bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro Biosynthesis of Pseudouridine at the Polynucleotide Level by an Enzyme Extract from Escherichia coli
Authors: Johnson Lee , Söll Dieter
Published: May 2006

DNA from
Mycoplasma sp.
Kid which was enriched for tRNA genes (containing about 10% tDNA) was transcribed by
E. coli
RNA polymerase. The RNA transcription product labeled with [
14
C]uridine was formed in good yield (70-fold net synthesis). After incubation of this [
14
C]uridine-labeled RNA with
E. coli
extracts, nucleotide analyses revealed that [
14
C]pseudouridine was formed. The experiments support the idea that the conversion of uridine to pseudouridine takes place at the macromolecular level. Furthermore, the conversion was shown to be specific for a uridine residue in tRNA-like material since neither [
14
C]polyuridylic acid nor the [
14
C]uridine-labeled RNA transcribed from λ DNA served as substrate for the pseudouridine-forming enzyme(s).
Behavior of Tissue Culture Cells Infected with Polyoma Virus
Authors: Dulbecco Renato
Published: May 2006

Infection of tissue culture cells with the oncogenic polyoma virus, or its temperature-sensitive mutant Ts-a, causes several changes other than the previously known induction of cellular DNA synthesis. Cellular movement, survival, and mitotic rate are enhanced in low-serum medium, and morphology is changed; the cellular growth parameters, wound serum requirement, and topoinhibition are markedly decreased. The changes are similar to those that occur in cell transformation and are produced by viral functions known to be expressed in transformed cells. Clues as to the possible mechanisms of all these changes are analyzed and a possible mechanism is discussed.
Nuclear Magnetic Resonance Spectroscopy. A Stereospecific
3
J
CF
Coupling in the Low-Temperature
13
C Nmr Spectrum of 1,1-Difluorocyclohexane
Authors: Doddrell David , Charrier Claude , Roberts John D.
Published: May 2006

The proton-decoupled
13
C nmr spectrum of 1,1-difluorocyclohexane has been examined at room temperature and at -90°C. There are only minor changes in the one-bond and two-bond carbon-fluorine scalar coupling constants at the lower temperature; however, the triplet observed for C-3 (
3
J
CF
= 4.7 Hz) collapses to a doublet (
3
J
CF
= 9.5 Hz) at -90°C. It is proposed that only the equatorial fluorine is coupled with the C-3 carbon as the result of operation of a back-lobe orbital interaction.
Possible Mechanism of Liver Necrosis Caused by Aromatic Organic Compounds
Authors: Brodie Bernard B. , Reid Watson D. , Cho Arthur K. , Sipes Glenn , Krishna Gopal , Gillette James R.
Published: May 2006

Treatment of rats with phenobarbital, which stimulates the activity of the drug-metabolizing enzymes in the liver, potentiates hepatic necrosis elicited by bromobenzene and a number of other chemically inert halogenated aromatic hydrocarbons. Radioautographic studies indicate that [
14
C]bromobenzene is covalently bound at the sites of necrosis. From these results, it is inferred that the hepatotoxic effects of the halogenated aromatic hydrocarbons are mediated by chemically active metabolites formed in hepatocytes. In accord with this view, a number of aromatic halogenated hydrocarbons are converted by microsomes in vitro to active intermediates which form covalent complexes with glutathione (GSH).
pH as a Determinant of Cellular Growth and Contact Inhibition
Authors: Ceccarini Costante , Eagle Harry
Published: May 2006

1) Both the growth rate and the maximum population density of several normal, virus-transformed, and cancer cells were markedly pH-dependent; the optimum varied from pH 6.9 to 7.8. At the optimum pH, some diploid human cells attained population densities comparable to those of cancer or virus-transformed cells. Contact inhibition of growth is facilitated by repeated fluctuations of pH in nonphysiological ranges, and may not be an intrinsic and necessary attribute of diploid cells in culture. 2) At pH 8.3, at which there was little or no cellular multiplication, the protein content per cell increased 2- to 5-fold over a period of 10-16 days, and was slowly reversed to normal concentrations on restoration of pH to the optimal range. 3) Uridine uptake by contact-inhibited human cell cultures was stimulated by refeeding with salt solution, and to the same extent as by complete (serum-supplemented) growth medium; that immediate increase did not involve the reinitiation of cellular growth and multiplication. Contact inhibition was, however, reversed in 2-4 days by an appropriate increase in the serum concentration of the medium.
Cyclic Membrane Changes in Animal Cells: Transformed Cells Permanently Display a Surface Architecture Detected in Normal Cells Only during Mitosis
Authors: Fox Thomas O. , Sheppard John R. , Burger Max M.
Published: May 2006

A membrane site exposed only during mitosis in normal 3T3 cells, but exposed in all polyomavirus transformed 3T3 (Py3T3) cells, has been detected The site was identified by the specific binding of a wheat-germ agglutinin conjugated with fluorescein isothiocyanate.

