bluuebunny/crossref_metadata_2025 huggingface dataset:
The Anomalous Deuterium Isotope Effect on the Chemical Shift of the Bridge Hydrogen in the Enol Tautomer of 2,4-Pentanedione
Authors: Chan Sunney I. , Lin L. , Clutter Dale , Dea Phoebe
Published: May 2006

The nature of the intramolecular hydrogen bond in the enol tautomer of 2,4-pentanedione has been investigated by high resolution proton and deuteron magnetic resonance spectroscopy. An unusually large deuterium isotope effect on the chemical shift of the bridge hydrogen has been observed. This unexpected result, together with the observation of a pronounced temperature dependence for both the proton and deuteron resonances, suggests that two states with different chemical shifts for the bridge hydrogen are involved in rapid equilibrium and that the anomalous deuterium isotope effect has its origin in the effect of deuterium substitution on the energy separation between these states. It is proposed that these states correspond to the symmetrical and asymmetrical structures of the intramolecular hydrogen bond.
Interconversion of Phospho- and Dephospho- Forms of Pig Heart Pyruvate Dehydrogenase
Authors: Wieland Otto , Siess Elmar
Published: May 2006

Pyruvate dehydrogenase from pig heart exists in active and inactive forms. Interconversion from the active (dephospho) form into the inactive (phospho) form is catalyzed by an ATP-dependent kinase. Conversely the enzyme is reactivated by a phosphatase which removes the phosphate group from the protein. By gradient centrifugation pyruvate dehydrogenase was prepared free of phosphatase but still containing the kinase. Reactivation of pyruvate dehydrogenase is stimulated by adenosine 3′,5′-cyclic phosphate. There is incorporation of
32
P from γ-
32
P-ATP into the protein fraction containing the phosphatase and this phosphorylation reaction is also stimulated by adenosine 3′,5′-cyclic phosphate. The participation of this phosphate in the pyruvate dehydrogenase interconversion system suggests that, in heart muscle, pyruvate oxidation may be under hormonal control by a mechanism similar to that involved in the regulation of glycogen synthesis and breakdown.
Interpretation of the [ClIII] Lines in Gaseous Nebulae
Authors: Aller L. H. , Czyzak S. J. , Walker M. F. , Krueger T. K.
Published: May 2006

The intensity ratio of the green λλ5517 and 5537 lines of [ClIII] serves as an indicatrix of the electron density in many gaseous nebulae whose spectra can be observed with an image converter. Quantitative interpretation of the line ratio requires accurate values of the collisional strengths and transition probabilities. With improved values of these parameters we have revised electron densities for a number of nebulae; the results seem to be in good accord with those derived from other criteria.
Secondary Structure of the Cyclic Moiety of the Peptide Hormone Oxytocin and Its Deamino Analog
Authors: Urry D. W. , Ohnishi M. , Walter Roderich
Published: May 2006

The secondary structure of the cyclic moiety of oxytocin and deamino-oxytocin has been determined by nuclear magnetic resonance spectroscopy (220 MHz). Oxytocin, in a dimethylsulfoxide-methanol mixture, contains a β-turn involving the sequence -L-tyrosyl-L-isoleucyl-L-glutaminyl-L-asparaginyl-. Deamino-oxytocin, in addition to the β-turn, contains a hydrogen bond involving the amide hydrogen of the tyrosine residue and the peptide carbonyl group of the asparagine residue, resulting in an antiparallel β-type conformation for the ring component. An initial attempt has been made to relate conformational features of the hormonal peptides to their biological activity.
Suppression of Malignancy and Differentiation in Melanotic Melanoma Cells
Authors: Silagi Selma , Bruce Sarah A.
Published: May 2006

Tumorigenicity of mouse melanoma cells is reduced or lost upon growth
in vitro
in 1 to 3 μg/ml of 5-bromodeoxyuridine (BUdR). The rate of growth is very little affected by these concentrations. The morphology of the cells is altered, such that the cells grow in a flattened, often fibroblastic monolayer, showing contact inhibition, instead of the rounded, multilayered mounds characteristic of the line. Melanotic cells lose their pigment-producing ability within one week. These effects are reversible and the inclusion of thymidine with BUdR prevents their occurrence. The reduction in tumorigenicity, the effects on cell morphology, and the suppression of pigmentation occur in clones derived from single cells growing in BUdR as well as in mass populations. These clones appear capable of indefinite growth
in vitro
in BUdR with altered morphology. The suppression of cytodifferentiation in these melanoma cells and in embryonic cells, coupled with the modification of malignancy, leads to the hypothesis that both differentiation and malignancy are regulated by similar cellular mechanisms. These effects of BUdR offer promise of a powerful tool to probe these regulatory mechanisms.
Behavioral Activation of Rats during Intraventricular Infusion of Norepinephrine
Authors: Segal David S. , Mandell Arnold J.
Published: May 2006

Rats were infused with norepinephrine or saline intraventricularly in a free-field situation and while performing a continuous avoidance task (Sidman avoidance). The results indicate that central administration of norepinephrine may lead to behavioral activation in the rat.
Genetic Control of the Cell-Division Cycle in Yeast, I. Detection of Mutants
Authors: Hartwell Leland H. , Culotti Joseph , Reid Brian
Published: May 2006

Time-lapse photomicroscopy has been utilized to detect temperature-sensitive yeast mutants that are defective in gene functions needed at specific stages of the cell-division cycle. This technique provides two types of information about a mutant: the time at which the defective gene function is normally performed, defined as the
execution point
, and the stage at which cells collect when the function is not performed, defined as the
termination point
.

