bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship Between Post-Transcriptional Adenylation of Herpes Virus RNA and Messenger RNA Abundance
Authors: Silverstein S. , Bachenheimer S. L. , Frenkel N. , Roizman B.
Published: May 2006

Analysis of the hybridization kinetics of labeled DNA of herpes simplex virus with unlabeled excess RNA from infected cells showed that viral RNA sequences form two classes differing in molar concentration. The abundant class constituted 93.5-99.3% of total virus-specific RNA and was complementary to 14-16% of the early DNA (2 hr after infection) and to 19-22% of the late DNA (8 hr after infection) in the reproductive cycle of the virus. The early RNA sequences were found to be a subset of the late sequences. The scarce sequences constituted 0.7-6.5% of total virus-specific RNA and were complementary to 28-30% of DNA both early and late in the reproductive cycle. In this study, abundant and scarce sequences were quantitatively separated on the basis of the finding that abundant species are adenylated, i.e., contain post-transcriptionally added poly(A), whereas the scarce RNA is not. Thus, nuclear and polyribosomal adenylated RNA were complementary to 24 and 22%, respectively, of viral DNA and, in abundance competition tests, were found to compete with each other and with abundant RNA from infected cells after 8 hr. The nonadenylated polyribosomal RNA was complementary to 27% of total viral DNA of which 6% was also complementary to adenylated polyribosomal RNA. Hybridization kinetics indicated that each of the fractionated adenylated RNA formed two classes complementary to 6 and 21% of viral DNA.
Preliminary Evidence for a Microsomal Precursor to Human Parathyroid Hormone
Authors: Wong Edward T. , Lindall Arnold W.
Published: May 2006

Human parathyroid glands from a patient with chronic renal failure were used to study
in vitro
biosynthesis of immunoreactive parathyroid hormone. Parathyroid glands were incubated in the presence of [
3
H]leucine, and classical subcellular fractions were prepared. peptides from acetic acid extractions of the fractions were separated on Sephadex G-75 Superfine. Eluates were assayed for immunoreactive parathyroid hormone by a double-antibody technique. Leucine was incorporated into several large immunoreactive peptides of parathyroid hormone having estimated molecular weights of >25,000, 18,000, and 13,000. The large forms of immunoreactive parathyroid hormone were prominant in the microsomes. The secretion granule fraction, as well as the patient's serum, contained principally immunoreactive parathyroid hormone with an apparent molecular weight of 10,000.
Factor VIII Recombination After Dissociation by CaCl
2
Authors: Cooper Herbert A. , Griggs Thomas R. , Wagner Robert H.
Published: May 2006

Factor VIII is a large protein molecule of molecular weight 2,000,000 or larger that elutes in the void volume on agarose gel chromatography. It has been shown previously that high concentrations of alkali halides and, more specifically, 0.25 M Ca
2+
dissociate the molecule into a large carrier protein and a small fragment that retains the factor VIII activity. Factor VIII was prepared from normal canine plasma collected in sodium oxalate and heparin and adsorbed with BaSO
4
. Results with Ca
2+
dissociation were the same as those obtained with fraction prepared from canine plasma collected in sodium citrate. The addition of 0.1 M ε-aminocaproic acid in the dissociation step had no effect. Fractionation of canine hemophilic plasma produced preparations without activity, and no activity was found when these inert preparations were dissociated with Ca
2+
. These results indicate that the Ca
2+
dissociation is a true dissociation and not caused by enzymatic degradation by plasmin, thrombin, or activated factors VII, IX, or X. The apparent molecular weight of the small active fragment of factor VIII determined by gel chromatography was about 100,000. Finally, when the large carrier protein and the small active fragment of factor VIII were separated by gel chromatography, mixed, and dialyzed free of Ca
2+
, they recombined to form a large active molecule that appeared in the void volume on agarose gel chromatography.
Growth- and Density-Dependent Inhibition of Deoxyglucose Transport in Balb 3T3 Cells and Its Absence in Cells Transformed by Murine Sarcoma Virus
Authors: Bose Subir K. , Zlotnick Barbara J.
Published: May 2006