The receptor site has been studied previously. It binds wheat-germ agglutinin, causing the selective agglutination of Py3T3 cells, but not normal 3T3 cells. A short treatment with low concentrations of trypsin exposes cryptic sites in 3T3 cell membranes; this permits agglutination of these cells. The experiments reported here indicate that these sites normally are exposed during a brief period of the cell cycle for 3T3 cells. Specific hapten inhibitors of agglutination also inhibit the binding of the conjugated agglutinin and prevent fluorescence.
Human Skin Collagenase. The Role of Serum Alpha-Globulins in the Control of Activity
In Vivo
and
In Vitro
Authors: Eisen Arthur Z. , Bauer Eugene A. , Jeffrey John J.
Published: May 2006

An antibody against human skin collagenase obtained from tissue culture has been used to demonstrate the presence of immunoreactive collagenase in human skin extracts that have no detectable enzyme activity. Gel filtration of these skin extracts permits the separation of collagenase in its active form from the other proteins in the crude mixture. The recovery of enzymatically active collagenase appears to be due to the chromatographic separation of the enzyme from the serum antiproteases, alpha
1
-antitrypsin and alpha
2
-macroglobulin, suggesting that collagenase activity in fresh tissue extracts is masked by these known collagenase inhibitors. These findings are supported by
in vitro
studies untilizing human skin explants in tissue culture.

The demonstration of collagenase
in vivo
in human skin indicates that the enzyme is present at concentrations that are of physiologic significance in collagen remodeling. Evidence is also presented that these findings are not unique to human skin.
Conformal Solution Theory: Hard-Sphere Mixtures
Authors: Henderson Douglas , Leonard Peter J.
Published: May 2006

Conformal solution theory is examined. It is suggested that most difficulties associated with previous applications of this theory arise from the use of concentration-indepenent reference fluids. For the particular case of hard-sphere mixture, it is shown that if the reference fluid is chosen so as to make the first-order term in the theory vanish, good results are obtained.
The Isolation of Digoxin-Specific Antibody and Its Use in Reversing the Effects of Digoxin
Authors: Curd John , Smith Thomas W. , Jaton Jean-Claude , Haber Edgar
Published: May 2006

Specific antibodies to digoxin were isolated from antisera of sheep immunized with a digoxin-human serum albumin conjugate. The antibody was purified by adsorption to an immunoadsorbent, synthesized by coupling a ouabain-ribonuclease conjugate to bromoacetyl-cellulose, followed by elution with 25 mM ouabain. Ouabain was dissociated from antibody by denaturation in 6 M guanidine. The renatured antibody bound 1.6 mol of digoxin per mol and had an association constant of 1.6 × 10
8
M
-1
. At near-stoichiometric concentrations, either purified antibody to digoxin, or its papain-digested product (Fab-Fc), reversed digoxin-induced: (
a
) inhibition of
86
Rb transport in human erythrocytes, (
b
) increase in developed tension in isolated guinea-pig atrial strips, and (
c
) ventricular tachycardia in intact dogs, and also corrected digoxin-induced automaticity in isolated guineapig atrial strips.
On the Theory of Ion Transport Across the Nerve Membrane, III. Potassium Ion Kinetics and Cooperativity (with
x
= 4, 6, 9)
Authors: Hill Terrell L. , Chen Yi-Der
Published: May 2006

The calculations of Part II of this series have been extended to square (
x
= 4) and octahedral (
x
= 6) arrangements of subunits in a potassium channel (or gate). The conclusion is the same as before: experimental induction and superposition properties of
g
K(
t
), on depolarization, seem to rule out any significant degree of interaction or cooperativity between the (protein?) subunits of K
+
channel. Calculations for
x
= 4, 6, and 9 have also been made for a square lattice of interacting channels (periodic boundary conditions). Because of apparent rapid convergence with
x
, it seems fairly safe to conclude that this model is unsatisfactory. There is some difficulty with superposition but the principal shortcoming is a failure to produce induction behavior. Aggregation models for the K
+
channel are also discussed briefly here. They, too, appear rather unpromising (for the same reasons as seem to exclude conformational cooperativity within a channel).
Hormonal Control of Lecithin Synthesis in Barley Aleurone Cells: Regulation of the CDP-Choline Pathway by Gibberellin
Authors: Johnson Kenneth D. , Kende Hans
Published: May 2006

The enzymes of the cytidine diphosphate-choline pathway, which is involved in lecithin biosynthesis, are present in imbibed barley aleurone cells. The first enzyme, choline kinase (EC 2.7.1.32), is found in the soluble protein fraction. Its activity is not affected by prior treatment of aleurone layers with gibberellin. The second and third enzymes of the pathway, phosphorylcholine-cytidyl (EC 2.7.7.15) and phosphorylcholine-glyceride (EC 2.7.8.2) transferases, are associated with the particulate fractions. Their activities are greatly increased by gibberellin treatment during the lag phase (0-8 hr) of gibberellin-effected α-amylase synthesis. The hormonal effects are evident two hours after gibberellin treatment. Inhibitors that block gibberellin-effected α-amylase formation also inhibit the stimulation of these membrane-bound enzymes by the hormone.
Gap Junctions between Electrotonically Coupled Cells in Tissue Culture and in Brown Fat
Authors: Revel J. P. , Yee A. G. , Hudspeth A. J.
Published: May 2006

Although circumstantial evidence has suggested that gap junctions mediate intercellular electrotonic coupling, it has not been possible in most tissues to exclude the involvement of other, coexisting cell junctions. We have made an electron microscopic study of replicas of frozen-fractured BHK21 cells (from tissue culture) and of brown fat cells of newborn mice. Both of these cell types are known to exhibit intercellular electrical coupling. In each case, the only junctions found between the cells are small macular gap junctions (less than 1 μm in diameter) characterized by clusters of 6-nm (60 Å) particles or depressions on membrane cleavage faces. Several replicas confirm the association of these particles and depressions with regions of narrowing of the intercellular space, i.e., with the sites of cell junctions. We have also determined the frequency of occurrence of gap junctions on the membrane cleavage faces of both cell types. Gap junctions occupy about 1-2% of the surface area of brown fat cells, but only 0.05% of the surface area of BHK21 cells. These observations indicate that gap junctions, when they are the only intercellular junctions present, are sufficient to account for electronic coupling between cells.
Size Changes in Eukaryotic Ribosomes
Authors: Vournakis John , Rich Alexander
Published: May 2006

