bluuebunny/crossref_metadata_2025 huggingface dataset:
Glycolipid Synthesis in Normal and Virus-Transformed Hamster Cell Lines
Authors: Sakiyama Hisako , Gross Sonja K. , Robbins Phillips W.
Published: May 2006

Studies have been continued on the synthesis of glycolipids by the NIL 2 line of hamster cells. Several clones were isolated from this line. These clones vary in morphology, saturation density, and glycolipid composition. Contrary to expectation there was no correlation between saturation density and complexity of the glycolipid pattern. In fact, the clone with the highest saturation density was the only one to show the complete set of glycolipids found previously in NIL 2 cells.

All untransformed NIL clones show an increase in the level of “higher” (more than two saccharides/ceramide) glycolipids as the cells approach confluence. In the line containing all three “higher” neutral glycolipids, all three increased as cells approached saturation density. In the line containing only hematoside, this compound increased at confluence. Cells transformed by hamster sarcoma virus or polyoma virus showed no density-dependent glycolipid synthesis.
Infection of
Escherichia coli
by T2 and T4 Bacteriophages as Seen in the Electron Microscope: T4 Head Morphogenesis
Authors: Simon Lee D.
Published: May 2006

Bacteriophage T4 capsids seem to be assembled on
E. coli
protoplasmic membranes. This process seems to involve “lumps” of head protein, which convert to τ particles, which in turn give rise to empty heads. The empty heads leave the bacterial membrane and are then filled with DNA in the central region of the cell. T4 gene 16 and 17 products appear to be necessary for head filling.
Three Types of Gap Junctions Interconnecting Intestinal Epithelial Cells Visualized by Freeze-Etching
Authors: Staehelin L. Andrew
Published: May 2006

Gap junctions are specialized membrane regions that seem to mediate intercellular communication. They appear to contain closely packed arrays of equally sized particles all of which, upon freeze-cleaving, remain attached to one membrane leaflet and not to the other. One gap junction cleavage face, therefore, always exhibits a closely packed array of particles, while the other features a corresponding array of pits. By using these morphological criteria, we have been able to distinguish three different types of gap junctions interlinking adjacent epithelial cells of the small intestine. All three types may be found in close proximity to each other, and in all cases, the particles remain attached to the cleavage face of the cytoplasmic membrane leaflet (A-face). The most frequently encountered type-I gap junctions, which have already been observed in many other tissues, possess 8- to 9-nm (80- to 90-Å) particles with a center-to-center spacing of 9-10 nm (90-100 Å) when packed in a hexagonal lattice. Type-II gap junctions are always found in close association with type-I junctions. They can be distinguished from the type-I junctions by the greater size [10-11 nm (100-110 Å) in diameter] and the greater spacing (190-200 Å) of their hexagonally arrayed particles. In contrast, the particles of the type-III gap junctions are arranged in very small rectilinear arrays with a spacing of only 6-8 nm (60-80 Å). Gap junctions may be involved in the control of intercellular flow of different types of regulatory molecules.
Pollen Feeding and Reproductive Biology of
Heliconius
Butterflies
Authors: Gilbert Lawrence E.
Published: May 2006

Butterflies of the neotropical Genus
Heliconius
feed on pollen. This is the first known instance in butterflies of a habit that is well known for other insects. The butterflies remove amino acids and proteins from pollen; this feeding innovation plays a role in the reproductive and population biology of these insects. It is suggested that other animals may use pollen in a similar fashion.
Purification of Biologically Active Globin Messenger RNA by Chromatography on Oligothymidylic acid-Cellulose
Authors: Aviv Haim , Leder Philip
Published: May 2006

A convenient technique for the partial purification of large quantities of functional, poly(adenylic acid)-rich mRNA is described. The method depends upon annealing poly(adenylic acid)-rich mRNA to oligothymidylic acid-cellulose columns and its elution with buffers of low ionic strength. Biologically active rabbit globin mRNA has been purified by this procedure and assayed for its ability to direct the synthesis of rabbit globin in a cell-free extract of ascites tumor. Inasmuch as various mammalian mRNAs appear to be rich in poly(adenylic acid) and can likely be translated in the ascites cell-free extract, this approach should prove generally useful as an initial step in the isolation of specific mRNAs.
Biochemical Sequences in the Transformation of Normal Fibroblasts in Adolescent Rats
Authors: Reddi A. H. , Huggins Charles
Published: May 2006

Coarse powders of acid-insoluble matrix of diaphysis and calvarial parietal bone rapidly and consistently transformed fibroblasts into masses of cartilage and bone containing hemopoietic marrow. The transformant was encapsulated by fibroblasts within 24 hr to form a plaque. Transformation was restricted to the central thicknesses of the plaque. Under the stated conditions the alteration of the phenotype, fibroblast to chondroblast, was an unstable transformation, whereas the phenotype change, fibroblast to osteoblast, was stable. The transformation occurred on a rigid timetable of sequences. Measurements of alkaline phosphatase activity and incorporation of radioactive sulfate, phosphate, and calcium were sensitive and quantitative assays for the appearance of the transformed products, cartilage and bone.
Is Prolactin Mitogenic for Mammary Epithelium?
Authors: Oka Takami , Topper Yale J.
Published: May 2006

Prolactin administration to mature virgin mice leads to prolilferation of epithelium of the mammary gland. In organ culture, prolactin is not mitogenic, but insulin and insulin-free serum are. These observations are reconciled by the finding that insensitive epithelium is sensitized to insulin and/or serum by prolactin treatment
in vivo
. Thus, it appears that prolactin acts indirectly as a mitogen by rendering the cells susceptible to the aforementioned mitogens.
Purification and Biological Activity of Thymosin, a Hormone of the Thymus Gland
Authors: Goldstein Allan L. , Guha Arabinda , Zatz Marion M. , Hardy Mark A. , White Abraham
Published: May 2006

