bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid Loss of Translatable Messenger RNA of Phosphoenolpyruvate Carboxykinase During Glucose Repression in Liver
Authors: Tilghman Shirley M. , Hanson R. W. , Reshef Lea , Hopgood M. F. , Ballard F. J.
Published: May 2006

The rate of synthesis of phosphoenolpyruvate carboxykinase (EC 4.1.1.32) in rat liver decreased with a half-life of 30 min after fasted rats were refed either a chow diet or glucose. A requirement for both glucose and insulin to bring about this rapid deinduction was shown, as well as the ability of dibutyryl adenosine 3′:5′-cyclic monophosphate to block the decrease in enzyme synthesis. Estimates of the stability of messenger RNA of phosphoenolpyruvate carboxykinase were made by using the inhibitors actinomycin D and cordycepin to block further messenger RNA synthesis, and then measuring the decrease in specific enzyme synthesis. It is suggested that the use of actinomycin D yields an overestimation of the template stability. The results with cordycepin imply that the enzyme messenger RNA has a short half-life of approximately 1 hr. Thus, it is possible that deinduction may proceed by way of a decrease in messenger RNA production, leading to a rapid fall in the synthesis of phosphoenolpyruvate carboxykinase.
Human Tumors Detected by Nuclear Magnetic Resonance
Authors: Damadian Raymond , Zaner Ken , Hor Doris , DiMaio Theresa
Published: May 2006

Measurements of the water proton spinlattice relaxation (T
1
) in 106 human tumors confirms earlier results with animals [Damadian, R. (1971)
Science
171, 1151-1153]. T
1
of all the tumors studied were significantly longer than T
1
of the corresponding normal tissues. Mean standard error and range were reported for T
1
of every human organ and for all the tumor groups studied. The technique is now ready for use by pathologists as an adjunct to present methods of diagnosing malignancy.
Enhancement by Carbachol of Transmitter Release from Motor Nerve Terminals
Authors: Miyamoto Michael D. , Volle Robert L.
Published: May 2006

In the endplates of rat phrenic nerve-diaphragm, application of the acetylcholine-like compound, carbachol, causes a marked increase in transmitter release, as measured electrophysiologically using miniature endplate potential frequency. Washing out of carbachol reverses the increase in frequency. The ability of carbachol to increase transmitter release is greatly enhanced by perfusion of the preparation with Ringer solution containing elevated K
+
. At concentrations of carbachol greater than 30 μM, the onset of the postjunctional blocking action of carbachol is too rapid and obscures the increase in miniature potential frequency. The rate of increase in transmitter release is dependent on the concentration of carbachol applied and can be antagonized by
d
-tubocurarine (10-60 nM) and other blocking compounds. These findings, in contrast to previous reports, indicate that cholinergic nerve endings, like adrenergic nerve endings, respond to applied acetylcholine-like drugs with measurable increases in transmitter output.
Mechanism of Renaturation of Pyruvate Kinase of
Saccharomyces carlsbergensis:
Activation by L-Valine and Magnesium and Manganese Ions
Authors: Bornmann Lothar , Hess Benno , Zimmermann-Telschow Hildegard
Published: May 2006

Pyruvate kinase (EC 2.7.1.40) of
S. carlsbergensis
is a tetrameric enzyme, composed of four identical subunits each of which contains 1 mole of L-valine noncovalently bound. The enzyme readily dissociates into monomeric units. L-Valine and magnesium or manganese ions are specific primers of the renaturation process of the enzyme. The amino acid induces renaturation with a
K
0.5
of 17 μM and a pseudo first-order rate constant of 0.019 min
-1
at 25° with respect to the monomeric species, indicating that L-valine influences the folding of the monomeric form from a disordered state to its native conformation being followed by a spontaneous reassociation with formation of the tetrameric enzyme. Independently, magnesium and manganese ions induce the renaturation with a first-order rate constant of the same magnitude.
Partial Purification of Detergent-Soluble HL-A Antigen and Its Cleavage by Papain
Authors: Springer Timothy A. , Strominger Jack L. , Mann Dean
Published: May 2006

HL-A antigen solubilized with the non-ionic detergent, Brij 99, has been purified to about 50% of homogeneity from a cultured human lymphoblast line. It consists of two nonidentical subunits of 44,000 and 12,000 molecular weight (MW). Upon papain proteolysis the 44,000 MW peptide is converted by at least two cleavages to a 34,000 MW peptide, but the 12,000 MW peptide appears to be unchanged. Concomitantly, the apparent molecular weight in gel filtration chromatography under nondenaturing conditions in the presence of Brij 99 is reduced from 460,000 to 45,000. HL-A molecules produced by direct papain proteolysis of membranes and by papain treatment of purified detergent-soluble HL-A are identical.
Synthesis of Nerve Growth Factor by L and 3T3 Cells in Culture
Authors: Oger Joel , Arnason Barry G. W. , Pantazis Nicholas , Lehrich James , Young Michael
Published: May 2006

Mouse submaxillary gland nerve growth factor (NGF) has been covalently joined to bacteriophage and the resulting phage conjugates remain biologically active in stimulating neurite extension from sensory ganglia. A sensitive bacteriophage immunoassay has been developed to measure concentrations of NGF as low as 1 ng/ml. With this method, we find that mouse L and 3T3 cells in culture produce a biologically active nerve growth factor that is immunologically similar if not identical to mouse submaxillary gland NGF. Since L cells are known to be a source of “conditioned medium” for tissue culture, it could be that one or more of the conditioning factor activities secreted by these cells are due to NGF itself.
A Functional Mitotic Spindle Prepared from Mammalian Cells in Culture
Authors: Cande W. Zacheus , Snyder Judith , Smith Diana , Summers Keith , McIntosh J. R.
Published: May 2006