Evidence is presented that ribosomes active in protein synthesis and attached to messenger RNA on polysomes have a smaller diameter than free cytoplasmic single ribosomes. Measurements have been made on these two types of ribosomes of differences in sedimentation velocity and diffusion constant. Differences in these quantities suggest about a 20-Å decrease in the diameter of the ribosomes from chick embryo muscles when they are attached to messenger RNA. Similar differences are also observed in rabbit reticulocytes and mouse ascites tumor cells. These two ribosomal states have different sensitivity to Pronase digestion and dissociate into ribosomal subunits at different KCl concentrations. This size difference is not associated with a significant difference in overall ribosomal mass and appears not to be dependent upon the presence of nascent polypeptide chains.
Inhibition of Replication in Functional Mouse Adrenal Tumor Cells by Adrenocorticotropic Hormone Mediated by Adenosine 3′:5′-Cyclic Monophosphate
Authors: Masui Hideo , Garren Leonard D.
Published: May 2006

Adrenocorticotropic hormone (ACTH) inhibited replication in functional adrenal tumor cells with a concomitant stimulation of steroidogenesis and a characteristic change of morphology from a flattened to a spherical type. [
3
H]Thymidine incorporation into DNA was inhibited by about 50% 6 hours after ACTH treatment. Both cyclic AMP and dibutyryl cyclic AMP inhibited [
3
H]thymidine incorporation and caused the characteristic morphological change noted with ACTH. The extent of stimulation of steroidogenesis and the amount of inhibition of [
3
H]thymidine incorporation in response to various doses of ACTH were closely related and both were in parallel with the concentration of cyclic AMP in the cells. Cyclic GMP and cyclic IMP did not inhibit [
3
H]thymidine incorporation significantly, and did not change the morphology of the cells. AMP inhibited [
3
H]thymidine incorporation into DNA and caused the characteristic morphological change. However, AMP did not increase the cyclic AMP content of the cells. CMP, GMP, and UMP showed a significant inhibition of [
3
H]thymidine incorporation into DNA, but the extent of the inhibition was much less than that with AMP. These nucleotides did not change the morphology of the cells.
Mechanism of Action of Bacitracin: Complexation with Metal Ion and C
55
-Isoprenyl Pyrophosphate
Authors: Stone K. John , Strominger Jack L.
Published: May 2006

The inhibition by bacitracin of the enzymatic dephosphorylation of C
55
-isoprenyl pyrophosphate is abolished by the addition of chelating agents. If, however, the chelating agent is added after a preincubation of bacitracin with a divalent cation and the lipid substrate, then its addition has little effect, indicating that bacitracin, metal ion, and C
55
-isoprenyl pyrophosphate form a complex. Various divalent cations can participate in complex formation, but monovalent cations are ineffective. A direct demonstration of the formation of a complex between the C
55
-isoprenyl pyrophosphate and bacitracin in the presence of metal ions was obtained. Molecular models that show one possible conformation for a complex between bacitracin and the C
55
-isoprenyl pyrophosphate, in which the metal ion acts as a bridge between the two compounds, are presented.
Synchronization of Converging Metabolic Pathways: Activation of the Cystathionine γ-Synthase of
Neurospora crassa
by Methyltetrahydrofolate
Authors: Selhub J. , Savin M. A. , Sakami W. , Flavin M.
Published: May 2006

Methyltetrahydrofolate synchronizes the activities of the two branches of the pathway of methionine biosynthesis in
Neurospora crassa
by serving as an essential activator of cystathionine γ-synthase and antagonizing the feedback inhibition of this enzyme by
S
-adenosylmethionine. Activation is specific for the methylated form of folate and increases with increasing glutamate content. The inability of extracts of
me-1
and
me-6
mutants to form cystathionine that has been previously reported is due to the absence of
N
5
-methyltetrahydrofolate from these preparations. Extracts of
me-1
mutants lack methyltetrahydrofolate because the organisms are deficient in methylenetetrahydrofolate reductase, and those of
me-6
because their methyltetrahydrofolate is quantitatively removed by the procedure employed in the preparation of extracts. The folate of the
me-6
organisms differs from that of wild type strains in consisting largely of the monoglutamate rather than higher conjugates.
Absence of a Natural Inhibitor of the tRNA Methylases from Fetal and Tumor Tissues
Authors: Kerr Sylvia J.
Published: May 2006

The inhibitor of tRNA methylases of normal adult tissues has been resolved into two fractions, a high molecular weight protein and a low molecular weight (<700) component. The high molecular weight component is absent from embryonic and tumor tissues, both of which are known to possess high tRNA methylase capacity.
Induction of
Staphylococcus aureus
Lactose Permease in the Absence of Glycerolipid Synthesis
Authors: Mindich Leonard
Published: May 2006

Glycerol auxotrophs of
S. aureus
were isolated and shown to cease phospholipid synthesis immediately when deprived of glycerol. Second-step mutants with temperature-sensitive inducibility of the
lac
system were also isolated. When cells were induced by temperature shift to produce the products of the
lac
system in the absence of glycerol, the permease activity, relative to 6-phospho-β-galactosidase activity, was between 30 and 50% that of glycerol-supplemented cultures. However, the phosphotransferase activity for β-galactosides in isolated membranes was found to be normal when compared to the level of β-galactosidase. This indicated that the permeation system was induced and integrated into the membrane, but did not function efficiently for transport. Readdition of glycerol in the presence of chloramphenicol resulted in a slow increase in efficiency of the transport activity. Glycerol deprivation after induction led to a small loss of permease efficiency.
Isolation by Distance in Bougainville
Authors: Friedlaender Jonathan S.
Published: May 2006

