bluuebunny/crossref_metadata_2025 huggingface dataset:
Colicin E3: A Unique Endoribonuclease
Authors: Meyhack Bernd , Meyhack Irene , Apirion David
Published: May 2006

The question of whether or not a cellular ribonuclease is involved in the cleavage of 16S ribosomal RNA by colicin E3 was investigated. For this purpose ribosomes from strains devoid of some ribonucleases or ribosomes in which ribonucleases had been inactivated by heat or removed by extensive washings were used for the colicin reaction. Since the 16S RNA of all these different ribosomes, and even of the most extensively washed ribosomes, was cleaved by colicin E3, it is suggested that cellular ribonucleases are not involved in colicin E3 action. Thus, colicin E3 seems to be a unique endoribonuclease.
Release of Infectious Epstein-Barr Virus by Transformed Marmoset Leukocytes
Authors: Miller George , Lipman Muriel
Published: May 2006

Marmoset blood leukocytes transformed
in vitro
by Epstein-Barr virus regularly release extracellular infectious Epstein-Barr virus with high titers of transforming activity. By comparison, human umbilical cord leukocytes and adult human leukocytes transformed by Epstein-Barr virus release either no extracellular infectious virus or small amounts, irregularly.
Immunochemical Demonstration of Increased Accumulation of Tyrosine Hydroxylase Protein in Sympathetic Ganglia and Adrenal Medulla Elicited by Reserpine
Authors: Joh Tong Hyub , Geghman Cathya , Reis Donald
Published: May 2006

Chronic administration of reserpine to rats increases, in sympathetic ganglia and adrenal medulla, the activity of tyrosine hydroxylase (EC 1.14.3.x), the enzyme catalyzing the rate-limiting step in the biosynthesis of catecholamines. Immunochemical titration of the enzyme in both adrenal gland and innervated superior cervical ganglia demonstrates that enhanced enzyme activity is entirely attributable to accumulation of more specific enzyme protein and not activation of preexistent enzyme molecules.
A New Concept for Energy Coupling in Oxidative Phosphorylation Based on a Molecular Explanation of the Oxygen Exchange Reactions
Authors: Boyer Paul D. , Cross Richard L. , Momsen William
Published: May 2006

The P
i
⇄ HOH exchange reaction of oxidative phosphorylation is considerably less sensitive to uncouplers than the P
i
⇄ ATP and ATP ⇄ HOH exchanges. The uncoupler-insensitive P
i
⇄ HOH exchange is inhibited by oligomycin. These results and other considerations suggest that the relatively rapid and uncoupler-insensitive P
i
⇄ HOH exchange results from a rapid, reversible hydrolysis of a tightly but noncovalently bound ATP at a catalytic site for oxidative phosphorylation, concomitant with interchange of medium and bound P
i
. Such tightly bound ATP has been demonstrated in submitochondrial particles in the presence of uncouplers, P
i
, and ADP, by rapid labeling from
32
P
i
under essentially steady-state phosphorylation conditions. These results lead to the working hypothesis that in oxidative phosphorylation energy from electron transport causes release of preformed ATP from the catalytic site. This release could logically involve energy-requiring protein conformational change.
Linear Association Between Cellular DNA and Epstein-Barr Virus DNA in a Human Lymphoblastoid Cell Line
Authors: Adams Alice , Lindahl Tomas , Klein George
Published: May 2006

High-molecular-weight DNA from cell line Raji (derived from Burkitt's lymphoma), which contains 50-60 copies of Epstein-Barr virus DNA per cell, was fractionated in neutral solution by several cycles of CsCl gradient centrifugation in fixed-angle rotors. Under the fractionation conditions used, intact Epstein-Barr virus DNA from virus particles can be separated from the less-dense cellular DNA. In contrast, a large proportion of the intrinsic Epstein-Barr virus DNA component of Raji cells remains associated with cellular DNA, as determined by nucleic acid hybridization. This interaction, which is resistant to Pronase and phenol treatment, is not the result of aggregation. When the molecular weight of Raji DNA is reduced by hydrodynamic shear, the amount of virus DNA associated with cell DNA decreases. However, some virus DNA still remains bound to fragments of cellular DNA after shearing. The association is completely destroyed in alkaline solution. Molecular weight analysis of Raji DNA after denaturation showed that the alkali-induced release of Epstein-Barr virus DNA was specific and not the result of random single-strand breaks. These data indicate that Epstein-Barr virus DNA is linearly integrated into Raji cell DNA by alkali-labile bonds.
Biosynthesis of the Juvenile Hormones of
Manduca sexta:
Labeling Pattern from Mevalonate, Propionate, and Acetate
Authors: Schooley David A. , Judy Kenneth J. , Bergot B. John , Hall M. Sharon , Siddall John B.
Published: May 2006

Using organ culture, high-resolution liquid chromatography, and microchemical techniques, we demonstrated the efficient incorporation
in vitro
of several radiolabeled precursors into the two juvenile hormones of
Manduca sexta
. JH II, a homosesquiterpene hormone, reported from
M. sexta
as well as several other insects, incorporates radiolabel from acetate, mevalonate, and propionate. JH III, a sesquiterpene hormone recently reported as a natural product of
M. sexta
, incorporates label from acetate and mevalonate, but not from propionate. Based on the position of the labeled atoms in the precursors and upon the position of incorporation obtained from label-distribution data, a scheme for juvenile hormone biosynthesis is advanced.
Size and Structure of Yeast Chromosomal DNA
Authors: Petes Thomas D. , Byers Breck , Fangman Walton L.
Published: May 2006

