bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Selective Inhibition of Transformed Cell Growth by a Protease Inhibitor
Authors: Chou Iih-Nan , Black Paul H. , Roblin Richard O.
Published: May 2006

The protease inhibitors
N
-tosyl-L-phenylalanylchloromethyl ketone (TPCK) and
N
-tosyl-L-lysylchloromethyl ketone (TLCK) have previously been shown to selectively inhibit growth of simian virus 40-transformed cells, suggesting that proteolytic enzymes play a role in loss of cellular growth control following viral transformation. In contrast, this study shows that TPCK-mediated growth inhibition is non-selective, since the growth of both simian virus 40-transformed and untransformed 3T3 cells is similarly reduced by TPCK treatment. Under certain conditions, TPCK treatment of simian virus 40-transformed cells yields a reversible “growth plateau” condition which mimics, but is not equivalent to, contact inhibition of growth. The growth inhibitory effects of TPCK are due to inhibition of protein synthesis, since TPCK treatment resulted in a diminution of protein synthesis and since the “growth plateau” effect was also observed in cultures treated with cycloheximide.
Decarboxylation to Tyramine: A Major Route of Tyrosine Metabolism in Mammals
Authors: David Jean-Claude , Dairman Wallace , Udenfriend Sidney
Published: May 2006

Metabolism of tyrosine was examined in mice, some of which had been treated with an inhibitor of aromatic-L-amino-acid decarboxylase. The results of the study indicate that as the plasma and tissue levels of tyrosine are elevated, decarboxylation to tyramine becomes the predominant route of metabolism. At the highest dose of tyrosine used (1.5 g/kg), it was found that 42% of the administered dose was decarboxylated within 6 hr and only 11.5% was metabolized by the tyrosine aminotransferase pathway.
NS-1 (Nervous System Antigen-1), a Glial-Cell-Specific Antigenic Component of the Surface Membrane
Authors: Schachner Melitta
Published: May 2006

A methylcholanthrene-induced glioblastoma of the C57BL/6 inbred mouse strain was used to raise antibodies in C57BL/6 and C57BL/10 inbred mice and in (C57BL/6 × DBA/2) and (C57BL/6 × Balb/c) F
1
hybrids. When examined by the cytotoxicity test, these antibodies define a cell-surface component (or components) found exclusively on brain tissue of all mouse strains studied and of several other mammalian species including man. The antigen, named NS-1 (nervous system antigen-1), is present on cells of three of the four mouse-glial-cell tumors tested, but not on the C1300 neuroblastoma, a tumor of neuronal origin. NS-1 occurs in higher concentration in regions of the nervous system richer in white than in gray matter, and in lower than normal concentrations in brains of myelindeficient neurological mutant mice. The concentration of NS-1 gradually increases postnatally and reaches the adult level between the third and fourth week. The existence of more than one allele or genetic locus controlling NS-1 activity is suggested by the occurrence of higher amounts of NS-1 in brains of the A and C57BL/6 than of the Balb/c and DBA/2 mouse strains. NS-1 is the first cellsurface component to be described that is not only unique to nervous tissue, but specific for glial cells.
Facilitation of Development of Resistance to Morphine Analgesia by Desglycinamide
9
-Lysine Vasopressin
Authors: Krivoy William A. , Zimmermann Emery , Lande Saul
Published: May 2006

Desglycinamide
9
-lysine vasopressin facilitates development of resistance to the analgesic action of morphine in mice if morphine is administered before the peptide. Desglycinamide
9
-lysine vasopressin is not a morphine antagonist, and does not appear to cause either hyperalgesia or alteration of the response to the technique used for evaluating analgesia.
Investigation of Very Slowly Tumbling Spin Labels by Nonlinear Spin Response Techniques: Theory and Experiment for Stationary Electron Electron Double Resonance
Authors: Smigel Murray D. , Dalton Larry R. , Hyde James S. , Dalton Lauraine A.
Published: May 2006

The investigation of very slowly tumbling spin labels by nonlinear electron spin response techniques is discussed. Such techniques permit characterization of rotational processes with correlation times from 10
-3
to 10
-7
sec even though the linear spin response (ESR) technique is insensitive to motion in this region. Nonlinear techniques fall into two categories: (
a
) Techniques (referred to as passage techniques) in which the distribution of saturation throughout the spin system is determined both by the applied magnetic field modulation of the resonance condition and by the modulation of the resonance frequency induced by the molecular motion. The time dependence of this distribution produces phase and amplitude changes in the observed signals. (
b
) Techniques that measure the integral of the distribution function of the time required for saturated spin packets to move between pumped and observed portions of the spectrum [stationary and pulsed electron electron double resonance (ELDOR) techniques]. Quantitative analysis of passage ESR and stationary ELDOR techniques can be accomplished employing a density matrix treatment that explicitly includes the interaction of the spins with applied radiation and modulation fields. The effect of molecular motion inducing a random modulation of the anisotropic spin interactions can be calculated by describing the motion by the diffusion equation appropriate to the motional model assumed. For infinitesimal steps the eigen-functions of the diffusion operator are known analytically, while for random motion of arbitrary step size they are determined by diagonalizing the transition matrix appropriate for the step model used. The present communication reports investigation of the rotational diffusion of the spin label probes 2,2,6,6-tetramethyl-4-piperidinol-1-oxyl and 17β-hydroxy-4′,4′-dimethylspiro-[5α-androstane-3,2′-oxazolidin]-3′-oxyl in
sec
-butylbenzene. Experimental spectra are compared with computer simulations of spectra carried out for isotropic Brownian (limit of infinitesimal step size) and free diffusion (arbitrary step size) models.
Vitamin E Deficiency: Immunochemical Evidence for Increased Accumulation of Liver Xanthine Oxidase
Authors: Catignani George L. , Chytil Frank , Darby William J.
Published: May 2006

