bluuebunny/crossref_metadata_2025 huggingface dataset:
A Bovine Pancreatic Enzyme Catalyzing the Conversion of Proinsulin to Insulin
Authors: Yip C. C.
Published: May 2006

An enzyme that catalyzes the conversion of bovine proinsulin to insulin has been purified from a bovine pancreatic extract. The product of conversion was identified as insulin by aminoacid analysis and determination of carboxyl terminal aminoacid residues. The purified enzyme preparation showed one major protein band on polyacrylamide gel disc electrophoresis; it had a molecular weight of about 70,000 and an isoelectric point (pI) at a pH of 4.82.
In Vitro
Detection of Cytotoxic Cellular Immunity Against Tumor-Specific Antigens by a Radioisotopic Technique
Authors: Jagarlamoody S. M. , Aust J. C. , Tew R. H. , McKhann C. F.
Published: May 2006

[
3
H]Thymidine-labeled tumor cells are used to evaluate the cytotoxic cellular immune response against tumor-specific antigens; the loss of label due to destruction and detachment of target cells from the surface of the culture vessel is measured. Spleen cells from mice immunized against Moloney virus-induced rhabdomyosarcoma specifically destroyed the sarcoma cells, while cells from normal syngeneic mice did not. Peripheral blood lymphocytes from patients with malignant tumors were specifically cytotoxic to autologous tumor cells and to allogeneic tumor cells histopathologically identical to the autologous tumor, but not to autologous nonmalignant fibroblasts, or to allogeneic tumor cells from a histologically dissimilar tumor. Serum from the same patients specifically protected autologous tumor cells from lymphocyte cytotoxicity. This serum-mediated protection of tumor cells against autologous cellular immunocytotoxicity also extended to histologically identical allogeneic tumor cells. Cross-reactivity of anti-tumor cellular immunocytotoxicity
in vitro
, and its “blocking” by autologous serum, strongly suggest the presence of common tumor antigens. The antagonism demonstrated
in vitro
between serum and cellular immunity may explain the continued growth of malignant tumors in the face of demonstrable cellular immunity.
Conformational Model of Active Transport: Role of Protons
Authors: Young John H. , Blondin George A. , Green David E.
Published: May 2006

A conformational model of monovalent cation transport in mitochondria is described. Because it incorporates the proton-generated membrane potential and pH differential of the chemiosmotic model, the model successfully rationalizes a wide variety of mitochondrial ion-transport phenomena.
Expression of Two X-Linked Genes in Human Hair Follicles of Double Heterozygotes
Authors: Goldstein Joseph L. , Marks James F. , Gartler Stanley M.
Published: May 2006

Expression of the two X-linked loci glucose-6-phosphate dehydrogenase (G6PD; EC 1.1.1.49) and hypoxanthine:guanine phosphoribosyltransferase (HGPRT; EC 2.4.2.8) was studied in single hair follicles of two females who were heterozygous for both of these genes (double heterozygotes). The coupling phase for these two loci was known to be
g6pd A
and
hyprt
-
on the maternal X chromosome and
g6pd B
and
hgprt
+
on the paternal X. Three phenotypic classes of hair follicles were observed in both double heterozygotes: G6pd A follicles with deficient HGPRT activity, G6pd B follicles with normal HGPRT activity, and G6pd AB follicles with intermediate HGPRT activity. These data directly demonstrate one of the predictions of the Lyon hypothesis that for two X-linked loci, those genes in
cis
position are turned on or off in a cell and its clone, while in
trans
only one gene or the other is expressed.
Specificity of the Antibody Receptor Site to D-Lysergamide: Model of a Physiological Receptor for Lysergic Acid Diethylamide
Authors: Vunakis Helen Van , Farrow John T. , Gjika Hilda B. , Levine Lawrence
Published: May 2006

Antibodies to D-lysergic acid have been produced in rabbits and guinea pigs and a radioimmunoassay for the hapten was developed. The specificity of this lysergamide-antilysergamide reaction was determined by competitive binding with unlabeled lysergic acid diethylamide (LSD), psychotomimetic drugs, neurotransmitters, and other compounds with diverse structures. LSD and several related ergot alkaloids were potent competitors, three to seven times more potent than lysergic acid itself. The
N
,
N
-dimethyl derivatives of several compounds, including tryptamine, 5-hydroxytryptamine, 4-hydroxytryptamine, 5-methoxytryptamine, tyramine, and mescaline, were only about ten times less effective than lysergic acid, even though these compounds lack some of the ring systems of lysergic acid. The pattern of inhibition by related compounds with various substituents suggests that the antibody receptor site recognizes structural features resembling the LSD molecule. In particular, the aromatic nucleus and the dimethylated ethylamine side chain in phenylethylamine and tryptamine derivatives may assume in solution a conformation resembling ring A and the methylated nitrogen in ring C of LSD. Among the tryptamine derivatives, a large percentage of the most potent competitors are also psychotomimetic compounds.
Transformation of Mouse 3T3 Cells by Murine Sarcoma Virus: Release of Virus-Like Particles in the Absence of Replicating Murine Leukemia Helper Virus
Authors: Bassin R. H. , Phillips L. A. , Kramer M. J. , Haapala D. K. , Peebles P. T. , Nomura Shigeko , Fischinger P. J.
Published: May 2006