Electron microscopic analysis indicates that yeast nuclear DNA can be isolated as linear molecules ranging in size from 50 μm (1.2 × 10
8
daltons) to 355 μm (8.4 × 10
8
daltons). Analysis indicates the data is consistent with the hypothesis that each yeast chromosome contains a single, linear DNA duplex. Mitochondrial DNA molecules have a contour length of 21 ± 2 μm and are mostly linear.
Herpes Simplex and Herpes Genitalis Viruses in Etiology of Some Human Cancers
Authors: Sabin Albert B. , Tarro Giulio
Published: May 2006

The results of complement fixation tests on 202 sera from people without cancer and from patients with cancer in 29 different areas of the body indicated that only those with nine varieties of
advanced
cancer (lip, mouth, oropharynx, nasopharynx, kidney, urinary bladder, prostate, cervix uteri, and vulva-all of 56 tested) gave positive specific reactions with nonvirion antigens induced by the DNA herpes simplex (HSV 1) and herpes genitalis (HSV 2) viruses. None of 57 people without cancer (including 10 with current and 18 with recurrent HSV 1 or HSV 2 infections), none of 81 patients with 20 other varieties of
advanced
cancer (gum, tongue, tonsil, salivary gland, accessory sinus, epiglottis, lung-bronchus, stomach, colon, breast, corpus uteri, ovary, testis, liver, thyroid, Wilms' embryonal kidney, melanoma, Hodgkin's disease, acute lymphocytic leukemia, and acute myelocytic leukemia), and none of four women with
early
malignant changes in the cervix uteri gave positive results. The seven patients with advanced cancer of the lip or oropharynx gave positive reactions with HSV 1
but not
with HSV 2 nonvirion antigens (compatible with involvement of only HSV 1), all of the 13 women with
advanced
cancer of the cervix uteri and the one woman with advanced cancer of the vulva gave positive reactions with
both
HSV 1
and
HSV 2 nonvirion antigens (compatible with involvement of only HSV 2), while among the 35 other positive patients only two (one with cancer of the kidney and one with cancer of the bladder) reacted with HSV 1 and not at all with HSV 2 nonvirion antigens. Positive sera failed to react with cells harvested at different times after high-multiplicity infection with the DNA vaccinia virus. Massive absorption of positive sera with trypsinized, uninfected human embryonic kidney cells
failed
to remove, or lower the titer of, the HSV 1 and HSV 2 nonvirion antibodies.

All of these data taken together are interpreted as indicating that HSV 1 and HSV 2 play an etiologic role in certain human cancers, because they provide the kind of evidence by which
virus-free experimental
cancers can be proved to have been originally induced by such DNA viruses as polyoma, Simian Virus 40, or certain types of adenovirus.
Patterns of Spatiotemporal Organization in an Allosteric Enzyme Model
Authors: Goldbeter A.
Published: May 2006

The behavior of a model for an allosteric enzyme oscillator activated by the reaction product is analyzed in the presence of diffusion. When the concentrations of the chemicals are fixed at the boundaries, dynamic dissipative structures are shown to arise in the form of propagating concentration waves. The model is applied to the phosphofructokinase reaction and suggests that a spatiotemporal organization may originate at a macroscopic (supracellular) level from the glycolytic system.
Antibodies with Multiple Binding Functions. Induction of Single Immunoglobin Species by Structurally Dissimilar Haptens
Authors: Varga Janos M. , Konigsberg W. H. , Richards Frank F.
Published: May 2006

Anti-hapten sera prepared in rabbits contain individual immunoglobulin species capable of binding several pairs of structurally diverse haptens A and B. (A = inosine, uridine, menadione, vitamin K
1
, ribonuclease; B = 2,4-dinitrophenyl). In antisera against hapten A subjected to isoelectric focusing, there are many anti-A immunoglobulin species, but only a small proportion of these bind both A and B. When rabbits are primed with haptens A coupled to a carrier and then challenged with hapten B-carrier complex, there is an early restricted response of those species that bind both A and B. Later, immunoglobulins appear which bind B, but not A. These results suggest that multiple-binding antibodies exist in antisera against hapten and that such multiple binding is functional; i.e., that when two diverse haptens A and B bind to an immunoglobulin, both haptens may stimulate the cell-surface receptor to induce production of this immunoglobulin. Such phenomena may also provide a molecular basis for maturation of the immune response.
Altered Growth Behavior of Malignant Cells Associated with Changes in Externally Labeled Glycoprotein and Glycolipid
Authors: Gahmberg Carl Gustav , Hakomori Sen-Itiroh
Published: May 2006

By use of galactose oxidase (EC 1.1.3.9), followed by reduction with tritiated sodium borohydride, the surface structures of transformed 3T3 and NIL cells, under ordinary growth conditions, were characterized by (
i
) deletion of the normally existing glycoprotein label and (
ii
) appearance or increase of a new glycoprotein label. NIL cells had a galactoprotein label with molecular weight 200,000 that was deleted in NIL cells transformed by polyoma virus. 3T3 cells had a glycoprotein label with molecular weight of 30,000 that was lost after transformation. Glycoproteins of transformed 3T3 cells, with molecular weight 105,000, and those of transformed NIL cells, with molecular weight 85,000, were not labeled in normal confluent cells, but became labeled after trypsin treatment. The label in glycolipids was quantitatively different in normal and transformed cells. The labeling pattern in glycoprotein and glycolipids of transformed NIL and 3T3 cells became similar to that of nontransformed cells when contact responses of transformed cells became conspicuous when cells were cultured in the presence of dextran sulfate or dibutyryl cyclic adenosine monophosphate, or in medium in which glucose was replaced with galactose.
Studies on Purified Eel Acetylcholine Receptor and Anti-Acetylcholine Receptor Antibody
Authors: Patrick Jim , Lindstrom Jon , Culp Bill , Mcmillan Jerri
Published: May 2006