The technique of population structure analysis based upon the model of Malécot is applied to blood polymorph, anthropometric, and demographic data collected from residents of south-central Bougainville Island, Territory of New Guinea. The results from these several analyses are relatively consistent and support the idea that this theoretical model can be applied successfully to real sets of biological data and that useful conclusions can be reached concerning the breeding structure of human populations. A comparison of population structures from various parts of the world reveals how fragmented the breeding structure in Melanesia is, and how relatively rapidly the coefficient of kinship declines over distance in that area.
Correlation Between Rate of Cell Growth and Rate of DNA Synthesis in
Escherichia coli
B/r
Authors: Ward C. B. , Glaser D. A.
Published: May 2006

The rates of cell growth and of DNA synthesis have been measured in synchronized cultures of
Escherichia coli
B/r growing with three different doubling times, from 27 to 80 min. Cell volume was found to increase linearly over the cell cycle, the rate of increase doubling at a precise cell age for each growth rate. The time at which the rate of cell growth doubled was also found to be the time at which new rounds of DNA synthesis were initiated. However, it was found that these two events could be separated in time by inhibiting DNA synthesis for a short period by the addition of nalidixic acid. It is concluded that neither event is the direct trigger for the other.
Isolation and Chromosomal Localization of Highly Repeated DNA Sequences in
Drosophila melanogaster
Authors: Botchan M. , Kram R. , Schmid C. W. , Hearst J. E.
Published: May 2006

The nuclear DNA of
D. melanogaster
contains DNA sequences that are repeated between ten and a hundred times more often than the next class of redundant DNA. This DNA, as a renatured duplex isolated on the basis of its renaturation kinetics, has a buoyant density of 1.691 (g/ml). In its native state it bands within the unique nuclear DNA peak (ρ = 1.701). These sequences have been localized by “
in situ
“ hybridization in the chromocenter of the chromosomes of the salivary gland. The properties of centromeres are discussed in terms of the occurrence of repeated sequences at this locus.
Heterogeneity, Complexity, and Repetition of the Chloroplast DNA of
Chlamydomonas reinhardtii
Authors: Bastia Deepak , Chiang Kwen-Sheng , Swift Hewson , Siersma Peter
Published: May 2006

The chloroplast DNA of wild-type
Chlamydomonas reinhardtii
was isolated in a CsCl density gradient as a single, homogeneous density class with a mean density of 1.695 g/cm
3
. Irrespective of sheared size, denatured chloroplast DNA renatured as a single homogeneous species. Compositional heterogeneity, presumably intramolecular, was revealed by the absorbance-temperature profile. The complement of unique nucleotide sequences of the chloroplast DNA, as determined by the rate of renaturation, was 1.94 × 10
8
daltons. This kinetic complexity is 26-fold less than the DNA content of a single gamete chloroplast, and 52-fold less than the chloroplast of a vegetative cell, which indicates that the chloroplast of
C. reinhardtii
possesses at least 26 copies of a unique nucleotide sequence.
Potassium Cyanate as an Inhibitor of the Sickling of Erythrocytes
In Vitro
Authors: Cerami Anthony , Manning James M.
Published: May 2006

The recent use of urea as a treatment for the crisis phase of sickle-cell anemia has prompted us to investigate the possibility that cyanate, which is in equilibrium with urea in solution, might itself prevent the sickling of erythrocytes. We have found that in contrast to the high concentration of urea (1 M) needed to prevent
reversibly
the
in vitro
sickling of 80% of the cells, potassium cyanate (0.01-0.10 M)
irreversibly
inhibits sickling to the same extent. The prevention of sickling is a function of the amount of [
14
C]cyanate incorporated into acidprecipitable protein (0.1-1.0 mol of cyanate per mol of hemoglobin). Most of the radioactivity is accounted for by carbamylation of the NH
2
-terminal valine residues of hemoglobin; there is no detectable carbamylation of the lysine or cysteine residues. The reactive species, HN=C=O (isocyanic acid), may be an analog of O=C=O since both compounds bind to the same valine residues of hemoglobin. Deoxygenated sickled cells also incorporate [
14
C]-cyanate, but the sickling is not reversed. Oxygenation results in normal morphology in 75% of these cells. Upon subsequent deoxygenation, these cells remain normal. Potassium cyanate (5 mM) was also found to be an effective inhibitor of the gelling of deoxyhemoglobin S.
Temperature Physiology of the Sea Snake
Pelamis platurus:
An Index of Its Colonization Potential in the Atlantic Ocean
Authors: Graham J. B. , Rubinoff I. , Hecht M. K.
Published: May 2006

The yellow-bellied sea snake
Pelamis platurus
occurs throughout the tropical Indian and Pacific Oceans from east Africa to Central America. Its latitudinal distribution limits coincide with the 18°C surface isotherm.
P. platurus
has upper and lower thermal tolerances of 36.0 and 11.7°C. With rapid cooling,
P. platurus
stops feeding at 16-18°C; however, it has a high resistance to cold temperature and can withstand 5°C for 1 hr. After 10 days' exposure,
P. platurus
does not acclimate to 17°C and, thus, would not be able to survive for long periods in water this cold.