Mitotic cells lysed into solutions of polymerizable microtubule protein contain a spindle which is similar to the living spindle in two respects: it will lose and gain birefringence when cooled and warmed, and it will move anaphase chromosomes to the opposite ends of the cell. Early anaphase cells lysed into buffers containing high molecular weight polyethylene glycol and nucleotide triphosphates will continue chromosome motion and spindle elongation in the absence of exogenous spindle subunits. These results suggest that while spindle growth requires microtubule polymerization, anaphase motions do not.
Chemical Conversion of Aspartic Acid 52, a Catalytic Residue in Hen Egg-White Lysozyme, to Homoserine
Authors: Eshdat Yuval , Dunn Arnold , Sharon Nathan
Published: May 2006

Hen egg-white lysozyme (EC 3.2.1.17) was specifically esterified at aspartic acid 52 by the affinity labeling reagent 2′,3′-epoxypropyl β-glycoside of di-(
N
-acetyl-D-glucosamine) [Eshdat
et al.
(1973)
J. Biol. Chem.
248
, 5892]. The disulfide bonds of the affinity-labeled enzyme and the aspartic acid 52-ester bond were reduced with dithiothreitol and sodium borohydride, respectively, resulting in the removal of the affinity label. The reduced protein contained 0.9 mole of homoserine and 1 mole less of aspartic acid per mole of protein, as compared to the native enzyme. It was reoxidized by a mixture of reduced and oxidized glutathione to yield a modified protein that possessed one-tenth of the activity of native lysozyme (presumably due to a contamination by regenerated lysozyme formed as a result of hydrolysis of the aspartic acid 52-ester bond during the chemical treatment). The native enzyme, after reduction and reoxidation in the same manner, retained its amino-acid composition, full enzymatic activity, and fluorescence properties. The modified lysozyme, containing homoserine 52, showed the same fluorescence spectrum as the native enzyme. With both proteins, the fluorescence maximum shifted to the blue to a similar extent upon the addition of the saccharide inhibitors tri-(
N
-acetyl-D-glucosamine) and the cell-wall tetrasaccharide (GlcNAc-MurNAc)
2
. The modified enzyme bound these two saccharides with nearly the same binding constants as those found for native lysozyme and for lysozyme that was reduced and reoxidized. Since the side chain of homoserine is similar in size to that of aspartic acid, it is concluded that the loss of enzymatic activity is the direct result of the chemical modification of the carboxyl side chain of aspartic acid 52, thus showing that this amino acid is essential for the catalytic action of the enzyme.
Changes in Activity and Molecular Properties of Fructose 1,6-Bisphosphatase During Fasting and Refeeding
Authors: Pontremoli S. , Melloni E. , Salamino F. , Flora A. De , Horecker B. L.
Published: May 2006

During prolonged starvation, fructose 1,6bisphosphatase (EC 3.1.3.11) activity in rabbit liver and kidney shows a transient decrease during the first 36 hr, before rising at 96 hr to levels severalfold higher than those found in the livers of fed animals. Proteolytic activity appears in the 105,000 ×
g
supernatant fraction within several hours of starvation, and continues to increase during the entire 96-hr period. On refeeding, the activities return to nearly the control levels within 24 hr. The catalytic properties of fructose 1,6-bisphosphatase isolated from the livers of fasted rabbits are similar to those of the enzyme from fed animals, but its structure is modified, since it no longer contains the single tryptophan residue located near the NH
2
-terminus in the native enzyme. Thus this tryptophan residue is not required for the neutral pH optimum. The structural changes and the transient decrease in activity may be related to the observed increase in “free” proteolytic activity.
The Amplified Ribosomal DNA of Dytiscid Beetles
Authors: Gall Joseph G. , Rochaix Jean-David
Published: May 2006

During oogenesis in many animals there is a massive extrachromosomal synthesis of the genes for ribosomal RNA. In Dytiscid beetles, as in the toad
Xenopus
, the amplified ribosomal DNA occurs as circular molecules of different sizes. The circles fall into size classes that are integral multiples of a unit circle. It is probable that the unit circle contains the coding sequence for one precursor ribosomal RNA molecule plus accompanying spacer sequences.
Facts and Theories on Viruses Causing Cancer and Leukemia
Authors: Gross Ludwik
Published: May 2006

It is possible to explain the familial incidence of cancer developing in several members of the same family tree, within the same as well as in successive generations, by an assumption that tumors and leukemia are caused by oncogenic viruses transmitted in a latent form from one generation to another in many animal species, presumably also in man. The term “vertical transmission” was coined to describe this form of transmission of pathogenic agents. In most instances the oncogenic viruses are invisible and harmless to their carrier hosts. Occasionally, however, under the influence of endogenous or exogenous inducing factors, these viruses become activated and cause cancer or leukemia. According to this concept, the law of obligate communicability established for all common infectious agents applies also to oncogenic viruses: each tumor or leukemia can be traced to another similar tumor which developed in one of the preceding generations as a result of “vertical” passage of the same oncogenic virus. This concept postulates that at one time, perhaps centuries ago, these viruses entered from outside the animal hosts and that, since then, they have been transmitted from one generation to another.