Rabbit antiserum against purified
Electrophorus electricus
acetylcholine receptor is studied using an immunoprecipitin assay to measure either antibody titer or concentration of toxin-binding sites in solubilized receptor preparations. This antiserum, unlike control serum, blocks the electrophysiological response of the electroplax to carbamylcholine. Toxin (α-neurotoxin,
Naja naja
) and several cholinergic ligands produce partial inhibition of the reaction of antiserum with purified acetylcholine receptor. Evidence is presented that some of the toxin-binding sites on receptor, purified by affinity chromatography on toxin-agarose conjugates, are occluded by toxin. In addition, evidence is presented that antireceptor antiserum will cause precipitation of more toxin-binding sites present in an initial extract than in purified receptor preparations.
Reticulocyte RNA-Dependent RNA Polymerase
Authors: Downey Kathleen M. , Byrnes John J. , Jurmark Bonnie S. , So Antero G.
Published: May 2006

A cytoplasmic, microsomal bound RNA-dependent RNA polymerase has been purified 2500-fold from rabbit reticulocyte lysates. The synthesis of RNA with the purified enzyme is absolutely dependent on the addition of an RNA template. The best template is hemoglobin messenger RNA, while bacteriophage RNA and poly(A,G) are less active, and DNA is completely inactive as a template. With poly(A,G) as a template, only UTP and CTP are incorporated into polynucleotide chains, indicating that the RNA polymerase is an RNA replicase and not a terminal transferase. With messenger RNA as a template, all four ribonucleoside triphosphates are required for maximal activity. The RNA-dependent RNA polymerase reaction is extremely sensitive to low concentrations of heme, rifamycin AF/013, and ribonuclease and resistant to actinomycin D and DNase. The discovery of RNA-directed RNA synthesis in reticulocytes offers an additional site for control of gene expression in mammalian cells and provides a possible mechanism for amplification of the expression of specific genes.
Thyroid Hormone Action in Cell Culture: Demonstration of Nuclear Receptors in Intact Cells and Isolated Nuclei
Authors: Samuels Herbert H. , Tsai Jir S.
Published: May 2006

Triiodothyronine and thyroxine induce a 3-fold increase in the rate of growth of GH
1
cells in culture. To study further the action of these hormones, we examined the binding of [
125
I]triiodothyronine and purified [
125
I]thyroxine to cellular fractions after incubation with intact cells in serum-free medium. High-affinity, low-capacity binding sites for the hormones were demonstrated in nuclear but not in mitochondrial or cytosol fractions. Chromatographic analysis of the bound nuclear radioactivity from cells incubated with [
125
I]thyroxine demonstrated 97% thyroxine, 1% iodide, and 1% triiodothyronine. Apparent equilibrium dissociation constants, determined by Scatchard analysis, were 29 pM for triidothyronine and 260 pM for thyroxine. The maximal binding capacity was identical for both hormones, with about 5000 sites per cell nucleus. [
125
I]Thyroxine binding was competitively inhibited by triiodothyronine. These data suggest that triiodothyronine and thyroxine interact with identical nuclear receptors, and that conversion of thyroxine to triiodothyronine may not be a prerequisite for biologic activity. Similar high-affinity, low-capacity nuclear binding sites were also demonstrated by incubation of [
125
I]triidothyronine directly with isolated nuclei. Incubation of cells with increasing concentrations of nonradioactive triidothyronine results in a subsequent increase in binding when [
125
I]triiodothyronine is then incubated directly with isolated nuclei. This result suggests that nuclear receptors are not fixed, but increase after exposure of intact cells to hormone. This increase in nuclear receptor content may result from the transfer of an unstable cytosol receptor to the nucleus.
Ribonucleic Acid Components of Murine Sarcoma and Leukemia Viruses
Authors: Maisel J. , Klement V. , Lai M. M-C. , Ostertag W. , Duesberg P.
Published: May 2006

Defective Kirsten murine sarcoma virus was present as leukemia virus pseudotype [Ki-MSV(MLV)] in a 10- to 100-fold excess over its helper, Kirsten murine leukemia virus (Ki-MLV), when the two viruses were propagated in an NRK rat cell line. The
s
ω,20
of the fastsedimenting RNA complex of Ki-MLV and of Ki-MSV-(MLV) was 62 S and 55 S, respectively. Gel electrophoresis in buffered aqueous or formamide solution of the dissociated 62S RNA complex of Ki-MLV showed a single major peak of molecular weight about 2.5 × 10
6
. Dissociated 55S RNA of Ki-MSV(MLV) was resolved into a major component with a higher electrophoretic mobility than that of Ki-MLV RNA and molecular weight about 2.3 × 10
6
. Occasionally, a minor component with the same electrophoretic mobility as Ki-MLV RNA was observed in Ki-MSV(MLV) RNA; it is thought to be the RNA of Ki-MLV present as helper virus in our stocks of Ki-MSV(MLV). The RNA of an endogenous rat C-type RNA virus was electrophoretically different from both Ki-MLV RNA and Ki-MSV(MLV) RNAs. Oligonucleotide fingerprinting of the RNAs digested with RNase T1 indicated that the RNAs of Ki-MSV(MLV) and Ki-MLV are different. However, the extent of the difference between the two RNAs could not be estimated by this method.

The heat-dissociated 50-70S RNAs of two other defective murine sarcoma-leukemia viruses; Harvey-MSV(MLV) and Moloney-MSV(MLV) and of defective spleen-focus-forming Friend virus were resolved electrophoretically into two components. The larger components had the same electrophoretic mobility as the RNA of Ki-MLV or Moloney MLV. The smaller were not present in leukemia virus. It is suggested that the small RNA components of the two murine viruses and of Friend virus represent specific genetic information of these replication-defective transforming viruses.