The purification and chemical properties of thymosin, obtained from bovine thymus tissue, are described. The biological activity of the thymic hormone has been assessed by a newly developed rosette assay, which permits measurement of thymus-dependent lymphoid cells. Thymosin activity is associated with a physico-chemically homogeneous protein of molecular weight 12,600. The hormonal activity is evident in
in vitro
incubation assay, after injection into adult thymectomized mice, and in prolonging survival of neonatally thymectomized mice and the reconstitution of their response to a skin allograft.
Coupling of a New, Active Morphine Derivative to Sepharose for Affinity Chromatography
Authors: Simon Eric J. , Dole William P. , Hiller Jacob M.
Published: May 2006

A new, pharmacologically active morphine derivative, 6-succinylmorphine, was synthesized. The properties of this compound and evidence for its structure are presented. Succinylmorphine was covalently coupled to ethylamino-Sepharose. Morphine-Sepharose containing up to 40 μg of morphine did not block the electrically stimulated contraction of isolated guinea pig ileum, but after alkaline hydrolysis of beads containing 2 μg of morphine the supernatant completely blocked contraction. This block was reversed by the specific morphine antagonist naloxone. Antibodies to morphine were removed from serum by morphine-Sepharose, but not by ethylamino-Sepharose, providing evidence of the efficacy of the beads for affinity chromatography.
Effect of Environmental pH on the Efficiency of Cellular Hybridization
Authors: Croce Carlo M. , Koprowski Hilary , Eagle Harry
Published: May 2006

The hybridization of a human and mouse cell was strikingly pH-dependent, with a well defined optimum at (about) pH 7.6-8.0. The yield of hybrid cell colonies (1 per 500-2000 heterokaryocytes) was several hundred times greater than that obtained at pH 6.8-7.2. Although there was a significant effect on the efficiency of cell fusion, the critical time for the pH effect was in the first 4-8 days after fusion, presumably while viable hybrids were being formed from the multinucleated heterokaryocytes.
Complex Lipid Requirements for Detergent-Solubilized Phosphoacetylmuramyl-Pentapeptide Translocase from
Micrococcus luteus
Authors: Umbreit Jay N. , Strominger Jack L.
Published: May 2006

Phospho-MurNAc-pentapeptide translocase activity in the membrane of
M. luteus
was lost upon addition of the detergent, Triton X-100, but could be restored by addition of lipid fractions to the assay. By assay in the presence of lipid, the activity of the Triton-solubilized enzyme could be measured. The synthesis of C
55
-isoprenyl-P-P-MurNAc-pentapeptide from UDP-MurNAc-pentapeptide required C
55
-isoprenyl-P, and was stimulated by a neutral lipid. The exchange reaction of UDP-MurNAc-pentapeptide with UMP required a polar lipid fraction, but the reaction was not affected by C
55
-isoprenyl-P or the neutral lipid. Thus, measurement of activity of the detergent-solubilized enzyme requires addition of three lipids, the lipid substrate (C
55
-isoprenyl-P), the neutral lipid, and a polar lipid.
A Fluorescent Analog of Nicotinamide Adenine Dinucleotide
Authors: Barrio Jorge R. , Secrist John A. , Leonard Nelson J.
Published: May 2006

Nicotinamide 1,
N
6
-ethenoadenine dinucleotide, a fluorescent analog of the coenzyme nicotinamide adenine dinucleotide, has been synthesized by the reaction of chloroacetaldehyde with the coenzyme. The technical fluorescence emission maximum of the analog is 410 nm, upon excitation at 300 nm. Its fluorescence yield is about 8% of that of the 1,
N
6
-ethenoadenine 5′-phosphate, and its fluorescence lifteime is shorter. Upon hydrolysis of the modified coenzyme analog with
Neurospora crassa
NADase or phosphodiesterase I at room temperature, the intensity of fluorescence was increased 10-fold, corresponding to separation of the nicotinamide and ethenoadenine rings. The spectroscopic results with nicotinamide 1,
N
6
-ethenoadenine dinucleotide are consistent with the concept of an intramolecular interaction between the modified adenine and pyridine moieties of the dinucleotide that is disrupted by enzymatic hydrolysis. The fluorescent analog showed reasonable activity as a substitute for NAD
+
in four different dehydrogenase-catalyzed reactions.
Sequence Relationships among the Variable Regions of Immunoglobulin Heavy Chains from Various Mammalian Species
Authors: Kehoe J. Michael , Capra J. Donald
Published: May 2006

Immunoglobulin heavy chains of myeloma proteins from dogs and cata have been subjected to automated sequence analysis. When the results were compared with human heavy-chain sequences, all the dog and cat proteins could be unequivocally assigned to the V
H
III subgroup. This pattern contrasts with that in human proteins in which only 25% of all heavy chains sequenced belong to this subgroup. The 30 residues at the NH
2
termini of dog, cat, and human heavy chains had sequence identities near or exceeding 90%, in contrast to established interspecies sequence homologies of constant regions of about 60%. Some genes of the immunoglobulin heavy-chain variable region thus appear to have been conserved through a considerable period of evolutionary time.