The theory of vertical transmission of latent oncogenic viruses is consistent with experimental and clinical observations made during the preceding two decades. We consider this concept to be a logical and most promising approach to the problem of viral etiology of neoplastic diseases.
Characteristics of Polarographic Catalytic Waves Observed with Bovine-Serum Albumin: Effects of Type of Buffers, pH, Ionic Strength, Calcium, and Tetraalkyl Salts
Authors: Kolthoff I. M. , Yamashita K. , Hie Tan Boen
Published: May 2006

Brdička currents observed with bovineserum albumin in ammoniacal buffers with Co(III) and Co(II) as catalysts are identical only when the concentrations of ammonia and ammonium chloride are at least 0.5 M and 0.05 M, respectively. When these conditions are not fulfilled, and in all Tris and borate buffers, the pattern of Brdička currents with Co(III) are quite different from those with Co(II). In such buffers the Co(II) is rapidly reduced at potentials slightly more negative than that at which the Brdička current attains a peak value. In several such buffers the Brdička current may then reduced to zero. In buffers of low ionic strength (about 0.02) and with Co(III), small concentrations of alkali salts greatly increase Brdička currents. When the ionic strength of the buffer is 0.05 M or greater, the effect of alkali salts (up to 0.2 M) is small, but even traces of calcium have a large effect in all buffers with Co(III) as catalyst. Evidence is presented that in the presence of calcium all 17 disulfide groups in bovine-serum albumin are reduced at the dropping mercury electrode. Traces of tetraalkyl salts greatly increase Brdička currents, but the effects is quite different from that of calcium.
The Molecular Structure of Yeast Phenylalanine Transfer RNA in Monoclinic Crystals
Authors: Quigley G. J. , Suddath F. L. , McPherson A. , Kim J. J. , Sneden D. , Rich Alexander
Published: May 2006

The molecular structure of monoclinic crystals of yeast phenylalanine tRNA is analyzed by comparing it to the orthorhombic crystals of the same material whose structure has been determined. Changing the packing of the molecule from the head-to-head, tail-to-tail arrangement in the orthorhombic lattice to a head-to-tail packing makes it possible to generate a proposed structure for the monoclinic unit cell. The structure factors for the proposed arrangement have been calculated and compared with those experimentally observed from monoclinic crystals. The residuals from this comparison are low enough to conclude that at 4-Å resolution, the three-dimensional structure of the molecule in the monoclinic crystal is essentially the same as that in the orthorhombic crystal. In addition, a correlation coefficient calculated from intensities based on a skeletal model of the molecule also confirmed the structure in the monoclinic cell. Electron density difference maps, as well as the presence of close contacts in the anticodon loop region of the monoclinic crystal, suggest that the anticodon loop may have a slightly different conformation than that observed in the orthorhombic crystals.
Regulation of Fructose 1,6-Bisphosphatase by Histidine under Gluconeogenic Conditions
Authors: Pontremoli S. , Melloni E. , De Flora A. , Horecker B. L.
Published: May 2006

Fructose 1,6-bisphosphatase (EC 3.1.3.11) requires a free divalent metal and a metal chelate for optimum activity in the neutral pH range. The latter requirement can be satisfied by histidine, which appears to function as the chelating metabolite
in vivo
. Under fasting conditions, the concentrations of histidine in rabbit liver vary in the range required for activation of fructose bisphosphatase, and the enzyme itself is modified so that it becomes more responsive to histidine.
Location of an Isoproterenol-Responsive Cyclic AMP Pool in Adrenergic Nerve Cell Bodies and Its Relationship to Tyrosine 3-Monooxygenase Induction
Authors: Otten U. , Mueller R. A. , Oesch F. , Thoenen H.
Published: May 2006

To decide whether adenosine 3′:5′-cyclic monophosphate (cyclic AMP) plays a role as a second messenger in the trans-synaptic induction of tyrosine 3-monooxygenase (EC 1.14.16.2), it is desirable to discriminate between neuronal and extraneuronal changes in cyclic AMP concentration. Treatment of newborn rats with nerve growth factor antiserum or 6-hydroxydopamine, leading to destruction of 61-85% of the adrenergic nerve cell bodies in the superior cervical ganglion, led to a decrease in cyclic AMP of only 16-28%. This observation demonstrates that a relatively small portion of cyclic AMP is localized in the adrenergic neurons. However, administration of isoproterenol produced an increase (12-fold) in cyclic AMP only in this neuronal pool. Neither single nor repeated injections of isoproterenol led to induction of tyrosine monoxygenase. This, together with previous observations that experimental conditions leading to induction of the enzyme do not produce significant increases of cyclic AMP in the whole ganglion, is taken as an indication that cyclic AMP is not acting as a second messenger in the trans-synaptic induction of tyrosine monooxygenase in the rat superior cervical ganglion. In the rat adrenal medulla, treatment with reserpine led to both a shortlasting (60-90 min) increase in cyclic AMP and a subsequent induction of tyrosine monooxygenase. However, the increase in cyclic AMP was almost completely prevented (40 compared to 320%) by pretreatment of the rats with propranolol while the induction of tyrosine monooxygenase was not diminished. This observation also argues against an exclusive key-function of cyclic AMP in trans-synaptic induction of tyrosine monooxygenase in the adrenal medulla.
Replication of Colicin E1 Plasmid DNA in Cell Extracts. Origin and Direction of Replication
Authors: Tomizawa Jun-Ichi , Sakakibara Yoshimasa , Kakefuda Tsuyoshi
Published: May 2006