Possible relationships between the RNAs of murine leukemia viruses and replication-defective murine sarcoma and Friend viruses are discussed.
Global Models of Growth and Competition
Authors: Gilpin Michael E. , Ayala Francisco J.
Published: May 2006

Very precise data on the dynamics of a competitive system of two species of
Drosophila
have been obtained. By a curvilinear regression approach, analytical models of competition have been fitted. By statistical and biological criteria of simplicity, reality, generality, and accuracy, the best of these models has been chosen. This model represents an extension of the Lotka-Volterra model of competition; it adds a fourth parameter that controls the degree of nonlinearity in intraspecific growth regulation. It represents a similar extension of the logistic model of population growth.
Nucleotide Modification
In Vitro
of the Precursor of Transfer RNA
Tyr
of
Escherichia coli
Authors: Schaefer K. P. , Altman S. , Söll D.
Published: May 2006

Certain nucleotides in precursor RNA of tRNA
Tyr
of
Escherichia coli
were modified
in vitro
with a preparation of partially purified
E. coli
enzyme containing ribothymidine- and pseudouridine-forming activity. The only nucleotides modified
in vitro
are the same as those found modified in mature tRNA. The best substrate for these modifying enzymes is the RNase P cleavage product of the precursor RNA, which contains the mature tRNA sequence. Of the two pseudouridines found in mature tRNA, one (in the TΨC sequence) can be formed in intact precursor RNA. The other (in the anticodon stem) can only be formed in the cleaved precursor RNA. The presence of modified nucleotides in the precursor RNA does not enhance its rate of cleavage by RNase P.
Changes in Membrane Structure Associated with Cell Contact
Authors: Scott Robert E. , Furcht Leo T. , Kersey John H.
Published: May 2006

Ultrastructural analysis of 3T3 fibroblasts by freeze-cleavage has demonstrated significant changes in cell-membrane structure associated with cell-to-cell contact and malignant transformation. These changes consist of a rearrangement and redistribution of intramembranous particles on the membrane fracture faces exposed by freeze-cleavage. The results show that noncontacted 3T3 cells in low density contain randomly distributed intramembranous particles. With the development of cell-to-cell contacts during the logarithmic phase of growth however, a pronounced aggregation of intramembranous particles is seen. A direct correlation between the degree of cell contact and the percentage of cells showing intramembranous-particle aggregation has been established. By contrast, transformed SV3T3 and SP3T3 cells show no evidence of intramembranous-particle aggregation even at cell densities where cell-to-cell contact is extensive. In view of recent reports that intramembranous particles represent foci of interaction between certain intrinsic membrane proteins and lipids, we propose that cell-to-cell contact of nontransformed 3T3 cells may initiate a change in the distribution of intrinsic membrane proteins associated with intramembranous particles and that these changes may influence control of cell proliferation.
Molecular Basis of the Biological Function of Molybdenum. The Relationship between Sulfite Oxidase and the Acute Toxicity of Bisulfite and SO
2
Authors: Cohen Harvey J. , Drew Robert T. , Johnson Jean L. , Rajagopalan K. V.
Published: May 2006

The administration of tungsten to rats maintained on a low molybdenum diet resulted in a dose- and time-dependent loss of sulfite oxidase (EC 1.8.3.1) and xanthine oxidase (EC 1.2.3.2) activities and hepatic molybdenum. These tungsten-treated animals appeared healthy, but were more susceptible to bisulfite toxicity. The median lethal dose for intraperitoneal bisulfite was found to be 181 mg of NaHSO
3
per kg for the animals deficient in sulfite oxidase, compared to 473 mg/kg for normal rats.

The survival time of rats exposed to SO
2
at concentrations of 590 ppm and higher was seen to be inversely related to the level of SO
2
. At 590 ppm and 925 ppm, control animals displayed symptoms of severe respiratory toxicity before death. At 2350 ppm of SO
2
, death was preceded by seizures and prostration, symptoms observed with the systemic toxicity of injected bisulfite. At 590 ppm, animals deficient in sulfite oxidase were indistinguishable from control animals. However, at 925 ppm and 2350 ppm, the deficient animals displayed symptoms of systemic toxicity and had much shorter survival times. It is concluded that sulfite oxidase is instrumental in counteracting the toxic systemic effects of bisulfite, either injected or derived from respired SO
2
. Respiratory death probably results from the toxicity of gaseous SO
2
before absorption as bisulfite and cannot be alleviated by sulfite oxidase. Sulfite oxidase does not appear to be inducible by either bisulfite or SO
2
.
Activation of Human Complement by Human Lymphoid Cells Sensitized with Histocompatibility Alloantisera
Authors: Ferrone S. , Cooper N. R. , Pellegrino M. A. , Reisfeld R. A.
Published: May 2006

Cultured human lymphoid cells sensitized with human histocompatibility (HL-A) antibodies were able to activate the human complement system
in vitro
. Some HL-A alloantisera selectively activated the alternate complement pathway while other antisera activated only the classical pathway. A third group of alloantisera was equally able to initiate complement action by way of either pathway. The mechanism of complement activation did not correlate with the HL-A antigen present on the cells or the HL-A specificity of the alloantisera, indicating that the antigenic determinants or distribution on the cell surface play on direct role in selecting the pathway of activation. In this completely homologous system the alternate pathway was found to have the same cytolytic potential as the classical pathway. Thus, an altered or damaged membrane is not a prerequisite for the production of cytolytic damage by the alternate pathway. A complete understanding of the mechanism of interaction of membrane bound antigens and antibodies with the complement system may provide a versatile tool for the investigation of membrane antigen expression.
The Purification of Choline Acetyltransferase of Squid-Head Ganglia
Authors: Husain S. S. , Mautner Henry G.
Published: May 2006