The analyses also showed that the presence of certain amino acids at certain positions in these heavy chains could be correlated with the species of origin. The occurrence of such “phylogenetically associated” residues is most consistent with the presence of a restricted number of genes in the heavy-chain variable region pool.
Stereochemistry of a Curare Alkaloid:
O,O′,N
-Trimethyl-
d
-Tubocurarine
Authors: Sobell Henry M. , Sakore T. D. , Tavale S. S. , Canepa F. G. , Pauling Peter , Petcher Trevor J.
Published: May 2006

The three-dimensional structure of
O,O′,N
-trimethyl-
d
-tubocurarine, a neuromuscular blocking agent, has been determined by x-ray crystallography. This may help to provide insight into its pharmacologic action.
Kinetics of Small Ising Systems: Deviations from Internal Equilibrium in a Tetrahedral Model
Authors: Paul Edward , Hill Terrell L.
Published: May 2006

Computer modeling is used to derive some of the exact kinetic properties of a small Ising system.
Rat Brain Microtubule Protein: Purification and Determination of Covalently Bound Phosphate and Carbohydrate
Authors: Eipper Betty A.
Published: May 2006

Microtubule protein purified from rat brain by published procedures contains nucleic acid and carbohydrate contaminants. Microtubule protein isolated from the soluble fraction of rat brain homogenates by a new procedure contains no covalently bound amino sugars and no more than 0.2% neutral sugar, but does contain covalently bound phosphate. Total phosphate analysis of rat brain microtubule protein indicates the presence of 0.8 mol of phosphate per mol of protein dimer (110,000 g). The presence of covalently bound phosphate has been confirmed by preparation of
32
P-labeled microtubule protein from rat brain slices maintained in tissue culture in the presence of [
32
P]orthophosphate. Furthermore, phosphorylation is specific to the more negatively charged microtubule protein subunit.
32
P-Labeled serine phosphate has been identified after partial acid hydrolysis of labeled microtubule protein.
The Upper Temperature Limit for Eukaryotic Organisms
Authors: Tansey Michael R. , Brock Thomas D.
Published: May 2006

An upper temperature limit near 60° for eukaryotic organisms is documented by results of a systematic search for fungi able to grow at higher temperatures. Samples from hot springs, thermal soils, self-heating coal waste piles, and other natural and man-made heated habitats did not yield fungi when enrichments were done at 62°, whereas fungi able to grow at 55-60° can be readily isolated from such habitats. Earlier work had shown that eukaryotic algae are also absent from environments with temperatures above 55-60°. It is suggested that the failure of eukaryotes to evolve members able to grow at higher temperatures is due to their inability to form organellar membranes that are both thermostable and functional.
Structure and Properties of a Synthetic Analogue of Bacterial Iron-Sulfur Proteins
Authors: Herskovitz T. , Averill B. A. , Holm R. H. , Ibers James A. , Phillips W. D. , Weiher J. F.
Published: May 2006

The compound (Et
4
N)
2
[Fe
4
S
4
(SCH
2
Ph)
4
] has been prepared and its structure determined by x-ray diffraction. The Fe
4
S
4
core of the anion possesses a configuration of D

2d

symmetry that is closely related to the Fe
4
S
4
active-site structures of the high-potential iron protein from
Chromatium
and the ferredoxin from
Micrococcus aerogenes
. Electronic properties of the tetrameric anion have been partially characterized by measurement of proton magnetic resonance, Mössbauer, photoelectron, and electronic spectra, and magnetic susceptibility. Comparison of corresponding properties of [Fe
4
S
4
(SCH
2
Ph)
4
]
2-
and the proteins implies that the oxidation levels of the synthetic tetramer, the reduced form of the high-potential protein, and the oxidized form of the 8-Fe ferredoxins are equivalent. The tetramer possesses the one-electron redox capacity associated with the 4-Fe centers of the ferredoxins. The structural and collective electronic features of [Fe
4
S
4
(SCH
2
Ph)
4
]
2-
reveal it to be the first well-defined synthetic analogue of the active site of an iron-sulfur protein.
Molecular Mechanism for Genetic Recombination
Authors: Sobell Henry M.
Published: May 2006

Symmetry considerations of proteinnucleic acid interaction suggest the existence of an alternate branched configuration for DNA induced by binding specific structural proteins to symmetrically arranged polynucleotide base sequences. The concept that such sequences exist at the ends of genes or operons leads to a molecular model for genetic recombination in eukaryotic cells.
Activation of Variants of Hypoxanthine-Guanine Phosphoribosyl Transferase by the Normal Enzyme
Authors: Bakay Bohdan , Nyhan William L.
Published: May 2006

Deficient hypoxanthine-guanine phosphoribosyl transferase (HGPRT; EC 2.4.2.8) enzymes from erythrocytes of patients with hyperuricemia and with the Lesch-Nyhan syndrome migrate 15% faster in polyacrylamide gel disc electrophoresis than the normal enzyme. A half-sister of two males with partial deficiency, who had 34% of normal HGPRT activity in her erythrocytes, yielded profiles containing two distinct zones of activity; one corresponded to the enzyme found in normal individuals and one to the variant of her half-brothers. However, in her profile her variant enzyme showed notably greater activity than that observed in her half-brothers. This increase was due to an activation of the variant by normal enzyme. Electrophoresis of mixtures of normal enzyme with partially deficient enzymes from patients with hyperuricemia and with the Lesch-Nyhan syndrome also led to activation of deficient HGPRT variants by normal enzymes. Deficient variants were also activated by normal enzyme on filtration through Sephadex G-25. Experiments in which deficient variant enzymes were activated with purified normal enzyme labeled with
125
I indicated that deficient enzymes incorporate components of the normal enzyme. No such activation of deficient enzymes was ever obtained when mixtures of deficient and normal enzymes were put together in a test tube.
Replication of Bacteriophage M13: Specificity of the
Escherichia coli dna
B Function for Replication of Double-Stranded M13 DNA
Authors: Olsen William L. , Staudenbauer Walter L. , Hofschneider Peter Hans
Published: May 2006