Mutants carrying lesions in three genes that control the cell-division cycle are described. All three genes,
cdc-1, cdc-2
, and
cdc-3
, execute early in the cell cycle at about the time of bud initiation, but differ in their termination points. Cells carrying the
cdc-1
mutation terminate at the execution point, most cells ending up with a tiny bud that does not develop further. Cells carrying the
cdc-2
mutation terminate at mitosis. Cells carrying the
cdc-3
mutation are defective in cell separation but show no definite termination point since other processes of the cell cycle, such as bud initiation and nuclear division, continue despite the block in cell separation.
Elevation of Guanosine 3′,5′-Cyclic Phosphate in Rat Heart after Perfusion with Acetylcholine
Authors: George W. J. , Polson J. B. , O'Toole A. G. , Goldberg N. D.
Published: May 2006

The levels of guanosine 3′,5′-cyclic phosphate (cGMP) and adenosine 3′,5′-cyclic phosphate (cAMP) were measured in rat hearts after perfusion with acetylcholine to determine if parallel or independent changes occurred in the levels of these two cyclic nucleotides. It was found that after perfusion with the cholinergic agent tissue, cGMP levels increased as much as 140%. This was accompanied by no change or slight decreases in cardiac cAMP concentrations. The increases observed in cGMP levels were found to parallel the negative inotropic but not the negative chronotropic effects of acetylcholine. Perfusion with isoproterenol led to increases in the rate and force of cardiac contractility and a lowering of cGMP levels. It was concluded that the tissue concentrations of cGMP and cAMP in the perfused rat heart can vary independently and that these two tissue cyclic nucleotides probably do not share the same metabolic or functional role in this tissue.
Cyclic AMP Receptor Protein of
E. coli:
Its Role in the Synthesis of Inducible Enzymes
Authors: Emmer Michael , deCrombrugghe Benoit , Pastan Ira , Perlman Robert
Published: May 2006

A cyclic AMP binding protein has been purified over 100-fold from
E. coli
extracts. Protein purified from wild-type strains binds cyclic AMP with an apparent dissociation constant of 1-2 × 10
-6
M
. Two mutant strains that are unresponsive to exogenous cyclic AMP have altered binding activity; the protein purified from one of these mutants has a decreased affinity for cyclic AMP (apparent dissociation constant = 2 × 10
-5
M
). Extracts of this mutant are deficient in their ability to support β-galactosidase synthesis
in vitro
. The addition of purified, wild-type binding protein to these extracts restores enzyme synthesis toward normal. Because this binding protein appears to be required for cyclic AMP action, we suggest it be called the cyclic AMP receptor protein (CR protein).
MURINE SARCOMA VIRUS TRANSFORMATION OF BALB/3T3 CELLS: LACK OF DEPENDENCE ON MURINE LEUKEMIA VIRUS
Authors: Aaronson Stuart A. , Jainchill John L. , Todaro George J.
Published: May 2006

Murine sarcoma virus induces foci of morphologically altered cells in BALB/3T3 cultures. Focus formation in mouse cells has been thought to require the presence of a helper, murine leukemia virus, which is present in murine sarcoma virus stocks but by itself does not induce any morphological transformation of mouse cells. The present studies show that early after infection, the titration pattern for murine sarcoma virus in BALB/3T3 cells is “two-hit” since only foci produced by virus spread can be detected. Such foci require the presence of both viruses in the initially infected cell. By seven days the titration pattern is “one-hit” under culture conditions which allow the growth and detection of small foci of transformed cells induced by murine sarcoma virus alone. The “two-hit” titration pattern results from the inability to detect these foci. We conclude that murine sarcoma virus is able to transform mouse cells without requiring murine leukemia virus.
Identification of Proinsulin and C-Peptide in Human Serum by a Specific Immunoassay
Authors: Melani Franco , Rubenstein Arthur H. , Oyer Philip E. , Steiner Donald F.
Published: May 2006

An immunoassay for the measurement of human proinsulin and C-peptide is described. By a combination of this system and an insulin immunoassay, proinsulin, insulin, and C-peptide were identified in acid-ethanol extracts of serum after gel filtration. In keeping with the results of biosynthetic studies, insulin and C-peptide were found to be present in equimolar amounts. The absolute values of serum proinsulin determined independently in the two assays corresponded closely.
Inference from Inadequate and Inaccurate Data, III
Authors: Backus George
Published: May 2006

Having measured
D
numerical properties of a physical object
E
which requires many more than
D
parameters for its complete description, we want to estimate
P
other numerical properties of
E
. Continuing the discussion in papers I
1
and II,
2
the present paper gives estimates when we believe it likely that we can guess an upper bound
M
on the Hilbert norm not of

h
E

, the model representing
E
in some Hilbert space, but of the orthogonal projection of

h
E

onto a sufficiently large subspace. In addition, the present paper simplifies the notation of I, and makes explicit the application of Bayesian subjective probability when there are errors in the data and we want to find the joint probability distribution of more than one prediction.
Diphosphoglycerate and Inosine Hexaphosphate Control of Oxygen Binding by Hemoglobin: A Theoretical Interpretation of Experimental Data
Authors: Ling Gilbert N.
Published: May 2006

A theoretical equation is presented for the control of cooperative adsorption on proteins and other linear macromolecules by hormones, drugs, ATP, and other „cardinal adsorbents.” With reasonable accuracy, this equation describes quantitatively the control of oxygen binding to hemoglobin by 2,3-diphosphoglycerate and by inosine hexaphosphate.
Overt and Covert Effects of Endogenous and Exogenous Ecdysone in Puparium Formation of Flies
Authors: Zdarek Jan , Fraenkel G.
Published: May 2006