The earliest measurable parameter that shows density-dependent inhibition is the uptake of [
3
H]deoxyglucose by Balb 3T3 cells. The rate decreases even during the exponential phase of growth and reaches a minimum, about 8- to 10-times lower than maximum, as the culture approaches the saturation density. Cells transformed by murine sarcoma virus fail to show either growth-dependent or density-dependent inhibition of deoxyglucose uptake. Treatment with dibutyryl cyclic AMP in the presence of theophylline results in premature cessation of growth and in an arrest in the decline of deoxyglucose transport. Culture in serum-deficient medium also produces rapid inhibition of growth at low cell density, but these cultures exhibit a markedly decreased rate of deoxyglucose uptake.
A Cell-Contact Model for Cellular Position Determination in Development
Authors: McMahon Daniel
Published: May 2006

The fate of a cell in a developing organism is a function of its position within the organism. The molecular mechanism that cells use to determine their position and to convert positional information into a form that can be used to regulate the expression of genes is not understood. This paper presents a model in which contacts between complementary molecules on plasma membranes of adjacent cells regulate the concentration of a morphogenetic substance and transmit positional information. This model is described by four equations that, when solved with realistic parameters, demonstrated that this mechanism will produce discrete populations of cells within a few hours from an initially undifferentiated array of cells. The model suggests an explanation for several phenomena that have been observed and suggests experiments to test it and to clearly differentiate it from other models for position determination.
Adhesive Recognition and Retinotectal Specificity
Authors: Barbera Anthony J. , Marchase Richard B. , Roth Stephen
Published: May 2006

An assay has been developed to test the hypothesis that neurons from a limited area of the retina will adhere preferentially to that part of the optic tectum near their normal synaptic termini. The method measures the adherence of
32
P-labeled cell bodies from either the dorsal or ventral half of the neural retina of chick embryos to dorsal and ventral tectal halves. When a labeled, single-cell suspension is prepared from dorsal half-retina, more cells bind to the ventral half of the tectum. When the labeled cells are from ventral half-retina, more bind to dorsal half-tecta. This preferential adhesion mimics the retinotectal projection found
in vivo
. Dorsal retinal cells show this preference shortly after dissociation with crude trypsin, and maintain it for at least 9 hr. Ventral retinal cells, however, require incubation in nutrient medium after trypsinization in order to display this selectivity. Comparable results are obtained when the cell suspension is prepared from pigmented retina. The data support an interpretation of neuronal specificity dependent on cell-surface interactions and demonstrate a clear correlation between selective adhesion and biological function.
Habituation of Tobacco Pith Cells for Factors Promoting Cell Division Is Heritable and Potentially Reversible
Authors: Binns Andrew , Meins Frederick
Published: May 2006

A type of heritable cellular change, known as habituation, occurs spontaneously in plant tissue and cell culture. This phenomenon is characterized by a newly acquired capacity of plant cells to produce growth regulatory substances. Using cloned lines of tobacco pith parenchyma cells, we demonstrated that a newly acquired character, in this instance an ability to produce a factor promoting cell division, is inherited by individual cells, that it persists for long periods of time, but that it is regularly reversible under completely defined experimental conditions. Evidence is presented that suggests that habituation results from heritable alterations in the pattern of gene expression and that it can, therefore, be used as a model for study of cell differentiation. The significance of these findings to the tumor problem is discussed.
General Homeostasis of the Frequency of Circadian Oscillations
Authors: Pittendrigh Colin S. , Caldarola Patricia C.
Published: May 2006

Some well-defined statistical regularities characterize the change in period (τ) of cockroach circadian oscillations subjected to a large temperature step. These are explainable in terms of the well-known temperature-compensation (homeostasis) of τ of circadian oscillations. The same regularities are detectable in published data on the effect of several other variables affecting several other circadian oscillations. The proposition is then developed that the temperature-compensation of τ is only a special case of a general homeostatic conservation of the frequency of circadian oscillations in the face of all changes they are likely to encounter in the cell. Such a general homeostasis of τ is a functional prerequisite for an oscillator to function as a useful “clock.”
Barrier Height for the Exchange Reaction F + HF → FH + F
Authors: O'Neil Stephen V. , Schaefer Henry F. , Bender Charles F.
Published: May 2006