Infection of the temperature-sensitive
E. coli
mutant HfrH 165/70 (
dna
B) with the filamentous single-stranded DNA phage M13 is abortive at the restrictive temperature. Upon infection at 41°, single-stranded phage DNA penetrates the cell and is converted in a rifampicin-sensitive step to the double-stranded replicative form (RF). The parental RF attaches to the cell membrane, but subsequent replication of the RF is blocked. It is concluded that in M13 infection semiconservative RF replication of a double strand to a double strand, in contrast to single-stranded DNA synthesis, depends specifically on the
dna
B function.
Group Selection on the Boundary of a Stable Population
Authors: Boorman Scott A. , Levitt Paul R.
Published: May 2006

A model of group selection is constructed for the case of differential extinction acting on small boundary populations of a large, fixed population. Consideration is restricted to extinction operators acting at or near to carrying capacity. Under the assumption that the extinction rate is large relative to individual genetic parameters affecting gene frequencies in boundary populations, we discuss the conditions under which differential extinction is most likely to produce a significant effect. In particular, a condition for bimodality in the distribution of gene frequencies in boundary populations (population polymorphism) is that there be some critical allele frequency at which the extinction rate jumps from high to low. An extinction operator linear in allele frequency produces no qualitative effect of this kind. In consequence, we are able to make precise rather limited circumstances under which group selection is likely to have a significant effect.
Stability of Cytoplasmic Messenger RNA in HeLa Cells
Authors: Murphy William , Attardi Giuseppe
Published: May 2006

The metabolic stability of pulse-labeled or long-term labeled messenger RNA (mRNA) from cytoplasmic free polysomes was measured in HeLa cells, with chase conditions that do not involve inhibitors of RNA synthesis, and chromatography on benzoylated-DEAE-cellulose or poly(T)-cellulose for isolation of mRNA. For these studies, a new chase technique was developed that allows analysis of the stability of mRNA labeled during a short [
3
H]uridine pulse. Pulse-labeled and long-term labeled mRNA were found to decay with an estimated average half-life of about 2 and 3 days, respectively, much longer than hitherto assumed.
Immunochemical Analysis of the Cross-Reacting Idiotypes of Mouse Myeloma Proteins with Anti-Dextran Activity and Normal Anti-Dextran Antibody
Authors: Carson Dennis , Weigert Martin
Published: May 2006

The idiotype of the mouse myeloma protein with anti-α-1,3 dextran activity, J558, has been characterized by a solid-phase radioimmunoassay. The idiotype of the J558 protein depends on a specific light and heavy chain interaction and is altered in the presence of the hapten, nigerose. Cross-reacting idiotypes were found on another mouse myeloma protein with α1,3 dextran specificity, normal anti-dextran antibody, and certain reconstructed myeloma proteins composed of the J558 heavy chain and heterologous light chains.
A Cellular Basis for Genetically Controlled Immunologic Unresponsiveness in Mice: Tolerance Induction in T-Cells
Authors: Gershon Richard K. , Maurer Paul H. , Merryman Carmen F.
Published: May 2006

H-2
q
mice (DBA/1) do not make an antibody response to a synthetic aminoacid polymer, (Glu, Ala,Tyr
10
), after an immunizing regimen that produces a good antibody response in mouse strains with other H-2 alleles. Their thymocytes, however, show evidence of recognizing this antigen since they synthesize DNA when they meet the antigen in the spleen. This recognition event does not lead to memory production, as it does in genetic responders, since the thymocytes fail to respond to a second immunization with (Glu,Ala,Tyr
10
). Nonresponder mice do make antibody to (Glu,Ala,Tyr
10
) when they are immunized with it complexed to an immunogenic carrier, but previous treatment with free polymer can temporarily abolish this response. Thus, we suggest that the basis for the unresponsiveness of these mice is that their T-cells (thymus-processed lymphocytes) have an inordinate propensity to become (or to induce other cells to become) immunologically tolerant.
Structure and Development of Neuronal Connections in Isogenic Organisms: Variations and Similarities in the Optic System of
Daphnia magna
Authors: Macagno E. R. , Lopresti V. , Levinthal C.
Published: May 2006

It is readily apparent upon examination and comparison of organisms of the same and related species that to a large extent genes control morphological features. One means to ascertain the role and degree of genetic control is to study in detail the anatomy and development of a particular structure, say an identifiable neuron, in a population with a fixed genome, and at different stages of morphogenesis. The small crustacean, Daphnia, is well suited for this type of study, since it reproduces parthenogenically, its development is easily staged, and its nervous system is reasonably simple. In this paper comparisons of detailed morphology of neurons in the visual system of adult
Daphnia magna
are considered. Results indicate that gross features of the system are reproduced within the clone, but some of the finer details are not reproduced.
Human Phosphoribosylpyrophosphate Synthetase: Increased Enzyme Specific Activity in a Family with Gout and Excessive Purine Synthesis
Authors: Becker Michael A. , Kostel Paul J. , Meyer Laurence J. , Seegmiller J. Edwin
Published: May 2006

Among affected members of a family (B. family) with excessive purine production and gout, activity of phosphoribosylpyrophosphate synthetase (EC 2.7.6.1) is 2.5- to 3.0-fold higher than among normal people. The molecular basis for this increased enzyme activity was studied. Antibody to purified human phosphoribosylpyrophosphate synthetase of erythrocytes was obtained from immunized rabbits. Studies with the IgG fraction of this antiserum show the presence of normal quantities of immunoreactive enzyme, but 2.5- to 3.0-fold higher activity per molecule in affected members of the B. family. In addition, by use of a stain for phosphoribosylpyrophosphate synthetase activity, a difference in electrophoretic mobility was demonstrated on cellulose acetate gel between the partially purified enzyme from normal people and an affected member of the B. family. These studies suggest that the enzyme aberration responsible for purine overproduction and gout in the B. family results from a structurally altered enzyme with increased activity per molecule.
A Family of Three Related Satellite DNAs in
Drosophila virilis
Authors: Blumenfeld Martin , Fox Allen S. , Forrest Hugh S.
Published: May 2006