Choline acetyltransferase (EC 2.3.1.6) isolated from the head ganglia of squid could be purified by use of mercurial-Sepharose columns as well as Sepharose columns to which the enzyme inhibitor
p
-(
m
-bromophenyl)vinyl pyridinium had been attached. These columns, in conjunction with 30-55% ammonium sulfate precipitation, 40-30% ammonium sulfate extraction, chromatography on sulfopropyl-Sephadex and on cellulose phosphate and hydroxylapatite columns, led to the isolation of three factions of choline acetyltransferase ranging in activity from 1000 to 4000 μmole/mg of protein/per hr. Polyacrylamide gel electrophoresis suggests that two of these fractions are homogeneous. The squid choline acetyltransferase is different from the mammalian-brain enzymes in having a larger molecular weight under the conditions used and in being relatively poorly inhibited by styryl pyridinium compounds.
Reverse Transcription by
Escherichia coli
DNA Polymerase I
Authors: Karkas John D.
Published: May 2006

E. coli
DNA polymerase I (EC 2.7.7.7) can engage in either DNA- or RNA-directed DNA synthesis with hybrid templates. The choice of the strand to be transcribed depends primarily on the relative lengths of the two strands of the hybrid, the longer strand serving as the template and the shorter as the primer. If a polynucleotide is reduced in size by exposure to an endonuclease before being hybridized to the complementary strand, the template efficiency of the latter increases several-fold. Under properly selected conditions, highly efficient reverse transcription of the all-ribonucleotide template-primers poly(A)·oligo(U), poly(C)·oligo(I), and poly(I)·oligo(C) can be achieved. “f1 RNA,” the RNA strand of an f1 DNA·RNA hybrid, can also serve as template for reverse transcription either after “nicking” of the hybrid with DNase, or after separation from the DNA strand and priming by DNase-treated f1 DNA.
The Binding of Riboflavin-5′-Phosphate in a Flavoprotein: Flavodoxin at 2.0-Å Resolution
Authors: Watenpaugh K. D. , Sieker L. C. , Jensen L. H.
Published: May 2006

The crystal structure of the oxidized form of flavodoxin from
Desulfovibrio vulgaris
has been studied at 2.0-Å resolution, and a detailed description of the region around the flavin mononucleotide binding site is now available. The flavin is between a tyrosine group, roughly parallel to it on one side, and a tryptophan, about 45° from being parallel, on the other side. The two carbonyl groups and two nitrogen atoms of the flavin are hydrogen bonded to the peptide chain of the protein, while the two methyl groups are exposed at the surface of the protein. The phosphate group of the flavin mononucleotide is inside the protein and extensively hydrogen bonded to it. The ribityl group is hydrogen bonded both to the protein and to water on the surface of the protein.
Surface Changes in Temperature-Sensitive Simian Virus 40-Transformed Cells
Authors: Noonan K. D. , Renger H. C. , Basilico C. , Burger M. M.
Published: May 2006

A binding assay that shows consistent differences in the amounts of tritium-labeled concanavalin A that bind to normal and virally transformed cells was used to study the kinetic changes of cell surface in SV40-transformed 3T3 cells that express the transformed phenotype in a temperature-sensitive manner (tsSV3T3 cells). The increase in concanavalin A binding, which paralleled the appearance of the characteristics of transformed cells, was dependent on the synthesis of cellular DNA. In agreement with the results of binding studies, exponentially growing tsSV3T3 cells agglutinated at much lower lectin titers (concanavalin A as well as wheat-germ agglutinin) at 32° than at 39°.
Effect of Environmental pH on Rescue of Simian Virus 40
Authors: Calothy G. , Croce C. M. , Defendi V. , Koprowski H. , Eagle H.
Published: May 2006

Rescue of SV40 virus after Sendai virus-mediated fusion of transformed mouse or hamster cell lines with permissive monkey cells was strikingly dependent on pH in the range 6.4-8.8, with a maximum at pH 8.4. The titer of virus recovered at pH 8.4 was 2 logs higher than that at pH 7.6, and 4 logs higher than that at pH 6.4. The pH-sensitive step was neither the number of heterokaryocytes formed, which was essentially the same at pH 7.6 and 8.4, nor the degree of SV40 replication in the monkey cells, which was also unaffected by pH variation in the range 7.2-8.4.
Purification of Hodgkin's Disease Tumor-Associated Antigens
Authors: Katz David H. , Order Stanley E. , Graves Mary , Benacerraf Baruj
Published: May 2006

Two antigens that exist in high frequency in tumor tissues of patients with Hodgkin's disease have been obtained in relatively concentrated form. Extracts of Hodgkin's spleen tumor tissue, when subjected to chromatography on Sephadex G-200, separate into three major protein peaks of which only the first (peak I) possesses the predominant antigenic activities associated with the disease. Antigenic analysis performed with hyperimmune rabbit antisera obtained after repeated immunizations with peak I proteins demonstrated that this fraction contained both F and S antigens associated with Hodgkin's disease and small contaminant amounts of an antigen associated with normal lymphocytes. The tissue distribution patterns of the Hodgkin's disease tumor-associated antigens suggest that they both originate in lymphoid tissues and that the F antigen may represent a product of reactive lymphocytes while the S antigen may be a dedifferentiation antigen expressed in very immature lymphocytes.
Evidence for 30-40S RNA as Precursor of the 60-70S RNA of Rous Sarcoma Virus
Authors: Canaani E. , Helm K. V. D. , Duesberg P.
Published: May 2006

Rous sarcoma virus harvested from cells at intervals of 3 min has the same density, sedimentation coefficient, and DNA polymerase as virus harvested at hourly intervals. The RNA of the Prague strain-C consists of a minor class of 60-70S RNA, a major class 30-40S RNA, and a 4-12S class of RNA present at variable concentration. The RNA of the Schmidt-Ruppin strain-A contains more 60-70S than 30-40S RNA. Upon incubation of virus harvested at 3-min intervals at 40° in cell growth medium or Tris-saline, most of the 30-40S RNA is converted to 60-70S RNA.