The structures of molecules of colicin E1 plasmid DNA that were in the process of being replicated
in vitro
were examined electron microscopically. Circular molecules containing a loop of approximately 7% of the length of the molecules were the major class of replicating molecules. The location of the loop was determined by treating the molecules with restriction endonuclease
Eco
R1, which introduced one unique double-strand break in the colicin E1 plasmid DNA molecules. The loops had a specific location with two branch points at approximately 17 and 24% of the molecular length from the endonuclease-sensitive site. Molecules with a larger loop were observed with a preparation labeled with 5-bromodeoxyuridine and enriched for these molecules. One of the branch points in these molecules was located at approximately 17% of the molecular length from the endonuclease-sensitive site independent of the size of the loops. These results indicate that the origin of replication of the plasmid DNA is located within the small loop and the replication proceeds unidirectionally. The molecules that had completed a round of replication had the monomeric twisted circular structure.
Rapid Inactivation of Ovalbumin Messenger Ribonucleic Acid after Acute Withdrawal of Estrogen
Authors: Palmiter Richard D. , Carey Norman H.
Published: May 2006

Synthesis of ovalbumin mRNA is induced and maintained in the avian oviduct by estrogen. When estrogen is rapidly removed from circulation, there is a general involution of the oviduct and an unusually rapid decay of ovalbumin mRNA activity. The kinetics of ovalbumin mRNA decay were not first order; instead, the rate of degradation increased about 10-fold over a 20-hr period after removal of estrogen. These results are in contrast with first-order decay kinetics observed for ovalbumin mRNA in estrogen-stimulated chicks (
t
1/2
= about 24 hr) and in cell-free extracts. The degradative response triggered by hormonal withdrawal becomes more rapid between 1 and 4 days of estrogen-stimulated growth. We conclude that in the process of inducing egg-white protein synthesis, estrogen produces a cellular environment in which the egg-white protein mRNAs are relatively stable; removal of estrogen initiates cellular catabolism in a manner that is not understood.
A Three-Dimensional Molecular Assembly Model of a Lipoprotein from the
Escherichia coli
Outer Membrane
Authors: Inouye Masayori
Published: May 2006

From the complete amino-acid sequence of a lipoprotein from the outer membrane of
E. coli
, a three-dimensional molecular assembly model was constructed. It is proposed that the model provides a tubular hydrophilic channel through the outer membrane, which serves as a passive diffusion pore. An α-helix is constructed from the sequence, and six of them are arranged to form a superhelix with a hydrophilic interior and hydrophobic outer surface. The superhelical assembly is stabilized by seven ionic interactions between adjacent α-helices. Since the height of the assembly is 76 Å, it could be inserted into the outer membrane and span the full 75-Å thick membrane. The assembly is stabilized in the outer membrane not only by hydrophobic interaction between the surface of the assembly and the lipid bilayer, but also by three hydrocarbon chains of fatty acids linked to the amino-terminal end of the lipoprotein, which are flipped back along the assembly and inserted into the lipid bilayer of the outer membrane. Any two α-helices in an assembly are linked to the peptidoglycan at their carboxyl-terminal ends so that the outer membrane is anchored on the peptidoglycan layer. Six or more α-helices can form an assembly of this type. However, assuming that an assembly consists of six helices, there are 1.25 × 10
5
per cell hydrophilic channels of a diameter of 12.5 Å and 35% of the cell surface is occupied by the assemblies.
A Characterization of Banach Spaces Containing
l
1
Authors: Rosenthal Haskell P.
Published: May 2006

It is proved that a Banach space contains a subspace isomorphic to
l
1
if (and only if) it has a bounded sequence with no weak-Cauchy subsequence. The proof yields that a sequence of subsets of a given set has a subsequence that is either convergent or Boolean independent.
Prolongation of the Life-Span in Mice Adapted to Large Amounts of L-Dopa
Authors: Cotzias George C. , Miller Samuel T. , Nicholson Alexander R. , Maston William H. , Tang Lily C.
Published: May 2006

Various concentrations of L-dopa (levodopa, L-3,4-dihydroxyphenylalanine) were incorporated in the diets of young male Swiss albino mice, and the highest concentrations to which these mice became adapted within 3 weeks were determined. One such concentration administered indefinitely eventually induced a youthful appearance, a significantly prolonged life-span, but also corneal opacities compatible with traumatic or chemical keratitis.
Kinetic Properties and Electron Paramagnetic Resonance Spectra of the Nitric Oxide Derivative of Hemoglobin Components of Trout (
Salmo irideus
)
Authors: Brunori Maurizio , Falcioni Giancarlo , Rotilio Giuseppe
Published: May 2006

The binding of nitric oxide to hemoglobin components of trout (
Salmo irideus
), i.e., Hb trout I and Hb trout IV, has been studied by optical and electron paramagnetic resonance spectroscopy. Kinetic studies show that the Root effect in Hb trout IV is operative also for NO, since a large increase in the dissociation velocity constant (
j
4
) is observed as the pH is decreased below 7. Moreover, the time course of the displacement of NO by CO is heterogeneous, suggesting that α and β chains may have different
j
4
values. Low-temperature X-band electron paramagnetic resonance spectra have been recorded with Hb trout I and IV saturated with NO at different pH values. The spectra of Hb trout IV are strongly pH-dependent. The high-pH form (pH 8.1) shows axial symmetry and no resolved hyperfine splitting, while the low-pH form is rhombic with a hyperfine splitting of 6.5 G in the

g
z

region. The latter form reflects a more distorted site with a more significant delocalization of the unpaired electron on the proximal histidine; both features indicate a destabilization of the ligand binding at low pH. On the other hand, spectra of Hb trout I are axial at both pH values, with hyperfine splitting of 16.5 G, indicating that the site is not distorted and interacts with the ligand very strongly at either pH.
Isolation of a Specialized Transducing Bacteriophage Lambda Carrying the
PolC
Locus of
Escherichia coli
Authors: Shizuya Hiroaki , Livingston Dennis M. , Richardson Charles C.
Published: May 2006