In the event of its transit through the proposed Central American Sea-Level Canal,
P. platurus
would colonize the Atlantic Ocean and, during the summer months, would be able to extend its north Atlantic distribution to as far as Cape Cod and the English Channel.
Serologic Evidence that a Herpes-Type Virus is the Etiologic Agent of Heterophile-Positive Infectious Mononucleosis
Authors: Hampar Berge , Hsu Konrad C. , Martos Lidia M. , Walker John L.
Published: May 2006

The antibody activity against herpes-type virus (HTV) of heterophile-positive infectious mononucleosis sera and “normal” sera from humans was determined with immunoferritin. The antiviral activity of the mononucleosis sera was associated with the IgM antibodies, while the antiviral activity of the “normal” human sera was associated with the IgG antibodies. It was concluded from these findings that the appearance of antibodies to herpes-type virus in heterophile-positive sera represents a primary immunogenic exposure to this virus, or to a serologically related virus. This conclusion, in turn, suggests that herpes-type virus or a serologically related virus is the etiologic agent of heterophile-positive mononucleosis.
The Origin of Novel Flavonoids in
Phlox
Allotetraploids
Authors: Levy Morris , Levin Donald A.
Published: May 2006

The flavonoids of two diploid species of
Phlox
and two of their allotetraploid derivatives were characterized. The tetraploids accumulate five flavonoids not observed in the parental species. Generally, novel compounds are less highly glycosidated than, but otherwise similar to, parental compounds that they partially or totally replace. We propose that hybridity and polyploidy have repressed or suppressed the activity of certain ancestral genes responsible for the production of glycosidating enzymes. Accordingly, the novel compounds are merely the accumulated or modified precursors of parental compounds.
Systems of Conservation Equations with a Convex Extension
Authors: Friedrichs K. O. , Lax P. D.
Published: May 2006

We discuss first-order systems of nonlinear conservation laws which have as a consequence an additional conservation law. We show that if the additional conserved quantity is a convex function of the original ones, the original system can be put into symmetric hyperbolic form. Next we derive an entropy inequality, which has also been suggested by I. Kružhkov, for discontinuous solutions of the given system of conservation laws.
On the Theory of Ion Transport Across the Nerve Membrane, II. Potassium Ion Kinetics and Cooperativity (with
x
= 4)
Authors: Hill Terrell L. , Chen Yi-Der
Published: May 2006

We use a tetrahedral model of four interacting protein subunits to represent the K
+
channel or gate in the squid nerve membrane. The kinetic predictions, with varying degrees of cooperativity, are compared with experimental observations, especially those of Hodgkin and Huxley (
J. Physiol. 117
, 500, 1952) and of Cole and Moore (
Biophys. J. 1, 1
, 1960). The tentative conclusion reached is that if there is any cooperativity present it must be rather weak. There is no indication here that cooperativity improves the Hodgkin-Huxley assumption of independent “subunits”. Other related models will be discussed in Part III. We also find evidence against the suggestion that there is cooperativity
between
K
+
channels arranged in patches of a two-dimensional lattice.
DNA Uptake during Genetic Transformation and the Growing Zone of the Cell Envelope
Authors: Tomasz Alexander , Zanati Eva , Ziegler Richard
Published: May 2006

Continuous cellular incorporation of choline molecules is essential for DNA binding to competent pneumococci. The choline molecules are incorporated into the cell surface at the equatorial region of the cocci. As a working hypothesis, it is proposed that DNA molecules enter these bacteria at the growing zone(s) of the cell envelope.
Grouping of RNA Phages Based on the Template Specificity of Their RNA Replicases
Authors: Miyake T. , Haruna I. , Shiba T. , Itoh Y. H. , Yamane K. , Watanabe I.
Published: May 2006

We attempted to apply a new criterion, the template specificity of RNA replicases of
Escherichia coli
RNA phages, for the grouping of these phages. Based on the template specificity, it was shown that (
a
) Qβ, VK, and ST belonged to one group (group III), and SP and FI to another group (group IV), and (
b
) some similarity existed between groups III and IV. Considering such template specificity in addition to previously reported properties of phage particles, we could separate RNA phages into four major groups (I-IV) with subgroups
a, b
, and
c
in group III, and subgroups
a
and
b
in group IV.
Specific Banding Patterns of Human Chromosomes
Authors: Drets Maximo E. , Shaw Margery W.
Published: May 2006

Individual pairs of human chromosomes can be reliably identified by a new method that does not require special optical equipment and that results in permanent preparations. This method, which is based on treatment of the chromosomes
in situ
with NaOH, followed by incubation in sodium chloride-trisodium citrate and Giemsa staining, results in highly specific banding patterns in characteristic regions of the chromosome arms. It should prove useful for the detection of small structural changes in chromosomes.
Regulation by Calcium of
In Vivo
Synthesis of 1,25-Dihydroxycholecalciferol and 21,25-Dihydroxycholecalciferol
Authors: Boyle I. T. , Gray R. W. , Deluca H. F.
Published: May 2006

Tritiated 1,25-dihydroxycholecalciferol accumulates in several tissues, to an extent that varies with dietary calcium content, 12 hr after the administration of 325 pmoles of tritiated 25-hydroxycholecalciferol to rats. As the dietary and serum calcium concentrations increase, the amount of 1,25-dihydroxycholecalciferol is diminished and the concentration of 21,25-dihydroxycholecalciferol increases. This correlation is especially evident in rats given vitamin D
3
. In vitamin D-deficient rats, the repression of 1,25-dihydroxycholecalciferol formation occurs with a diet containing 3% calcium and 20% lactose. The results suggest that the production of 1,25-dihydroxycholecalciferol, believed to be the metabolically active form of vitamin D in the intestine, is responsible for the adaptation of calcium absorption to low dietary concentrations of calcium.
Control of λ Repressor Synthesis
Authors: Reichardt Louis , Kaiser A. D.
Published: May 2006