Xanthine oxidase (EC 1.2.3.2) activity increases in liver of rabbits deficient in vitamin E. Immunochemical titration of the enzyme demonstrates that the elevation of activity is due to an increased accumulation of the enzyme protein rather than activation of preexisting enzyme molecules. Immunochemically, xanthine oxidase from deficient animals is indistinguishable from the enzyme from control animals. Incorporation of labeled leucine into immunoprecipitable xanthine oxidase is enhanced in vitamin E-deficient animals. This enhancement is interpreted as indicating that the accumulation of xanthine oxidase molecules reflects an accelerated
de novo
synthesis of the enzyme.
Mechanism of Enzymic Acetylation of des-Acetyl Citrate Lyase
Authors: Schmellenkamp H. , Eggerer H.
Published: May 2006

A new enzyme, acetate:SH-[acyl-carrier-protein] enzyme ligase (AMP), has been purified about 30-fold from cell-free extracts of
Klebsiella aerogenes
. The enzyme, in the presence of acetate and ATP, catalyzes the acetylation of enzymically inactive des-acetyl citrate lyase to enzymically active citrate lyase (EC 4.1.3.6). Acetate and ATP could be replaced by acetyl adenylate. Acetyl-CoA can act as acetyl donor in this activation only if trace amounts of adenine nucleotides and auxiliary enzymes are present. These allow formation of acetyl adenylate in acetate- and ATP-generating reactions.
Increased RNA Synthesis in Nuclear Monolayers of WI-38 Cells Stimulated to Proliferate
Authors: Bombik Bernd M. , Baserga Renato
Published: May 2006

Nuclear monolayers of WI-38 cells prepared by the method of Tsai and Green were used to determine RNA synthesis in isolated nuclei
in situ
. In nuclear monolayers, incorporation of [
3
H]UTP into RNA is dependent on the presence of the other three nucleotide triphosphate and is abolished by actinomycin D. The extent of RNA synthesis under these conditions was measured in density-inhibited WI-38 human diploid fibroblasts at various intervals after cell proliferation was stimulated by a change of medium.

RNA synthesis increases 15 min after the nutritional change and reaches a peak at 18 hr, which is also the peak of DNA synthesis. Thereafter RNA synthesis declines. Essentially similar results are obtained whether the endogenous RNA polymerase or a bacterial polymerase is used. Replacement of the stimulating medium by conditioned medium stops the increase in RNA synthesis that occurs in cultures subject to continuous stimulation. Finally, RNA synthesis in nuclear monolayers, using the endogenous RNA polymerase, occurs by chain elongation only, while re-initiation occurs with the bacterial RNA polymerase.
Specific Movement of Cell Membranes Fused with HVJ (Sendai Virus)
Authors: Okada Yoshio , Kim Jeman , Maeda Yumiko , Koseki Ignez
Published: May 2006

When Ehrlich ascites tumor cells fused with UV-inactivated HVJ (Sendai virus) were cultured, the viral envelope antigens, which had been integrated at random into the cell membranes, accumulated at one site on the fused cell. The site showed a specific structure, namely, a projection of the cytoplasm from the spherical fused cell surface with clusters of many long microvillilike protrusions from it. When the fused cells were conjugated with antibody against Ehrlich ascites tumor cells and cultured, the antigen-antibody complex also accumulated on the projection.

Associated with the development of the projection and accumulation of viral antigens, vacuoles developed at the base of the projection in the cytoplasm of the fused cells in culture. The development of the projection and vacuoles and the accumulation of viral antigens were all inhibited by glucose, mannose, galactose, sodium azide, and cycloheximide, and these inhibitions were reversible. All these structures were observed in multinucleated cells, but few in mononucleated cells after reaction with HVJ (Sendai virus). We consider that these three phenomena correlate with each other and may result from changes in cell-membrane systems caused by fusion of cells.
Interaction of Nerve Growth Factor with the Mouse-Brain Neurotubule Protein(s)
Authors: Calissano Pietro , Cozzari Costantino
Published: May 2006

Addition of nerve growth factor to a 105,000 ×
g
supernatant of mouse brain induces the formation of a precipitate whose main constituent is the microtubule protein(s) (tubulin). The binding of nerve growth factor to purified tubulin is not inhibited by colchicine and does not appear to depend on the presence of GTP or Mg
++
. GTP, however, and divalent cations, exert a marked effect on the increased turbidity induced by interaction of nerve growth factor with tubulin. These findings are tentatively interpreted with the hypothesis that binding of the factor to tubulin and the induced aggregation is a sequential two-step process; the latter but not the former would be influenced by GTP or divalent cations.
Dominance of the Senescent Phenotype in Heterokaryons Between Replicative and Post-Replicative Human Fibroblast-Like Cells
Authors: Norwood Thomas H. , Pendergrass William R. , Sprague Curtis A. , Martin George M.
Published: May 2006

