bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereochemical Correspondence among Chemically Disparate Systems: Spirocyclic Phosphoranes, Diarylmethanes, and Cognates
Authors: Gust Devens , Finocchiaro Paolo , Mislow Kurt
Published: May 2006

Certain chemical systems which differ greatly in many of their chemical properties may nevertheless exhibit stereochemically isomorphic behavior, i.e., they may be stereochemically correspondent. Two such systems are spirocyclic pentacoordinate molecules and molecules of the type Ar
2
ZX. The consequences of stereochemical correspondence between these two systems are explored in depth.
Isolation of Defective Mutant of Avian Sarcoma Virus
Authors: Kawai Sadaaki , Hanafusa Hidesaburo
Published: May 2006

A colony of transformed cells was isolated from chick-embryo cells infected with a stock of nondefective Schmidt-Ruppin strain of Rous sarcoma virus. The virus recovered from this colony was a stable defective mutant very similar to the Bryan strain of Rous sarcoma virus in the following characteristics: (
i
) noninfectiousness of virus particles released from transformed cells that lack helper factor; (
ii
) formation of infectious pseudotypes by coinfection with avian leukosis virus or by interaction with endogenous-helper factor in chicken cells; (
iii
) ability of the noninfectious form of virus to transform chick-embryo cells in the presence of ultraviolet light-inactivated Sendai virus; (
iv
) absence of glycoprotein in the noninfectious form; (
v
) failure to produce nondefective virus by recombination with avian leukosis virus; and (
vi
) segregation of polymerase-negative virus.

The morphology of transformed cells is characteristic of those infected by the Schmidt-Ruppin strain. The demonstration of segregation of such a defective virus from nondefective sarcoma virus and failure to detect revertants of this mutant suggest that the deletion of some genes may be involved in this mutation.
In Vitro
Synthesis of RNA That Contains Polyadenylate by Virion-Associated RNA Polymerase of Vesicular Stomatitis Virus
Authors: Banerjee Amiya K. , Rhodes Dennis P.
Published: May 2006

The RNA synthesized
in vitro
by the virion-associated RNA-instructed RNA polymerase of purified vesicular stomatitis virus contains polyadenylate sequences. These have been demonstrated by their partial resistance to pancreatic and T
1
ribonucleases and their capacity to bind to poly(U) filters and oligo(dT)-cellulose. The polyadenylate sequences range in apparent size from 50 to 200 bases, similar to the size of the poly(A) in mRNA from vesicular stomatitis virus-infected cells. Possible mechanisms of polyadenylylation of the
in vitro
RNA product are discussed.
A Wet Chemical Method for Rendering Scanning Electron Microscopy Samples Conductive and Observations on the Surface Morphology of Human Erythrocytes and Ehrlich Ascites Cells
Authors: Goldman Mark A. , Leif Robert C.
Published: May 2006

An alternate method to the common technique of evaporating a metallic coating on cells to render them conductive for scanning electron microscopy is described. This wet chemical technique is less expensive and easier to use, but is not as widely applicable as the evaporative technique. It should prove invaluable in the identification of artifacts by comparison of micrographs of material prepared in both manners. The first step in our application of this wet chemical method is to use the Centrifugal Cytology bucket to deposit the cells onto conductive polyethylene. After centrifugation and fixation with 4% glutaraldehyde, the sample is placed in a 50% glutaraldehyde solution. After a rinse in distilled water it is treated with ammoniacal silver nitrate. The reduced silver renders the sample conductive and, thus, for erythrocytes, eliminates artifacts due to charging and reduces these artifacts to virtually acceptable levels for larger cells. The surfaces of erythrocytes appear smooth with this technique while those coated by conventional vapor deposition of Au-Pd alloys often appear slightly wrinkled. Ehrlich ascites cells apparently can be divided into two classes by surface morphology. The surface structure of Ehrlich ascites cells rendered conductive by the wet method appears to be finer than conventionally prepared ones.
The Acquisition of Specificity in Cutaneous Sensory Neurons: A Reconsideration of the Integumental Specification Hypothesis
Authors: Sklar Joseph H. , Hunt R. K.
Published: May 2006

Neuronal specificity in cutaneous sensory nerve cells has been postulated to arise from “inductive interactions” between the cell's randomly outgrown peripheral neurite and local biochemical markers in the skin. Here was apply this integumental specification hypothesis to data recently obtained on the wiping-reflex behavior of frogs skin-grafted at various times during larval life. Deductions are generated about the developmental time course of the postulated nerve-skin interactions and two predictions are formulated and tested. Because the results of serial skin rotation experiments contradict the predictions, we conclude that the currently held hypothesis must be seriously questioned.
The Effect of Aspirin on Sickling and Oxygen Affinity of Erythrocytes
Authors: Furia F. G. de , Cerami A. , Bunn H. F. , Lu Y. S. , Peterson C. M.
Published: May 2006

The recent suggestion that the administration of aspirin might be useful in the treatment of sickle-cell anemia has been further studied and found to be without basis. After incubation with aspirin, sickle-cell erythrocytes are not inhibited from sickling after deoxygenation. In addition, although aspirin does transfer the acetyl group to hemoglobin both
in vitro
and
in vivo
, in our experiments the reaction does not result in any alteration in the oxygen equilibrium of either intact erythrocytes or hemoglobin in solution. Furthermore, patients maintained on long-term aspirin administration also showed no shift in the oxygen affinity of their blood.
Studies on the Orientation of Cyclic AMP-Dependent Protein Kinase in Human Erythrocyte Membranes
Authors: Rubin Charles S. , Rosenfeld Robert D. , Rosen Ora M.
Published: May 2006