Direct measurements of the intracellular level of λ repressor have been made by a DNA-filter assay and a radioimmune assay. Transcription of
cI
, the structural gene for repressor, appears to initiate at two different promoters,
prm
and
pre
. Promoter
pre
is activated during the establishment of lysogeny by the action of
cII
and
cIII
proteins at the DNA site
cY
. Phage mutated in
cII, cIII
, or
cY
do not make a normal burst of repressor after infection and do not efficiently lysogenize the cell.
Cro
product stops repressor synthesis midway in the infective cycle.

Promoter
prm
maintains the repressor level in established lysogens. Delection mapping places it very near the right operator (
Or
).
Prm
is activated by repressor bound to the right operator. In the absence of
cII
or
cIII
protein, repressor synthesis requires active repressor and only proceeds on genomes able to bind repressor at
Or
.
Fate of Mitochondrial DNA in Human-Mouse Somatic Cell Hybrids
Authors: Attardi Barbara , Attardi Giuseppe
Published: May 2006

Several hybrid lines between human and mouse somatic cells, containing one or two complements of mouse chromosomes and a reduced complement of human chromosomes, have been examined for the presence of mouse and human mitochondrial DNAs. For this analysis, advantage was taken of the fact that these two types of mitochondrial DNA have a buoyant density difference in CsCl gradients of 0.008 g/cm
3
. In all the hybrid clones analyzed, which retained an average number of human chromosomes estimated conservatively to vary from 5 to 23, only mitochondrial DNA of mouse character was detected. It seems likely that either repression of relevant human genes by the mouse genome or loss of human chromosomes is responsible for these results. If the latter explanation is true, since chromosome loss under the conditions used here was substantially a random process, one would have to assume that the activity of nuclear genes distributed in many chromosomes is required for the survival of mitochondrial DNA.
Evidence of Gene Diminution During the Formation of the Macronucleus in the Protozoan,
Stylonychia
Authors: Bostock C. J. , Prescott D. M.
Published: May 2006

The course of events by which a macronucleus is formed from a micronucleus after conjugation in the ciliated protozoan,
Stylonychia
, suggests that genetic diminution may occur. This idea is supported by determinations of the density profiles and melting curves for micro- and macronuclear DNAs. Macronuclear DNA consists of a single density component and melts as if it were a single component. Micronuclear DNA consists of four or more density components and melts as if it were a mixture of several DNAs of different base compositions. These data indicate that at least 60% of the micronuclear DNA components are absent from the macronuclear DNA.
Neurotransmitter Synthesis by Neuroblastoma Clones
Authors: Amano Takehiko , Richelson Elliott , Nirenberg Marshall
Published: May 2006

Neuroblastoma clones were examined for choline acetyltransferase (EC 2.3.1.6), tyrosine hydroxylase (EC 1.14.3.a), acetylcholinesterase (EC 3.1.1.7), and also for neurite formation. One clone does not form axons or dendrites. Three types of clones were found with respect to neurotransmitter synthesis: cholinergic, adrenergic, and clones that do not synthesize acetylcholine or catechols. All clones contain acetylcholinesterase. These results show that genes determining neurotransmitter species can be expressed in dividing cells, that the parental programs of gene expression are inherited, and that dividing cells can be programmed with respect to their ability to communicate with other cells.
Appearance of Acetylcholine Receptors During Differentiation of a Myogenic Cell Line
Authors: Patrick Jim , Heinemann Stephen F. , Lindstrom Jon , Schubert Dave , Steinbach Joe Henry
Published: May 2006

Acquisition of acetylcholine receptors during differentiation of a clonal myoblast cell line was monitored with a neurotoxin isolated from venom of the Indian Cobra
Naja naja
. Toxin bound specifically and reversibly to acetylcholine receptors of the differentiated cells. Specificity of the binding reaction was assayed by measurement of the ability of various cholinergic agonists and antagonists to compete with neurotoxin for its binding site. The rate of toxin binding paralleled the rate of inactivation of functional acetylcholine receptors, as measured by iontophoretic application of acetylcholine. Bound toxin was released from the cells with a half-life of about 7 hr. This release was not associated with a decrease in the total number of toxin-binding sites. A slow hyperpolarizing response to acetylcholine seen in myoblasts was insensitive to toxin; the appearance of toxin-binding sites parallels the appearance of fused fibers during differentiation of the muscle cells in tissue culture.
Bidirectional Replication of the Chromosome in
Escherichia coli
Authors: Prescott D. M. , Kuempel P. L.
Published: May 2006

E. coli
cells initiating chromosome replication after release from amino-acid starvation were incubated in [
3
H]thymine of moderate specific activity, followed by incubation in [
3
H]thymine plus [
3
H]thymidine of very high specific activity. The grain tracks produced in autoradiographs of chromosomes were denser on both ends than in the middle. The autoradiographic patterns are, therefore, evidence that replication of the chromosome in
E. coli
is bidirectional.
Repair of the Lethal Developmental Defect in
Deep Orange
Embryos of
Drosophila
by Injection of Normal Egg Cytoplasm
Authors: Garen Alan , Gehring Walter
Published: May 2006

The eggs produced by
deep orange
females (
dor
/
dor
) of
Drosophila melanogaster
have a defect that causes early death of the
deep orange
embryos derived from these eggs. Ovaries transplanted from
deep orange
females to normal female hosts continue to produce defective eggs, showing that the
dor
mutation directly affects an ovarian function. In heterozygous embryos (
dor
+
/
dor
) derived from eggs of
deep orange
females, the presence of a paternal
dor
+
gene enables normal development to occur in about half of the embryos. Thus, the egg defect caused by the
dor
mutation is repairable after fertilization by the action of a
dor
+
gene.