In heterokaryons between senescent and young diploid fibroblast-like cells, dominance of the former with respect to nuclear DNA synthesis (incorporation of [
3
H]thymidine) was demonstrated. For identification of the respective partners, double-layer autoradiography was used after the old cells were labeled with [
3
H]methionine and the young cells were labeled with [
14
C]thymidine. Synchrony of nuclear labeling (i.e., all nuclei in a cell labeled with [
3
H]thymidine) was observed in the majority of di- and polykaryons during the second and third of three 24-hr periods of labeling with [
3
H]thymidine. The results are compatible with either terminal differentiation or error theories of clonal senescence.
Localization of Replicating DNA of Simian Virus 40 in Monkey Kidney Cells
Authors: LeBlanc Donald J. , Singer Maxine F.
Published: May 2006

Approximately 80-85% of the DNA synthesized by cells infected with simian virus 40 during a short pulse with [
3
H]thymidine is associated with host nuclear membrane components, as defined by the M-band technique. A substantial portion of this membrane-associated DNA has been shown to be viral specific by sedimentation studies and by DNA·DNA hybridization. Examination of DNA associated and unassociated with nuclear M-band by neutral sucrose gradient analysis suggested that while replicating DNA of simian virus 40 is attached to the nuclear membrane, mature component I DNA of simian virus 40 is released from the membrane upon completion of replication.
Coupling Between Mitochondrial Mutation and Energy Transduction
Authors: Mahler Henry R. , Bastos Roberto N.
Published: May 2006

Upon incubation with ethidium bromide (Etd Br) isolated mitochondria of
Saccharomyces cerevisiae
have been shown to be capable of performing five novel reactions: (
a
) a single scission of their DNA (mtDNA) coincident with (
b
) the incorporation of Etd Br into the product (mtDNA → 2 mtDNA′-Etd Br); (
c
) an energy- (and probably ATP-) requiring degradation of mtDNA′-Etd Br to acid-labile products. These reactions acting in series generate (
d
) a DNase dependent on both Etd Br and an energy supply with mtDNA′-Etd Br as an obligatory intermediate. Coincident with (
d
) there occurs (
e
) an activation of adenosinetriphosphatase. Experiments with specific inhibitors suggest that the enzyme responsible is the mitochondrial adenosinetriphosphatase complex itself, and that it and the ability to carry out reactions (
a
) through (
e
) are tightly coupled to the energy-transducing functions of the particle.
A Proposed Hydrogen Transfer Function for Cytochrome
c
Authors: Harrison John E.
Published: May 2006

Outlines of proposed mechanisms for cytochrome
c
oxidoreduction are presented which differ in detail from those previously published. The mechanisms, while accommodating the fact that cytochrome
c
is a net electron acceptor and donor in its catalytic cycle, dictate that the enzyme catalyses hydrogen transfer. It is shown that the mechanism of cytochrome
c
reduction fulfills a recent proposal that the transition state is an analogue of the structure of ferricytochrome
c
2
. The implications of a hydrogen transfer role of cytochrome
c
are discussed.
Rapid Enhancement of Chick Intestinal DNA-Dependent RNA Polymerase II Activity by 1α,25-Dihydroxyvitamin D
3
,
In Vivo
Authors: Zerwekh Joseph E. , Haussler Mark R. , Lindell Thomas J.
Published: May 2006

1α,25-dihydroxyvitamin D
3
was examined for its ability to affect the DNA-dependent RNA polymerases (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) of rachitic chick intestinal cell nuclei
in vivo
. Nucleoplasmic (form II) RNA polymerase activity was stimulated 2-fold (
P
< 0.05) within 2-3 hr after an oral dose of 0.27 μg (0.65 nmol) of 1α,25-dihydroxyvitamin D
3
to rachitic chicks. The form II polymerase activity returned to control values by 5-9 hr after dosing with the sterol. In contrast, the nucleolar (form I) RNA polymerase was not increased within this period. Solubilization of nuclear protein and resolution of the two RNA polymerases on DEAE-Sephadex also revealed that there was an increase in polymerase II activity when assayed on exogenous DNA template. This evidence suggests that 1α,25-dihydroxyvitamin D
3
acts at the level of the enzymology of intestinal cell transcription and that increased mRNA synthesis after administration of this hormone cannot be due solely to a change in chromatin template activity.
Effect of Poliovirus Double-Stranded RNA on Viral and Host-Cell Protein Synthesis
Authors: Celma M. L. , Ehrenfeld E.
Published: May 2006

Cell-free protein-synthesizing systems that initiate on endogenous messenger RNA have been developed from uninfected and poliovirus-infected HeLa cells. Poliovirus double-stranded RNA is an effective inhibitor of protein synthesis in these extracts, and both cell-directed and virus-specific protein synthesis are equally sensitive to the inhibitory action of double-stranded RNA. The concentrations of double-stranded RNA required for inhibition are not achieved in the infected cell at early times after infection when host-cell shut-off occurs, but rather are achieved only late in infection when virus-specific protein synthesis begins to decline. This indicates that double-stranded RNA does not act as a direct agent to inhibit host cell protein synthesis following infection by poliovirus. The possible significance of inhibition by double-stranded RNA of poliovirus-specific protein synthesis is discussed.
Receptor Mobility and the Mechanism of Cell-Cell Binding Induced by Concanavalin A
Authors: Rutishauser Urs , Sachs Leo
Published: May 2006