The topographic location of cyclic AMP-dependent protein kinase has been studied in preparations of permeable and sealed membranes derived from human erythrocytes. Both the catalytic and cyclic AMP-binding components of protein kinase are localized on the inner, cytoplasmic, surface of the plasma membrane.
Specificity of the DNA Product of RNA-Dependent DNA Polymerase in Type C Viruses: II. Quantitative Analysis
Authors: Okabe Hiromi , Gilden Raymond V. , Hatanaka Masakazu
Published: May 2006

A number of mammalian Type C viruses were analyzed for relatedness by the technique of DNA·RNA hybridization. Viral DNAs were prepared in single-stranded form from complexes with 70S viral RNA formed during endogenous polymerase reactions. Extent of hybridization was assayed with the single-strand nuclease (S-1) from
Aspergillus oryzae
. Results obtained indicated a high degree of viral specificity, with significant cross-reactions being observed only with viruses obtained from within a species, as in the case of mouse and cat viruses, or in the special case of woolly monkey-gibbon comparisons. Comparisons of RD-114 virus, recently determined to be of feline origin, and conventional feline Type C viruses (FeLV), revealed minimal relatedness, especially when feline virus was grown on human cells, thus indicating the possibility of coexistence of greatly disparate Type C viruses within one species. A rat-specific virus, recovered from tumors induced by murine sarcoma virus, was found to contain genetic material common to both the original mouse virus and viruses indigenous to the rat, even though only rat-specific proteins have been detected during infection by this virus.
Still More Genetic Variability in Natural Populations
Authors: Bernstein Shelly C. , Throckmorton Lynn H. , Hubby John L.
Published: May 2006

Heat-denaturation studies of xanthine dehydrogenase have revealed many more additional alleles at the locus controlling this enzyme than are revealed by electrophoretic studies. In natural populations of species in the virilis group of the genus
Drosophila
, heat-denaturation studies of flies from the same locality revealed 1.74 times as many alleles as did electrophoretic studies. Similarly, studies of several species over their geographic range also revealed 1.74 times as many alleles. In addition, for the nine species studied, electrophoretic analysis had revealed only 11 alleles within the group, whereas heat-denaturation studies revealed a total of 32 alleles. These findings are discussed in the light of the continuing controversy over Darwinian and non-Darwinian theories of evolution.
Apparent Helix-Coil Transition for Poly(L-Alanine) as Measured by Nuclear Magnetic Resonance
Authors: Goodman Murray , Toda Fujio , Ueyama Norikazu
Published: May 2006

The previous contention by several groups that double peaks that arise in NMR spectra from NH and α-CH protons of poly L-alanines are caused by the coexistence of helical and random-coil structures in solution is disputed.
Mitochondrial Protein Synthesis: RNA with the Properties of Eukaryotic Messenger RNA
Authors: Perlman S. , Abelson H. T. , Penman S.
Published: May 2006

A heterogeneous RNA fraction with properties resembling those of messenger RNA was identified in mammalian mitochondria. Synthesis of contaminating RNA of nuclear origin was suppressed by treatment with camptothecin. Labeling of the messenger-like RNA is completely inhibited by ethidium bromide, a specific inhibitor of mitochondrial functions.

Although mitochondrial protein synthesis resembles that of prokaryotes in several regards, the messenger-like RNA is covalently linked to poly(adenylic acid) [poly(A)]. Poly(A) has thus far been found only in eukaryotic cells. The poly(A) segment has a gel electrophoretic mobility of about 4 S, corresponding to a length of 50-80 nucleotides, and thus resembles in size the poly(A) found in some mammalian viral RNAs. The messenger RNA can be released from the mitochondrial protein-synthesizing structure by treatment with puromycin.
Demonstration of a Cell-Surface Antigen Associated with Murine Sarcoma Virus by Immunoelectron Microscopy
Authors: Aoki T. , Stephenson J. R. , Aaronson S. A.
Published: May 2006

Cells transformed by murine sarcoma virus have been examined for the presence of a new virus-associated cell-surface antigen by immunoelectron microscopy. A common antigen has been detected on the surface of nonproductively transformed cells that were induced by two different strains of murine sarcoma virus, Kirsten and Moloney. This antigen shows crossreaction with cell lines transformed by murine sarcoma virus that were produced in two different mammalian species, rats and mice. Further, this antigen is distinct from previously described antigens on the surfaces of cells infected by murine leukemia virus, on the viral envelope, and on the surfaces of spontaneously transformed cell lines or cell lines transformed by x-irradiation.
Inhibition of 5-Oxoprolinase by 2-Imidazolidone-4-Carboxylic Acid
Authors: Van Der Werf Paul , Stephani Ralph A. , Orlowski Marian , Meister Alton
Published: May 2006

L-2-Imidazolidone-4-carboxylic acid is an effective competitive inhibitor of the reaction catalyzed by 5-oxoprolinase, in which 5-oxo-L-proline (L-pyroglutamic acid, L-2-pyrrolidone-5-carboxylic acid, L-5-oxopyrrolidine-2-carboxylic acid) is converted to L-glutamate, with concomitant cleavage of ATP to ADP and orthophosphate. L-2-Imidazolidone-4-carboxylate decreased the rate of metabolism of 5-oxo-L-[
14
C]proline to
14
CO
2
by rat-kidney slices but had no effect on the metabolism of [
14
C]glutamate. Mice injected with L-2-imidazolidone-4-carboxylate exhibited greatly reduced ability to metabolize 5-oxo-L-proline, but metabolized glutamate at an essentially normal rate. The findings provide an approach to an animal model for the human condition 5-oxoprolinuria, in which there is apparently a deficiency of renal 5-oxoprolinase activity. The evidence indicates that 5-oxoproline is a normal metabolite.
Demonstration and Distribution of Phenylethanolamine in Brain and Other Tissues
Authors: Saavedra Juan M. , Axelrod Julius
Published: May 2006