We have isolated a specialized transducing phage carrying the
polC
locus of
E. coli
K-12. A strain of
E. coli
lacking the lambda attachment site was infected with bacteriophage λ. Lysogens carrying λ at the
tonA
locus were isolated by selecting λ-immune, T5-resistant strains. Transducing phages of
dapC, dapD
and
polC
, which map within 0.2 min of
tonA
, were obtained in lysates prepared from two of the lysogens. The isolated phage, λ
dpolC
, is defective but can transduce four different
polC
temperature-sensitive mutants. After lysogenation with the transducing phage, DNA polymerase III activity is restored to normal levels in extracts of a
polC
strain lacking polymerase III activity. However, attempts to obtain increased levels of DNA polymerase III in extracts of induced lysogens carrying λ
dpolC
have been unsuccessful.
Studies of Transfer RNA Tertiary Structure by Singlet-Singlet Energy Transfer
Authors: Yang Chih-Hsin , Söll Dieter
Published: May 2006

Five species of tRNAs bearing two different fluorescent groups were synthesized. These were suitable for intramolecular distance measurements by singlet-singlet energy transfer. The efficiency of energy transfer was determined from the sensitized emission of the energy acceptor. With the assumption that the relative orientation of donor and acceptor is random, the apparent distances between the 5′-end and the 3′-end, the 4-thiouridine and the 3′-end, the pseudouridine and 3′-end, the pseudouridine and the dihydrouridine in
Escherichia coli
formyl methionine tRNA, and between the 2-thiouridine (in the anticodon) and the 3′-end in
E. coli
glutamate tRNA were calculated to be 24 Å, 38 Å, 55 Å, 36 Å, and >65 Å, respectively.
Control of the Initiation of DNA Synthesis in 3T3 Cells: Serum Factors
Authors: Holley Robert W. , Kiernan Josephine A.
Published: May 2006

The initiation of DNA synthesis in 3T3 cells can be controlled by a variety of different factors. Cells that are quiescent because of limited serum initiate DNA synthesis in response to the fibroblast growth factor of Gospodarowicz, to insulin, and to dexamethasone, as well as to other, unidentified biological materials. Interactions are seen between the effects of different factors.
Long Pyrimidine Tracts of L-Cell DNA: Localization to Repeated DNA
Authors: Straus N. A. , Birnboim H. C.
Published: May 2006

Like HeLa DNA, L-cell DNA contains a significant number of unexpectedly long pyrimidine tracts. 1.3% of the thymidine residues of L-cell DNA are found in these long polypyrimidine tracts. Analysis of L-cell DNA fractions with different rates of reassociation indicates that polypyrimidine tracts are associated with “repeated” DNA. Longer pyrimidine tracts appear to have a higher repetition frequency than shorter tracts, and some may be repeated as many as 5 × 10
4
times in L-cell DNA.
Differentiation Between Intracellular and Cell Surface Glycosyl Transferases: Galactosyl Transferase Activity in Intact Cells and in Cell Homogenate
Authors: Deppert Wolfgang , Werchau Hermann , Walter Gernot
Published: May 2006

Intact BHK (baby hamster kidney) cells catalyze the hydrolysis of UDP-galactose to free galactose. The generation of galactose from UDP-galactose and its intracellular utilization impede the detection of possible galactosyl transferases on the cell surface of intact cells. Several independent procedures have been used to distinguish between intracellular and cell surface glycosyl transferases. With these procedures, no evidence was obtained for the presence of detectable amounts of galactosyl transferase activity on the surface of BHK cells. The data suggest that galactosyl transferases do not play a general role in the phenomena of cell adhesion and contact inhibition.
Escherichia coli
RNA-Polymerase Binding Sites on DNA Are Only 14 Base Pairs Long and Are Located between Sequences That Are Very Rich in A+T
Authors: Giacomoni Paolo U. , Le Talaer Jean Yves , Le Pecq Jean Bernard
Published: May 2006

E. coli
DNA-dependent RNA-polymerase binding sites on DNAs of T5, T7, and lambda coliphages have been isolated according to three different methods in order to analyze the binding sites themselves as well as the nearest neighboring regions. It is shown that the binding sites are regions that are rather rich in G+C, are about 14 base pairs long and are located between DNA sequences highly enriched in A+T. The biological implications of this result are discussed.
On the Interpretation of Experiments on Osmotic Pressure
Authors: Hobbie Russell K.
Published: May 2006

Scholander and his coworkers have described in
These Proceedings
several experiments in which the osmotic pressure exerted by colloidal particles appears to be altered when the particles are subject to an external force; they interpret the experiments as showing that the traditional explanation of osmotic pressure is wrong (
Proc. Nat. Acad. Sci. USA
68, 1093-1094; 68, 1569-1571; 70, 124-128). (In their view the osmotic pressure is determined by the concentration of the colloidal particles at the free surface rather than at the semipermeable membrane.) This note shows that one must also consider the way in which the external force changes the total hydrostatic pressure in the liquid. When that is done, the experiments of Scholander
et al.
are quantitatively consistent with the traditional interpretation of osmotic pressure.
Specific Recognition of Single-Stranded Regions in Ultraviolet-Irradiated and Heat-Denatured DNA by Tryptophan-Containing Peptides
Authors: Toulmé Jean-Jacques , Charlier Michel , Hélène Claude
Published: May 2006