Small numbers of virus-like particles were observed by electron microscopy in each of two cloned lines of 3T3 cells transformed by murine sarcoma virus, even though these lines were free of detectable quantities of infectious leukemia and sarcoma virus. The morphology and occurrence of the particles were identical to those of the murine leukemia-sarcoma group. Moreover, the particles incorporated uridine and had a buoyant density of 1.16 g/ml in sucrose gradients. No evidence of sarcoma or leukemia virus infectivity was associated with the particles in cells of several susceptible species under various conditions, including both cosedimentation with leukemia virus and infection in the presence of inactivated Sendai virus. The particles may represent a form of murine sarcoma virus deficient in one or more of the viral components necessary for infectivity.
Social Recovery by Isolation-Reared Monkeys
Authors: Harlow Harry F. , Suomi Stephen J.
Published: May 2006

Total social isolation of macaque monkeys for at least the first 6 months of life consistently produces severe deficits in virtually every aspect of social behavior. Experiments designed to rehabilitate monkeys reared in isolation are described. While young isolates exposed to equal-age normal peers achieved only limited recovery of simple social responses, some mothers reared in isolation eventually exhibited acceptable maternal behavior when forced to accept infant contact over a period of months, but showed no further recovery; isolate infants exposed to surrogates were able to develop crude interactive patterns among themselves. In contrast to the above results, 6-month-old social isolates exposed to 3-month-old normal monkeys achieved essentially complete social recovery for all situations tested. It is postulated that social stimulation that both permits subjects to achieve contact acceptability and provides an interactive medium conducive to gradual development of sophisticated social behaviors will result in almost complete recovery of social capabilities previously obliterated by rearing in isolation.
Interchain and Intrachain Disulfide Bridges of a Human Immunoglobulin M: Detection of a Unique Fragment
Authors: Frangione B. , Prelli F. , Mihaesco C. , Franklin E. C.
Published: May 2006

Studies of the amino acid sequences around half-cystine residues in an immunoglobulin M have revealed an unexpectedly high number. At least 14 different sequences were found in the μ chain (V
HIII
subclass). Four of these were involved in interchain disulfide bridges and at least 10 in intrachain bridges. Five came from the κ chain (κ
III
subclass, Inv b). Several others, although having a high degree of homology, were not identical with those of either the μ or κ chains. These results support the concept of an additional fragment in γM molecules, although its function and localization remain to be determined.
Ultrastructural Comparison of a Virus from a Rhesus-Monkey Mammary Carcinoma with Four Oncogenic RNA Viruses
Authors: Kramarsky Bernhard , Sarkar Nurul H. , Moore Dan H.
Published: May 2006

The ultrastructure and morphogenesis of Mason-Pfizer monkey virus, isolated from a mammary carcinoma in a Rhesus monkey, was compared with those of murine mammary tumor virus, murine leukemia virus, L1210 leukemia-associated virus, and avian myeloblastosis virus. The simian virus resembled murine mammary tumor virus and the L1210 virus in that it produced intracytoplasmic particles that were enveloped during budding. It resembled L1210 virus and murine leukemia virus in budding with smooth envelopes. It differed from all the others in being more fragile. These similarities, combined with biochemical characteristics reported elsewhere in this issue, suggest that the monkey virus is an oncogenic RNA virus.
Specific Heterologous Enhancement of Immune Responses
Authors: Rubin Arnold S. , Coons Albert H.
Published: May 2006

In suspension cultures of mouse spleen cells, the addition of small amounts (1-100 ng) of a heterologous antigen to which the donor mice had been primed significantly increased the number of anti-sheep erythrocyte plaques appearing after stimulation with sheep erythrocytes. A similar addition to identical cultures from unprimed donors produced a small depression in the number of such plaques.
Cytoplasmic DNA synthesis Induced by RNA Tumor Viruses
Authors: Hatanaka M. , Kakefuda T. , Gilden R. V. , Callan E. A. O.
Published: May 2006

Infection of mouse embryo cells with two strains of murine sarcoma virus and one strain of murine leukemia virus was followed rapidly by synthesis of DNA in the cytoplasm. Persistently infected cells have not shown such synthesis, and ultraviolet-irradiated virus did not induce DNA synthesis. This new DNA presumably represents an intermediate in the virus replication cycle specified by the virion DNA polymerase(s). Failure to observe cytoplasmic DNA synthesis in persistently infected cells suggests, in keeping with the results of inhibitor experiments, that the new “viral” DNA becomes associated with cellular DNA in some form of stable interaction.
Divergence between Immunosuppression and Immunocompetence during Virus-Induced Leukemogenesis
Authors: Cerny Jan , McAlack Robert F. , Ceglowski Walter S. , Friedman Herman
Published: May 2006

Mice were infected with Friend leukemia virus and later immunized with either
Vibrio cholerae
vaccine or sheep erythrocytes. The primary antibody response to the bacteria (as judged by the number of plaque-forming cells) was slightly enhanced by the viral infection, whereas the response to sheep erythrocytes was inhibited. The difference appeared due to sensitization of mice to antigens crossreacting with those of sheep erythrocytes; no natural immunity to
V. cholerae
is detectable. However, the response of mice infected with Friend leukemia virus to a secondary challenge with the cholera bacteria was markedly inhibited. Even though the number of plaque-forming cells during the primary response was not reduced, accumulation of the cells in distinct splenic foci was suppressed. These results suggest that the effect of Friend leukemia virus on immunocompetent cells is selective. The immune response appears to be susceptible to leukemia virus-induced immunosuppression only when there has been a previous stimulation of immunocytes by antigen.
Electron Spin Resonance of an Irradiated Single Crystal of 5-Chlorouridine
Authors: Reiss Keith W. , Gordy Walter
Published: May 2006