A specific and sensitive assay for phenylethanolamine in tissues is described. By this assay, phenylethanolamine was detected in many peripheral tissues and brains of rats. It is unequally distributed in rat brain, with the highest concentration present in hypothalamus and midbrain. Concentrations of brain phenylethanolamine were elevated after administration of phenylethylamine, phenylalanine,
p
-chlorophenylalanine, and monoamine oxidase inhibitors and decreased after administration of dopamine-β-hydroxylase inhibitors. Denervation of sympathetic nerves caused a moderate fall in phenylethanolamine concentrations. These results indicate that phenylethanolamine is synthesized intraneuronally from phenylalanine and phenylethylamine, but that only part of the phenylethanolamine is stored in sympathetic nerves.
A Crystalline Fragment of the Double Helix: The Structure of the Dinucleoside Phosphate Guanylyl-3′,5′-Cytidine
Authors: Day Roberta Ogilvie , Seeman Nadrian C. , Rosenberg John M. , Rich Alexander
Published: May 2006

The sodium salt of guanylyl-3′,5′-cytidine crystallizes in a monoclinic unit cell with one molecule in the asymmetric unit. Each molecule is related to another molecule by a 2-fold rotation axis which results in the formation of an antiparallel, right-handed double helix with complementary hydrogen bonding between the guanine and cytosine residues. The crystal is heavily hydrated with 36 water molecules in the unit cell. The geometry of this crystalline double helix is very similar to those which have been derived from studies of fiber x-ray diffraction patterns of double-stranded RNA, even though the latter do not yield data at atomic resolution.
A Transmissible Plasmid Controlling Camphor Oxidation in
Pseudomonas putida
Authors: Rheinwald J. G. , Chakrabarty A. M. , Gunsalus I. C.
Published: May 2006

Earlier papers demonstrated an extensive genetic exchange among fluorescent Pseudomonads; this one documents for genes specifying enzymes of peripheral dissimilation an extrachromosomal array, segregation, and frequent interstrain transfer. An hypothesis is presented of a general mechanism for the formation and maintenance of metabolic diversity. The example used, the path of oxidative cleavage of the carbocyclic rings of the bicyclic monoterpene D- and L-camphor, terminates in acetate release and isobutyrate chain debranching. By transduction, two gene linkage groups are shown for the reactions before and after isobutyrate. The group for reactions before isobutyrate is plasmid borne, contransferable by conjugation, mitomycin curable, and shows a higher segregation rate from cells that are multiplasmid rather than carrying a single plasmid. The genes that code for isobutyrate and essential anaplerotic and amphibolic metabolism are chromosomal. By conjugation plasmid-borne genes are transferred at a higher frequency than are chromosomal, and are transferred in homologous crosses more frequently than between heterologous species. Most isobutyrate-positive fluorescent pseudomonad strains will accept and express the camphor plasmid.
Facilitation of Inhibition in the Compound Lateral Eye of
Limulus
Authors: Graham Norma , Ratliff Floyd , Hartline H. K.
Published: May 2006

In the compound eye of
Limulus
the inhibitory effect of a burst of impulses from one group of ommatidia on the response of a neighboring ommatidium is greater when that burst is preceded by another burst of impulses. This facilitation of inhibition decays slowly, with a time constant of several seconds. Facilitation of inhibition accumulates as the number of impulses in the first burst increases, but there is a maximum that it cannot exceed. The facilitation is localized; one group of ommatidia does not facilitate the inhibition exerted by another group. The mechanism of this facilitation may be similar to that which has been postulated for facilitation of excitatory influences at the neuromuscular junction.
An RNA that Multiplies Indefinitely with DNA-Dependent RNA Polymerase: Selection from a Random Copolymer
Authors: Biebricher Christof K. , Orgel Leslie E.
Published: May 2006

We have selected from a mixture of random polynucleotides an RNA that is able to replicate in the presence of the DNA-dependent RNA polymerase of
Escherichia coli
, provided the medium contains Mn
2+
and ITP, in addition to ATP, CTP, and UTP. The RNA consists of a chain of about 125 (±25) nucleotides and appears to have a defined, nonrepetitive sequence.
Stimulation by Insulin of Cell Elongation and Microtubule Assembly in Embryonic Chick-Lens Epithelia
Authors: Piatigorsky Joram , Rothschild Sonia S. , Wollberg Miriam
Published: May 2006

Both fetal-calf serum and insulin cause cell elongation in explanted chick-lens epithelia from 6-day-old embryos. We show that 1 μg/ml of insulin, like serum, stimulates a doubling of cell length and an assembly of longitudinally oriented microtubules; colchicine treatment inhibits this cell elongation. In contrast to serum, insulin neither promotes further lens-cell elongation nor appreciably stimulates the synthesis of bulk proteins or of delta crystallin under the present conditions. These data indicate that the early morphological events of lens fiber differentiation can be initiated by insulin in a chemically defined, serum-free medium without significant affects upon protein synthesis.
Continuous Propagation of Radiation Leukemia Virus on a C57BL Mouse-Embryo Fibroblast Line, with Attenuation of Leukemogenic Activity
Authors: Lieberman Miriam , Niwa Ohtsura , Declève Alain , Kaplan Henry S.
Published: May 2006