Fluorescence studies of the binding of peptides containing lysyl and tryptophyl residues to nucleic acids show that two types of complexes are formed. One of them involves a direct interaction of the tryptophyl ring with nucleic acid bases, which leads to fluorescence quenching. Comparison with proton magnetic resonance and circular dichroism data indicates that this fluorescence quenching is due to a stacking of the indole ring with bases. Quantitative analysis of fluorescence data leads to the conclusion that stacking is favored in single-stranded regions of DNAs, which are produced either by heating or by UV-irradiation of the native DNA sample. The binding of the peptide Lys-Trp-Lys is about ten times tighter in these single-stranded regions as compared with double-stranded ones. A short tripeptide such as Lys-Trp-Lys is, therefore, able to discriminate between single-stranded and double-stranded regions. Moreover, bound peptide molecules photosensitize the splitting of thymine dimers in UV-irradiated DNA, thus providing a model for DNA photoreactivation.
Regulation of Newly Synthesized Acetylcholinesterase in Muscle Cultures Treated with Diisopropylfluorophosphate
Authors: Wilson B. W. , Walker C. R.
Published: May 2006

Brief treatment with 0.1 mM diisopropylfluorophosphate inhibited an average of 89% of the acetylcholinesterase (EC 3.1.1.7; acetylcholine hydrolase) activity of cultures of chick embryo muscle. As long as protein synthesis occurred, an average of 78% of the activity returned within 4 hr. Newly synthesized acetylcholinesterase did not stain cytochemically, was rapidly and extensively degraded or released in the presence of 10 μM cycloheximide, and consisted mainly of low-molecular-weight forms. Acetylcholinesterase activity first appeared around the nucleus, about 4 hr after treatment with diisopropylfluorophosphate, and then spread to the rest of the cell about the time release of acetylcholinesterase was detected in the medium. With time, more and more of the enzyme was retained in the cells after treatment with cycloheximide, and the proportions of low-molecular-weight forms decreased and high-molecular-weight forms increased. The results suggest that newly synthesized acetylcholinesterase undergoes an orderly process of binding, movement, and assembly in diisopropylfluorophosphate treated, and probably also in untreated, embryo muscle fibers.
The Mechanism of Muscle Contraction
Authors: Szent-Györgyi Albert
Published: May 2006

Muscular contraction is essentially the shortening of the S
2
subunits of heavy meromyosin, integrated to macroscopic motion by the thick and thin filaments.
Interactions of a Photo-Affinity ATP Analog with Cation-Stimulated Adenosine Triphosphatases of Human Red Cell Membranes
Authors: Haley Boyd E. , Hoffman Joseph F.
Published: May 2006

To identify and isolate ATP binding and hydrolyzing sites of human red cell membranes we have synthesized a photo-activated ATP analog, 8-azido adenosine triphosphate (N
3
ATP). In the absence of ultraviolet light it is a substrate for both the Mg-ATPase and the ouabain-sensitive, Na,K-ATPase. Hydrolysis of N
3
ATP is prevented by increasing concentrations of ATP. Photolysis of N
3
ATP with red cell membranes results in covalent incorporation and irreversible inhibition of both ATPase activities. Also, only three protein components of the red cell membranes are labeled. This labeling is completely abolished by appropriate concentrations of ATP.
Role of DNA-Dependent RNA Polymerases II and III in Transcription of the Adenovirus Genome Late in Productive Infection
Authors: Weinmann Roberto , Raskas Heschel J. , Roeder Robert G.
Published: May 2006

DNA-dependent RNA polymerases I, II, and III were isolated and partially purified from KB (human) cells 18 hr after infection with adenovirus 2. As reported previously for the enzymes from other animal cells, RNA polymerase II was completely sensitive to low concentrations of α-amanitin (50% inhibition at 0.02 μg/ml), RNA polymerase III was completely sensitive to high concentrations of α-amanitin (50% inhibition at 20 μg/ml) and RNA polymerase I was totally resistant to concentrations of α-amanitin less than or equal to 200 μg/ml. RNA synthesis by the endogenous RNA polymerase activities in nuclei isolated from infected cells was completely sensitive to α-amanitin, thus suggesting that RNA polymerase I is not involved in viral DNA transcription even though it is present in these cells. The α-amanitin inhibition curve was biphasic and showed inflection points at about 0.02 and 20 μg/ml, suggesting the participation of both RNA polymerases II and III in the synthesis of RNA in these nuclei. Furthermore, at least a large fraction of the synthesis of the nuclear precursors to viral mRNA, monitored by hybridization to viral DNA, showed the same sensitivity to α-amanitin as did RNA polymerase II; and the synthesis of both viral 5.5S RNA and (presumably cellular) 5S RNA in the isolated nuclei exhibited the same sensitivity to α-amanitin as did purified RNA polymerase III. Thus, these data provide strong supporting evidence for previous studies which suggested the involvement of an RNA polymerase II in transcription of the adenovirus genome and demonstrate the role of an RNA polymerase III activity in the synthesis of viral 5.5S RNA and cellular 5S RNA.
The Role of the Skin in Active Specific Immunization Against Leukemia in Guinea Pigs
Authors: Gross Ludwik , Dreyfuss Yolande
Published: May 2006