Electron spin resonance signals from radicals of different types have been observed in γ-irradiated 5-chlorouridine. The strongest absorption, a broad resonance with
g
values ranging from 2.2 to 3.0, must arise from spin density concentrated on chlorine, probably from trapped atoms. However, hyperfine structure expected from Cl nuclei could not be resolved, evidently because of the low symmetry and diversity of the trapping sites and the large anisotropy in the nuclear coupling and
g
tensor. A very much weaker resonance, which in the single crystal has a resolvable hyperfine structure, was found to be similar to that observed in normal uridine subjected to thermal H atoms. It is concluded that an H atom, probably released by irradiation from the ribose group, replaces the Cl atom on the basic ring to form normal uridine, and that a second H atom later adds to the uridine to form the observed H-addition radical. The differences in the electron spin resonance constants of this radical from those of uridine bombarded with H can be attributed to the proximity of the trapped Cl atoms and to differences in the crystal structure of the chlorouridine from that of normal uridine.
Insulin-Sepharose and the Dynamics of Insulin Action
Authors: Oka Takami , Topper Yale J.
Published: May 2006

In terms of the rate of accumulation of α-aminoisobutyric acid, mammary epithelial cells from mature virgin mice respond rapidly to insulin covalently bound to sepharose particles, but do not respond initially to soluble insulin
in vitro
. The response to insulin-sepharose is prevented if the cells are first exposed to insulin. These observations may provide new insight into the dynamics of insulin action.
Dihydropteridine Reductase: Implication on the Regulation of Catecholamine Biosynthesis
Authors: Musacchio José M. , D'Angelo Gale L. , McQueen Charlene A.
Published: May 2006

The low tissue concentrations of tetrahydrobiopterin, as well as the antagonism between the catecholamine feedback inhibition of tyrosine hydroxylase and the reduced cofactor concentrations, suggest that dihydropteridine reductase may play an important role in the regulation of catecholamine biosynthesis.

The interaction of the different components involved in the hydroxylation of tyrosine was studied
in vitro
in a complex system composed of tyrosine hydroxylase, dihydropteridine reductase, and the different cofactors. This system has several important characteristics: (
a
) the rate of dihydroxyphenylalanine formation can be controlled by the concentration of dihydropteridine reductase; (
b
) low concentrations of catecholamines (2 × 10
-5
M) can produce a marked inhibition of tyrosine hydroxylase activity; and (
c
) the catecholamine feedback-inhibition of tyrosine hydroxylase can be antagonized by increasing concentrations of dihydropteridine reductase.

The properties of the
in vitro
tyrosine hydroxylase-dihydropteridine reductase system suggest that dihydropteridine reductase may have an important role
in vivo
in the determination of the rates of dihydroxyphenylalanine formation and on the effectiveness of the catecholamine feedback-inhibition of tyrosine hydroxylase activity.
Induction of Sterility in
Drosophila paulistorum:
Effect of Cytoplasmic Factors
Authors: Williamson D. L. , Ehrman Lee , Kernaghan R. P.
Published: May 2006

Male hybrids from Mesitas and Santa Marta (Colombia) strains of
Drosophila paulistorum
are sterile. Homogenates of males belonging to these strains and from the hybrids were injected into Mesitas or Santa Marta females, which were crossed to males of their own strains, so that their progenies were genetically nonhybrid. Nevertheless, some of the males from these progenies were sterile. Male progenies of females that were injected with homogenates from males that disagreed in the source of cytoplasm with the recipients were sterile. No sterility was induced if the donors and the recipients had similar cytoplasm.
Conversion-Associated Recombination in Yeast
Authors: Hurst Donald D. , Fogel Seymour , Mortimer Robert K.
Published: May 2006

Gene conversion and conversion-associated reciprocal recombination have been studied in various
Saccharomyces cerevisiae
hybrids. In a sample of 11,023 unselected meiotic tetrads, 907 conversions were observed at the
arg4, thr3, his1
, and
SUP6
loci. Of these conversions, 445 (or 49.1%) were associated with reciprocal recombination of bracketing markers no more than 20-centimorgans apart. For conversions of two other loci,
his2
and
thr1
, for which the bracketing markers were more than 20-centimorgans apart, recombination frequencies were significantly greater than 50%. These findings are discussed in terms of current models of genetic recombination. It is suggested that all meiotic crossing-over is characterized by the recombination events that are associated with conversion.
Detection and Quantitation of Simian Virus 40 Genetic Material in Abortively Transformed BALB/3T3 Clones
Authors: Smith Helene S. , Gelb Lawrence D. , Martin Malcolm A.
Published: May 2006

Infection with simian virus 40 is known to induce many cells to synthesize DNA and to divide in a medium lacking serum protein growth factor(s) that is essential for growth of uninfected cells (factor-free medium). Cells infected under these conditions then go through several rounds of division, since colonies containing more than 100 cells are formed. Many of these colonies are abortively transformed since, upon subsequent passage of the cells in standard medium, they can no longer grow in factor-free medium and show no other properties of viral transformation. We have examined these abortively transformed cells for the presence of simian virus 40 DNA sequences. Of the three clones tested, two were found to contain viral genetic material despite the fact that they were phenotypically normal.