Mature larvae of
Sarcophaga argyrostoma
fail to form puparia when kept in contact with water, but pupariate after having been subsequently exposed to dryness for 30 hr. They become increasingly more sensitive to injected ecdysone the longer the exposure to dry conditions. A second wet treatment halts the production of hormone that had occurred during the dry period, and reduces a sensitization to injected ecdysone during the intervening dry treatment. Apparently, injected ecdysone had cumulative effects not with the endogenous or exogenous hormone, but with its covert effects which had arisen during the dry period and persisted throughout the second wet period. The hind parts of larvae ligated at the end of a wet period pupariate when injected with either one massive dose of ecdysone, or a far smaller total of several subsequent doses. In the case of two unequal doses, the effect was greater when the smaller dose was injected first. In order to get pupariation with minimal effective doses, a continuous supply of the hormone during a certain period is required. It is suggested that the inhibition of pupariation by moisture has arisen as an adaptation to unfavorable conditions.
On a Third Kind of Characteristic Numbers of the Spheroidal Functions
Authors: Rhodes Donald R.
Published: May 2006

A set of real positive numbers γ

α
n

(
c
) was found recently to be associated with the spheroidal functions of real order α > -1 as a consequence of their double orthogonality on (-1, 1) and (- ∞, ∞). In the range -1 < α < 0 these numbers are shown to be determined by the eigenvalues of a new integral equation for the spheroidal functions. Thus they represent a third kind of characteristic numbers. The new equation ceases to be an integral equation above the range -1 < α < 0 but it leads to computational formulas for γ

α
n

(
c
) that appear from numerical results to be valid for all real α > -1.
Steric and Electronic Relationships among Some Hallucinogenic Compounds
Authors: Kang Sungzong , Green Jack Peter
Published: May 2006

Stereochemical considerations and total valence electron calculations suggest congruities among the ostensibly dissimilar hallucinogenic compounds, D-lysergic acid diethylamide (LSD), indolcalkylamines, and methoxylated amphetamines. In LSD the aromatic benzene ring A and the N-6 nitrogen are essential for hallucinogenic activity; these sites may react with the receptor. The conformations of amphetamines and indolealkylamines at the receptor are such that the aromatic benzene ring lies like ring A of LSD and the alkylamino nitrogen lies like the N-6 of LSD. Ring A may interact with the receptor by forming a π-molecular complex, as suggested by the correlation between hallucinogenic activity and energy of the highest occupied molecular orbital (

E
H

) of congeneric series. The N-6 nitrogen of LSD and the sterically congruent nitrogen of the other hallucinogenic compounds may react with the receptor by forming a donor acceptor complex of the
n
-π
*
or
n
-σ
*
type. Other portions of the hallucinogenic molecules confer a favorable

E
H
:

these include the methoxy and hydroxyl groups of the amphetamines (and mescaline), and the indolealkylamines; and the pyrrole ring of LSD and the indolealkylamines.
Progesterone „Receptors” in the Cytoplasm and Nucleus of Chick Oviduct Target Tissue
Authors: O'Malley B. W. , Sherman M. R. , Toft D. O.
Published: May 2006

This report demonstrates that the chick oviduct, a specific target organ for progesterone, contains both cytoplasmic and nuclear macromolecules which bind progestins. These binding molecules can be clearly distinguished from transcortin by centrifugation through sucrose gradients of low ionic strength and by agarose gel filtration. The cytoplasmic progesterone-binding molecules also bind 5-α-pregnane-3,20-dione, but have significantly lower affinity for cortisol, estrone, or aldosterone. They are absent from blood and nontarget organs such as lung and spleen. The tissue-specific binding components appear to be heat-labile proteins with an average dissociation constant for progesterone of about 8 × 10
-10
M at 2°C. These results are consistent with the identification of the progesterone-binding molecules as the functional hormone receptors. In further support of this concept is the finding that treatment of the chicks with estrogen coordinately induces a 20-fold increase in the number of progesterone-binding molecules and enhances the capacity of progesterone to induce avidin synthesis.

A progesterone-„receptor” complex can be detected in both the cytoplasm and nuclei of oviduct tissue after an injection of [
3
H]progesterone to estrogen-treated chicks. By contrast, incubation of oviduct tissue with [
3
H]progesterone
in vitro
at 2°C for 5 min leads to labeling of the cytoplasmic „receptor” only. Transfer of the „receptor”-steroid complex into the nucleus then appears to occur upon subsequent incubation
in vitro
at 37°C. This observation suggests that the transfer of bound progesterone across the nuclear membrane may be an energy-requiring enzymatic process.
Induction of δ-Aminolevulinic Acid Synthetase in Chick Embryo Liver Cells in Culture
Authors: Sassa Shigeru , Granick S.
Published: May 2006

δ-Aminolevulinic acid synthetase is induced in chick embryo liver culture by the natural steroid, etiocholanolone, and by the foreign chemical, 3,5-dicarbethoxy-1,4-dihydrocollidine at the level of transcription. Alternatively, inducing chemicals such as allylisopropylacetamide and γ-hexachloro-cyclohexane act primarily at the level of translation. Hemin (K
i
= 5 μM) inhibits the induction at the level of translation. In liver cell culture, the half-life of δ-aminolevulinic acid synthetase is 3 hr, that of mRNA about 5 hr.
Ecological Consequences of Island Colonization by Southwest Pacific Birds, I. Types of Niche Shifts
Authors: Diamond Jared M.
Published: May 2006