There exists a body of conflicting data as to the existence or nonexistence of FHF, ClHCl, BrHBr, and IHI as chemically bound molecular species.
Ab initio
quantum mechanical electronic structure calculations are presented which predict linear symmetric FHF to be unstable. The barrier height for the F + HF exchange reaction is suggested to be no less than 18 kcal/mol, much larger than expected either intuitively or on the basis of certain experiments on related systems. The expected reliability of the calculations is based upon comparable results for diatomic molecules and the F + H
2
and H + F
2
potential energy surfaces.
Synthesis of Diphtheria
tox
-Gene Products in
Escherichia coli
Extracts
Authors: Murphy J. R. , Pappenheimer A. M. , Borms S. Tayart De
Published: May 2006

In a protein-synthesizing system extracted from
E. coli
, purified DNA from corynephages βc
tox+
and β45c was used to direct the
in vitro
synthesis of diphtheria toxin and of the related nontoxic protein, CRM45, as well as of other β-phage proteins. When βc
tox+
-DNA or βc-DNA was added to a similar system extracted from the nonlysogenic
Corynebacterium diphtheriae
strain, C7
s
(-)
tox-
, neither toxin nor the CRM45 protein was produced, although other β-phage proteins were synthesized in amounts equivalent to those produced in the
E. coli
system from the same amount of β-phage DNA. Preliminary experiments suggest that both toxinogenic and nontoxinogenic strains of the diphtheria bacillus contain a factor that specificially blocks expression of the
tox
gene. Synthesis of toxin and the CRM45 protein in the
E. coli
system could not be inhibited by relatively high concentrations of inorganic iron, but could be inhibited by extracts from the C7
s
(-)
tox-
strain of
C. diphtheriae
.
Restoration of the Conversion of Desmosterol to Cholesterol in L-Cells after Hybridization with Human Fibroblasts
Authors: Croce C. M. , Kieba I. , Koprowski H. , Molino M. , Rothblat G. H.
Published: May 2006

Hybrids between different human cells (which synthesize cholesterol) and mouse cells (whose end-product of sterol synthesis is desmosterol) were analyzed for the ability to convert desmosterol to cholesterol. Conversion of [
14
C]desmosterol to cholesterol and incorporation of [
14
C]acetate into the end-product sterol were studied in the parental and hybrid cells. Concordant segregation of the conversion of desmosterol to cholesterol and the human chromosome F-20 was observed.
Evidence That the AKR Murine-Leukemia-Virus Genome Is Complete in DNA of the High-Virus AKR Mouse and Incomplete in the DNA of the “Virus-Negative” NIH Mouse
Authors: Chattopadhyay Sisir K. , Lowy Douglas R. , Teich Natalie M. , Levine Arthur S. , Rowe Wallace P.
Published: May 2006

The AKR mouse has a high titer of murine leukemia virus early in life, and virus-negative cells derived from embryos of this mouse strain can be activated to yield murine leukemia virus by treatment with 5-iododeoxyuridine. In contrast to this high-virus strain, the NIH Swiss mouse has a low incidence of leukemia and no murine leukemia virus has been isolated from it (virus-negative). We have investigated this difference between AKR and NIH mice by examining the sequences specific for murine leukemia virus in nucleic acids of these mice. A single-stranded viral-DNA probe synthesized
in vitro
using murine-leukemia-virus from the AKR mouse contains at least 87% of the sequences present in the 70S viral RNA; most of these sequences are in proportions similar to their content in the 70S RNA. Using this probe in nucleic acid hybridization experiments, we have shown that NIH-mouse-cell DNA and AKR-mouse-cell DNA differ with respect to sequences specific for AKR murine-leukemia-virus: NIH-mouse-cell DNA lacks some of the virus-specific sequences present in AKR-mouse-cell DNA, and there are two distinct sets of virus-specific sequences in AKR-mouse-cell DNA, whereas there is only one set in NIH-mouse-cell DNA.