The L
2
C leukemia strain, which originated as spontaneous leukemia in “strain 2” guinea pigs, is transmissible by cell-graft in animals of this line; on subcutaneous inoculation it induces consistently generalized and progressive stem-cell leukemia in 99% of the inoculated animals. The leukemia thus induced never regresses. However, when very small doses of leukemic cell suspensions (0.05 ml of a 10
-6
or 10
-7
dilution) were inoculated intradermally, 86 out of 180 intradermal tumors (48%) regressed spontaneously. Most of the animals that recovered from the intradermal tumors were resistant to a challenging reinoculation of leukemic cells. This resistance could be substantially increased by a second intradermal inoculation of leukemic cells. Females were more resistant than males. When 55 immunized females and 36 males received a challenging subcutaneous reinoculation (0.5 ml each) of a leukemic cell suspension of 10
-2
dilution, only two females and six males developed leukemia; the remaining 83 animals (91%) remained in good health. In a control experiment, 126 untreated “strain 2” guinea pigs were inoculated subcutaneously with the same dose, and all but one (99%) developed leukemia. The immunity thus induced could not be transferred to other animals by a serum collected from immunized guinea pigs.
Morphology of Nucleolar Cistrons in a Plant Cell,
Acetabularia mediterranea
Authors: Trendelenburg Michael F. , Spring Herbert , Scheer Ulrich , Franke Werner W.
Published: May 2006

The structural organization of transcriptionally active DNA that contains cistrons for precursor molecules of ribosomal RNA is described in positively stained spread preparations from nuclei and nucleoli isolated from the green alga,
Acetabularia mediterranea
Lmx. These nuclei contain large aggregates of nucleolar subunits in which fibril-covered regions, the putative active cistrons for precursors of ribosomal RNA, alternate with fibril-free intercepts, the “spacers.” The length distribution of the different intercepts of this DNA is given, and the pattern is compared with those shown in animal cell systems. The data are discussed in relation to problems of transcription and of amplification of ribosomal RNA genes.
Major DNA Polymerases Common to Different
Xenopus laevis
Cell Types
Authors: Tatò Franco , Gandini Domenica Attardi , Tocchini-Valentini Glauco P.
Published: May 2006

DNA polymerases from
Xenopus laevis
oocytes, unfertilized eggs, and kidney cells grown in culture have been characterized. The same three major DNA polymerase activities are present in all cell types examined. We attempt to relate the characteristics of amphibian enzymes to those of mammalian polymerases.
Evidence for de novo production of self-replicating and environmentally adapted RNA structures by bacteriophage Qbeta replicase.
Authors: Sumper M , Luce R
Published: May 2006

Highly purified coliphage Qbeta replicase when incubated without added template synthesizes self-replicating RNA species in an autocatalytic reaction. In this paper we offer strong evidence that this RNA production is directed by templates generated de novo during the lag phase. Contamination of the enzyme by traces of RNA templates was ruled out by the following experimental results: (1) Additional purification steps do not eliminate this RNA production. (2) The lag phase is lengthened to several hours by lowering substrate or enzyme concentration. At a nucleoside triphosphate concentration of 0.15 mM no RNA is produced although the template-directed RNA synthesis works normally. (3) Different enzyme concentrations lead to RNA species of completely different primary structure. (4) Addition of oligonucleotides or preincubation with only three nucleoside triphosphates affects the final RNA sequence. (5) Manipulation of conditions during the lag phase results in the production of RNA structures that are adapted to the particular incubation conditions applied (e.g., RNA resistant to nuclease attack or resistant to inhibitors or even RNAs "addicted to the drug," in the sense that they only replicate in the presence of a drug like acridine orange). RNA species obtained in different experiments under optimal incubation conditions show very similar fingerprint patterns, suggesting the operation of an instruction mechanism. A possible mechanism is discussed.
DNA strand breaks measured within 100 milliseconds of irradiation of Escherichia coli by 4 MeV electrons.
Authors: Johansen I , Brustad T , Rupp W D
Published: May 2006

A method was developed in which E. coli cells were irradiated with four MeV electrons and transferred to alkaline detergent within a fraction of a second. This technique minimizes the amount of repair of radiation damage before analysis without the necessity of using physical or chemical treatments to inhibit repair and alter the physiological condition of the cells. The yield of DNA strans breaks formed in covalent circular superhelical lambda DNA molecules superinfecting E. coli lysogens was about 4-fold greater when the cells were irradiated in oxygen than when they were irradiated under nitrogen anoxia. The same yields were obtained in phosphate buffer at 3 degrees and 22 degrees as well as in growth medium at 37 degrees, and the yields were not altered by the polA1 mutation. When E. coli lysogenic cells superinfected with lambda were irradiated with doses sufficient to introduce at least seven breaks in the phage DNA, the chromosomal DNA and the superinfecting phage DNA sedimented similarly in alkaline sucrose gradients, indicating that both DNAs were broken to a similar extent during irradiation. However, the yield of breaks calculated for chromosomal DNA in similar experiments was greater than the yield calculated from the first break introduced into covalent circular lambda DNA molecules. These apparently contradictory results are explicable either if the initial break in a superhelical molecule occurs with an efficiency different from that for subsequent breaks, or if the pulsed electron radiation produces a high proportion of double-strand breaks.
Xeroderma pigmentosum cells with normal levels of excision repair have a defect in DNA synthesis after UV-irradiation.
Authors: Lehman A R , Kirk-Bell S , Arlett C F , Paterson M C , Lohman P H , de Weerd-Kastelein E A , Bootsma D
Published: May 2006

Cells cultured from most patients suffering from the sunlight-sensitive hereditary disorder xeroderma pigmentosum are defective in the ability to excise ultraviolet light (UV)-induced pyrimidine dimers from their DNA. There is, however, one class of these patients whose cells are completely normal in this excision repair process. We have found that these cells have an abnormality in the manner in which DNA is synthesized after UV-irradiation. The time taken to convert initially low-molecular-weight DNA synthesized in UV-irradiated cells into high-molecular-weight DNA similar in size to that in untreated cells is much greater in these variants than in normal cells. Furthermore, this slow conversion of low to high-molecular-weight newly synthesized DNA is drastically inhibited by caffeine, which has no effect in normal cells. Two cell lines from classes of xeroderma pigmentosum that are defective in excision-repair show intermediate effects, with regard to both the time taken to convert newly synthesized DNA to high molecular weight and the inhibition of this process by caffeine.
The Alkali Ion-DNA Interaction as Reflected in the Nuclear Relaxation Rates of
23
Na and
87
Rb
Authors: Reuben Jacques , Shporer Mordechai , Gabbay Edmond J.
Published: May 2006