The radiation leukemia virus (RadLV), a murine leukemia virus derived from thymic lymphomas induced by x-irradiation in strain C57BL/Ka mice, has been successfully propagated in sustained high titer
in vitro
in a newly established line, BL-5, of C57BL/Ka mouse-embryo fibroblasts. In addition, the production of endogenous virus, presumed to be RadLV, has been induced and sustained through multiple serial passages after treatment of BL-5 cell cultures with 5-bromodeoxyuridine. The chronically RadLV-infected subline, designated BL-5 (RadLV), sheds virus into the supernatant culture fluids that is biologically active
in vitro
in the XC cell plaque assay, in interference assays for focus-formation by murine sarcoma virus, and in the intracellular induction of group-specific antigens detectable by immunofluorescence, but is apparently devoid of leukemogenic activity after intrathymic inoculation into neonatal or immunosuppressed C57BL/Ka mice. Although BL-5 cells exhibited morphological alterations suggestive of transformation
in vitro
and gave rise to fibrosarcomatous ascites tumors after intraperitoneal inoculation with C57BL/Ka mice, the chronically infected BL-5(RadLV) cells remained normal in morphology and failed to yield fibrosarcomas
in vivo
.
Recircularization and Autonomous Replication of a Sheared R-Factor DNA Segment in
Escherichia coli
Transformants
Authors: Cohen Stanley N. , Chang Annie C. Y.
Published: May 2006

Controlled shearing of R-factor DNA leads to formation of fragments carrying an antibiotic resistance gene present on, but not expressed by, the intact R-factor. Transformation of CaCl
2
-treated
E. coli
by such fragments yields an autonomously replicating tetracycline-resistance plasmid (Tc6-5) that contains only a small fraction of the genome of the parent R-factor, and lacks both its fertility functions and its other drug-resistance determinants. Although the Tc6-5 plasmid is not self-transmissible, it can interact and/or recombine with conjugally-proficient plasmids that promote its transfer to other bacteria.
Acetylation of Sickle Cell Hemoglobin by Aspirin
Authors: Klotz Irving M. , Tam Joseph W. O.
Published: May 2006

Incubation of HbS (or HbA) with aspirin leads to incorporation of acetyl groups into the protein. Incorporation was followed by the use of aspirin labeled with
14
C in the acetyl group. The acetylated hemoglobins show an increase in oxygen affinity compared to the parent proteins. If acetylation also occurs
in vivo
, administration of aspirin might ameliorate the severity of sickle cell disease.
Cell-Free Synthesis of Procollagen: L-929 Fibroblasts as a Cellular Model for Dermatosparaxis
Authors: Kerwar S. S. , Cardinale George J. , Kohn Leonard D. , Spears Carlos L. , Stassen Frans L. H.
Published: May 2006

A cell-free system that actively synthesizes collagen was prepared from L-929 fibroblasts. Chromatographic and electrophoretic techniques were used to demonstrate that the only collagenous products are pro α
1
and pro α
2
chains. The collagen synthesized by the cell-free system was also compared to the collagen extracted from the cells. The cellular collagen was composed of aggregates of pro-α chains, while no α chains were found. Procollagen peptidase activity could not be detected in the cells, and the activity present in the medium was low, comparable to that in dermatosparaxic cell cultures. These properties indicate that L-929 cells may be a model system for dermatosparaxis.
Orientation and Motion of Amphiphilic Spin Labels in Hexagonal Lipid Phases
Authors: Boggs J. M. , Hsia J. C.
Published: May 2006

The acyl chain of spin-labeled fatty acids intercalates between the lipid hydrocarbon chains in hexagonal and micellar phases with the carboxyl group anchored at the lipid water interface. The spectra are characteristic of anisotropic motion and cannot be distinguished from the spectra of these probes in lamellar dispersions. In the hexagonal and micellar phases the molecular motion of the spin label increases as it is moved further away from the carboxyl group, similar to the behavior in the lamellar phase (Jost
et al.
(1971)
J. Mol. Biol.
59, 77-98). The similarity in packing of the acyl chains in the hexagonal and lamellar phases suggests that localized regions of hexagonal phase are compatible with a bilayer matrix.
The Influence of Nearest-Neighbor Amino Acids on the Conformation of the Middle Amino Acid in Proteins: Comparison of Predicted and Experimental Determination of β-Sheets in Concanavalin A
Authors: Kabat Elvin A. , Wu T. T.
Published: May 2006

A 20 × 20 table of tripeptides has been compiled that may be used to locate β-sheet breaking and α-helix breaking residues in proteins. It is based on the definition of an α-helical and a β-sheet domain on the (ϕ, Ψ) map based on the occurrences of α-helices and β-sheets in 12 known proteins whose sequence and three-dimensional structure have been determined. Each entry in the 20 × 20 table lists three numbers, the frequency of occurrences of the middle amino acid (
n
) in relation to its nearest neighbors (
n
- 1) and (
n
+ 1) in the α-helical domain, the β-sheet domain and outside these regions. The regions between two β-sheet-breaking residues would be permissively β-sheet regions. The sequence of concanavalin A has been examined in this manner and of the 13 β-strands defined by x-ray crystallography, 10 were in agreement with the permissively β-sheet regions and, in the remaining three, β-sheet-breaking residues were the third in one, and the third, fourth, and fifth residues in another, and the sixth residue in the third from the beginning of the β-strands. The findings provide strong support for the role of nearest-neighboring amino acids in determining secondary structure of proteins.
Bacteriophage T4 Head Morphogenesis. Isolation, Partial Characterization, and Fate of Gene 21-Defective Tau-Particles
Authors: Luftig Ronald B. , Lundh Nancy P.
Published: May 2006