RNA from virus-negative AKR-mouse cells grown in tissue culture contains some, but not all, virus-specific RNA sequences; however, within 48 hr after initiating treatment of these cells with 5-iododeoxyuridine, the complete viral genome is represented in cellular RNA.
Evidence That Tetrodotoxin and Saxitoxin Act at a Metal Cation Binding Site in the Sodium Channels of Nerve Membrane
Authors: Henderson R. , Ritchie J. M. , Strichartz G. R.
Published: May 2006

The effects of monovalent, divalent, and trivalent cations on the binding of tetrodotoxin and saxitoxin to intact nerves and to a preparation of solubilized nerve membranes have been examined. All eight divalent and trivalent cations tested, and the monovalent ions Li
+
, Tl
+
, and H
+
appear to compete reversibly with the toxins for their binding site. The ability of lithium to reduce toxin binding is paralleled by its ability to reduce tetrodotoxin-sensitive ion fluxes through the nerve membrane. We conclude that the toxins act at a metal cation binding site in the sodium channel and suggest that this site is the principal coordination site for cations (normally Na
+
ions) as they pass through the membrane during an action potential. The dissociation constant for Li
+
is 0.1-0.2 M and for Na
+
> 0.6 M, reflecting the weak binding necessary for rapid passage of sodium ions through the channel.
Structure of Antibodies with Shared Idiotypy: The Complete Sequence of the Heavy Chain Variable Regions of Two Immunoglobulin M Anti-Gamma Globulins
Authors: Capra J. Donald , Kehoe J. Michael
Published: May 2006

The complete amino acid sequence of the heavy chain variable regions of two different molecules of immunoglobulin M anti-gamma globulin has been determined. These proteins, from different human patients, had independently been shown to share idiotypic specificity. Only eight sequence differences were discernible for the entire length of their heavy chain variable regions. Five of the differences occurred outside hypervariable regions, while three were placeable within such regions. A comparison of these molecules of anti-gamma globulin with the seven human V
H
III variable region sequences presently available for immunoglobulins without known antibody activity showed that the great majority of sequence differences between the two idiotypically similar antibodies and these seven proteins were confined to hypervariable regions.

This study illustrates in precise terms a convergence of the distinct immunological properties of idiotypy, hypervariable region structure, and combining site specificity as they relate to the variable region of the immunoglobulin molecule. To a great degree these properties now appear to be a reflection of the same structural attributes of the variable region.
Evidence for the Involvement of Sulfhydryl Oxidation in the Regulation of Fat Cell Hexose Transport by Insulin
Authors: Czech Michael P. , Lawrence John C. , Lynn William S.
Published: May 2006

Previous studies have shown that the oxidants Cu
++
, H
2
O
2
, and diamide mimic the stimulatory effect of insulin on 3-
O
-methylglucose transport in isolated fat cells. The present experiments were designed to determine whether sulfhydryl oxidation plays a key role in the activation of the glucose transport system. It was found that reductants such as dithiothreitol inhibited 3-
O
-methylglucose transport rates and that this effect was reversible when cells were washed free of reducing agent. Treatment of cells with 1 mM
N
-ethylmalcimide for 5 min completely blocked the actions of insulin and oxidants on hexose transport without affecting control transport system activity. Under these conditions, binding of
125
I-labeled insulin to fat cell surface receptors was inhibited by only about 50%. Addition of insulin or oxidants to fat cells for 10 min before addition of
N
-ethylmaleimide completely prevented the inhibitory effect of
N
-ethylmaleimide on the activated transport system. This protective effect on transport rates appears to reside at a site that is altered by insulin subsequent to hormone-receptor interaction, since prior treatment of fat cells with insulin did not prevent the partial inhibitory effect of
N
-ethylmaleimide on insulin receptors. Furthermore, treatment of cells with
N
-ethylmaleimide after incubation with insulin prevented the elevated transport rates from returning to control levels when either the cells were washed free of hormone or insulin binding to its receptors was disrupted by trypsin digestion. However, transport rates in these cells treated with
N
-ethylmaleimide remained sensitive to cytochalasin B, phlorizin, and reductants. These data suggest that a component of the glucose transport system in isolated fat cells must be maintained in its disulfide state for expression of transport activity. Further, the results are consistent with the concept that the binding of insulin to cell surface receptors triggers sulfhydryl oxidation in this component, which prevents its reaction with
N
-ethylmaleimide.
Investigation of the Structure of Yeast tRNA
Phe
by Nuclear Magnetic Resonance: Paramagnetic Rare Earth Ion Probes of Structure
Authors: Jones Claude R. , Kearns David R.
Published: May 2006