The number of simian virus 40 genome equivalents present was determined by measurement of DNA reassociation kinetics on hydroxyapatite. Two of the abortively transformed lines contained approximately five viral genome equivalents per diploid cell, while the DNA from a third abortive transformant was indistinguishable from that of uninfected BALB/3T3 cells. A standard simian virus 40 transformant, isolated under similar conditions, contained two copies of the viral genome per cell. The abortive transformants also appear to contain the entire viral genome rather than multiple partial copies. Subclones of one abortively transformed line containing five copies per cell had 2.7-10 copies of viral genetic material per diploid cell.
Potentiation of Rifampicin and 5-Fluorocytosine as Antifungal Antibiotics by Amphotericin B
Authors: Medoff G. , Kobayashi G. S. , Kwan C. N. , Schlessinger D. , Venkov P.
Published: May 2006

Amphotericin B potentiates the antifungal effects of 5-fluorocytosine and rifampicin, probably by increasing the penetration of these agents through the fungal cytoplasmic membrane.
Glutamic Acid as a Precursor to N-Terminal Pyroglutamic Acid in Mouse Plasmacytoma Protein
Authors: Twardzik Daniel R. , Peterkofsky Alan
Published: May 2006

Cell suspensions derived from a mouse plasmacytoma (RPC-20) that secretes an immunoglobulin light chain containing N-terminal pyroglutamic acid can synthesize protein
in vitro
. Chromatographic examination of an enzymatic digest of protein labeled with glutamic acid shows only labeled glutamic acid and pyroglutamic acid; hydrolysis of protein from cells labeled with glutamine, however, yields substantial amounts of glutamic acid in addition to glutamine and pyroglutamic acid. The absence of glutamine synthetase and presence of glutaminase in plasmacytoma homogenates is consistent with these findings. These data indicate that N-terminal pyroglutamic acid can be derived from glutamic acid without prior conversion of glutamic acid to glutamine. Since free or bound forms of glutamine cyclize nonezymatically to pyroglutamate with ease, while glutamic acid does not, the data suggest that N-terminal pyroglutamic acid formation from glutamic acid is enzymatic rather than spontaneous.
Synthesis of Epstein-Barr Virus After Activation of the Viral Genome in a “Virus-Negative” Human Lymphoblastoid Cell (Raji) Made Resistant to 5-Bromodeoxyuridine
Authors: Hampar Berge , Derge Jeffery G. , Martos Lidia M. , Walker John L.
Published: May 2006

The Raji line of human lymphoblastoid cells, which does not show expression of Epstein-Barr virus, was made resistant to 5-bromodeoxyuridine. Within several weeks after removal of the drug, Epstein-Barr virus particles were detected in the cells. The sequence of virus appearance in the 5-bromodeoxyuridine-resistant cells indicated drug-induced activation of a repressed Epstein-Barr virus genome.
Structure of Inserted Bacteriophage Mu-1 DNA and Physical Mapping of Bacterial Genes by Mu-1 DNA Insertion
Authors: Hsu Ming-Ta , Davidson Norman
Published: May 2006

It is shown, by electron microscope observation of the structures of heteroduplexes, that Mu-1 DNA inserted into the bacterial episomes F
lac
and F
8
[1] is collinear with, rather than a circulation permutation of, the DNA of the mature Mu-1 bacteriophage. Observation of the position of the inserted Mu defines a point within the gene that has been inactivated (the
lacI
gene for F
lac
and a transfer gene in F
8
[1] in these particular instances). These examples illustrate a new, general method for physical gene mapping. The episome with Mu DNA inserted into F
8
[1] [i.e., F
8
[1](Mu)], although derived from a single colony, is heterogeneous in that a self-renatured sample shows a nonhomology loop of length 3.0 kb. This nonhomology loop, which has previously been observed in mature Mu-1 DNA, is due to an inversion.
Distribution Function Inequalities for Singular Integrals
Authors: Coifman R. R.
Published: May 2006

This paper describes some distribution function inequalities between maximal functions and singular integral operators.
Adenosine 3′:5′-Cyclic Monophosphate Control of the Enzymes of Glutamine Metabolism in
Escherichia coli
Authors: Prusiner Stanley , Miller Richard E. , Valentine Raymond C.
Published: May 2006

The effect of cAMP on the intracellular levels of five enzymes concerned with the interconversion of glutamate and glutamine in
E. coli
has been examined. Cyclic AMP added to the culture medium increases the levels of glutamate dehydrogenase (EC 1.4.1.4) and glutamine synthetase (EC 6.3.1.2); it decreases the levels of glutamate synthase (EC 1.4.1.X), and glutaminase A (EC 3.5.1.2). Cyclic AMP did not affect the level of glutaminase B (EC 3.5.1.2). These alterations in enzyme levels by cAMP require cyclic AMP receptor protein, since the levels of these enzymes were unchanged by cAMP in a mutant lacking this receptor. Chloramphenicol also abolished the effects of cAMP, a result that implies protein synthesis is necessary for these changes in enzyme levels to occur. The reciprocal effects of cAMP on the levels of these enzymes may play an important role in the cellular regulation of nitrogen metabolism.
Assembly of Tobacco Mosaic Virus
In Vitro:
Effect of State of Polymerization of the Protein Component
Authors: Butler P. J. G. , Klug A.
Published: May 2006

We previously proposed that the assembly of tobacco mosaic virus is initiated by disks of 34 protein subunits attaching to the RNA, after which the particle grows by the addition of further disks. Other workers have reported growth from “A-protein” instead. We now report experiments that confirm our previous results and show that the contrary findings are largely due to a nonequilibrium form of A-protein that has a “memory” for the disk state and rapidly reaggregates, either in solution or on the growing particle.
Recognition of Nonsense Codons in Mammalian Cells
Authors: Hatfield Dolph
Published: May 2006