A lysozyme-detergent procedure was developed for isolation of tau-particles from cells infected by gene-21 mutants of T4 bacteriophage. These particles have a sedimentation coefficient of 440 ± 10 S. They contain less than 1% detectable nuclease-resistant DNA, are smaller (650 × 850 Å) than normal bacteriophage heads (800 × 1100 Å), and exhibit two major bands on 7.5% Na dodecyl sulfate-acrylamide gels. The more prominent band (55,000 daltons) corresponds to the uncleaved, major capsid polypeptide (P23); the other band (32,000 daltons) corresponds to the gene-22 product (P22). Temperature-shift experiments with cells infected with
ts
N8 (gene 21) mutants were used to study the fate of tau-particles accumulated under nonpermissive conditions. 50 Min after
ts
N8-infected cells were shifted from the nonpermissive (41.5°) to the permissive (25°) temperature, a phage burst occurred that was 75% of that observed with wild-type phage. However, in “pulse-chase” temperature-shift experiments, the radioactive tau-particle peak only slightly decreased (by 10-14%) by 50 min after the shift, whereas an increased amount of radioactivity (about four times as much as the tau-particle decrease) appeared in phage particles. The results suggest that at least two pools of head polypeptides coexist in cells infected with gene-21 mutants. One pool is composed of head subunits assembled into tau-particles, which are mostly aberrant structures; the second pool is composed of head subunits that are incorporated into mature phage when the gene-21 product becomes functional.
Pleiotypic Control by Cyclic AMP: Interaction with Cyclic GMP and Possible Role of Microtubules
Authors: Kram Raphael , Tomkins Gordon M.
Published: May 2006

Previous studies have shown that exogenous dibutyryl cyclic AMP inhibits the uptake of uridine, leucine, and 2-deoxyglucose by cultured mouse fibroblasts. 3′:5′-cyclic GMP is shown here to counteract these inhibitory effects as well as the inhibition of precursor transport and leucine incorporation into proteins produced by prostaglandin E
1
. We conclude, therefore, that cyclic GMP antagonizes the “pleiotypic” effects of cyclic AMP in these cells.

Colcemid and vinblastine, but not cytochalasin B, reverse the transport inhibition caused by cyclic AMP without affecting the intracellular concentrations of cyclic AMP. These results suggest the possibility that cyclic AMP regulates the membrane transport of certain substrates by influencing the organization of microtubules.
Reduction of Ferricytochrome
c
by Dithionite Ion: Electron Transfer by Parallel Adjacent and Remote Pathways
Authors: Creutz Carol , Sutin Norman
Published: May 2006

The kinetics of the reduction of horseheart ferricytochrome
c
by sodium dithionite (phosphate buffer-sodium chloride; pH 6.5, μ = 1.0, 25°) features two reaction pathways; one with the rate constant
k
3
= 1.17 × 10
4
M
-1
sec
-1
, the other with the rate constant
k
1
k
2
/
k
-1
= 6.0 × 10
4
M
-1
sec
-1
. These pathways are interpreted in terms of remote attack (possibly by way of the exposed edge of the porphyrin system) and adjacent attack (requiring the opening of the heme crevice). The limiting rate for the adjacent pathway (
k
1
= 30 sec
-1
) is in good agreement with the rate of heme-crevice opening of ferricytochrome
c
determined in other studies. The implication of the adjacent attack pathway to the function of cytochrome
c in vivo
is discussed.
Effects of a Snake α-Neurotoxin on the Development of Innervated Skeletal Muscles in Chick Embryo
Authors: Giacobini G. , Filogamo G. , Weber M. , Boquet P. , Changeux J. P.
Published: May 2006

The evolution of the cholinergic (nicotinic) receptor in chick muscles is monitored during embryonic development with a tritiated α-neurotoxin from
Naja nigricollis
and compared with the appearance of acetylcholinesterase. The specific activity of these two proteins reaches a maximum around the 12th day of incubation. By contrast, choline acetyltransferase reaches an early maximum of specific activity around the 7th day of development, and later continuously increases until hatching. Injection of α-toxin in the yolk sac at early stages of development causes an atrophy of skeletal and extrinsic ocular-muscles and of their innervation. In 16-day embryos treated by the α-toxin, the endplates revealed by the Koelle reaction are almost completely absent. The total content and specific activities of acetylcholinesterase and choline acetyltransferase in atrophic muscles are markedly reduced.
A New Enzymatic Assay for Guanosine 3′:5′-Cyclic Monophosphate and Its Application to the Ductus Deferens of the Rat
Authors: Schultz G. , Hardman J. G. , Schultz K. , Davis J. W. , Sutherland E. W.
Published: May 2006

A sensitive enzymatic procedure has been developed for the determination of guanosine 3′:5′-cyclic monophosphate (cyclic GMP). It is based on the conversion of cyclic GMP to GMP by cyclic nucleotide phosphodiesterase and on the transfer of
32
P from [γ-
32
P]ATP to GMP by the action of a specific ATP:GMP phosphotransferase (EC 2.7.4.8). The [
32
P]GDP is separated from the remaining [
32
P]ATP by enzymatic degradation of ATP by myosin and by precipitation of the
32
P
i
formed. The reaction blank, which is mostly caused by the nucleotide content of the enzymes, is doubled by about 0.1 pmol of cyclic GMP. The procedure has advantages in speed and/or accuracy over other methods in current use.

Cyclic nucleotide concentrations were studied in the ductus deferens of the rat; two agents were used, carbachol and norepinephrine, which cause contraction. Incubation with 0.1 mM carbachol caused a 3-fold increase in cyclic GMP content, which was maximal about 2 min after carbachol addition. Cyclic AMP concentrations were not significantly changed. Addition of 0.01 mM norepinephrine increased cyclic GMP content by about 25% within 1 min and by 40% within 3 min; cyclic AMP concentrations were only slightly increased. A 3-min incubation with the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine (0.1 mM) doubled the cyclic GMP content and increased cyclic AMP concentration by 50%.
A Cytoplasmic Regulatory Mutant of
Euglena:
Constitutivity for the Light-Inducible Chloroplast Transfer RNAs
Authors: Goins Diane J. , Reynolds R. J. , Schiff Jerome A. , Barnett W. Edgar
Published: May 2006