The binding of paramagnetic rare earth ions to yeast tRNA
Phe
shifts some resonances in the low-field nuclear magnetic resonance spectrum that have been assigned to ring nitrogen protons of specific Watson-Crick base pairs. The changes in the nuclear magnetic resonance spectrum as the tRNA is titrated with Eu
3+
indicate that 4 (or 5) Eu
3+
ions are tightly bound, that the metal binding is in the fast exchange limit, and that the binding to different sites in the molecule is sequential rather than cooperative. The first metal bound simultaneously shifts resonances associated with the dihydrouridine and the -C-C-A stem. This permits us to conclude that the folding of the tRNA
Phe
in solution brings the phosphate backbone of the -C-C-A and the dihydrouridine stems into close proximity. A model of the three-dimensional structure of tRNA
Phe
incorporating this new information appears to be compatible with the results obtained from x-ray diffraction.
Particles with Characteristics of Leukoviruses in Cultures of Marrow Cells from Leukemic Patients in Remission and Relapse
Authors: Mak T. W. , Manaster J. , Howatson A. F. , McCulloch E. A. , Till J. E.
Published: May 2006

An enzyme activity with the characteristics of RNA-directed DNA polymerase (reverse transcriptase) was detected in marrow from patients with leukemia in relapse and in firm hematological remission. Material having the enzyme activity, when analyzed in sucrose gradients, appeared as two distinct homogeneous bands of particles with densities of about 1.17 and 1.23 g/ml. The enzyme activity was stimulated by exogenous template poly(rC)·(dG)
12-18
but not by (dT)
12-18
. The enzyme activities in these bands also increased (1.7- to 24-fold) after culture, and both bands with enzyme activity were obtained from the cultured cells and from the supernatant medium. Electron microscopic studies showed that the two bands contained particles resembling leukoviruses or their cores.
Synergistically Stimulated (Na
+
,K
+
)-Adenosine Triphosphatase from Plasma Membrane of a Marine Diatom
Authors: Sullivan C. W. , Volcani B. E.
Published: May 2006

An ATP-hydrolyzing activity with the properties of a Mg
2+
-dependent (Na
+
,K
+
)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) from a 20-fold purified plasma membrane fraction of the marine diatom,
Nitzschia alba
is described.

The basal activity requires Mg
2+
and further stimulation by Na
+
or Na
+
plus K
+
is dependent on the presence of Mg
2+
; Mn
2+
or Co
2+
can partially substitute for the divalent cation requirement but Ca
2+
equimolar with Mg
2+
inhibits the activity by 54%. ATP is the preferred substrate for the Na
+
plus K
+
stimulated activity, while CTP, UTP, and ADP are only slightly hydrolyzed. The apparent

K
m

is 8 × 10
-4
M ATP.

The ATP hydrolysis-rate is dependent on the relative concentrations of Na
+
and K
+
; the
K
0.5
for Na
+
and K
+
are 2 mM and 50 mM, respectively. Basal activity is synergistically stimulated by Na
+
plus K
+
only at certain ion concentrations and shows a strong specificity for both cations.

In the presence of Na
+
at 5 mM and K
+
at 350 mM, the ATPase is completely inhibited by
p
-chloromercuric benzoic acid 10
-4
M,
N
-ethyl maleimide 10
-3
M, and iodoacetamide 10
-2
M, but is insensitive to ouabain at 10
-7
to 10
-3
M.

This study demonstrates for the first time that algal plasma membrane contains an ATPase that is synergistically stimulated by Na
+
and K
+
.
Physical and Physiological Evidence for Two Phase Transitions in Cytoplasmic Membranes of Animal Cells
Authors: Wisnieski Bernadine J. , Parkes Joel G. , Huang Yoshie O. , Fox C. Fred
Published: May 2006

Electron spin resonance analysis of suspensions of animal cell plasma membranes consistently reveals four characteristic temperatures for lateral phase separations in the membrane lipids. Similar analysis of an aqueous dispersion of lipids extracted from these membranes reveals only two characteristic temperatures, indicating that some aspect of lipid organization in membranes is destroyed by the extraction procedure. The characteristic temperatures for surface membranes from two different species of homeothermic animals were nearly identical and were approximately 37°, 31°, 21°, and 15°. A treatment of the physical data revealed that these temperatures could identify independent phase transitions for two hydrocarbon compartments of approximately equal size with lower and upper characteristic temperatures of 21° and 37°, and of 15° and 31°. The analysis of the effects of temperature on a number of physiological parameters indicates that 21° and 37° are likely to define the boundaries for lateral phase separations in the inner monolayer and 15° and 31° the boundaries for lateral phase separations in the outer monolayer.
An Analysis of Survival in Haploid and Diploid Cell Cultures after Exposure to ICR Acridine Half-mustard Compounds Mutagenic for Bacteria
Authors: Mezger-Freed Liselotte
Published: May 2006

