chloro-2,4-dinitrobenzene, 1,2-dichloro-4-nitrobenzene, iodomethane, ethacrynic acid, and bromosulfophthalein. The proteins, isolated by distinct methods, have the same specificity for substrates and for ligands, react in identical fashion to antibody produced against ligandin, bear entirely similar physical characteristics and amino acid composition, and are both induced in response to phenobarbital. Indocyanine green, one of the ligands that is not effective as a substrate, was shown to competitively inhibit the conjugation reaction. It is suggested that specificity is directed toward compounds with electrophilic sites.
L
p

-multipliers for Noncompact Symmetric Spaces
Authors: Clerc J. L. , Stein E. M.
Published: May 2006

Let
G
be a real noncompact semi-simple Lie group with finite center and
K
a maximal compact sub-group. The symmetric space
M = G/K
carries a measure invariant under the action of
G
. The operators which map

L
p

(
M
) continuously into itself and commute with the action of
G
, can be easily characterized when
p
= 2 or
p
= 1. This note gives some results on “singular integrals” which map

L
p

into itself (1 <
p
< + ∞).
Characterization of Fourier Transforms of Hardy Spaces
Authors: Coifman Ronald R.
Published: May 2006

Characterizations of Fourier transforms of boundary distributions of functions in

H
p

(
R
) or

H
p

(
T
), 0 <
p
≤ 1, are given. These results are applied to obtain Fourier multiplier theorems on

H
p

.
Vitamin D: Concerning the Relationship Between Molecular Topology and Biological Function
Authors: Okamura William H. , Norman Anthony W. , Wing Richard M.
Published: May 2006

Structure-function relationships for vitamin D, its metabolites, and analogs are discussed with particular emphasis on the A-ring conformation. It is emphasized that the A-ring of these seco-steroids consists of a pair of rapidly equilibrating chair conformers. As a consequence, different chair conformations produce different orientations of substituent groups in the A-ring. It is proposed that the 1α-hydroxyl of 1α,25-dihydroxyvitamin D
3
or its geometric equivalent in analogs must occupy the equatorial, as opposed to the axial, orientation for optimization of biological activity. This proposal is discussed in relation to existing published data on structure-function relationships and the steroid hormone model of action for the biologically active form of vitamin D. This three-dimensional topological model suggests the synthesis of other vitamin D analogs.
Cholesterol as a Bioregulator in the Development and Inhibition of Leukemia
Authors: Inbar M. , Shinitzky M.
Published: May 2006

Leukemia in mice and humans is accompanied by a marked deficiency of unesterified cholesterol in the surface membrane of leukemic cells as compared to normal leukocytes. This deficiency induces a significant reduction in their membrane microviscosity. Since cholesterol in the cell surface membrane is exchangeable with cholesterol in the serum lipoproteins, concomitant to the cellular deficiency of cholesterol, the average level of cholesterol in the blood serum of leukemic patients is substantially below the average normal level. Based on these observations and the effect of membrane microviscosity on biological functions, a working hypothesis that describes the role of cholesterol in the development and inhibition of leukemia is suggested. This hypothesis can also account for the effect of cholesterol and membrane microviscosity on various other cellular activities of leukocytes.
Cobalt Induction of Hepatic Heme Oxygenase; with Evidence That Cytochrome
P
-450 Is Not Essential for This Enzyme Activity
Authors: Maines M. D. , Kappas Attallah
Published: May 2006

Treatment of rats
in vivo
with cobalt chloride stimulated heme oxidation by hepatic microsomes to levels up to 800% above controls. This treatment also caused increases in liver weight and in total microsomal protein; in contrast, marked decreases were produced in microsomal oxidation of ethylmorphine (80%), and in cytochrome
P
-450 (60-70%) and heme (30-50%) contents. Cobalt chloride treatment did not affect heme oxidation by the spleen heme oxygenase system.

The rate of heme oxidation by hepatic microsomal enzymes and the microsomal content of cytochrome
P
-450 were found to be unrelated. This conclusion was reached from studies in which microsomal heme oxygenase activity from cobalt-treated animals could be increased by 900% above control levels in the same microsomal preparation in which cytochrome
P
-450 content was decreased to spectrally unmeasurable amounts after incubation with 4 M urea. The same treatment eliminated ehtylmorphine demethylation and decreased microsomal NADPH-cytochrome
c
reductase (EC 1.6.2.4) activity by 75%.

It is concluded that (
i
) the hepatic microsomal enzyme system that oxidizes heme compounds is not the same as that which metabolizes drugs, (
ii
) cytochrome
P
-450 is not essential for the oxidation of heme by liver cells, (
iii
) there is no direct relationship between the rate of heme oxidation and the level of NADPH-cytochrome
c
reductase activity, and (
iv
) the oxidation of heme is protein-dependent and the active proteins are inducible, but are different from those involved in drug metabolism.