The tritiated trinucleotide UGA was used in a binding assay to detect transfer RNAs that recognize this nonsense codon from calf-liver cells. Acylation of transfer RNA with labeled amino acids and determination of codon responses of aminoacyl-tRNAs demonstrate that a species of seryl-tRNA and a species of arginyl-tRNA recognize the codon UGA. Slight responses of cysteinyl-tRNA and of trytophanyl-tRNA to the codon UGA were also observed.
Mammalian Cells with Altered Forms of RNA Polymerase II
Authors: Chan V. L. , Whitmore G. F. , Siminovitch Louis
Published: May 2006

Mutants of Chinese hamster ovary cells that are resistant to α-amanitin can be isolated. At least some of these mutants contain an altered form of DNA-dependent RNA polymerase II, as indicated by its resistance to α-amanitin. These results indicate that mutation to α-amanitin resistance involves a change of a structural gene.
Mixed Conformations of Deoxyribonucleic Acid in Chromatin: A Preliminary Report
Authors: Hanlon Sue , Johnson R. S. , Wolf Barry , Chan Aurelia
Published: May 2006

We have established empirical limits for the circular dichroism spectra appropriate for aqueous solutions of the B, C, and A forms of calf-thymus DNA and have analyzed DNA conformations in biological structures. The circular dichroism spectrum above 250 nm of purified calf-thymus chromatin can be satisfactorily accounted for as a linear combination of contributions of the B and C reference spectra without invoking higher-order structures such as supercoils. The amount of A contribution, if any, is below the limit of detection (≤4%). The fraction of bases in the B conformation depends on the method of isolation of nucleohistone, and ranges from 30-50%. The B content of a given preparation is increased by addition of a chelating agent and decreased by addition of divalent ions. More radical increases ensue upon protein removal. Nuclease treatment results in a dramatic decrease in B content. The fraction of bases melting out in the lower transitions of the complex melting profile of a given chromatin preparation corresponds to its B content. We propose a model for chromatin structure in which part of the DNA duplex is exposed or accessible to the solvent and is in the B conformation. The remainder of the base pairs and ribophosphate backbone are protected from interaction with the solvent by efficient histone coverage and are in the C conformation. Divalent ions modulate the distribution of bases between these two conformations.
Kinetic and Equilibrium Analysis of Estradiol in Uterus: A Model of Binding-Site Distribution in Uterine Cells
Authors: Williams David , Gorski Jack
Published: May 2006

Kinetic and equilibrium binding studies indicate that the process by which the complex of estradiol-binding protein is transferred to the cell nuclei is very rapid and is readily reversible in intact cells; that is, the cytosol and nuclear binding sites are in a rapidly reversible equilibrium. Binding of the hormone appears to shift this equilibrium such that a large percent of the filled binding sites become associated with the nuclear fraction. A model is presented to show that the quantity of filled nuclear binding sites present at any estradiol concentration can be determined strictly by the initial binding between the hormone and the cytosol binding sites.
Specific Glycine-Accumulating Synaptosomes in the Spinal Cord of Rats
Authors: Arregui Alberto , Logan William J. , Bennett James P. , Snyder Solomon H.
Published: May 2006

Subcellular fractionation of rat spinal cord on continuous sucrose density gradients provides evidence for the existence of a specific synaptosomal fraction (enriched in pinched-off nerve endings) that accumulates glycine selectively by way of a high-affinity transport system. The particles in this fraction sediment to a less-dense portion of sucrose gradients than do particles that accumulate neutral, basic, aromatic, and acidic amino acids. Particles accumulating γ-aminobutyric acid are even less-dense than those storing exogenous glycine. The glycine-specific synaptosomal fraction also exists in the brain stem but not in the cerebral cortex. These findings provide neurochemical support for the suggestion that glycine has a specialized synaptic function, perhaps as neurotransmitter, in mammalian spinal cord.
Luteinizing Hormone Receptors: Specific Binding of Human Luteinizing Hormone to Homogenates of Luteinized Rat Ovaries
Authors: Lee Ching Yung , Ryan Robert J.
Published: May 2006

Binding of human [
125
I]luteinizing hormone to homogenates of luteinized rat ovaries is dependent upon time, temperature, and pH and is saturable. Injection of human chorionic gonadotropin
in vivo
or addition of unlabeled human chorionic gonadotropin or human or ovine luteinizing hormone
in vitro
inhibits binding, whereas follicle stimulating hormone or prolactin is without effect. The dissociation constant for binding of luteinizing hormone receptor is 0.79 nM. The number of binding sites is 94 femtomol/mg of wet weight. NaCl, KCl, MgSO
4
, and CaCl
2
at concentrations below 10 mM have no effect on binding, while all salts significantly inhibit binding at 150 mM. Binding of [
125
I]luteinizing hormone to its receptors is destroyed by proteolytic enzymes and by phospholipase C and D. The total binding activity is quantitatively recovered in the 2000 ×
g
pellet of the homogenate.
Synthesis of Inducible Tyrosine Aminotransferase in a Cell-Free Extract from Cultured Hepatoma Cells
Authors: Beck Jean-Paul , Beck Giselle , Wong K. Y. , Tomkins Gordon M.
Published: May 2006

A cell-free extract from cultured rat hepatoma cells is described that incorporates amino acids into chains of tyrosine aminotransferase that are identical, by several criteria, with tyrosine aminotransferase from rat liver. Extracts from steroid-induced cells are 6-to 10-times more active for tyrosine aminotransferase synthesis than extracts from uninduced cells, although the total incorporation rates are identical.
Translation of Encephalomyocarditis Viral RNA in Oocytes of
Xenopus laevis
Authors: Laskey R. A. , Gurdon J. B. , Crawford L. V.
Published: May 2006