An ultraviolet-induced cytoplasmic mutant (G
1
BU) of
Euglena gracilis
Klebs var.
bacillaris
Pringsheim is described. G
1
BU, in addition to being golden in color and containing smaller amounts of chlorophyll than wild type when grown in the light, is a regulatory constitutive mutant for the light-inducible chloroplast isoleucine and methionine tRNAs; i.e., these two tRNAs are present in dark-grown G
1
BU cells at approximately the levels present in light-grown wild-type cells. Six other mutants were also examined for normal control of plastid tRNA biosynthesis; all four of the aplastidic mutants (lacking appreciable plastid structures and detectable plastid DNA) are incapable of chloroplast tRNA biosynthesis, whereas two other color mutants that do contain plastids and chloroplast DNA have normal plastid tRNA regulation.
The Genetic System in Parthenogenetic Strains of
Drosophila mercatorum
Authors: Carson Hampton L.
Published: May 2006

Five parthenogenetic laboratory strains of
Drosophila mercatorum
have been examined for their mode of diploidization in the eggs of females. Diploidization occurs either by pronuclear duplication leading to complete homozygosity or by nuclear fusion. If the latter occurs between pronuclei from different secondary oocytes, heterozygosity can be maintained. Each of the five strains shows some nuclear fusion and three show significantly different amounts, ranging from about 21% to less than 1%. Even in strains with a strong tendency towards homozygosity, it is argued that this dual system of nuclear reconstitution provides for genetic recombination; thus, the strains retain considerable evolutionary potential.
Mating Types and Macrocyst Formation in
Dictyostelium discoideum
Authors: Erdos Gregory W. , Raper Kenneth B. , Vogen Linda K.
Published: May 2006

Strains of
Dictyostelium discoideum
were paired in various combinations. Certain pairings resulted in the production of macrocysts, which are thought to be the sexual stage in the cellular slime molds. One selfcompatible strain was found. Other strains produced macrocysts only when paired with an alternate mating type. Two strains were found to form macrycysts when paired with either mating type but not alone or with each other. Several strains did not form macrocysts under any circumstances. Strains were graded according to their mating competency based on the number of macrocysts produced relative to the aggregated myxamoebae observed in the pairings.
The Use of Iodinated RNA for Gene Localization
Authors: Prensky Wolf , Steffensen D. M. , Hughes W. L.
Published: May 2006

Carrier-free iodination of 5S RNA with
125
I yields a probe suitable for use in cytological RNA-DNA hybridization studies. The genes coding for 5S ribosomal RNA in
Drosophila
could be localized by autoradiography after a 2-day exposure, whereas a 2-month exposure is needed when the best available [
3
H]RNA is used. The procedure introduces one covalently bound
125
I atom per 100 nucleotides, resulting in a specific activity of over 10
8
dpm/μg of RNA. The method may be readily applied to other problems involving molecular hybridization techniques.
Carbon Dioxide Hydration Activity of Carbonic Anhydrase: Paradoxical Consequences of the Unusually Rapid Catalysis
Authors: Khalifah Raja G.
Published: May 2006

The kinetic parameters for carbon dioxide hydration catalysis by carbonic anhydrase (EC 4.2.1.1) present an apparent paradox. The assumption of H
2
CO
3
as the hydration product requires the rate of recombination of H
2
CO
3
with enzyme to be faster than the diffusion limit. The alternative assumption of HCO
3
-
as the product of hydration likewise requires active-site ionization rates to exceed the diffusion limit. We previously postulated the presence of special means for rapid active-site ionization. It is shown here that when proton transfer between enzyme and buffer species is taken into account, there is no need to invoke rates exceeding the diffusion limit. Bicarbonate ion thus appears as the most probable hydration product and dehydration substrate.
Genetic Analysis of Developmental Stages of the Cellular Slime Mold
Dictyostelium purpureum
Authors: Yamada T. , Yanagisawa K. O. , Ono H. , Yanagisawa K.
Published: May 2006

71 Mutants of
Dictyostelium purpureum
, unable to carry out normal development, were isolated. These mutants fall into three phenotypic classes. The mutants of the first class do not aggregate. Those of the second class develop a little further and form conical aggregates. The mutants of the third class progress still further, and the conical aggregates are transformed into finger-shaped masses, but no fruiting bodies are formed. Mutants of each class were able to form fruiting bodies when mixed with mutants of other classes. Pairs of mutants belonging to the same class, however, never responded synergistically. This result indicates the presence of three distinct developmental stages in the process of the fruiting-body formation. Experiments with actinomycin D suggested that genes controlling the developmental process of
D. purpureum
were divided into three groups which were identical to those identified by the analysis of synergism.
A Tumor-Associated Antigen in Human Nephroblastomas
Authors: Burtin P. , Gendron M. C.
Published: May 2006

Antisera prepared against extracts of human nephroblastomas (Wilms' tumors) allowed the characterization in these extracts, and in a few extracts of tumors of other organs, of a tumor-associated antigen. This antigen is different from all previously described antigens, and was named W antigen (W for Wilms). It does not seem to be a carcinoembryonic antigen, and hence it could be of viral origin.
Virus-Specific Messenger RNA and Nascent Polypeptides in Polyribosomes of Cells Replicating Murine Sarcoma-Leukemia Viruses
Authors: Vecchio G. , Tsuchida N. , Shanmugam G. , Green M.
Published: May 2006

We present evidence that virus-specific RNA is present in polyribosomes of transformed cells replicating the murine sarcoma-leukemia virus complex and that it serves as messenger RNA for the synthesis of viral-coded proteins. Both virus-specific RNA (detected by hybridization with the [
3
H]DNA product of the viral RNA-directed DNA polymerase) and nascent viral polypeptides (measured by precipitation with antiserum to purified virus) were found in membrane-bound and free polyribosomes. Membrane-bound polyribosomes contained a higher content of both virus-specific RNA and nascent viral polypeptides. From 60 to 70% of viral RNA sequences were released from polyribosomes with EDTA, consistent with a function as messenger RNA. Maximum amounts of both virus-specific RNA and nascent viral polypeptides were found in the polyribosome region sedimenting at about 350 S.
Conformational Studies of Oxytocin, Lysine Vasopressin, Arginine Vasopressin, and Arginine Vasotocin by Carbon-13 Nuclear Magnetic Resonance Spectroscopy
Authors: Walter Roderich , Prasad K. U. M. , Deslauriers Roxanne , Smith Ian C. P.
Published: May 2006