The cell-cell binding induced by concanavalin A between single cells has been analyzed by use of cells attached to nylon fibers. Binding of a concanavalin A-coated cell to an untreated cell was found to a high degree between two lymphoma tumor cells, less frequently between a lymphoma cell and a normal lymphocyte, and only rarely between two normal lymphocytes. The binding was inhibited by the presence of a saccharide inhibitor of concanavalin A, but could not be reversed by addition of the inhibitor after the cells had bound to each other. Although no binding was obtained when both cells were coated with lectin or fixed with glutaraldehyde, fixation of a cell before coating with concanavalin A enhanced its ability to bind an untreated cell. The results indicate that cell-cell binding induced by concanavalin A requires short-range lateral movement of cell receptors for the lectin, that only one cell has to have mobile receptors, and that some receptors must be unoccupied by lectin molecules before cell-cell contact. Clustering of the receptors is not necessary and seems to hinder cell-cell binding. It is suggested that the short-range movement is required for alignment of individual receptors so as to form multi-point bridges between two cells by lectin molecules. The bridging is then followed by the formation of irreversible bonds between the cells. The receptors on tumor cells appear to have a greater ability than receptors on normal cells to align themselves for cell-cell binding.
Estimation of the Number of Genes Coding for the Constant Part of the Mouse Immunoglobulin Kappa Light Chain
Authors: Faust C. H. , Diggelmann H. , Mach B.
Published: May 2006

As previously shown, purified 14S RNA of mouse myeloma MOPC-41 forms a single peak on sucrose gradients and gel electrophoresis and codes for a single polypeptide chain, the immunoglobulin light chain produced by the same myeloma
in vivo
. This 14S mRNA was used for the enzymatic synthesis of DNA (cDNA) which is complementary to the RNA template. A DNA fraction was isolated which has an average size of 300 nucleotides. Kinetic studies of the hybridization of the 14S RNA with the cDNA indicate that about 40% of the RNA consists of a single RNA sequence. From the size of the cDNA fraction and from the direction of DNA synthesis, it can be concluded that the cDNA includes the sequence complementary to the constant region of light chain mRNA. This radioactive cDNA was used for DNA·DNA reannealing experiments with unlabeled DNA from mouse liver or myeloma tumor in 3 × 10
6
-fold excess. This allowed the determination of the number of copies in the mouse genome of those sequences represented in the cDNA. The data show no significant reiteration in either liver or myeloma DNA and suggest that the gene coding for the constant part of immunoglobins is present in the haploid genome in one to five copies. Furthermore, this gene is not “amplified” in nuclear DNA of myeloma plasmocytes.
The Thermosensitive Lesion in the Replication of the Drug Resistance Factor, Rts1
Authors: DiJoseph C. G. , Kaji Akira
Published: May 2006

The DNA of the thermosensitive R factor, Rts1, has been examined by the technique of sedimentation in alkaline sucrose density gradients. Rts1 DNA was found as closed covalent circles in only a few copies per cell in an
Escherichia coli
host at the permissive temperature. Rts1 DNA appears to be synthesized at the nonpermissive temperature, but was not found as closed covalent circles. However, circular DNA could be recovered upon shift down to the permissive temperature. The large number of plasmid-negative cells which accumulate after prolonged culture at non-permissive temperature may be due to a strong selective pressure favoring the growth of rare R
-
segregants.
Demonstration of Dopamine-sensitive Adenylate Cyclase in Malignant Neuroblastoma Cells and Change in Sensitivity of Adenylate Cyclase to Catecholamines in “Differentiated” Cells
Authors: Prasad Kedar N. , Gilmer Katrina N.
Published: May 2006

Adenylate cyclase (EC 4.6.1.1) activity was stimulated by low concentrations of dopamine and apomorphine, but not by low concentrations of norepinephrine in homogenates of malignant mouse neuroblastoma cells. In cyclic AMP-induced “differentiated” cells, dopamine concentration required for a maximal increase in adenylate cyclase activity was about 10-fold less than that required for a similar increase in control cells, and norepinephrine-sensitive adenylate cyclase activity became apparent at low norepinephrine concentrations. The pharmacological properties of dopamine-sensitive adenylate cyclase were different from those of norepinephrine-sensitive enzyme. For example, dopamine-stimulated adenylate cyclase activity was markedly reduced by low concentrations of haloperidol and phentolamine, whereas norepinephrine-stimulated enzyme activity required higher concentrations of these blocking agents for a similar amount of inhibition. Norepinephrine-stimulated enzyme activity was markedly blocked by low concentrations of propranolol, whereas dopamine-stimulated enzyme activity required a much higher concentration of this blocking agent for a similar amount of inhibition. Low concentrations of isoproterenol increased adenylate cyclase activity in malignant cells, but in “differentiated” cells even a high concentration failed to do so. The fact that dopamine and norepinephrine produced an additive stimulatory effect on adenylate cyclase activity suggests that they interact at different receptor sites. This suggestion is further supported by the observation that the combination of prostaglandin E
1
and norepinephrine produced an additive stimulatory effect of enzyme activity. The observation that the effects of dopamine and prostaglandin E
1
are not additive, coupled with the observation that a low concentration of phentolamine blocked the effect of prostaglandin E
1
, suggests that these two agents may interact at a common site.
Homology Between Bakers' Yeast Cytochrome
b
2
and Liver Microsomal Cytochrome
b
5
Authors: Guiard B. , Groudinsky O. , Lederer F.
Published: May 2006