RNA from encephalomyocarditis virus was injected into oocytes of
Xenopus laevis
. After incubation of the oocytes in [
35
S]methionine, polyacrylamide gel electrophoresis showed that a new series of polypeptides had been synthesized. They were identical in size to the polypeptides that appeared in ascites cells after infection with this virus. Electrophoretic and chromatographic analysis of the methionine-containing tryptic peptides from three of the induced polypeptides confirmed that they were virus-specific. All of the bands that appeared in ascites cells after infection also appeared in oocytes after injection of RNA from the virus. We conclude that
Xenopus
oocytes translate a mammalian viral mRNA faithfully and extensively, and perform normal post-translational modifications.
Assembly of Rod-Shaped Virus
In Vitro:
Reconstitution with Cucumber Green Mottle Mosaic Virus Protein and Tobacco Mosaic Virus RNA
Authors: Ohno Takeshi , Inoue Hideo , Okada Yoshimi
Published: May 2006

In vitro
assembly of tobacco mosaic virus (TMV) from its constituent RNA and protein occurs in two steps: formation of the initial complex by interaction of the 5′-end of TMV-RNA with 20S protein aggregate, and growth of the helical rod by sequential addition of protein subunits.

Such a process was also observed in the assembly of cucumber green mottle mosaic virus, which is also a rodshaped virus. The 13S virus-protein aggregate, probably a single-ring structure, is needed for formation of the initial complex, instead of the 20S double-ring structure for TMV. The 13S aggregate cannot effect growth of the initial complex to a long infective rod. Rod elongation takes place by the sequential addition of protein subunits.

In general, the assembly of rod-shaped viruses occurs in two steps, and the protein aggregate is essential only for initiation of the reaction, not for rod elongation.
Eight Transfer RNAs Induced by Infection of
Escherichia coli
with Bacteriophage T4
Authors: McClain William H. , Guthrie Christine , Barrell B. G.
Published: May 2006

Bacteriophage T4 induces the synthesis of eight transfer RNAs upon infection of
E. coli
. The tRNAs are easily detected and resolved into pure species by polyacrylamide gel electrophoresis of RNA labeled with
32
P after T4 infection. Two-dimensional fingerprints of RNase T
1
products derived from individual gel bands give patterns characteristic of single tRNAs. Furthermore, the T
1
digest of each gel band has a single oligonucleotide that contains the minor nucleotides Tp and Ψp, a characteristic feature of all known tRNAs.

Four larger RNAs are also seen in the polyacrylamide gels. Fingerprint and genetic analyses demonstrate that these molecules are related to the tRNAs, but the exact nature of this relationship is not known.
Hapten-Conjugated Antibodies and Visual Markers Used to Label Cell-Surface Antigens for Electron Microscopy: An Approach to Double Labeling
Authors: Lamm Michael E. , Koo Gloria C. , Stackpole Christopher W. , Hämmerling Ulrich
Published: May 2006

Haptens can be coupled to mouse immunoglobulin with retention of antibody specificity. Such hapten-coupled alloantibody, when bound to cells, can be bridged to an electron microscopic marker in two ways: (
i
) by a hybrid antibody, i.e., anti-hapten:anti-marker, and (
ii
) by untreated bivalent anti-hapten antibody if the marker is also haptenized. Through the use of immunologically non-crossreactive haptens and markers it should be possible to localize multiple, different antigens on the surface of an individual cell. Double labeling has been achieved with the first method.
Nuclear DNA Sequences Present in Human Leukemic Cells and Absent in Normal Leukocytes
Authors: Baxt W. G. , Spiegelman S.
Published: May 2006

The central purpose of the present study was to test the proposition that the nuclear DNA of every human cell contains whatever information is necessary and sufficient for transformation to malignancy. The experiments were made possible by our earlier identification in human leukemic cells of particulate elements encapsulating 70S RNA and RNA-directed DNA polymerase. The [
3
H]DNA synthesized by these particles was used as a probe, through molecular hybridization, to normal and leukemic DNA. The results obtained establish that leukemic nuclear DNA contains particle-related sequences that cannot be detected in normal leukocytes. This outcome does not support the virogene-oncogene theory, which postulates the inclusion of at least one complete copy of oncogenic information in the genome of every normal cell.

The data suggest that we may not be forced to cope with an omnipresent DNA segment coding for malignancy. Under the circumstances, we can perhaps entertain more hopeful pathways leading to the control and cure of cancer.
A DNA Fragment of Herpes Simplex 2 and Its Transcription in Human Cervical Cancer Tissue
Authors: Frenkel Niza , Roizman Bernard , Cassai Enzo , Nahmias Andre
Published: May 2006

A human cervical tumor, free of detectable infectious herpes simplex 2 virus, contained a fragment comprising 39% of herpes viral DNA. Renaturation kinetics indicate that an average of 1 to 3.5 DNA fragments of herpes simplex virus are present per cell, depending on the ploidy of the cells in this particular tumor. Virus-specific sequences were found linked to highly repetitive sequences of host DNA, which reassociated under conditions designed to preclude reassociation of viral sequences. The tumor also contained RNA transcripts complementary to 5% of the viral DNA. The fraction of viral DNA template transcribed in the cervical tumor is considerably less than that transcribed in productively infected cells (50%).
An Immunologic Approach to the Conformational Equilibria of Polypeptides
Authors: Sachs David H. , Schechter Alan N. , Eastlake Ann , Anfinsen Christian B.
Published: May 2006