Isolated single DNA strands of satellites II or III of
Drosophila virilis
form hybrid duplexes with the complementary single strands of satellite I. The hybrids denature at a higher temperature than controls, renature rapidly, and form bands of hybrid density in neutral CsCl. Isolated single strands of satellite II do not form clear-cut duplexes with the complementary strands of satellite III. Mixtures of satellites II and III denature at the same temperature as controls, and do not form bands in neutral CsCl. Therefore, satellite I-II and I-III complexes are extensively base paired, while satellite II-III complexes are minimally base paired. These experiments demonstrate partial homology among the three satellites, and suggest an evolutionary relationship among them. They also suggest that satellites and other repeated sequences from related species, which do not form hybrids
in vitro
, could have a common evolutionary origin, but have accumulated enough base substitutions to lose interspecific homology demonstrable by hybrid duplex formation.
Oxidation-Reduction Potentials of Bound Iron-Sulfur Proteins of Photosystem I
Authors: Ke Bacon , Hansen Raymond E. , Beinert Helmut
Published: May 2006

Digitonin - fractionated photosystem - I subchloroplasts were titrated potentiometrically between -450 and -610 mV at pH 10. Examination of the titrated subchloroplasts by low-temperature (13°K) electron paramagnetic resonance spectroscopy revealed resonances centered at values of 2.05, 1.94, 1.92, 1.89, and 1.86 on the
g
-factor scale. The peak heights depended on the potentials at which the chloroplasts were poised. The resonances of at least three iron-sulfur centers can be recognized: one with lines at
g
= 2.05 and 1.94; one with lines at
g
= 2.05, 1.92, and 1.89; and one for which only a line at
g
= 1.86 has been resolved. The midpoint potentials of the iron-sulfur species fall into two distinctly separate regions: the titration profile of the
g
= 1.94 signal, the first segment of the
g
= 2.05 plot, and the rise phase of the
g
= 1.86 signal had a value of -530 ± 5 mV; the upper segment of the
g
= 2.05 plot, the decrease phase of the
g
= 1.86 signal, and the
g
= 1.89 profile had a midpoint potential estimated to be [unk] -580 mV. The oxidation-reduction reaction of each of the bound iron-sulfur species, as represented by the changes of the electron paramagnetic resonance spectra, was reversible and apparently involved a two-electron change.

Titration at pH 9 could only be carried to -560 mV, and essentially only the first half of the titration behavior as found at pH 10 was seen. At any given potential more positive than -560 mV, the part of the iron-sulfur protein that was not reduced electrochemically could be reduced photochemically, but only to the maximum extent reduced electrochemically at -560 mV. Whereas, chloroplasts illuminated at room temperature and then frozen while still being illuminated developed a signal similar to that produced by electrochemical reduction at -610 mV, illumination at 77°K did not bring about photoreduction beyond that accomplished electrochemically at about -560 mV.

Dithionite alone in the dark and under anaerobic conditions brought about a partial reduction to the extent of the first electrochemical reduction step. Dithionite plus illumination at room temperature or dithionite plus methyl viologen in the dark produced the maximum signal. Electron paramagnetic resonance spectra due to either light or electrochemically reduced iron-sulfur proteins showed no detectable decay for at least 3 days when samples were stored in the dark at 77°K.
Effect of Circularity and Superhelicity on Transcription from Bacteriophage λ DNA
Authors: Botchan Peter , Wang James C. , Echols Harrison
Published: May 2006

We studied RNA synthesis
in vitro
from closed-circular λ DNA molecules with varying degrees of superhelicity. The four circular templates examined had
0, -50, -110
, and
-160
superhelical turns under the conditions of the transcription assay. We found that the total amount of RNA synthesis increases as the template acquires more negative superhelical turns. This increased transcription results from more frequent initiation of RNA chains. Transcription of circular DNA with no superhelical turns appears to mimic RNA synthesis
in vivo
more closely than transcription from either highly superhelical or linear DNA with regard to two criteria: preferential transcription of the region corresponding to early genes and sensitivity to repression by λ
c
I protein. We suggest that the physical basis for the increased initiation of RNA chains from superhelical DNA is the fact that unwinding events are energetically favored on a DNA molecule with negative superhelical turns. Possible general mechanisms are: (
a
) RNA polymerase must unwind the DNA duplex as a prelude to initiation; (
b
) the DNA itself must assume a new conformation at the promoter site which requires an unwinding of the DNA duplex.
Chromosome Replication During Meiosis: Identification of Gene Functions Required for Premeiotic DNA Synthesis
Authors: Roth Robert
Published: May 2006

Recent comparisons of chromosome replication in meiotic and mitotic cells have revealed significant differences in both the rate and pattern of DNA synthesis during the final duplication preceding meiosis. These differences suggested that unique gene functions might be required for premeiotic replication that were not necessary for replication during growth. To provide evidence for such functions, we isolated stage-specific mutants in the yeast
Saccharomyces cerevisiae
which permitted vegetative replication but blocked the round of replication before meiosis. The mutants synthesized carbohydrate, protein, and RNA during the expected interval of premeiotic replication, suggesting that their lesions preferentially affected synthesis of DNA. The mutations blocked meiosis, as judged by a coincident inhibition of intragenic recombination and ascospore formation. The lesions were characterized as recessive nuclear genes, and were designated
mei-1, mei-2
, and
mei-3
; complementation indicated that the relevant gene products were not identical.
DNA of Epstein-Barr Virus Detected in Tissue of Burkitt's Lymphoma and Nasopharyngeal Carcinoma
Authors: Nonoyama M. , Huang C. H. , Pagano J. S. , Klein G. , Singh S.
Published: May 2006