The electrophoretic mobility of the 30-40S RNA of the Rous virus harvested at 3-min intervals is lower than that of the 30-40S subunits of completely dissociated 60-70S RNA; after heating, their mobilities are identical. Heating also releases some small RNAs from 30-40S RNA of virus harvested at 3-min intervals, but five times more 4S RNA is released if the 30-40S RNA is allowed to convert to 60-70S in the virus. The template activity for Rous virus DNA polymerase of the 30-40S RNA of Rous virus harvested at 3-min intervals is about five times lower than that of 60-70S RNA. It is suggested that association of 30-40S RNAs with some RNAs of the 4-12S class may take place simultaneously with their conversion to 60-70S RNA.
Structure and Development of Neuronal Connections in Isogenic Organisms: Cellular Interactions in the Development of the Optic Lamina of
Daphnia
Authors: Lopresti V. , Macagno E. R. , Levinthal C.
Published: May 2006

Some details of the growth and initial cellular interactions of optic nerve axons were examined in a parthenogenetic clone of
Daphnia magna
. Results are summarized as follows: (
i
) the final structure of the optic lamina is dependent upon interactions between growing optic nerve fibers and optic lamina neuroblasts closest to the midplane of the animal, which trigger the morphological differentiation of the neuroblasts; the specificity of connections is achieved by well-defined sequences of cell migration in the ganglion; (
ii
) only one of the eight optic nerve axons growing back from each ommatidium in the eye possesses a structure similar to the growth cones seen on termini of nerve fibers growing
in vitro;
and (
iii
) undifferentiated neuroblasts in the ganglion react to surface contact by this “lead axon” by enveloping the axon in a glial-like relationship.
Three Adjacent Transfer RNA Genes in
Escherichia coli
Authors: Squires Craig , Konrad Bruce , Kirschbaum Joel , Carbon John
Published: May 2006

A defective ϕ80 transducing phage has been isolated that carries a small section of the
E. coli
chromosome from the region near
argH
(77 min). This phage contains three
E. coli
tRNA genes, termed

glyTsu
+
36
, tyrT

, and
thrT
. These genes specify the structures of tRNA
2
Gly
(su
+
36
) tRNA
2
Tyr
, and tRNA
3
Thr
, respectively. Induction of a single lysogen bearing this phage brings about selective synthesis and amplification of only these three tRNAs.
Illicit Transport: The Oligopeptide Permease
Authors: Ames Bruce N. , Ames Giovanna Ferro-Luzzi , Young Janis Dillaha , Tsuchiya Dorinne , Lecocq Jean
Published: May 2006

The oligopeptide permease of
Escherichia coli
has been characterized by Payne, Gilvarg, and their colleagues. We have confirmed its existence in
Salmonella typhimurium
, and have isolated a series of mutants lacking the permease. We use this transport system for smuggling a histidine biosynthetic intermediate, histidinol phosphate ester, into the bacteria as its glycylglycyl derivative, Gly-Gly-histidinol phosphate. Free histidinol phosphate ester is not transported into
Salmonella
. Several amino-acid analogues are shown to be much more inhibitory to
Salmonella
when presented to the bacteria in the form of tripeptides than as the free amino acids. The implications of this work for practical purposes are discussed. The synthesis of Gly-Gly-histidinol phosphate is described.
Detection of Hepatic Phenylalanine 4-Hydroxylase in Classical Phenylketonuria
Authors: Friedman Paul A. , Fisher Daniel B. , Kang Ellen S. , Kaufman Seymour
Published: May 2006

An extract from a liver biopsy of a patient with classical phenylketonuria contains phenylalanine 4-hydroxylase (EC 1.14.3.1) with a specific activity 0.27% of the normal activity of the hydroxylase. This enzyme from a patient with phenylketonuria is a structurally altered form of phenylalanine 4-hydroxylase that probably results from a mutation in the gene coding for the hydroxylase.
Nuclear Magnetic Resonance Shift Reagents: Abnormal
13
C Shifts Produced by Complexation of Lanthanide Chelates with Saturated Amines and
n
-Butyl Isocyanide
Authors: Marzin Claude , Leibfritz Dieter , Hawkes Geoffrey E. , Roberts John D.
Published: May 2006

Lanthanide-induced shfits of
13
C nuclear magnetic resonances are reported for several amines and
n
-butyl isocyanide. Contact contributions to such shifts, especially of β carbons, are clearly important for the chelates of Eu
+3
and Pr
+3
. The importance of contact terms is shown to change in a rather predictable manner with the structure of the amine.
A New Complement-Mediated Cytolytic Mechanism—the C1-Bypass Activation Pathway
Authors: May Joseph E. , Frank Michael M.
Published: May 2006

A new cytolytic pathway is described whereby cells sensitized with cytotoxic antibody can be specifically lysed in the complete absence of intact, classical complement pathway function. Evaluation of this model with sera deficient in the 4th (C4), 2nd (C2), and 6th (C6) components of complement has revealed that this new lytic mechanism, termed the C1-bypass activation pathway, is initiated by the antibody-mediated activation of C1. Utilizing components of the previously described alternate complement pathway, this pathway bypasses C4 and C2 to activate the third to ninth components of complement (C3-9) with induction of membrane damage.
Occlusion of Brain Capillaries by Endothelial Swelling in Mycoplasma Infections
Authors: Manuelidis Elias E. , Thomas Lewis
Published: May 2006