Population changes induced by acridine mustards in haploid and diploid cultured cell lines from
Rana pipiens
were compared to test the expectation that recessive mutations will be expressed in diploid cells with a frequency equal to the square of that in haploid cells, and to investigate the usefulness of such comparison for the screening of possible mutagens. The differences in survival frequency after treatment were much smaller than predicted on the basis of the expression of lethal (recessive) mutations alone. Survival was also affected by culture conditions, drug-resistance phenomena, and other cell properties. It is suggested that with the evolution of epigenetic processes for the production of stable phenotypes, the vertebrate cell also acquired more efficient means to prevent the expression of gene mutation and that the acridine compounds may affect both epigenetic and genetic changes.
Phosphoprotein Phosphatase Activity Associated with Estrogen-Induced Protein in Rat Uterus
Authors: Vokaer Alain , Iacobelli Stefano , Kram Raphaël
Published: May 2006

Estrogen-induced protein was purified from rat uteri and assayed for several enzymatic activities involved in the metabolism and action of cyclic nucleotides. No adenylate and guanylate cyclase (EC 4.6.1.1 and 4.6.1.2, respectively), protein kinase (EC 2.7.1.33), and cyclic nucleotide binding activities could be demonstrated in three independent preparations of the protein. However, all three preparations exhibited significant phosphoprotein phosphatase activity (EC 3.1.3.16) on phosphorylated protamine and histones F1. This activity is optimal at neutral pH, inhibited by Zn
++
, and unaffected by cyclic AMP or cyclic GMP.
Similar Idiotypes in Antibody-Forming Cells and in Cells Synthesizing Immunoglobulins Without Detectable Antibody Function
Authors: Cazenave P. -A. , Ternynck T. , Avrameas S.
Published: May 2006

The occurrence of immunoglobulins with and without antibody specificity and with and without idiotypic specificity was studied, by use of enzyme-labeled antigen and antibodies, in lymph node cells of rabbits immunized with horse-radish peroxidase and hen ovalbumin. Some cells, containing immunoglobulins without detectable antibody function, were shown to contain idiotypes similar to those found in antibody-producing cells.
Type C Viral Antigens in Man. I. Antigens Related to Endogenous Primate Virus in Human Tumors
Authors: Sherr Charles J. , Todaro George J.
Published: May 2006

Partially purified extracts from 33 human tumors of several histologic types were used as competing antigens in a radioimmunoassay for the p30 protein of an endogenous primate type C virus (M7). Antigens immunologically related to the p30 protein of the M7 virus were detected in two tumors. Like viral p30 antigens previously identified in tissues of several other primates, the antigens found in human tumors crossreact with the p30 protein of the feline RD-114 virus but are unrelated by similar immunologic criteria to the p30 proteins of several other mammalian type C viruses. Gel filtration shows that most of the antigenic activity co-chromatographs with authentic p30 protein. These results, along with those showing nucleic acid sequences related to those of an endogenous primate type C virus in the DNA of human cells, make it clear that humans, like other primates, have type C viral sequences in their genome and can, in some circumstances, express at least one type C viral protein.
Total Reconstitution of Functionally Active 50S Ribosomal Subunits from
Escherichia coli
Authors: Nierhaus Knud H. , Dohme Ferdinand
Published: May 2006

Total reconstitution of 50S subunits from
E. coli
was achieved by a two-step incubation procedure. In the first step, 23S RNA, 5S RNA, and the total proteins from 50S subunits were incubated for 20 min at 40° in the presence of 4 mM Mg
++
and 400 mM NH
4
Cl. In the second step, the Mg
++
concentration was raised to 20 mM and the incubation was performed for 90 min at 50°. No requirement for 30S subunits or other components (e.g., polyamine) was found. The reconstituted particle has the same sedimentation coefficient as the native 50S subunit and is highly active in protein synthesis with natural (R17 RNA) and artificial [poly(U)] messengers as well as in tests for peptidyltransferase (fragment assay) and for binding of antibiotics (chloramphenicol).
Does RNA Pass from Mesenchyme to Epithelium During an Embryonic Tissue Interaction?
Authors: Grainger Robert M. , Wessells Norman K.
Published: May 2006