The association of Epstein-Barr virus (EBV) DNA with African tumors was examined by the method of hybridization with complementary RNA. 22 out of 23 biopsies of Burkitt's lymphoma and 18 out of 23 biopsies of nasopharyngeal carcinoma were found to contain EBV DNA. The number of EBV genome equivalents per cell ranged from four to 113. Five out of 24 other African tumors, two adenocarcinomas, and one each of melanoma, reticulum cell sarcoma, and carcinoma of the antrum, also contained EBV DNA.
Specific Photoaffinity Labeling of the Adenosine 3′:5′-Cyclic Monophosphate Receptor in Intact Ghosts from Human Erythrocytes
Authors: Guthrow C. Earl , Rasmussen Howard , Brunswick David J. , Cooperman Barry S.
Published: May 2006

[
3
H]
N
6
-(Ethyl 2-diazomalonyl)-adenosine 3′:5′-cyclic monophosphate is incorporated into intact ghosts from human erythrocytes on photolysis at 253.7 nm. Incorporation is blocked in the presence of adenosine 3′:5′-cyclic monophosphate (cyclic AMP) and does not occur in the absence of irradiation. Sodium dodecyl sulfate disc gel electrophoresis of solubilized ghosts shows that one protein is labeled. The position of this protein on the gel corresponds exactly to that previously found. [
J. Biol. Chem.
247, 8145 (1972)] for the endogeneous protein substrate of the endogenous, cyclic AMP-dependent, protein kinase.
On the Amino-Acid Sequence of Flagellin from
Bacillus subtilis
168: Comparison with Other Bacterial Flagellins
Authors: Delange Robert J. , Chang Joyce Y. , Shaper Joel H. , Martinez Rafael J. , Komatsu Stanley K. , Glazer Alexander N.
Published: May 2006

A partial amino-acid sequence of
Bacillus subtilis
168 flagellin is presented. The region of unassigned sequence in this 304-residue polypeptide chain spans residues 158-173. Comparison of the 27-residue aminoterminal CNBr peptide of
B. subtilis
168 flagellin with that derived from the flagellin of the serologically unrelated strain of
B. subtilis
, W23, shows only three conservative substitutions, whereas the 16-residue carboxyl-terminal peptides derived from these flagellins were identical. The comparison of the very limited sequence information available on the flagellins of
Salmonella
and
Proteus
with that on
B. subtilis
indicates homology between these proteins.
Molecular Orbital Calculations of Magnetic Circular Dichroism Spectra: A Benzene-Indole Sequence
Authors: Miles Daniel W. , Eyring H.
Published: May 2006

The magnetic circular dichroism of benzene and indole derivatives was measured down to 190 nM. The following pairs of molecules have magnetic circular dichroisms of the opposite sign in the

B
2u

absorption region: aniline and benzonitrile, indene and indoline, indole and 4-aminoindole, and 4-aminoindole and 5-aminoindole. The sign and magnitude of the magnetic circular dichroisms observed are in good agreement with those calculated by the semiempirical self-consistent field with configuration interaction Pariser-Parr-Pople method with incorporation of variable π-electronegativity and σ-polarization. The energy dominator in the magnetic rotational strength expression serves to limit the important contributions to a few terms only.
Sodium Uptake Associated with Activation of Action Potential Ionophores of Cultured Neuroblastoma and Muscle Cells
Authors: Catterall William A. , Nirenberg Marshall
Published: May 2006

Veratridine, an activator of action potential Na
+
ionophores, stimulated passive Na
+
uptake by electrically excitable neuroblastoma and muscle cells but had no effect on clonal cell lines defective in Na
+
-ionophore activity. Veratridine-dependent Na
+
uptake was completely inhibited by tetrodotoxin, a specific inhibitor of the action potential Na
+
ionophore. Half-maximal inhibition was obtained with 11 nM tetrodotoxin. Thus, veratridinedependent Na
+
uptake provides a specific and convenient means of assaying populations of cultured cells for action potential Na
+
-ionophore activity.
The Function of the Two Subunits of Thermophilic Aminopeptidase I
Authors: Stoll Erwin , Ericsson Lowell H. , Zuber H.
Published: May 2006

The thermophilic high-molecular-weight aminopeptidase I (EC 3.4.11.1) from
Bacillus stearothermophilus
is composed of 12 subunits of two different types (α,β) which can combine in various ratios. Only one type of subunit (α) is needed for the degradation of neutral peptides, but dipeptides having amino-terminal aspartic or gultamic acid are substantially hydrolyzed only by enzyme containing the other subunit (β) as well. Asp-Gly inhibits the enzymatic hydrolysis of glutamic acid 1-(4-nitroanilide) very strongly but hardly affects the hydrolysis of leucine
p
-nitroanilide. These results indicate that both types of subunit have hydrolytic activity but different specificity. The two subunits have identical molecular weights and their amino-terminal regions are homologous, suggesting that the two chains originate from a single ancestral gene by gene duplication and independent mutation.
Mechanism of Puromycin Action: Fate of Ribosomes after Release of Nascent Protein Chains from Polysomes
Authors: Azzam M. E. , Algranati I. D.
Published: May 2006