The land and fresh-water birds of the southwest Pacific islands derive mainly from New Guinea and offer a favorable situation for studying ecological consequences of island invasions. The reduction of competition on species-poor islands permits some colonizing species to expand their niches spatially, by occupying altitudinal bands, types of habitats, and/or vertical strata of the forest from which they are excluded by other species on species-rich islands. Expansions to higher altitudes, or from second-growth into forest, are especially frequent. Other colonists become more abundant in the same type of habitat preferred on New Guinea. Instances of a change in diet are rare. Changes in foraging technique are noted mainly for those colonists that have been isolated long enough to have undergone morphological divergence. Approximately half of the colonizing populations experience no niche shift.
DNA Ligase Mutants of
Escherichia coli
Authors: Gellert Martin , Bullock Minnie L.
Published: May 2006

A procedure is described for the isolation of
Escherichia coli
mutants with either excess or deficient DNA ligase activity. A mutant that overproduces DNA ligase supports the growth of ligase-defective (gene 30 mutant) T4 phages. Even T4
r
II-gene 30 double mutants, which are able to grow in normal
E. coli
, cannot grow in cells deficient in DNA ligase. A functional DNA ligase, supplied either by the phage or the host, thus seems to be required for T4 growth. An
E. coli
strain that makes a temperature-sensitive DNA ligase becomes radiation-sensitive at high temperature, but otherwise grows normally and shows no obvious defect in DNA replication.
Photo-Affinity Labeling of Specific Acetylcholine-Binding Sites on Membranes
Authors: Kiefer Hansruedi , Lindstrom Jon , Lennox Edwin S. , Singer S. J.
Published: May 2006

Acetylcholinesterase of intact red blood cell membranes and the acetylcholine receptor at the neuromuscular junction of whole-frog sartorius muscle have been irreversibly inactivated by photo-affinity labeling with two quaternary ammonium aryl azides. The inactivation requires that the azides, at the time of their photolytic conversion to highly reactive nitrenes, are reversibly bound to the specific acetylcholine-binding sites.
S100 Brain Protein: Correlation with Behavior
Authors: Hydén Holger , Lange Paul W.
Published: May 2006

The brain-specific acidic protein, S100, in the pyramidal nerve cells of the hippocampus was investigated as a possible correlate to learning during transfer of handedness in rats. The amount of S100 increased during training. Intraventricular injection of antiserum against the S100 protein during the course of training prevented the rats from further increases in learned behavior but did not affect motor function in the animals. Antibodies against the S100 protein could be localized after injection by immunofluorescence, in hippocampal structures, penetrating presumably through slight ependymal lesions caused by the injection. By contrast, control animals subjected to the same training and injected with S100 antiserum that had been absorbed with S100 protein or with other antisera against γ-globulins showed no decrease in their ability to learn. The conclusion is that the brain-specific protein, S100, is linked to the learning process, at least within the training used.
Rate of Somatic Mutation in Immunoglobulin Production by Mouse Myeloma Cells
Authors: Coffino Philip , Scharff Matthew D.
Published: May 2006

Cultures of mouse myeloma cells which secrete both heavy (H) and light (L) immunoglobulin chains were cloned in soft agar. Variants that synthesized neither chain, or only light chains, were detected by overlaying the growing colonies with antiserum specific for the individual immunoglobulin chains. The rate of conversion of heavy plus light chain producers to light chain producers was 1.1 × 10
-3
per cell per generation, as determined by fluctuation analysis.
Leucyl Transfer RNA Synthetase Changes during Soybean Cotyledon Senescence
Authors: Bick Michael D. , Strehler Bernard L.
Published: May 2006

Previous work has shown the complement of leucyl transfer RNA (tRNA
Leu
) isoaccepting species present in soybean cotyledons to change during cotyledon senescence. Of the six tRNA
Leu
species resolved by Freon-column chromatography, the capacity of species 1-4 to accept leucine is decreased between 5 and 21 days of age. Parallel changes in tRNA
Leu
synthetase activity are reported here during the same time period. There is a reduction in the capacity of the synthetase from 21-day-old cotyledons to aminoacylate tRNA
Leu
1-4, while the capacity to charge tRNA
Leu
5-6 remains high. When tRNA
Leu
derived from 5-day-old cotyledons is maximally charged with the 21-day synthetase, the subsequent addition of synthetase from 5-day-old cotyledons promotes additional charging, primarily of species 1-4. These results suggest the presence of tRNA
Leu
“subspecies” within the individual peaks resolved on a Freon column, differing in synthetase specificity.
DNA and Gene Therapy: Transfer of Mouse DNA to Human and Mouse Embryonic Cells by Polyoma Pseudovirions
Authors: Qasba Pradman K. , Aposhian H. Vasken
Published: May 2006

It was demonstrated previously that polyoma pseudovirions (DNA fragments encapsidated by polyoma virus coats) are adsorbed to and uncoated by mouse-embryo cells. 24 hr after infection of secondary mouse-embryo cells with [
3
H]thymidine-labeled pseudovirus, 24% of the total radioactivity found in cells occurred in the nuclear fraction. This nuclear radioactivity represents pseudovirus DNA, as shown by its hybridization with mouse-embryo DNA. Since much of the radioactive material found in the nuclear fraction is sensitive to pancreatic DNase, it is available as uncoated DNA.