Antibodies reactive with distinct regions of the staphylococcal nuclease molecule were prepared both by immunization with polypeptide fragments of nuclease and by immunization with intact nuclease followed by fractionation of the antiserum on immuno-absorbent columns bearing the corresponding fragments. Comparisons of the interactions of these antibody preparations with nuclease, by quantitative precipitin assays and enzyme inhibition studies, showed marked differences attributable to the conformation of the immunizing antigens. An interpretive model is proposed in which antibodies fractionated from anti-nuclease serum react effectively only with the “native format determinants” of polypeptide fragments of nuclease. It is postulated that such determinants are generated in polypeptide fragments by spontaneous and reversible folding of the polypeptide chain. The model permits experimental determination of parameters,
K
conf
, for the proposed conformational equilibria.
Curing of an
Escherichia coli
Episome by Rifampicin
Authors: Bazzicalupo Paolo , Tocchini-Valentini Glauco P.
Published: May 2006

Low doses of rifampicin, an antibiotic that specifically inhibits RNA polymerase, cure F
+
cells from the episome. An
E. coli
mutant, whose RNA polymerase is resistant to rifampicin, does not show the curing. The growth of Hfr strains, which replicate the chromosome by the F-replication system, is inhibited by low doses of the antibiotic.
Isolation of the Insulin Receptor of Liver and Fat-Cell Membranes
Authors: Cuatrecasas Pedro
Published: May 2006

Extraction of liver and fat-cell membranes with the nonionic detergent Triton X-100 prevents specific binding of
125
I-labeled insulin to these membranes. This loss of binding to particulate material is quantitatively recovered in a high-speed (300,000 ×
g
, 2 hr) supernatant of the extract. Specific and reversible insulin binding to soluble proteins is readily demonstrable by gel filtration. A simple and sensitive assay for detection of specific macromolecule-insulin complexes has been developed based on the selective precipitation of the complex by polyethylene glycol. Extraction of membrane lipids with organic solvents or by phospholipase digestion does not impair the subsequent extraction of the insulin-binding protein with detergent. Binding of insulin to the soluble protein is a saturable and dissociable process having a dissociation constant of about 100 nM. Derivatives of insulin compete for binding in direct proportion to their biological activity; other peptide hormones are without effect. The quantitative features of the detergent extractions and the specific insulin-binding properties of the material so obtained indicate that the protein solubilized is the biologically significant insulin receptor, whose insulin-binding function is essentially unaltered.
On the Identity of DOPA Decarboxylase and 5-Hydroxytryptophan Decarboxylase
Authors: Christenson James G. , Dairman Wallace , Udenfriend Sidney
Published: May 2006

Simultaneous immunological titration of DOPA and 5-hydroxytryptophan decarboxylase activities, from a number of tissues of various species, showed that the two activities were not distinguishable with a monospecific antiserum to hog kidney decarboxylase. Together with previous findings, these data firmly establish the concept that in mammalian tissues the two enzyme activities are associated with a single protein, namely aromatic L-amino acid decarboxylase.
Stimulation of DNA and Protein Synthesis in Fetal-Rat Liver Cells by Serum from Partially Hepatectomized Rats
Authors: Paul Dieter , Leffert Hyam , Sato Gordon , Holley Robert W.
Published: May 2006

Primary cultures of differentiated liver cells from fetal rats respond to serum from partially hepatectomized rats by an increased uptake of [
3
H]thymidine and [
3
H]leucine as compared with cultures incubated with normal rat serum. These findings are discussed in relation to the mechanism of induction of DNA synthesis and growth in liver cells during liver regeneration.
RNA in Human Leukemic Cells Related to the RNA of a Mouse Leukemia Virus
Authors: Hehlmann R. , Kufe D. , Spiegelman S.
Published: May 2006

Molecular hybridization with radioactively labeled DNA complementary to the RNA of the Rauscher leukemia virus was used to probe for homologous RNA in the polysome fraction of human leukemic cells. The leukocytes of 24 out of 27 patients examined contained RNA possessing homology to that of the mouse leukemia agent, but not to that of the unrelated viruses causing mammary tumors in mice or myeloblastosis in chickens. Further, no control human leukocytes or other adult and fetal tissues showed significant levels of the leukemia-specific RNA. It would appear that human leukemic cells contain RNA sequences homologous to those found in a viral agent known to cause leukemia in an experimental animal. The fact that human sarcomas have also been shown to contain this type of RNA points to a remarkable parallelism in the leukemias and sarcomas of mice and men.
Chemical Control of Cancer
Authors: Zubrod C. Gordon
Published: May 2006

Improvement of the present mortality from cancer depends upon a means of controlling those cancers that have spread from the original site to distant organs. Killing of tumor cells by means of drugs, whether used by themselves or in combination with surgery or irradiation, provides the strategy most likely to achieve this goal in the near future. There are now 10 disseminated cancers in man wherein drug treatment has resulted in normal life expectancy. The biological pattern of growth of these tumors is different from that of the tumors that have not been so susceptible to drugs. The new knowledge concerning the interdependence of growth pattern and drug susceptibility has led to rational animal models for selection of active drugs, in which more confidence can be placed than upon empiric models. Similarly, the prediction of drug toxicity and pharmacology from animal models has been placed on a firm scientific base. Recent developments in molecular biochemistry hold forth the hope that some day the selection of safe and effective antitumor drugs may be based on a knowledge of
in vitro
biochemistry.
Isolation and Properties of a Macromolecular, Water-Soluble, Immuno-Adjuvant Fraction from the Cell Wall of
Mycobacterium smegmatis
Authors: Adam Arlette , Ciorbaru Rita , Petit Jean-François , Lederer Edgar
Published: May 2006

Trypsin- and chymotrypsin-treated delipidated cell walls of
Mycobacterium smegmatis
were digested overnight with lysozyme. The water-soluble products thus obtained were filtered on a column of Sephadex G-50; the first peak, excluded from the column, has immunological adjuvant activity. The material of the excluded peak is obtained after lyophilization as a snow-white, fluffy material, soluble in water and insoluble in organic solvents. It behaves as a slightly polydisperse macromolecule in an ultracentrifuge, with an approximate molecular weight of 20,000. All the constituents of this material are typical bacterial cell-wall constituents; thus, the water-soluble adjuvant is considered to be an “oligomer” of the cell wall.