Oxytocin, arginine vasopressin, lysine vasopressin, arginine vasotocin, as well as their cyclic and acyclic analogs, were studied by carbon-13 nuclear magnetic resonance spectroscopy in deuterium oxide and deuterated dimethylsulfoxide. Fourier-transformed spectra were obtained at 25.16 MHz. The resonances of all carbon atoms have been assigned in both solvent systems; this includes tentative assignments of the carbonyl carbons. The spectra of arginine vasopressin and lysine vasopressin are essentially identical when compared in D
2
O or dimethylsulfoxide, but they differ from those of oxytocin. The spectrum of arginine vasotocin in D
2
O is intermediate between those of oxytocin and the vasopressins. These spectral differences are not only due to variations in constituent amino acids but are also a reflection of conformational differences of oxytocin, arginine vasotocin, and the vasopressins. All hormones are sensitive to changes in hydrogen ion concentration in both solvents; this was not observed with deamino analogs, which lack the terminal amino group.
Characterization and Separation of Viral DNA Polymerase in Mouse Milk
Authors: Howk R. S. , Rye L. A. , Killeen L. A. , Scolnick E. M. , Parks W. P.
Published: May 2006

Two DNA polymerase with properties of viral RNA-directed DNA polymerase can be found in RIII mouse milk. One enzyme is the polymerase of type-C viruses; this enzyme prefers manganese to magnesium with poly(rA)·oligo(dT) as synthetic template, is inhibited by specific sera, and has an apparent molecular weight of 70,000. Milk from BALB/c and NIH Swiss mice contain a vast predominance of this type-C enzyme. The other DNA polymerase from RIII mouse milk prefers magnesium to manganese, is not inhibited by type-C antipolymerase serum, and appears larger on gel chromatography than the type-C viral polymerase. Its presence in milk from RIII mice and absence from milk of mice with low content of mammary tumor virus correlates to the relative degree of type-B virus expression in these mice. The DNA polymerase of Mason-Pfizer monkey virus, isolated from a rhesus monkey breast tumor, also has a marked preference for magnesium with poly(rA)·oligo(dT), is not immunologically related to primate type-C viruses, and appears larger than the gibbon type-C enzyme on gel chromatography.
Temperature-Dependent Expression of Transformation by a Cold-Sensitive Mutant of Murine Sarcoma Virus
Authors: Somers Kenneth , Kit Saul
Published: May 2006

Morphological transformation of normal rat kidney cells by a murine sarcoma virus was found to be cold-sensitive. Cells transformed by the virus expressed their transformed phenotype at the permissive temperature (39°) but not at the nonpermissive temperature (33°), as judged by the criteria of morphological changes and colony-forming ability on monolayers of normal rat kidney cells. Cold-sensitive expression of transformation was specific for focus-derived normal rat kidney cells transformed by the virus, readily reversible, and not lost during serial propagation of the cells. The genome of the murine sarcoma virus can be rescued by superinfection with Moloney leukemia virus at the permissive or nonpermissive temperature, and the rescued virus exhibited the same cold-sensitive properties as the original transforming virus. These results suggest that maintenance of the transformed state is continuously dependent on a cold-sensitive viral function.
Identification of Chloramphenicol-Binding Protein in
Escherichia coli
Ribosomes by Affinity Labeling
Authors: Pongs Olaf , Bald Rolf , Erdmann Volker A.
Published: May 2006

Monoiodoamphenicol, a synthetic analogue of chloramphenicol, has been shown by competition experiments with chloramphenicol and lincomycin to bind at the same site of 70S ribosomes as chloramphenicol. At — 2° it forms a 1:1 complex with 70S ribosomes having a value of
K
(7.5 × 10
4
M
-1
) that is one order of magnitude lower than that of chloramphenicol. At 37°, monoiodoamphenicol irreversibly inhibits the protein-synthesizing activity of
E. coli
ribosomes. It is shown that the analogue reacted preferentially with protein L16 of
E. coli
70S ribosomes, and we therefore conclude that protein L16 belongs to the chloramphenicol-binding site of
E. coli
ribosomes.

Since the chemically reactive group of monoiodoamphenicol resembles iodoacetamide, the reaction of
E. coli
70S ribosomes with monoiodoamphenicol was compared to that with iodoacetamide. Iodoacetamide did not react with protein L16, but it predominantly reacted with proteins S18 of the 30S subunit. Furthermore, monoiodoamphenicol was reacted with
E. coli
ribosomal subunits. Isolated 50S subunits bound monoiodoamphenicol by about one order of magnitude less than 70S ribosomes. Again, protein L16 reacted with the affinity label. Monoiodoamphenicol reacted with protein S18 in isolated 30S subunits; it also bound to 70S ribosomes of
Bacillus stearothermophilus
, however, it did not bind irreversibly to these 70S ribosomes.
Properties of Opiate-Receptor Binding in Rat Brain
Authors: Pert Candace B. , Snyder Solomon H.
Published: May 2006