24 hr after infection of human embryo cells with [
3
H]thymidine-labeled pseudovirions, 7% of the total cellular radioactivity is found in the nuclear fraction of the cells. That this radioactivity represents uncoated pseudoviral DNA was shown by sedimentation of the disrupted nuclear fraction through a neutral sucrose gradient. The pseudoviral DNA in the nuclear fraction has been nicked to some extent, as shown by the heterogeneity of the peaks found after sedimentation of the disrupted nuclear fraction through alkaline sucrose. The experiments demonstrate that polyoma pseudovirions deliver DNA to human cells.
Nerve Growth Factor from Mouse Submaxillary Gland: Amino Acid Sequence
Authors: Angeletti Ruth Hogue , Bradshaw Ralph A.
Published: May 2006

The complete amino-acid sequence of the 2.5S nerve growth factor from male-mouse submaxillary glands has been determined. The unambiguous alignment of peptides derived from tryptic, chymotryptic, thermolytic, and peptic digestion of
S
-carboxymethyl-,
S
-aminoethyl-, and native growth factor indicates that the primary subunit is composed of 118 amino acids, with amino-terminal serine and carboxyl-terminal arginine. The molecular weight of this subunit, calculated from the primary sequence, is 13,259. Thus, the native protein, which is composed of two of the subunits, has a molecular weight of 26,518. These values, as well as the final amino-acid composition, are in excellent agreement with those determined by direct measurement with undigested growth factor. The alignment of the three disulfide bonds, determined from a combination of peptic and thermolytic digestions, is I-IV, II-V, and III-VI. The latter two pairs are located in a closed loop of 14 amino acids, by virtue of the fact that half-cystinyl residues V and VI are separated by only a single residue in the linear sequence. Assignment of the side-chain amides showed that 7 of 11 aspartic acid residues and 2 of 8 glutamic acid residues are present as amides. This distribution of charged residues is entirely consistent with the observed isoelectric point of 9.3.
Collagen Biosynthesis: Synthesis and Secretion of a High Molecular Weight Collagen Precursor (Procollagen)
Authors: Church R. L. , Pfeiffer S. E. , Tanzer M. L.
Published: May 2006

Sodium dodecyl sulfate-acrylamide gel electrophoresis and molecular-sieve chromatography on 8% agarose demonstrate the existence of a very high molecular weight (500,000-600,000), proline-rich protein in cultured 3T6 fibroblasts that appears to be the precursor molecule (procollagen) of collagen. The kinetics of [
3
H]-proline uptake indicate that this precursor is synthesized at a different rate than are other cell proteins and is secreted apparently unchanged into the medium, where it undergoes modification; it then precipitates around the cells as collagen fibrils that contain the characteristic tropocollagen polypeptide chains. The solubility of this precursor in hot 5% Cl
3
CCOOH, its hydroxyproline to proline ratio, and its sensitivity to highly-purified bacterial collagenase all indicate that this molecule is of collagenous nature, but that it has considerable regions of noncollagen peptide (about half of the molecule is collagenase sensitive, and it has half of the normal amount of hydroxylated proline residues).

These results support the concept of a procollagen molecule, of molecular weight about 500,000-600,000, that contains large regions of noncollagen peptides, which might allow the collagen α-chain regions to associate in register and that also can provide the correct chain composition for tropocollagen. Upon secretion of the procollagen molecule, the intercollagen-peptide regions are cleaved and the finished tropocollagen molecule then polymerizes into typical intercellular fibrils.
The Significance of the Evidence about Ascorbic Acid and the Common Cold
Authors: Pauling Linus
Published: May 2006

Only four independent double-blind studies have been reported of the effect of ascorbic acid regularly ingested in daily amounts more than 100 mg, in comparison with a placebo, in decreasing the incidence and integrated morbidity of the common cold for subjects exposed to cold viruses in the ordinary way and without colds when the test period began. A statistical analysis of these four studies leads to rejection of the null hypothesis that ascorbic acid has no more protective power than the placebo at the 99.86% level of confidence for the incidence of colds and the 99.9978% level of confidence for the integrated morbidity.
Synthesis of α and β Chains of Rabbit Hemoglobin in a Cell-Free Extract from Krebs II Ascites Cells
Authors: Housman David , Pemberton Russell , Taber Robert
Published: May 2006

An RNA sedimenting at 10 S, with a molecular weight of 2.3 × 10
5
, was isolated from rabbit reticylocyte polyribosomes. When this RNA is added to a cell-free extract from Krebs II ascites cells, both α and β chains of rabbit hemoglobin are synthesized; β chains are made in about 50% excess over α chains.
Synthesis of DNA Complements of Natural RNAs: A General Approach
Authors: Spiegelman S. , Watson K. F. , Kacian D. L.
Published: May 2006

The availability of a purified RNA-instructed DNA polymerase (reverse transcriptase) from avain myeloblastosis virus provided the opportunity to explore whether this enzyme could be used as a general tool for synthesizing DNA complements of a wide variety of natural RNAs. The results described show that this potentially useful situation is in fact realized. The avian viral transcriptase can mediate the synthesis of DNA complementary to RNAs of such widely divergent origins as Qβ bacteriophage and Moloney sarcoma virus. These findings open up novel pathways for the experimental resolution of several interesting problems. Thus, given a purified RNA message, one should be able to synthesize the corresponding DNA genetic material. If suitably labeled, the synthetic DNA has various obvious uses, including its use via molecular hybridization as an analytical probe for the corresponding gene on the chromosomes or for its message in a complex mixture of RNA molecules.