The exchange of ribosomal subunits during the release of growing polypeptide chains by puromycin has been investigated in a bacterial cell-free system engaged in protein synthesis. The addition of spermidine, used as a stabilizing agent of 70S monomers, caused a strong inhibition of the subunit exchange. This result led us to conclude that upon premature release of unfinished protein chains by the antibiotic, the ribosomes fall off mRNA as 70S particles. This behavior is different from that occurring during physiological termination of translation, where the ribosomes detach in a dissociated form. Some implications of the postulated mechanism are also discussed.
Purine Metabolism in Normal and Thioguanine-Resistant Neuroblastoma
Authors: Wood Alexander W. , Becker Michael A. , Minna John D. , Seegmiller J. Edwin
Published: May 2006

Purine metabolism has been examined in a clonal line of mouse neuroblastoma cells resistant to the cytotoxic effects of 6-thioguanine. Comparative studies in the resistant and parental lines indicate that the former cells have less than 1% of normal hypoxanthine phosphoribosyltransferase (EC 2.4.2.8) activity. The activities of other enzymes important in the
de novo
and salvage pathways of purine biosynthesis were not significantly different in the two lines. Hypoxanthine phosphoribosyltransferase deficiency in this neuroblastoma line was associated with increased intracellular concentrations of 5-phosphoribosyl-1-pyrophosphate, an increased rate of purine biosynthesis
de novo
, and failure to incorporate hypoxanthine, but not adenine, into nucleotides. There are essentially the same alterations in purine metabolism that occur in hypoxanthine phosphoribosyltransferase-deficient fibroblasts or lymphoblasts derived from individuals with the Lesch-Nyhan syndrome. Clonal lines of hypoxanthine phosphoribosyltransferase-deficient neuroblastoma cells may therefore be of use in elucidating the mechanisms by which the enzyme defect leads to the neurologic dysfunction seen in children with this disease.
Regulation of the Expression of the
N
Gene of Bacteriophage Lambda
Authors: Greenblatt Jack
Published: May 2006

A quantitative assay for the
N
protein of bacteriophage λ has been used to study the
in vivo
regulation of
N
gene expression. The assay makes use of the observation that in a cell-free protein-synthesizing system from
Escherichia coli
programmed with λ
N
-
DNA the λ endolysin is made only if
N
protein is added to the reaction.

The rate of synthesis of
N
protein
in vivo
is negatively controlled by the products of the
CI
and
tof
genes of the phage. Furthermore,
N
protein activity is extremely unstable
in vivo
. During normal cell growth at 35°, the half-life of
N
protein is about 2 min.
Enzymatic Synthesis of DNA Complementary to Purified 14S Messenger RNA of Immunoglobulin Light Chain
Authors: Diggelmann H. , Faust C. H. , Mach B.
Published: May 2006

The 14S messenger RNA, which contains poly(adenylic acid), of MOPC 41 (mouse plasmocytoma) immunoglobulin light chain, purified to a single peak as shown by polyacrylamide gel electrophoresis, was used to synthesize complementary DNA with the RNA-dependent DNA polymerase of avian myeloblastosis virus. DNA synthesis is entirely dependent on added RNA template and oligo(dT) primer. Both the size and the concentration of the primer affect the reaction. The product behaves similarly to DNA during centrifugation in cesium sulfate density gradients. It is shown by hybridization that the DNA made is complementary to the purified template, light-chain mRNA. The high specific activity of the complementary DNA should make it suitable for gene-dosage experiments. According to alkaline sucrose gradient analyses, some complete complementary DNA transcripts of the 14S mRNA seem to be made. Oligo(dG) can also function as a primer for DNA synthesis, possibly by annealing to an internal cluster of cytidines in the mRNA, that correspond to the bases coding for amino-acids 119 and 120 of the MOPC 41 light chain.
Protective Effect of Ascorbic Acid on Hepatotoxicity Caused by Sodium Nitrite Plus Aminopyrine
Authors: Kamm Jerome J. , Dashman Theodore , Conney A. H. , Burns J. J.
Published: May 2006

The oral treatment of rats with sodium ascorbate in combination with sodium nitrite and aminopyrine prevents the rise in serum alanine aminotransferase (EC 2.6.1.2) observed when nitrite and aminopyrine are given alone. Ascorbic acid also affords protection, whereas dehydroascorbic acid exerts no protective effect.
The Role of the Histocompatibility-2-Linked
Ss-Slp
Region in the Control of Mouse Complement
Authors: Démant P. , Capková Jana , Hinzová Eva , Vorácová Bela
Published: May 2006

The
Ss-Slp
region of the mouse genome is located between the two loci,
H-2K
and
H-2D
, of the major histocompatibility system. It controls the level of a serologically detectable serum globulin, the Ss protein, and its allotypic forms, Slp
a
and Slp
o
. Evidence is presented that the
Ss-Slp
region is involved in control of the complement system. Mice of congenic resistant strains differing only at the
H-2
gene complex show differences in complement levels. A comparison of
H-2
recombinants demonstrated that complement level correlates with the
Ss-Slp
genotype and not with the
H-2K, H-2D
, or
Ir
genotypes. Among the 13 congenic strains tested, those with the
Ss
h
Slp
a
allele had higher complement levels than those with the
Ss
h
Slp
o
or
Ss
l
Slp
o
alleles. Mice with recombinant
H-2
haplotypes had complement levels similar to those of the parental strain that provided the
Ss-Slp
segment. It was also shown that anti-Ss serum inhibits complement activity of mouse serum
in vitro
.
Regulation of Phosphorylation of a Specific Protein in Toad-Bladder Membrane by Antidiuretic Hormone and Cyclic AMP, and Its Possible Relationship to Membrane Permeability Changes
Authors: DeLorenzo Robert J. , Walton Kenneth G. , Curran Peter F. , Greengard Paul
Published: May 2006