Occlusion of cerebral capillaries due to acute swelling of the endothelial cells has been demonstrated in the brains of turkeys with encephalopathy caused by
Mycoplasma gallisepticum
(S-6 strain) infection. Similar capillary lesions were seen in rats with rolling disease, caused by
M. neurolyticum
toxin. Such lesions may be the basis of ischemic necrosis of the brain.
Initiation and Continuation of DNA Replication Are Not Associated with the Nuclear Envelope in Mammalian Cells
Authors: Wise Gary E. , Prescott D. M.
Published: May 2006

For determination of whether DNA replication is initiated at the nuclear envelope, synchronized Chinese hamster ovary cells labeled with [
3
H]thymidine were examined by electron microscope radioautography. The cells were synchronized initially by mitotic shake-off and held at the G
1
-S border by 5-fluorodeoxyuridine plus amethopterin. Cells were fixed at 1, 5, 10, and 30 min after the inhibitors were counteracted with [
3
H]thymidine. Radioautographic silver grains in each case were present over the more central parts of nuclei and were generally absent from the region of the nuclear envelope. We conclude that neither initiation nor continuation of DNA replication is associated with the nuclear envelope.
An Attempt at an Integral Interpretation of Nerve Excitability
Authors: Neumann Eberhard , Nachmansohn David , Katchalsky Aharon
Published: May 2006

A qualitatively consistent integral interpretation of biochemical, electrophysiological, and biophysical data on nerve activity is given in terms of a basic excitation unit. This operational term models a dynamically coupled assembly of membrane components accounting for graded and all-or-none responses upon stimulation. The analysis contains a series of suggestions linking controversial interpretations and is aimed at stimulation of experimental studies providing the basis for a quantitative integral theory of nerve excitation.
Relaxation Spectra of Potassium Channel Noise from Squid Axon Membranes
Authors: Fishman Harvey M.
Published: May 2006

Power density spectra of electrical fluctuations in potential and current (during voltage clamp) in the steady state, measured from electrically isolated patches of squid axon membrane, contain a noise component that is of the form [1 + (
f
/

f
c

)
2
]
-1
. For potential and temperature changes

f
c

= (2πτ
n
)
-1
, where τ
n
is the Hodgkin-Huxley relaxation time for the potassium channel. These and other data strongly suggest that this noise is due to the potassium ion passage process in the membrane. Furthermore, by comparison of the values of

f
c

from relaxation spectra of membrane channel noise with those from calculated (Hodgkin-Huxley equations) power spectra, it is possible to relate and compare channel models that previously could only be applied to macroscopic potassium conductance data. An initial result of this comparison suggests that a two-state (open-closed) conductance model, which is based upon a literal interpretation of the Hodgkin-Huxley equations, is not likely to be correct.
Acetylcholine Receptor and Ion Conductance Modulator Sites at the Murine Neuromuscular Junction: Evidence from Specific Toxin Reactions
Authors: Albuquerque Edson X. , Barnard Eric A. , Chiu Tieh H. , Lapa Antonio J. , Dolly J. Oliver , Jansson Sten-Erik , Daly John , Witkop Bernhard
Published: May 2006

The perhydro derivative of histrionicotoxin reversibly blocks the excitatory ionic transduction system in the synaptic and sarcolemmal membranes of mammalian skeletal muscle cells. The efficacy of perhydrohistrionicotoxin as an antagonist at the post-synaptic membrane is increased by the transient presence of acetylcholine in the endplate of innervated muscles and at extrajunctional receptors in denervated muscles. α-Bungarotoxin and [
3
H]monoacetyl-α-bungarotoxin block the endplate acetylcholine receptors, each binding to the same extent. The effect of bungarotoxin is partially reversible. These electrophysiological results, together with the effects of perhydrohistrionicotoxin and/or
d
-tubocurarine on the binding of [
3
H]monoacetyl-α-bungarotoxin at endplates of murine diaphragm muscle and on the bungarotoxin-elicited irreversible blockade of neuromuscular transmission, suggest that at least two types of sites participate in the synaptic excitation by acetylcholine. One site, competitively blocked by bungarotoxin and by curare, is presumably the acetylcholine receptor. Binding of bungarotoxin at this site is responsible for an irreversible blockade of neuromuscular transmission. The second site, competitively blocked by bungarotoxin and perhydrohistrionicotoxin, is proposed to be part of the cholinergic ion conductance modulator. Binding of bungarotoxin to this site does not result in an irreversible blockade.
Transformation of Chick-Embryo Fibroblasts by Wild-Type and Temperature-Sensitive Rous Sarcoma Virus Alters Adenylate Cyclase Activity
Authors: Anderson Wayne B. , Johnson George S. , Pastan Ira
Published: May 2006

The activity of the enzyme adenylate cyclase, a component of the plasma membrane, has been determined in chick-embryo fibroblasts and in cells transformed by either Bryan high-titer strain of Rous sarcoma virus (RSV-BH) or a temperature-sensitive mutant of this virus (RSV-BH-Ta). Adenylate cyclase activity is reduced in cells transformed by the wild-type virus and also by the temperature-sensitive mutant when the cells are grown at the permissive temperature (37°). Transformation results in an altered affinity (

K
m

) for the substrate (Mg ATP). The apparent

K
m

ATP is 0.23 mM in normal cells and 1.1 mM in cells transformed with wild-type virus. The