Of immediate practical interest is the import of these findings for viral oncology. They imply that for many purposes we will not be compelled to isolate or use the “reverse transcriptase” from each oncogenic virus in order to synthesize its complementary DNA. The ability of one enzyme to accept a variety of oncogenic RNAs will obviate many of the logistical difficulties that arise, particularly in attempts to illuminate the etiology of human cancer.
Cattanach's Translocation: Cytological Characterization by Quinacrine Mustard Staining
Authors: Francke Uta , Nesbitt Muriel
Published: May 2006

Metaphase chromosomes of mice carrying Cattanach's translocation, which is the deletion of material from a medium-sized autosome and its insertion into an X chromosome, were stained with quinacrine mustard. Comparison of the fluorescence patterns of these chromosomes with those of the chromosomes of normal mice has allowed the identification of the autosome involved in the translocation and localization of the transposed material within the X chromosome. Since the material inserted into the X chromosome in Cattanach's translocation is known to carry part of linkage group I, we are now able to assign linkage group I to a specific chromosome pair of the normal fluorescent karyotype of the mouse.
Slow Joining of Newly Replicated DNA Chains in DNA Polymerase I-Deficient
Escherichia coli
Mutants
Authors: Okazaki Reiji , Arisawa Mikio , Sugino Akio
Published: May 2006

In
Escherichia coli
mutants deficient in DNA polymerase I, newly replicated short DNA is joined at about 10% of the rate in the wild-type strains. It is postulated that DNA polymerase I normally functions in filling gaps between the nascent short segments synthesized by the replication complex. Possible implications of the finding are discussed in relation to other abnormal properties of these mutants.
In Vitro
Formation of Assimilatory Reduced Nicotinamide Adenine Dinucleotide Phosphate: Nitrate Reductase from a
Neurospora
Mutant and a Component of Molybdenum-Enzymes
Authors: Nason Alvin , Lee Kuo-Yung , Pan Su-Shu , Ketchum Paul A. , Lamberti Antonio , DeVries James
Published: May 2006

An active
Neurospora
-like assimilatory NADPH-nitrate reductase (EC 1.6.6.2), which can be formed
in vitro
by incubation of extracts of nitrate-induced
Neurospora crassa
mutant
nit-1
with extracts of (
a
) certain other nonallelic nitrate reductase mutants, (
b
) uninduced wild type, or (
c
) xanthine oxidizing and liver aldehyde-oxidase systems was also formed by combination of the
nit-1
extract with other acid-treated enzymes known to contain molybdenum. These molybdenum enzymes included (
a
) nitrogenase, or its molybdenum-iron protein, from
Clostridium, Azotobacter
, and soybeannodule bacteroids, (
b
) bovine liver sulfite oxidase, (
c
) respiratory formate-nitrate reductase from
Escherichia coli
, (
d
) NADH-nitrate reductase from foxtail grass (
Setaria faberii
), and (
e
) FADH
2
- and reduced methyl viologennitrate reductase preparations from certain
Neurospora
mutants. Several molybdenum-amino-acid complexes, as possible catalytic models of nitrogenase, were inactive (as were some previously tested 20 nonmolybdenum enzymes) in place of the acid-treated molybdenum-containing enzymes. The results imply the existence of a molybdenum-containing component shared by the known molybdenum-enzymes.
Specific Inhibitors of the Three RNA Polymerases from the Aquatic Fungus
Blastocladiella emersonii
Authors: Horgen Paul A. , Griffin David H.
Published: May 2006

Specific inhibitors of each of the three RNA polymerases of
Blastocladiella emersonii
have been found. Cycloheximide specifically inhibited the
in vitro
activity of the DEAE-fraction I enzyme, alpha-amanitin specifically inhibited the DEAE-fraction II enzyme, and rifampicin specifically inhibited the fraction III enzyme. DNA stimulation and dependency on the four riboside triphosphates were shown to be characteristic of each of the three fractions. Optimum concentrations of magnesium ions required were shown to differ among the three fractions and to be somewhat higher than optimum concentrations of manganese ions. The effect of pH on activity was essentially identical for each of the three fractions. Kinetic experiments and nuclease assays indicated the presence of some interfering substances in the partially purified RNA polymerase fractions.
Immunochemical Specificity of Lactate Dehydrogenase-X
Authors: Goldberg Erwin
Published: May 2006

Sperm-producing testes of mammals and some birds contain a unique form of lactate dehydrogenase (EC 1.1.1.27) which is a tetramer composed of C subunits, rather than the A and B subunits of lactate dehydrogenase isozymes 1-5. Immunochemical evidence is presented which confirms the hypothesis that the C subunit is encoded in a separate gene from the A and B polypeptides. The evolutionary relationships of these genes are discussed.
Morphological Transformation of Chinese Hamster Cells by Dibutyryl Adenosine Cyclic 3′:5′-Monophosphate and Testosterone
Authors: Hsie Abraham W. , Puck Theodore T.
Published: May 2006

Treatment of Chinese hamster ovary cells
in vitro
with dibutyrl adenosine cyclic 3′:5′-monophosphate converts the culture from one of compact, randomly oriented cells that grow in multilayers to a monolayer of elongated, fibroblast-like cells growing parallel to one another. Testosterone propionate, which has a similar though smaller effect at high concentrations and after prolonged incubation, potentiates the action of dibutyryl cyclic AMP even when added at very low concentrations. The transformation is recognizable within one hour, affects cells throughout all or most of the life cycle, and is completely reversible. Both cell forms can reproduce, with approximately the same generation time. Agents like colcemid and vinblastine, which inhibit assembly of microtubules, prevent the transformation to the fibroblast-like form. It is postulated that the dibutyryl cyclic AMP and testosterone act by promoting organization of microtubules from protein monomers.
Cytological and Biochemical Correlation of Late X-Chromosome Replication and Gene Inactivation in the Mule
Authors: Cohen Maimon M. , Rattazzi Mario C.
Published: May 2006