Phosphorylation of a specific protein was decreased in intact toad bladders by exposure to either antidiuretic hormone or monobutyryl cyclic AMP. The decrease in phosphorylation caused by these agents preceded the change in electrical potential difference (an indicator of the rate of sodium ion transport) observed in response to the same compounds. The addition of cyclic AMP to homogenates of toad bladder led to a decrease in phosphorylation of the same, or a similar, protein. In subcellular fractionation studies, the effect of cyclic AMP on the phosphorylation of this protein was observed in those fractions rich in membrane fragments, but not in the nuclear or cell-sap fractions. These and other results are compatible with the possibility that the regulation by vasopressin and cyclic AMP of sodium and/or water transport in toad bladder may be mediated through regulation of the phosphorylation of this specific protein.
Detection and Isolation of an Endoperoxide Intermediate in Prostaglandin Biosynthesis
Authors: Hamberg Mats , Samuelsson Bengt
Published: May 2006

An earlier proposed endoperoxide intermediate in the biosynthesis of prostaglandins was detected in short-time incubations of arachidonic acid with the microsomal fraction of homogenates of sheep vesicular glands. Conversion of the endoperoxide into prostaglandin E
2
was stimulated by reduced glutathione but suppressed by
p
-mercuribenzoate and
N
-ethylmaleimide. The methyl ester of an unknown compound was isolated by solvent extraction and thin-layer chromatography after short-time incubation of arachidonic acid with the microsomal fraction and
p
-mercuribenzoate. This derivative was identical to the methylester of the endoperoxide, as shown by its conversion into the methyl esters of 11-dehydroprostaglandin F
2α
and prostaglandin E
2
by spontaneous rearrangement and its conversion into the methyl ester of prostaglandin F
2α
by mild chemical reduction. The smooth muscle-stimulating activity of the endoperoxide ester on the isolated rabbit aortas trip was 4- to 8-times higher than that of the methyl ester of prostaglandin E
2
.
Adaptive Linkage Disequilibrium Between Two Esterase Loci of a Salamander
Authors: Webster T. Preston
Published: May 2006

In some populations of the salamander
Plethodon cinereus
, two polymorphic esterase loci are in linkage disequilibrium. Short-term stability of the linkage disequilibrium is demonstrated by an age class analysis. Long, perhaps very long, term stability is suggested by its distribution. This stability and concordant geographic variation in allelic frequencies imply selective origin and maintenance. Data on the frequencies of two color morphs suggest that formation of the linkage disequilibrium is dependent on the genetic background.
Messenger RNA for Hepatic Tryptophan Oxygenase: Its Partial Purification, Its Translation in a Heterologous Cell-free System, and Its Control by Glucocorticoid Hormones
Authors: Schutz G. , Beato M. , Feigelson P.
Published: May 2006

Messenger RNA from rat liver was partially purified by chromatography on cellulose on the basis of its poly(A) content. Microgram amounts of this RNA stimulate protein synthesis manyfold in a heterologous cell-free system, derived from Krebs ascites cells supplemented with reticulocyte initiation factors. The messenger RNA directs the initiation, synthesis, and release of a product that was identified as complete subunits of hepatic tryptophan oxygenase (EC 1.13.1.12) by immunoprecipitation with monovalent antibodies prepared against homogeneous tryptophan oxygenase and subsequent sodium dodecyl sulfate-polyacrylamide electrophoresis of the solubilized immunoprecipitate. This may represent the first complete translation in a heterologous system of a mammalian messenger RNA coding for an enzyme protein. Analysis of the messenger RNA content of the liver after glucocorticoid administration demonstrates that the hormonally enhanced rate of synthesis of tryptophan oxygenase is accompanied by an increased quantity of its corresponding messenger RNA.
Isolation and Characterization of Two Glycoproteins from Patients with Alveolar Proteinosis
Authors: Passero Michael A. , Tye Ross W. , Kilburn Kaye H. , Lynn William S.
Published: May 2006

The saline-insoluble particulate material obtained by pulmonary lavage from four patients with alveolar proteinosis was analyzed for total lipid (52%), protein (44%), and carbohydrate (4%). Sodium dodecyl sulfate-gel electrophoresis revealed only three major peptides in these patients. Molecular weights (from the gels) were 69,000, 62,000, and 36,000, and the latter two peptides were periodic acid-Schiff stain-positive. Amino-acid and sugar analyses were performed on the peptides cut from the gels and on peptides purified by Sephadex G-200 chromatography. The 69,000-molecular-weight peptide contained no carbohydrate. Antibody studies and aminoacid analysis indicated that it was albumin. The 62,000-molecular-weight peptide contained 1% hydroxyproline, 1% hydroxylysine, 10% glycine, and 9% carbohydrate. The 36,000-molecular-weight peptide contained 1.2% hydroxyproline, 1% hydroxylysine, 13% glycine, 1.4% sialic acid, 2.6% glucose, 2.4% galactose, 2% mannose, 0.8% fucose, 0.4% glycosamine, and 0.6% galactosamine. Proteins extracted from kidney glomeruli with similar amino-acid and carbohydrate composition have been observed previously.
An Informative Solution to a Seismological Inverse Problem
Authors: Gilbert Freeman , Dziewonski Adam , Brune James
Published: May 2006

Preliminary results are presented that infer that 2 sec should be added to the tabular values for
P
phases and 4 sec to the tabular values for
S
phases of seismic travel times. From seismic evidence, the radius of the inner core of the Earth is 1229-1250 km; the radius of the outer core is 3482-3485 km. Data are presented relating resolving power with error of measurement for the Earth's mantle.