K
m

ATP of the cells infected with RSV-BH-Ta is 0.67-1.0 mM at 37° and 0.28 mM at 42°. The enzyme from normal cells appears to have two binding sites for Mg
++
, one at the catalytic site and a second at a regulatory site. Transformation by RSV-BH or RSV-BH-Ta (37°) apparently alters this second Mg
++
site. A decrease in adenylate cyclase activity occurs within 10 min after cells infected with RSV-BH-Ta are shifted from 42° to 37°; the activity falls to one-half that of normal cells 30 min after the temperature shift. Our observations indicate that a viral function lowers cyclic AMP content by lowering the activity of adenylate cyclase, probably through some modification of the plasma membrane.
Repair of DNA Containing Interstrand Crosslinks in
Escherichia coli:
Sequential Excision and Recombination
Authors: Cole Ronald S.
Published: May 2006

The repair of DNA containing interstrand crosslinks induced by psoralen-plus-light in
E. coli
cells has been investigated. During a 30-minute incubation after psoralen-plus-light treatment, crosslinks were excised and the cellular DNA was cut into discrete pieces. The molecular weight of these pieces corresponds to about twice the single-strand distance between crosslinks, as measured by sedimentation velocity in alkaline sucrose. During further incubation, these DNA fragments were covalently joined into high molecular weight DNA. This joining did not occur in cells carrying a mutation at
recA
; in these strains the DNA was further degraded to smaller polynucleotides and acid-soluble material. The possibility that repair of crosslinked DNA involves strand exchanges between homologous duplexes was investigated. Cells were grown in
13
C,
15
N-containing medium for several generations, then switched to medium of normal density that also contained [
3
H]thymidine for about 0.5 generation. After the crosslinking treatment, the cells were incubated in medium of normal density in order for repair to occur. The DNA was extracted and centrifuged in alkaline CsCl density gradients, where the light and heavy strands were separated. Molecules of intermediate density that contained
3
H accumulated during repair in wild-type cells, but not in control cells or treated
recA
-
cells. After molecular weight reduction of the intermediate-density DNA, the
3
H could be separated from the heavy strands, demonstrating that covalent joining between heavy and light strands of homologous duplexes accompanies repair. A mechanism involving sequential excision and genetic recombination is proposed for the repair of DNA containing interstrand crosslinks.
Protein Hal: Partial Deletion of a “γ” Immunoglobulin Gene(s) and Apparent Reinitiation at an Internal AUG Codon
Authors: Frangione Blas , Lee Loretta , Haber Edgar , Bloch Kurt J.
Published: May 2006

Protein Hal is a human γ4 heavy-chain disease protein whose molecular weight is reduced from 55,000 to 25,000 in 6 M guanidine due to the lack of disulfide bonds between heavy chains. Studies of aminoacid sequence indicate that it contains a gap of about 240 residues, starting 10 residues from the N-terminal end and including the rest of the Fd fragment, as well as the hinge region. Normal sequence apparently resumes at a methionine residue (position 252) in the second constant domain (C
H
2) and seems normal from there to the carboxyl end of the molecule. These results imply that reinitiation of translation at an internal AUG codon occurs in protein Hal.
A Temperature-Sensitive Mutation Affecting 28S Ribosomal RNA Production in Mammalian Cells
Authors: Toniolo Daniela , Meiss Harriet K. , Basilico Claudio
Published: May 2006

We have characterized a temperature-sensitive (ts) mutant of the hamster cell line BHK 21 that appears to have a defect in the processing of ribosomal RNA precursors at 39°. Mutant ts 422E grows at a normal rate at 33°, but upon shift to 39° growth stops after about one cell doubling. The appearance of 28S rRNA and large ribosomal subunits in the cytoplasm of ts 422E at 39° is inhibited by about 95%, when compared to wild-type BHK cells. Production of 18S rRNA and small ribosomal subunits is unaffected. Shift-up experiments show that the defect in 28S rRNA production can be detected as early as 2-3 hr after the shift to 39°. Synthesis of the larger rRNA precursor is normal at high temperature, but the processing appears to be arrested after the formation of 32S rRNA. 32S rRNA accumulates to some extent in the nucleoli of ts 422E. ts 422E cells appear to have a single mutation, directly affecting the conversion of 32S to 28S rRNA. The reduced amount of 28S rRNA in the cytoplasm of ts 422E cells at 39° seems therefore responsible for their inability to grow at this temperature.
Magnetic Dipole-Dipole Coupled Cu(II) Pairs in Nitric Oxide-Treated Tyrosinase: A Structural Relationship Between the Active Sites of Tyrosinase and Hemocyanin
Authors: Uiterkamp A. J. M. Schoot , Mason H. S.
Published: May 2006

The

T
r

and
T
[unk] states of tyrosinase were treated with NO. EPR spectra of the products observed at 14°K and at 113°K showed mixtures of two signals. One had components in the region of g = 2, about 1200 G wide, and in the region of g = 4, showing hyperfine splitting. The other signal was similar to that arising from isolated Cu(II) ions in an axially symmetric environment. The first signal was indicative of Δ
m
= 1 and Δ
m
= 2 transitions arising from magnetic dipole-dipole coupled Cu(II) ion pairs. It closely resembled previously reported EPR spectra obtained from NO-treated hemocyanin, which were confirmed in this study. The normal Curie behavior of the signals between 230°K and 14°K ruled out significant exchange coupling between the ion pairs. The Δ
m
= 2 signals were not saturable up to 350 mW at 14°K. The broad Δ
m
= 1 signals could be separated from accompanying signals by the saturation characteristics of the latter at about 10 mW at 14°K. The results establish the presence of a pair of copper ions at the active site of tyrosinase, and a clsoe structural relationship between this active site and that of hemocyanin.