The correlation between late X-chromosome replication and the quantitation of different X-linked glucose-6-phosphate dehydrogenase electrophoretic forms was studied in a natural hybrid, the female mule. In all four animals examined, a significant deviation from the expected 1: 1 ratio of random X-chromosome inactivation was observed, with the donkey X-chromosome the more frequently late-replicating one. The relative amounts of horse and donkey enzymes activities in lysates of mule skin fibroblasts and in peripheral blood were in agreement with this finding: the donkey enzyme was the minor component. Although random expression of the enzymes from the two parent species was not observed, sampling, selection, or adaptation may actually be responsible for the apparent “preferential inactivation”. These studies support the hypothesis that late DNA replication indicates genetic inactivation.
Serum Factor Requirements of Normal and Simian Virus 40-Transformed 3T3 Mouse Fibroblasts
Authors: Paul Dieter , Lipton Allan , Klinger Ingrid
Published: May 2006

Evidence is presented to show the presence in normal rat serum of four different serum factors essential for growth of 3T3 or SV40-transformed 3T3 mouse fibroblasts: a factor that specifically promotes growth of normal 3T3 cells; two factors that specifically promote growth of transformed 3T3 cells; and a factor that sustains viability of both normal and transformed 3T3 cells in serum-free medium, probably without inducing growth of the cells. These factors are separated and partially purified.
Absence of Histones from the Chromosomal Proteins of Fungi
Authors: Leighton T. J. , Dill B. C. , Stock J. J. , Phillips Cornell
Published: May 2006

Interphase chromosomes were isolated in good yield from four species of fungi. In no case does the chromatin contain histones such as are characteristic of the chromosomes of other eukaryotic organisms.
Some Cohomology Classes in Principal Fiber Bundles and Their Application to Riemannian Geometry
Authors: Chern Shiing-Shen , Simons James
Published: May 2006

We define some new global invariants of a fiber bundle with a connection. They are cohomology classes in the principal fiber bundle that are defined when certain characteristic curvature forms vanish. In the case of the principal tangent bundle of a riemannian manifold, they are invariant under a conformal transformation of the metric. They give necessary conditions for conformal immersion of a riemannian manifold in euclidean space.
Release, Identification, and Isolation of Messenger RNA from Mammalian Ribosomes
Authors: Blobel Günter
Published: May 2006

The puromycin-induced dissociation, at high ionic strength, of active ribosomes from reticulocytes resulted in the release of protein-free, apparently undegraded, messenger RNA for globin, which was identified by centrifugation on a sucrose density gradient. This procedure should make messenger RNA from various cells available for isolation on a large scale, and has several advantages over procedures that use detergents or magnesium chelators.
Isolation of a Polyoma-Nucleoprotein Complex from Infected Mouse-Cell Cultures
Authors: Green Melvin H. , Miller Henry I. , Hendler Sheldon
Published: May 2006

A complex containing polyoma (py) DNA and protein (py complex) was isolated from polyoma-infected mouse-cell cultures. The complex sedimented unimodally at about 55 S. When labeled for long periods (2-3 hr) between 20 and 40 hr after infection, most of the [
3
H]DNA in the py complex was in the form of covalently closed, circular polyoma DNA (component I). When labeled for 5 min, the [
3
H]DNA in the py complex was nicked in one or both of the strands, as shown by alkaline sucrose gradient centrifugation. Under all conditions studied, no free py DNA was extracted from mouse cells by the two methods described.
Temperature-Sensitive Mutations in
Drosophila melanogaster
, VII. A Mutation (

para
ts

) Causing Reversible Adult Paralysis
Authors: Suzuki David T. , Grigliatti Thomas , Williamson Rodney
Published: May 2006

A temperature-sensitive mutation,

para
ts

, in
Drosophila melanogaster
causes an immediate, but reversible, paralysis of adult flies when they are shifted from 22°C to 29°C. The mutation is a sex-linked recessive that maps 2.8 units to the left of
f
. Wild-type flies observed for 2-hr periods exhibited normal mobility at all temperatures between 22°C and 35°C. From 22°C to 25°C,

para
ts

flies were wild type in walking, climbing, and flying ability. At 1-degree intervals above 25°C,

para
ts

flies became increasingly debilitated; at 29°C, complete paralysis occurred. After flies were maintained for prolonged intervals at 29°C, some activity could be recovered at that temperature. Studies of the behavior of mosaics at 29°C revealed a requirement of the (+) allele in the head for mobility, and a thoracic component for proper leg movement. Normal electroretinograms were obtained at both 22°C and 30°C. The results suggest a temperature-sensitive defect in the nervous system.
Transduction of the Nitrogen-Fixation Genes in
Klebsiella pneumoniae
Authors: Streicher Stanley , Gurney Elizabeth , Valentine Raymond C.
Published: May 2006

The bacteriophage P1 infects and functions as a generalized transducing phage for nitrogen-fixing strains of the coliform bacterium
Klebsiella pneumoniae
. Bacterial mutants (
nif
-
) unable to grow on molecular nitrogen as a nitrogen source were found to be deficient in nitrogenase activity as assayed by the conversion of acetylene to ethylene. These mutants regained normal nitrogenase activity and the ability to grow on N
2
after transduction with lysates of P1 phage prepared from wild-type bacteria. Transductional analysis with P1 revealed that several
nif
genes are located on the genetic linkage map of
Klebsiella
near the histidine operon.
Acetyl CoA Carboxylase: The Purified Transcarboxylase Component
Authors: Alberts Alfred W. , Gordon Stuart G. , Vagelos P. Roy
Published: May 2006

Acetyl CoA carboxylase of
Escherichia coli
has been resolved into three functionally dissimilar proteins: (
1
) biotin-carboxyl carrier protein (BCCP); (
2
) a biotin carboxylase component that catalyzes the Mn-ATP-dependent carboxylation of BCCP to form CO
2
-
-BCCP; and (
3
) a transcarboxylase component that catalyzes the transfer of the carboxyl group from CO
2
-
-BCCP to acetyl CoA to form malonyl CoA.