The amino-acid sequence of the hemebinding region of bakers' yeast cytochrome
b
2
[L-(+)-lactate dehydrogenase, EC 1.1.2.3] has been determined. It shows a strong similarity with the sequence of microsomal cytochrome
b
5
, and appears to be compatible with the same kind of peptide-chain folding, in agreement with data obtained previously by various physiochemical methods. The comparison shows that the fifth and sixth heme ligands must be histidine residues, thus substantiating previous conclusions drawn in particular from photooxidation experiments and nuclear magnetic resonance studies. The data reported in this paper suggest a common origin for the two proteins. Implications for their biochemical evolution are presented.
Kinetics of the Crystalline-Liquid Crystalline Phase Transition of Dimyristoyl
L-α
-Lecithin Bilayers
Authors: Tsong Tian Yow
Published: May 2006

Aqueous dispersions of synthetic dimyristoyl
L-α
-lecithin undergo a sharp decrease in turbidity in the temperature range where the crystalline-liquid crystalline phase transition occurs. Equilibrium transition curves, monitored by the absorbancy change at 300 nm, reproduce all the important features of a calorimetric melting curve [Hinz & Sturtevant (1972)
J. Biol. Chem.
247, 6071]. A rapid temperature-jump of the dispersion, measured by the same absorbancy change, has detected several different molecular processes depending on the magnitude of the perturbation. These processes include a phase transition, permeation of ions and water across the membrane, and repture, annealing, or fusion of the bilayer structures. When the temperature-jump is limited to 1 degree, only reactions associated with the phase transition are detectable and no signal is generated after a temperature-jump except for those which end within or extend beyond the transition zones.

At least two relaxation times are resolved for the phase transition reactions. The faster one in the millisecond time range is strongly temperature-dependent and has an activation energy close to one million calories per mole. The second one, in the 100-msec time range, appears to have a much smaller activation energy. These observations indicate that strongly cooperative nucleation processes and energy-dependent fast propagation steps occur during the phase transition. Since the kinetics of the transition are complex, intermediate state or transient structures must exist in the transition regions of the bilayer dispersions. These thermal fluctuations of the bilayer structures may have important effects on the lateral diffusion and permeation of molecules and ions in the membrane structure.
Effect of Development on the Translation of Messenger RNA in
Artemia salina
Embryos
Authors: Sierra José M. , Meier Dankwart , Ochoa Severo
Published: May 2006

Cell-free preparations from encapsulated
Artemia salina
embryos readily translate poly(U), but there is no endogenous protein synthesis or translation of added natural mRNA until development resumes upon incubation in saline. High-salt-washed 80S ribosomes and highspeed supernatant (cytosol) were prepared from undeveloped eggs and from eggs allowed to develop to a stage prior to hatching. Endogenous protein synthesis occurs only with ribosomes from developed embryos, whether with undeveloped or developed cytosol. This is mainly elongation of preformed polypeptide chains, for it is largely resistant to edeine, an inhibitor of chain initiation. Edeinesensitive translation of added natural mRNA occurs with both developed and undeveloped ribosomes but requires developed cytosol. Translation of brome mosaic virus RNA is not much, if at all, further stimulated by high-saltwash of developed ribosomes, but that of globin mRNA is markedly enhanced. Levels of the chain initiation factor EIF-1 are the same before and after development. These results are consistent with the view that resumption of developemtn is triggered by transcription, with ensuing translation of the resulting messengers to yield, among other proteins, mRNA-recognizing initiation factors of the IF-3 type which are partly free in the cytosol and partly ribosome-bound. The data also suggest that different factors may be involved in the translation of brome mosaic virus RNA and globin mRNA by this system.
An Immunological Assay for the Sigma Subunit of RNA Polymerase in Extracts of Vegetative and Sporulating
Bacillus subtilis
Authors: Tjian Robert , Losick Richard
Published: May 2006

The activity of the σ subunit of
Bacillus subtilis
RNA polymerase decreases markedly during the first hours of sporulation [T.G. Linn
et al.
(1973)
Proc. Nat. Acad. Sci. USA
70, 1865-1869]. We have prepared antibody against RNA polymerase holoenzyme to determine the fate of σ polypeptide during spore formation. This antiserum specifically and independently precipitates σ and core polymerase from crude extracts of
B. subtilis
as judged by both sodium dodecyl sulfate and urea gel electrophoresis of the precipitates. We report that crude extracts of sporulating cells lacking σ activity contain as much σ polypeptide as extracts of vegetative cells. However, σ polypeptide in extracts from sporulating cells is apparently only weakly associated with RNA polymerase, as indicated by the failure of σ to co-purify efficiently with core enzyme during phase partitioning.

The loss of σ activity and the weak binding of σ to core enzyme occurs normally in a mutant blocked at an intermediate stage of sporulation (
SpoII
-4Z) and in wild-type bacteria sporulating in 121B medium, Difco sporulation medium, or Sterlini-Mandelstam resuspension medium. In contrast, σ in two mutants (
SpoOa
-5NA and
SpoOb
-6Z) blocked at an early stage of spore formation remains active and tightly associated with RNA polymerase during stationary phase.
The Effect of Prednisolone® upon the Metabolism and Action of 25-Hydroxy and 1,25-Dihydroxyvitamin D
3
Authors: Carré Michel , Ayigbedé Otegbeye , Miravet Livia , Rasmussen Howard
Published: May 2006