When added to Freund's incomplete adjuvant with an antigen (e.g., ovalbumin) and injected into hind-foot pads of guinea pigs, this water-soluble adjuvant increases the amount of precipitating antibodies and induces hypersensitivity to ovalbumin and the biosynthesis of γ
2
-type precipitating antibodies. The water-soluble material has a stronger adjuvant activity than equal amounts of whole bacteria, cell walls, or wax D, and seems to be the first well-defined, water-soluble, adjuvant-active fraction isolated from Mycobacteria.
Biochemical Physiology of a Respiration-Deficient Mutant of the Photosynthetic Bacterium
Rhodopseudomonas capsulata
Authors: Marrs Barry , Stahl Carol L. , Lien Stephen , Gest Howard
Published: May 2006

Nonsulfur purple photosynthetic bacteria generally possess the adaptive capacity to grow anaerobically (photosynthetically) and aerobically in darkness (energy obtained by respiratory phosphorylation). To develop a test system for study of interactions between the photosynthetic energy-conversion and dark respiration systems and the mechanism by which O
2
inhibits bacteriochlorophyll synthesis, we have isolated a mutant of
Rhodopseudomonas capsulata
that is incapable of dark aerobic growth. Both the parent strain and the mutant strain Z-1 (
aer
-
13
) grow readily anaerobically in the light with either malate or succinate as the source of carbon and reducing power. They differ, however, in that membrane fragments (“chromatophores”) from the mutant show severely impaired ability to use reduced nicotinamideadenine dinucleotide (NADH) as a source of electrons for respiration, oxidative phosphorylation, or “redox buffering” of the photophosphorylation system. The results presented indicate that the genetic lesion responsible for greatly diminished capacity to oxidize NADH can account for inability of
Rps. capsulata
Z-1 (
aer
-
13
) to grow aerobically in darkness.
Protein Synthesis in Simian Virus 40-Infected Monkey Cells
Authors: Walter Gernot , Roblin Richard , Dulbecco Renato
Published: May 2006

The proteins of purified Simian virus 40 (SV40) were examined by sodium dodecyl sulfate-acrylamide gel electrophoresis and compared with the polypeptides synthesized in SV40-infected monkey cells. Purified virions contain two major components, with molecular weights of 44,000 and 31,000. Together they make up 83% of the total virion proteins. In addition, the virus contains 12 minor polypeptides, which are believed to be cellular proteins, or peptides derived from proteolytic degradation of the 44,000 molecular weight polypeptide. Pulse-label experiments show that about 90% of the polypeptides synthesized after SV40 infection are host-cell proteins; 10% represent the two major structural components of the virion. A small fraction (about 0.5%) consists of three polypeptides (molecular weights 70,000, 60,000, and 8,000) that are neither part of the virion nor detectable in uninfected cells. They are either virus-induced cellular proteins or, more likely, proteins coded for by the SV40 genome.
The Low Polarity of Many Membrane Proteins
Authors: Capaldi Roderick A. , Vanderkooi Garret
Published: May 2006

The polarities of a large number of soluble and membrane proteins have been calculated by summing the mole fractions of polar amino acids. It was found that 85% of the 205 soluble proteins considered in this study had polarities of 47 ± 6%. Only 2% of the soluble proteins had polarities below 40%, whereas 47% of the 19 membrane proteins had polarities below 40%. The membrane proteins with polarities below 40% could be separated from their respective membranes only by detergents or organic solvents, indicating the importance of hydrophobic forces in their interaction with other membrane components. It is concluded that the majority of “intrinsic” membrane proteins have low polarity, and that the polarity index is therefore a useful parameter for characterization of membrane proteins.
Regulation of Melanin Synthesis in Mammalian Cells: Effect of Gene Dosage on the Expression of Differentiation
Authors: Davidson Richard L.
Published: May 2006

Near-tetraploid (2S), pigmented, Syrian hamster cells (3460
2
) were hybridized with unpigmented mouse fibroblasts to produce hybrids that contained two pigment cell genomes and one fibroblast genome per cell (3
2
D). Half of the hybrids were pigmented and showed high activity of the enzyme dihydroxyphenylalanine oxidase; the other half of the hybrids were unpigmented and devoid of the activity of this enzyme. (In contrast, all the previously isolated hybrids containing only one pigment cell genome and one fibroblast genome were unpigmented.) Analyses of the chromosome complement and of a series of enzymes unrelated to melanin synthesis did not reveal any great differences between the pigmented and unpigmented 3
2
D hybrids. Upon the isolation of subclones, unpigmented 3
2
D hybrids produced only unpigmented colonies, whereas pigmented hybrids produced both pigmented and unpigmented colonies. Although the mechanism that results in the formation of some pigmented and some unpigmented hybrids in these experiments is not known, it is clear that the number of pigment cell genomes in a hybrid affects the expression of pigmentation.