The transcarboxylase has been purified 1700-fold. Evidence that this protein catalyzes the transcarboxylase step includes the demonstration that it (
a
) catalyzes the carboxylation of BCCP, (
b
) catalyzes the BCCP-dependent exchange between [
14
C]acetyl CoA and malonyl CoA, (
c
) binds labeled acetyl CoA and malonyl CoA, and (
d
) catalyzes the decarboxylation of CO
2
-
-BCCP. On the basis of this evidence, it is concluded that the transcarboxylase component contains sites for the acyl CoA group and for biotin, the covalently bound prosthetic group of BCCP.
Natural Thymocytotoxic Autoantibody and Reactive Antigen in New Zealand Black and Other Mice
Authors: Shirai Toshikazu , Mellors Robert C.
Published: May 2006

Naturally occurring thymocytotoxic autoantibody (NTA) was detected by cytotoxic test in the sera of very young New Zealand Black mice (within 1 month after birth); the incidence was 100% at 3 months of age. Some mice from other strains also had NTA, but at an older age and with lower incidence and antibody titer. NTA had optimal activity at 4°C but was also strongly reactive at 37°C. It was cytotoxic for thymocytes of all strains of mice tested. Whereas only thymocytes were highly sensitive to NTA, the reactive antigen was demonstrated by absorption test in the thymus, lymph node, spleen, and brain of adult mice. It could be demonstrated only in the thymus of newborn mice.

The distribution of NTA-reactive antigen suggests the presence of an antigen distinct from any so far described on the cell surface of mouse thymocytes. Gel filtration of NZB mouse serum suggests that NTA is an IgM. Mouse thymocytes sensitized with NTA
in vitro
became highly susceptible to phagocytosis by syngeneic macrophages.
Primer Requirement and Template Specificity of the DNA Polymerase of RNA Tumor Viruses
Authors: Baltimore David , Smoler Donna
Published: May 2006

Polyribonucleotides will act as efficient templates for the DNA polymerases found in the virions of avian myeloblastosis virus and mouse leukemia virus if a short complementary oligodeoxyribonucleotide primer is added. Synthesis of the complementary polydeoxyribonucleotide continues until an amount of polymer equal to the amount of initial template has been produced. The two viruses show slightly different specificities toward the four homoribopolymers. Polydeoxyribonucleotides are generally much poorer templates than the homologous polyribonucleotides, in most cases yielding no detectable synthesis. The DNA polymerase of RNA tumor viruses, therefore, have the same requirements for activity as do other DNA polymerases, except that they prefer polyribonucleotides over polydeoxyribonucleotides as templates.
Transcriptional Organization of the Ribosomal RNA Cistrons in
Escherichia Coli
Authors: Doolittle W. Ford , Pace Norman R.
Published: May 2006

The data presented support the hypothesis that 16S, 23S, and 5S ribosomal RNAs of
Escherichia coli
are transcribed
in vivo
from transcriptional units consisting of single cistrons for these species arranged in the order 16S-23S-5S, with transcription beginning at the 16S end.
Folding of Staphylococcal Nuclease: Magnetic Resonance and Fluorescence Studies of Individual Residues
Authors: Epstein Henry F. , Schechter Alan N. , Cohen Jack S.
Published: May 2006

The reversible unfolding and folding of staphylococcal nuclease in the acid transition has been studied by 220 MHz proton magnetic resonance spectroscopy. The values of area, line-width, and chemical shift of each of the imidazole C2 proton resonances of the four histidine residues have been measured in this transition. The change of areas of three histidine resonances and the change of fluorescence of the single tryptophan residue, as a function of pH, appear to follow a single equilibrium. In contrast, a fourth histidine resonance follows a biphasic transition. These findings indicate that local conformational changes can be detected by magnetic resonance spectroscopy in the cooperative transition of the overall structure.
Theoretical Analysis of Emission Spectra of Electronic Transitions of Molecules in Dense Media
Authors: Lin S. H. , Colangelo L. J. , Erying H.
Published: May 2006

The purpose of this paper is to investigate the nature of band shapes of emission spectra and their relation to the rate of nonradiative processes. Two cases are discussed, one in which the Franck-Condon principle applies and the other in which the electronic transition is symmetry-forbidden but vibronic-allowed. The moment relations of emission spectra have been derived and their applications demonstrated.

The vibrational structuring in emission spectra is discussed and empirical equations for calculation of the shapes of vibrational bands are derived. It is found that from the shapes of vibrational bands one can obtain the information of intermolecular vibration and from the areas under vibrational bands one can determine the Franck-Condon factors of intramolecular vibration.
Improved Cryofixation Applicable to Freeze Etching
Authors: Bachmann L. , Schmitt W. W.
Published: May 2006

Freeze etching of solute model systems (e.g., glycerol or ferritin solutions) demonstrates that cryofixation can introduce serious artifacts due to the segregation of the dissolved or dispersed material from the solvent. Since, in principle, this problem can be reduced by increasing the cooling rate, a new technique has been developed which combines spray freezing with freeze etching. This spray-freeze-etching is applied by first spraying the specimen into a liquid cryomedium. The frozen droplets are then “glued” together with butylbenzene to form a regular freeze-etch specimen, while the temperature of the sample is kept at -85°C. The results obtained by spray-freeze-etching are far superior to those obtained by standard freezing. Our results, using 5% glycerol as a test specimen, are equivalent to those obtained by the high-pressure method (1). The reduction of segregation during freezing makes freeze etching a method applicable for the investigation of solute systems. Furthermore, the study of unicellular organisms or cellular fractions by freeze etching without the use of antifreeze is made possible.