The
deep orange
egg defect has also been repaired by injection of cytoplasm from unfertilized normal eggs into
deep orange
embryos at the syncitial preblastoderm stage of development. About one-third of the injected
deep orange
embryos were able to continue their development to an advanced stage of embryogenesis. This developmental response can serve as a bioassay for the identification of the defective component in eggs of
deep orange
females.
Bidirectional Replication of Simian Virus 40 DNA
Authors: Danna Kathleen J. , Nathans Daniel
Published: May 2006

SV40 (Simian Virus 40) DNA was pulse-labeled with [
3
H]thymidine in infected monkey cells, and the distribution of label within newly completed molecules was determined by analysis of specific fragments produced by restriction endonuclease from
Hemophilus influenzae
. From these data, an order of synthesis or temporal order of the fragments was deduced. Comparison of the temporal order with the physical order of the fragments in the SV40 DNA molecule indicates a correspondence in these orders for two separate groups of fragments. From an analysis of the results, we conclude that SV40 DNA replication begins at a specific site and proceeds bidirectionally, terminating about halfway around the circular molecule from the initiation point.
Stimulated Normal Human Lymphocytes Contain a Ribonuclease-Sensitive DNA Polymerase Distinct from Viral RNA-Directed DNA Polymerase
Authors: Bobrow Samuel N. , Smith R. Graham , Reitz Marvin S. , Gallo Robert C.
Published: May 2006

Ribonuclease-sensitive DNA synthesis is demonstrated in a cytoplasmic particulate fraction of normal human blood lymphocytes stimulated with phytohemagglutinin, but not in unstimulated lymphocytes. DNA polymerase purified from this fraction does not transcribe the heteropolymeric regions of 70S RNA from RNA tumor viruses, thus distinguishing this enzyme from the RNA-directed DNA polymerase (reverse transcriptase) found in oncogenic RNA viruses and human leukemic cells.
Ab Initio
Calculations on Large Molecules Using Molecular Fragments. Evidence of Hydrogen Bonding in Polypeptides of Glycine
Authors: Shipman Lester L. , Christoffersen Ralph E.
Published: May 2006

Ab initio
calculations on di-, tri-, tetra-, and pentapeptides of glycine in various conformations are reported. Hydrogen bonding is observed as an important stabilizing force in α-helical conformations. These studies on polypeptides of glycine of reasonable size show for the first time that the forces acting to stabilize polypeptide conformations can be extracted directly from theoretical studies, without prior postulation of their existence or need for concern that neglect or approximation of various integrals may have biased the results.
Location of Ribosomal DNA in the Human Chromosome Complement
Authors: Henderson A. S. , Warburton D. , Atwood K. C.
Published: May 2006

Hybridization of
3
H-labeled ribosomal RNA to human chromosomes on slides resulted in specific labeling of the satellite regions of chromosomes 13, 14, 15, 21, and 22, with an over-all efficiency of about 5%. Differences between D and G chromosomes, and between associated and unassociated satellites, were not significant. Labeling of all other parts of the preparations was nonspecific, and increased in the order: extrachromosomal regions < chromosome arms < centric regions.
Changes in Intrinsic Circular Dichroism of Several Homogeneous Anti-Type III Pneumococcal Antibodies on Binding of a Small Hapten
Authors: Holowka David A. , Strosberg A. Donny , Kimball John W. , Haber Edgar , Cathou Renata E.
Published: May 2006

Three homogeneous antibodies against the capsular polysaccharide of Type III pneumococci of similar specificities and affinities were purified from a single bleeding of an individual rabbit and fractionated by isoelectric focusing. A comparison of the circular dichroic spectra of the three antibodies revealed differences among them, although the spectra were generally similar to those obtained previously for heterogeneous rabbit antibodies [Cathou, R. E., Kulcycki, A., Jr. & Haber, E. (1968)
Biochemistry
7, 3958].

On binding of the hexasaccharide, -[→3)-β-D-glucuronic acid-(1→4)-β-D-glucose-(1-]
3
→, significant changes in all three circular dichroic spectra were observed. Since the oligosaccharide alone shows no transitions above 220 nm, these spectral changes can be attributed to changes in the intrinsic optical activity of the antibodies. Calculated difference circular dichroism spectra (of antibody minus that of antibody-hapten complex) of the three antibodies are different from each other, and resemble spectra of tryptophan and tyrosine derivatives. These changes in optical activity can be ascribed to changes in the asymmetric environments of aromatic chromophores directly in the combining site and/or to changes in orientation inside or beyond the site.