[
3
H]Naloxone, a potent opiate antagonist, binds stereospecifically to opiate-receptor sites in rat-brain tissue. The binding is time, temperature, and pH dependent and saturable with respect to [
3
H]naloxone and tissue concentration. The [
3
H]naloxone-receptor complex formation is bimolecular with a dissociation constant of 20 nM. 15 Opiate agonists and antagonists compete for the same receptors, whose density is 30 pmol/g. Potencies of opiates and their antagonists in displacing [
3
H]naloxone binding parallel their pharmacological potencies.
Avian Tumor Virus RNA: A Comparison of Three Sarcoma Viruses and Their Transformation-Defective Derivatives by Oligonucleotide Fingerprinting and DNA-RNA Hybridization
Authors: Lai Michael M. C. , Duesberg Peter H. , Horst Jürgen , Vogt Peter K.
Published: May 2006

Earlier electrophoretic analyses have shown that the 60-70S RNA of avian sarcoma viruses contains a characteristic subunit, termed class
a
subunit, which has a lower electrophoretic mobility than class
b
subunit found in transformation-defective derivatives of sarcoma viruses and in avian leukosis viruses. We have compared the RNAs of three nondefective avian sarcoma viruses, B77 and Prague and Schmidt-Ruppin strains of Rous sarcoma virus, with those of their transformation-defective (
td
) derivatives,
td
B77,
td
PR-C, and
td
SR-A, respectively, to determine the chemical basis for the difference between class
a
and
b
subunits.

It was found by “fingerprinting” that (
1
) all (about 20-25) large T1 RNase-resistant oligonucleotides present in class
b
subunits of transformation-defective viruses have homologous counterparts in the class
a
subunits of corresponding nondefective sarcoma viruses and that (
2
) class
a
subunits contain a few (one or two) additional oligonucleotides that are not present in class
b
. By contrast the oligonucleotide fingerprints of avian tumor viruses of different strains and subgroups were very different.

Cross hybridization of classes
a
and
b
RNA of sarcoma virus B77 with DNA transcribed from a corresponding transformation-defective virus
td
B77 showed that the two RNAs share at least 60% and differ by about 10% of their sequences.

It is suggested that the structural relationship of class
a
and
b
subunits of corresponding viruses may be expressed as
a
=
b
+
x
, and that all the oligonucleotides present only in RNAs of sarcoma viruses but not in transformation-defective viruses of the corresponding strains are part of sequence(s)
x
. The possibility that
x
represents genetic information directly or indirectly involved in transformation of fibroblasts is discussed.
Carcinogens are Mutagens: A Simple Test System Combining Liver Homogenates for Activation and Bacteria for Detection
Authors: Ames Bruce N. , Durston William E. , Yamasaki Edith , Lee Frank D.
Published: May 2006

18 Carcinogens, including aflatoxin B
1
, benzo(a)pyrene, acetylaminofluorene, benzidine, and dimethylamino-
trans
-stilbene, are shown to be activated by liver homogenates to form potent frameshift mutagens. We believe that these carcinogens have in common a ring system sufficiently planar for a stacking interaction with DNA base pairs and a part of the molecule capable of being metabolized to a reactive group: these structural features are discussed in terms of the theory of frameshift mutagenesis. We propose that these carcinogens, and many others that are mutagens, cause cancer by somatic mutation. A simple, inexpensive, and extremely sensitive test for detection of carcinogens as mutagens is described. It consists of the use of a rat or human liver homogenate for carcinogen activation (thus supplying mammalian metabolism) and a set of
Salmonella
histidine mutants for mutagen detection. The homogenate, bacteria, and a TPNH-generating system are all incubated together on a petri plate. With the most active compounds, as little as a few nanograms can be detected.
Synthetic Analogs of the Active Sites of Iron-Sulfur Proteins. Structure and Properties of Bis[
o
-xylyldithiolato-μ
2
-sulfidoferrate(III)], an Analog of the 2Fe-2S Proteins
Authors: Mayerle J. J. , Frankel R. B. , Holm R. H. , Ibers James A. , Phillips W. D. , Weiher J. F.
Published: May 2006

The synthetic analog approach has been applied to a clarification of the active sites of 2Fe-2S
*
proteins. The compound (Et
4
N)
2
[FeS(SCH
2
)
2
C
6
H
4
]
2
, derived from
o
-xylyl-α,α′-dithiol, has been prepared and its structure has been determined by x-ray diffraction. The centrosymmetric anion contains two tetrahedrally coordinated ferric ions bridged by two sulfide ions and separated by 2.70 Å. Comparison of electronic, Mössbauer, and proton magnetic resonance spectra and magnetic susceptibility of the anion with the corresponding properties of the oxidized forms of the proteins reveals significant degrees of similarity. The anion also exhibits the essential redox capacity of the proteins. We conclude that [FeS(SCH
2
)
2
C
6
H
4
]
2
2-
possesses the same total oxidation level and electronic configuration as the active sites of the oxidized proteins, and that its structure provides a feasible representation of the minimal structure of the active site. [FeS(SCH
2
)
2
C
6
H
4
]
2
2-
is thus the first well-defined synthetic analog of the active sites of two-iron ferredoxins.
Cyclic Adenosine Monophosphate Receptor: Loss of cAMP-Dependent DNA Binding Activity after Proteolysis in the Presence of Cyclic Adenosine Monophosphate
Authors: Krakow Joseph S. , Pastan Ira
Published: May 2006

The cAMP receptor requires cAMP for DNA binding at pH 8.0 but shows cAMP-independent DNA binding at pH 6.0. Incubation of the cAMP receptor with proteolytic enzymes in the presence of cAMP results in loss of DNA-binding ability at pH 8, while it is still able to bind cAMP and DNA at pH 6. Incubation with proteolytic enzyme in the absence of cAMP does not affect the DNA-binding properties of the cAMP receptor. After proteolysis in the presence of cAMP, analysis by sodium dodecyl sulfateacrylamide-gel electrophoresis shows that the 22,500-dalton subunit characteristic of the untreated protein has been completely replaced by a 12,500-dalton fragment.