Treatment of vitamin D-deficient rats with Prednisolone® does not alter the rate of conversion of [
3
H]25-hydroxyvitamin D
3
to [
3
H]1,25-dihydroxyvitamin D
3
, but the further conversion of [
3
H]1,25-dihydroxyvitamin D
3
to a more polar metabolite is more rapid in the Prednisolone®-treated animals. This more polar metabolite is biologically inactive, periodate-insensitive, and persists in the intestine as long as 1,25-dihydroxyvitamin D
3
. Also, the time course of action of 1,25-dihydroxyvitamin D
3
upon intestinal calcium transport is altered by Prednisolone® treatment. Treatment with Prednisolone® did not change the magnitude of the initial response to 1,25-dihydroxyvitamin D
3
at 7 hr, but did decrease the response at 24 and 48 hr after a single dose of 1,25-dihydroxyvitamin D
3
. The present results show that one of the means by which large doses of adrenal corticoids alter intestinal calcium transport is by stimulating the further metabolism of 1,25-dihydroxyvitamin D
3
to a more polar, biologically inactive intestinal metabolite.
The
In Vitro
Synthesis of Avian Myeloblastosis Viral RNA Sequences
Authors: Jacquet Michel , Groner Yoram , Monroy Gladys , Hurwitz Jerard
Published: May 2006

Isolated nuclei, prepared from myeloblasts of chicks infected with avian myeloblastosis virus, synthesize RNA sequences present in avian myeloblastosis viral RNA. These sequences are also formed during transcription of chromatin, isolated from myeloblasts, by DNA-dependent RNA polymerases purified from
Escherichia coli
or calfthymus. In the latter case, transcription is α-amanitin sensitive. Formation of hybrids between RNA and avian myeloblastosis virus DNA probes has been monitored by the combined use of ribonucleases A, T
1
, and H, and ribonucleases specific for single strands.
Charged Pair Current Networks in Bioenergetics
Authors: Kemeny Gabor
Published: May 2006

The operation of bioenergetic systems is postulated to be based on charged pair networks. The basic elements of the networks are pairs of opposite charges accompanied by conformational changes of the protein medium. The elementary events are the separation and recombination of charged pairs and partner exchange between two such pairs. The last event makes the construction of networks possible and provides for the flexibility of coupling modes in mitochondria. Bioenergetic systems appear to use electricity in a hitherto unsuspected way. The networks are constructed entirely on electrostatic principles. The possibility of generalization to include mechanical elements is discussed.
Differences Between the Integration of Avian Myeloblastosis Virus DNA in Leukemic Cells and of Endogenous Viral DNA in Normal Chicken Cells
Authors: Evans R. M. , Baluda M. A. , Shoyab M.
Published: May 2006

The nature of integrated viral DNA in normal and leukemic chicken cells has been studied by sequential nucleic acid hybridization procedures that localize the viral specific DNA in cellular DNA regions differing in reiteration frequency. First, DNA·DNA reassociation was employed to fractionate cellular DNA sequences according to their reiteration frequencies. Next, the DNA in each fraction was denatured, immobilized on nitrocellulose filters, and then hybridized with viral [
3
H]RNA. In normal cells, endogenous viral DNA appears to be associated with cell sequences reiterated 1200 times, and each integration unit appears to have a maximal size approximately equivalent to the 35S RNA subunit of the virion. In infected cells, additional viral sequences are found which reassociate as if they integrated adjacent to unique cellular DNA, or in tandem with endogenous viral DNA.
Home Range Orientation and Territoriality in Harvesting Ants
Authors: Hölldobler Bert
Published: May 2006

Trunk trails, used by
Pogonomyrmex barbatus
and
P. rugosus
during foraging and homing, have the effect of avoiding aggressive confrontations between neighboring colonies of the same species. They channel the mass of foragers of hostile neighboring nests into diverging directions, before each ant pursues its individual foraging exploration. This channeling subtly partitions the foraging grounds and allows a much denser nest spacing pattern than a foraging strategy without trunk trails, such as that employed by
P. maricopa
.
Reversible “Transformation” of Bromodeoxyuridine-Dependent Cells by Bromodeoxyuridine
Authors: Davidson Richard L. , Horn Diane
Published: May 2006

The growth characteristics of a bromodeoxyuridine-dependent cell line that was derived from a non-contact-inhibited Syrian hamster melanoma line were studied. The dependent cells require high concentrations of bromodeoxyuridine not only for optimal growth but also for the maintenance of the non-contact-inhibited state. When grown in the absence of bromodeoxyuridine, the dependent cells become contact-inhibited. The transition to the contact-inhibited state is reversed when bromodeoxyuridine is added back to the medium, if the bromodeoxyuridine is incorporated into dividing cells. The effects of bromodeoxyuridine on growth rate and on contact inhibition are separable.
Biological Activity of a Growth Factor for Ovarian Cells
Authors: Jones Kenneth L. , Gospodarowicz Denis
Published: May 2006

The biological activity of a protein growth factor is described. This factor was isolated from bovine pituitary tissue, and its activity was tested on cells of rat ovarian origin. Activity was assayed as growth-promoting potential measured by cell counts and is concentrationdependent. Similar growth stimulation was not produced by several cyclic nucleotides tested, neither was there crossreactivity between this growth factor and a chemically similar one produced by rat liver cells.
Detection and Localization of Virus-Specific DNA by
In Situ
Hybridization of Cells During Infection and Rapid Transformation by the Murine Sarcoma-Leukemia Virus
Authors: Loni Maria Carla , Green Maurice
Published: May 2006