Since the hapten-antibody interactions are different in the three antibodies, as shown by the difference spectra, the structures of the combining sites are presumably also different. We have interpreted these observations to mean that a relatively simple ligand may be bound by several different complementary sites.
Control of the Synthesis of Fatty-Acid Synthetase in Rat Liver by Insulin, Glucagon, and Adenosine 3′:5′ Cyclic Monophosphate
Authors: Lakshmanan M. R. , Nepokroeff Carl M. , Porter John W.
Published: May 2006

The usual increase in the activity of liver fatty-acid synthetase that occurs on refeeding of a fat-free diet to previously fasted rats is abolished in diabetic animals. Insulin specifically restores this increase by enhancement of the rate of synthesis of fatty-acid synthetase. However, glucagon and cyclic AMP inhibit the increase in the activity of fatty-acid synthetase. Therefore, the concentration of fatty-acid synthetase in rat liver is under the control of the relative concentrations of insulin and glucagon.
Release of Polypeptide Chain Initiation Factor IF-2 During Initiation Complex Formation
Authors: Lockwood Arthur H. , Sarkar Probir , Maitra Umadas
Published: May 2006

Polypeptide chain initiation factor IF-2 binds to 30S ribosomal subunits. This binding is enhanced by IF-1 and IF-3. During GTP-dependent formation of a 70S initiation complex, IF-2 is released from the ribosome. During 70S initiation complex formation dependent on the methylene analogue of GTP, GMPPCH
2
P, IF-2 is not released, but remains bound to the 70S ribosome. This result suggests that IF-2 release requires GTP hydrolysis. In agreement with this presumed requirement, IF-2 functions catalytically with GTP, but stoichiometrically with GMPPCH
2
P, in bringing about 70S initiation complex formation.
The Evolutionary Development of Modifier Genes
Authors: Karlin Samuel , Mcgregor James
Published: May 2006

The main findings of a study of the evolution of modifier gene frequencies in models of deterministic population genetics are presented. A wide variety of random mating systems are subject to selection with modifiers operating, in different cases, on mutation rates, dominance, migration between subpopulations, and linkage between other loci. In all these instances the modifier frequencies evolve in such a way as to maximize the mean fitness of the population at equilibrium. This is remarkable since, except for the dominance modifier, the modifier genes are selectively neutral in the sense that they do not affect the fitness of their individual carriers. In nonrandom mating systems the mean fitness concept is not well defined, and there does not appear to be such a simple principle governing the evolution of modifier frequencies. In assortative mating systems modifiers favoring reduced assortment propensities tend to increase. In contrast, for selfing-outcrossing systems modifiers favoring increased selfing tend to increase.
Two Heat-Resistant, Low Molecular Weight Proteins from
Escherichia coli
That Stimulate DNA-Directed RNA Synthesis
Authors: Cukier-Kahn Regine , Jacquet Michel , Gros François
Published: May 2006

Two heat-stable protein factors, designated as H
1
and H
2
, have been purified from a DNA-protamine sulfate complex obtained in an early step in the preparation of
E. coli
RNA polymerase. Gel electrophoresis under denaturing conditions indicates that H
1
and H
2
behave as pure entities, with molecular weights below 10,000. Their purity is confirmed by aminoacid composition data, and in the case of H
1
, by immunological assays. H
1
and H
2
both strongly stimulate transcription of DNA from bacteriophages λ and ϕ80 by the
E. coli
polymerase holoenzyme; no effect was observed with single-stranded templates. That the amount of H
1
required for maximal stimulation is proportional to the amount of DNA present in the assay, and that both H
1
and H
2
strongly bind to native DNA in a synergestic fashion, suggests that these low molecular weight factors stimulate RNA synthesis by modifying the properties of the DNA template.
Role of Calcium and Adenosine-3′:5′-Cyclic Monophosphate in Controlling Fly Salivary Gland Secretion
Authors: Prince William T. , Berridge Michael J. , Rasmussen Howard
Published: May 2006

The action of 5-hydroxytryptamine (5-HT) on an insect salivary gland was associated with a rise in adenosine-3′:5′-cyclic monophosphate (cAMP) concentration and an increase in calcium uptake. An increase in secretion induced either by 5-HT or exogenous cAMP required extracellular calcium. Both 5-HT and exogenous cAMP increased
45
Ca efflux from previously labeled glands, but only 5-HT caused an increase in calcium uptake. The transepithelial potential in this tissue became more negative after addition of 5-HT, but more positive after addition of cAMP. 5-HT and cAMP induced a more negative potential when calcium was removed from the medium. It was concluded that both calcium and cAMP serve as intracellular messengers when 5-HT acts upon fly salivary gland.
Group-Specific Antigens of RNA Tumor Viruses as Markers for Subinfectious Expression of the RNA Virus Genome
Authors: Gilden Raymond V. , Oroszlan Stephen
Published: May 2006

Antigenic markers associated with the major internal protein of RNA tumor viruses of the C-type have proven extremely useful in natural history studies of these viruses. This protein possesses species-specific antigenic determinants, and, in the case of mammalian C-type viruses, the protein possesses crossreactive determinants as well. These determinants are, thus, useful for species identification and classification of mammalian viruses. A unique distribution of antigens in embryonic tissues of several species (where tests are available) was detected, and in addition, antigen expression in tissues appears to be controlled by a dominant gene. These data have contributed greatly to the theory that RNA tumor-virus information is inherited as part of the cellular genome.
Enduring Behavioral Changes in Rats with Experimental Phenylketonuria
Authors: Andersen Arnold E. , Guroff Gordon
Published: May 2006

Several criticisms of past attempts to produce experimental phenylketonuria are discussed, and a model that appears to meet these criticisms is presented. This model uses inhibition in rats of phenylalanine hydroxylase (EC 1.14.3.1) by
p
-chlorophenylalanine and supplementation with phenylalanine to produce a high ratio of phenylalanine to tyrosine in their blood. By this method, an experimental subject is produced whose behavioral, neurological, and biochemical characteristics are similar to those of clinical patients with phenylketonuria.