Longitudinal relaxation rates of
23
Na and
87
Rb in aqueous solutions of DNA were measured and interpreted in terms of contributions of “bound” and free species. The frequency dependence of the
23
Na relaxation rate sets an upper limit of 5.5 nsec for the correlation time characteristic of the alkali ion-DNA interaction. The plausible description of the alkali ion-DNA interaction emerging from the results is one in which the “bound” ions comprise a highly mobile ionic cloud around the lattice of phosphate groups with a population characterized by an apparent dissociation constant of 10.9 mM. Any specific binding to phosphate groups involving severe restrictions of motional freedom must be much (at least two orders of magnitude) weaker and of a very short duration (<5.5 nsec).
Paired moving charges in mitochondrial energy coupling. II. Universality of the principles for energy coupling in biological systems.
Authors: Green E , Reible S
Published: May 2006

The thesis is developed that an acceptable model of biological energy coupling must have universal application. The paired moving charge model of mitochondrial energy coupling is examined from the standpoint of this thesis. Fundamental to this model is the notion that energy coupling involves interaction between paired uncompensated charged species in two vectorially aligned and spatially separated reaction centers. The two charge-separating devices are assumed to be the electron transfer chain (in chloroplast and mitochondria) and intrinsic ionophores (in all transducing organelles and kinases). The universality of the ionophore principle becomes then the crucial test of the validity of the paired moving charge model. The multiple facets of ionophore-mediated couples processes are explored, e.g., coupled hydrolysis of ATP, hormonal control of ion movements, and active transport.
Ribonucleoprotein particles containing heterogeneous nuclear RNA in the cellular slime mold Dictyostelium discoideum.
Authors: Firtel R A , Pederson T
Published: May 2006

As in higher eukaryotes, heterogeneous nuclear RNA (HNRNA) in the cellular slime mold Dictyostelium discoideum is associated with proteins in the form of ribonucleoprotein particles. Mixing experiments with deproteinized hnRNA establish that the nuclear ribonucleoprotein particles are not formed artificially during isolation. In contrast to comparable material from mammalian cells (polydisperse, 40-25- S), Dictyostelium heterogeneous nuclear ribonucleoprotein particles sediment at only 55 S in sucrose gradients, possibly reflecting the smaller size of slime mold hnRNA relative to the large hnRNA found in higher eukaryotes. The RNA of the nuclear 55S ribonucleoprotein particles is shown to be hnRNA by virtue of its size (15S), content of polyadenylate sequences, and hybridization kinetics at DNA excess. The hnRNA-associated porteins are electrophoretically complex and have molecular weights between 20,000 and 150,000. In 0.35 M NaCl most of the proteins are released from the hnRNA. However, a single protein of 72,000-74,000 molecular weight remains bound, as indicated by its co-chromatography with the RNA on poly(U)-Sepharose and banding in Cs2SO4. The same protein is recovered when heterogeneous nuclear ribonucleoprotein is digested with T1 ribonuclease under conditions where the poly(A) is nuclease-resistant. The 73,000 molecular weight protein appears to be specifically bound to polyadenylate sequences in Dictyostelium hrRNA.
Cell-cell interactions: enhancement of glycosyl transferase ectoenzyme systems during Chlamydomonas gametic contact.
Authors: McLean R J , Bosmann H B
Published: May 2006

Glycosyl transferase ectoenzyme systems that transfer galactose, glucose, N-acetylglucosamine, N-acetylneuraminic acid, mannose, and fucose have been detected on vegetative cells and gametes of Chlamydomonas moewusii. Gametes have higher levels of activity of the transferase ectoenzyme systems than morphologically identical vegetative cells, as determined by transfer of monosaccharide onto endogenous cell surface acceptors. When (plus) and (minus) gametes are mixed, there is a significant increase in the activity of transferase ectoenzyme systems. No enhancement in activity of transferase ectoenzyme systems occurs when (plus) and (minus) vegetative cells are mixed. Flagellar membrane vesicles obtained from (plus) and (minus) gametes show high activity of transferase ectoenzyme systems per mg of protein and also demonstrate enhanced activity upon mixing. Therefore, glycosyl transferases and acceptors seem to be located on the flagellar membrane and appear to have a function particularly related to gametic cells. The mechanism of cellular adhesion or recognition proposed by Roseman (1970, Chem. Phys. Lipids 5, 270-297), involving glycosyl transferases and acceptors, is strongly suggested by our data for the mating reaction in Chlamydomonas.
A new chemical procedure for 32P-labeling of ribonucleic acids at their 5'-ends after isolation.
Authors: Rapaport E , Zamecnik P C
Published: May 2006

A new technique, which utilizes the chemical reaction between [32P]diimidazolidate of orthophosphate and the cetyltrimethylammonium salt of high-molecular-weight RNA in nonaqueous dimethyl formamide, has been developed for the 32P-labeling of RNAs after isolation. The radioactive label of high specific activity is introduced onto a phosphorylated 5'-end of the RNA and renders it suitable for 5'-terminal group analysis. When the labeling reaction was applied to the 70S RNA of avian myeloblastosis virus, a labeled 35S RNA was isolated on sucrose-dimethyl sulfoxide gradients without apparent degradation.