Cytological preparations of interphase nuclei and chromosomes from mouse 3T6 cells prepared at various times after infection with the murine sarcomaleukemia virus complex were hybridized with the [
3
H]DNA product of the viral RNA-directed DNA polymerase. While uninfected nuclei had an average of 4 autoradiographic grains, infected nuclei had 30 grains at 5 hr after infection and 63-65 grains at 11 and 25 hr. Virus-specific grains were localized in the chromocenters of interphase nuclei and were found also in the centromeric heterochromatin region of metaphase chromosomes. These findings provide evidence that the viral RNA-directed DNA polymerase functions to synthesize virus-specific DNA early after infection and that newly synthesized viral DNA rapidly becomes associated with or integrated into specific intranuclear sites.
The Contribution of Subunits of Thyroid Stimulating Hormone to the Binding and Biological Activity of Thyrotropin
Authors: Wolff J. , Winand Roger J. , Kohn Leonard D.
Published: May 2006

The binding of bovine TSH (thyroid stimulating hormone), LH (luteinizing hormone), and their subunits to the TSH receptor of beef thyroid membranes was compared to stimulation by these agents of adenylate cyclase [ATP pyrophosphate-lyase(cyelizing), EC 4.6.1.1] in the same membranes, glucose oxidation in dog thyroid slices, and the secretory process in mouse thyroids
in vitro
(colloid droplet formation) and
in vivo
(hormone release). The β-subunits of TSH and LH can bind to the TSH receptor and can activate thyroid function
in vitro
. In contrast, the α-subunit of TSH binds negligibly to the TSH receptor and has very low potency for stimulation of thyroid function (except for colloid droplet formation). Neither binding nor the biological activity of the β-subunits can be accounted for by TSH contamination, whereas this cannot be ruled out for α-TSH. LH binds to the TSH receptor even better than the β-subunit of TSH but the increased binding does not result in a corresponding activation of thyroid function. Neither α- nor β-TSH alone can induce more than 4-8% of the response to intact TSH in any of the investigated parameters. It is proposed that the β-subunit has within its structure the primary determinants which are necessary to stimulate biological activity, whereas the α-subunit imposes conformational changes on the β-subunit which in intact TSH promote binding
and
biological activity commensurately but in LH promote only binding.
Sequence Arrangements in Clonal Isolates of Polyoma Defective DNA
Authors: Robberson Donald L. , Fried Mike
Published: May 2006

Five clonal isolates of purified polyoma defective DNA [Fried, M. (1974)
J. Virol.
13, 939-946] have been examined by electron microscopy. Four isolates (D-92, D-74, D-50, and D-47) are largely homogeneous in sequence, whereas, the fifth isolate (D-80) is somewhat heterogeneous.

Polyoma nondefective DNA is cleaved in a unique region of the genome by the EcoR
I
endonuclease. Hybridization of the resulting linear molecules with randomly nicked defective DNA reveals distinguishable types of heteroduplex structures for each of the different defective DNAs. Although the defective DNAs are shorter than polyoma nondefective DNA, the heteroduplex experiments demonstrate that they are not simply deletion mutants containing only a portion of the viral genome. Three isolates (D-92, D-50, and D-47) contain regions of homology to polyoma DNA covalently linked to non-homologous regions. One isolate (D-74) contained no regions of detectable homology to polyoma DNA. Another isolate (D-80) contained a large proportion of molecules with duplicated-inverted regions. Some of these isolates of defective DNA may contain specific host sequences at the site(s) of integration of the polyoma genome during the lytic cycle in mouse cells. A process we term “abortive replication” may explain the formation of different types of defective DNAs.
Change in State of Spin Labels Bound to Sarcoplasmic Reticulum with Change in Enzymic State, as Deduced from Ascorbate-Quenching Studies
Authors: Tonomura Yuji , Morales Manuel F.
Published: May 2006

The ATPase (EC 3.6.1.3) of sarcoplasmic reticulum vesicles was reacted to various extents with thiol-directed spin labels. By suspension of the preparation in appropriate solutions, the enzyme could be placed and held in certain intermediate states of the ATPase cycle, or it could be set into steady-state catalysis. Ascorbate added to the system destroyed the spin-label signals with undetectable distortion of the electron paramagnetic resonance spectrum. In general, in the presence of ascorbate, undestroyed signal as a function of time could be described as the sum of two first-order reductions going on in separate compartments with different ascorbate concentrations. In different enzymatic states the proportion of total signal in the two compartments was different, but the first-order velocity constants remained the same. If the labeled membrane was first attacked with Triton, then exposed to ascorbate, signal was destroyed according to a single first-order constant, equal to the faster of the two constants observed with intact membrane, and equal to the constant whereby ascorbate attacks free label in solution. The data were reconciled by a simple rotary model, envisioning that an enzymatic state corresponds to an average angular position of the ATPase and thereby determines the proportion of labeled thiols exposed to external and internal ascorbate concentrations.
Refinement of the X-ray Structure of Rubredoxin by Conformational Energy Calculations
Authors: Rasse Daniel , Warme Paul K. , Scheraga Harold A.
Published: May 2006

The x-ray structure of rubredoxin has been refined by energy minimization. The computed structure is constrained to have standard bond lengths, bond angles, and planar
trans
peptide groups. Also, since most of the steric overlaps have been relieved, it has a very low energy. As judged by the root mean square (RMS) deviation of the computed coordinates from those of the x-ray structure, the two are very similar. The reliability index
R
for the computed structure (determined from the structure factors for the calculated conformation) is 0.37, which is comparable to that for other proteins.
Slow evolutionary loss of the potential for interspecific hybridization in birds: a manifestation of slow regulatory evolution.
Authors: Prager E M , Wilson A C
Published: May 2006

Birds have lost the potential for interspecific hybridization slowly. This inference emerges from protein comparisons made on 36 pairs of bird species capable of hybridization. Micro-complement fixation tests show that hybridizable pairs of bird species differ by an average of 12 units of albumin immunological distance and 25 units of transferrin immunological distance. As these proteins evolve at a known and rather steady rate, it is inferred that the average hybridization species pair diverged from a common ancestor about 22 million years ago. The corresponding period for frog species pairs capable of hybridization is about 21 million years, while for hybridizable placental mammals it is only 2 to 3 million years. Thus birds resemble frogs in having lost the potential for interspecific hybridization about 10 times as slowly as have mammals. Birds have also been evolving very slowly at the anatomical level, particularly within the last 25 million years, according to Simpson, Romer, and many other vertebrate zoologists. In this respect they resemble frogs and differ from placental mammals, which have been undergoing unusually rapid anatomical evolution. Chromosomal evolution is also thought to have proceeded very slowly in both birds and frogs, relative to mammals. The above observations are consistent with the hypothesis that evolutionary changes in regulatory systems, that is, changes in the patterns of gene expression, provide the basis for both anatomical evolution and the evolutionary loss of hybridization potential.
Human globin gene expression and linkage in bone marrow and fetal liver.
Authors: Lanyon W G , Ottolenghi S , Williamson R
Published: May 2006

During embryonic development there is a transition from embryonic and fetal to adult beta-type globin chains. The high-molecular-weight RNA found in nuclei from embryonic and adult human erythropoietic tissues, fetal liver, and bone marrow, have been investigated for the presence of gamma(fetal)- and beta(adult)-globin messenger RNA sequences by molecular hybridization. Unlike alpha- and beta-globin mRNA sequences, gamma-globin mRNA sequences are absent from both total and high-molecular-weight nuclear RNA isolated from adult bone marrow. The amount of cytoplasmic gamma-globin mRNA is proportional to the level of gamma-chain synthesis, demonstrating that translational control is not a major control mechanism in the expression of globin genes. Since the gamma-, delta-, and beta-globin genes are known to be closely linked genetically, transcriptional control can discriminate between similar gene sequences that are spatially adjacent to one another.
Condensation Time of the Solar Nebula from Extinct
129
I in Primitive Meteorites
Authors: Lewis Roy S. , Anders Edward
Published: May 2006

Mineral separates from five carbonaceous chondrites were dated by extinct 16 million year
129
I, in an attempt to establish the condensation time of the solar nebula. Two Fe
3
O
4
or Fe
3
O
4
-FeS samples from the Murchison and Orgueil meteorites are older than any other material dated thus far, and apparently formed within 2 × 10
5
years of each other. The great age, close isochronism, and primitive nature of the samples suggest that the event recorded was the condensation stage of the solar nebula. It provides a suitable zero point for the chronology of the early solar system. The
129
I/
127
I ratio during condensation of the nebula was (1.46 ± 0.04) × 10
-4
. The recrystallized C4 chondrite Karoonda began to retain
129
Xe 1.8 ± 0.5 million years after the above event. This short cooling time implies rapid aceretion (≤1 million years) and a shallow origin (≤10 km) below the surface of its parent body.
Mechanism of action of cholera toxin and the mobile receptor theory of hormone receptor-adenylate cyclase interactions.
Authors: Bennett V , O'Keefe E , Cuatrecasaş P
Published: May 2006

Rat liver membrane adenylate cyclase (EC 4.6.1.1) that has been stimulated more than 10-fold by cholera toxin (choleragen) has a 3-fold greater sensitivity to stimulation by glucagon. Choleragen similarly increases the sensitivity of cyclase to other peptide (ACTH, vasoactive intestinal polypeptide) and nonpeptide (catecholamines) hormones in this and other tissues. The rate of 125I-labeled glucagon-membrane dissociation is decreased about 2-fold in toxin-treated liver membranes. Toxin-activated cyclase activity of fat cell membranes is retained upon solubilization with Lubrol PX. Provided 125I-labeled choleragen is first incubated with cells under conditions resulting in enzyme activation, the solubilized cyclase activity migrates with a component of 125I-labeled choleragen on gel filtration chromatography. Agarose derivatives containing the "active" subunit (molecular weight 36,000) of the toxin can specifically adsorb solubilized adenylate cyclase. Toxin-stimulated cyclase can be immunoprecipitated with antitoxin or anti-"active" subunit antibodies. There is a large excess of membrane receptors (ganglioside GM1) which, with the use of choleragenoid, can be shown to be functionally equivalent with respect to cyclase activation. Choleragenoid, an inactive competitive antagonist of toxin binding, can occupy and block a large proportion of toxin receptors without affecting toxin activity. A scheme of toxin action is proposed that involves lateral membrane diffusion of the initially inactive toxin-receptor complex with subsequent direct interaction with and modulation of adenylate cyclase. The basic features of this scheme may be pertinent to the mechanisms by which hormone receptors normally modulate adenylate cyclase.
Complementation in cytoplasmic petite mutants of yeast to form respiratory competent cells.
Authors: Clark-Walker G D , Miklos G L
Published: May 2006

Complementation has been observed in cytoplasmic respiratory deficient yeast cells (petites) to yield respiratory competent diploids. This successful demonstration depended on the use of spontaneous petites of recent origin and on crosses involving all possible apirwise combinations between the many different petite isolates of opposite mating type. The possibility of deletion of a single unique region of yeast mitochondrial DNA as the initial lesion in petite formation has been eliminated by using strains isogenic for their mitochondrial DNA.