Chick and mouse embryonic lung mesenchyme were incubated
in vitro
with an equimolar mixture of
12
C- and
15
N-labeled adenosine, guanosine, cytidine, and uridine, and trace amounts of the four tritiated ribonucleosides. This permits an unambiguous method for detecting transfer of macromolecular RNA from such a pre-incubated mesenchyme to responding lung epithelium across a Millipore filter, and for purifying any RNA transferred for further characterization. During the important period of mesenchymal support of epithelial morphogenesis, no detectable transfer of RNA was found. The level of sensitivity of these experiments was such that less than 0.01% of the labeled RNA in the mesenchyme could have been detected in the epithelium, corresponding to less than 75 labeled RNA molecules transferred to each epithelial cell. No detectable transfer of DNA from mesenchyme to epithelium was found during the inductive period, using the same approach, although with much lower sensitivity.
Extension of the Lifespan of Cultured Normal Human Diploid Cells by Vitamin E
Authors: Packer Lester , Smith James R.
Published: May 2006

Inclusion of vitamin E (DL-α-tocopherol) in the culture medium for human diploid cells greatly prolongs their
in vitro
lifespan. The addition of 100 μg of DL-α-tocopherol per ml of medium has allowed us to culture WI-38 cells for more than 100 population doublings to date. (These cells normally have an
in vitro
lifespan of 50 ± 10 population doublings.) Cells at the 100th population doubling have a normal diploid karyotype, appear to behave in all other respects like young WI-38 cells, and are still actively dividing. We interpret this result as support for the free radical theory of aging.
Focal Erythrocyte Membrane Perturbations Caused by Nitroxide Lipid Analogues
Authors: Bieri V. G. , Wallach D. F. H. , Lin P. S.
Published: May 2006

Three classes of lipoidal nitroxide spin probes reversibly perturb erythrocyte membranes at low concentrations (10
-10
-10
-5
M). This is manifest in (
a
) decreased osmotic fragility and (
b
) alterations of surface topology. At bulk phase nitroxide concentrations providing maximal osmotic stabilization, the erythrocytes exhibit a classic echinocyte morphology. At nitroxide concentrations very slightly higher than those yielding minimal osmotic fragility (10
-5
-10
-4
M), the cellus undergo a sphering reaction and lyse. The morphologic sequence seen in intact cells is not observed in erythrocyte ghosts. We suggest that the spin probes initially concentrate in focal domains, which expand into echinocytic protrusions primarily due to localized weakening of membrane cohesion. We propose that cell lysis involves an irreversible breakdown in membrane domain structure.
Gamma-Aminobutyric Acid Binding to Receptor Sites in the Rat Central Nervous System
Authors: zukin Stephen R. , Young Anne B. , Snyder Solomon H.
Published: May 2006

[
3
H]Gamma-aminobutyric acid (GABA) binds to synaptic membrane fractions of rat brain in a selective fashion representing an interaction with postsynaptic GABA receptors. Inhibition of [
3
H]GABA binding by a variety of amino acids closely parallels their ability to mimic the synaptic inhibitory actions of GABA and does not correlate with their relative affinity for the presynaptic synaptosomal GABA uptake system. [
3
H]GABA binding is saturable with an affinity constant of about 0.1 μM. The GABA antagonist bicuculline inhibits [
3
H]GABA binding with half maximal effects at 5 μM, whereas it requires a concentration of 0.5 mM to reduce synaptosomal GABA uptake by 50%. In subcellular fractionation experiments [
3
H]GABA binding is most enriched in crude synaptic membranes. [
3
H]GABA binding is greatest in the cerebellum, least in the spinal cord and medulla oblongatapons, with intermediate values in the thalamus, hippocampus, hypothalamus, cerebral cortex, midbrain, and corpus striatum.
A Peculiar Substructure in the Postsynaptic Membrane of
Torpedo
Electroplax
Authors: Orci Lelio , Perrelet Alain , Dunant Yves
Published: May 2006

Freeze-etching of
Torpedo marmorata
electroplax reveals an unusual substructure in one of the fracture faces of the postsynaptic membrane. This substructure consists of a lattice of closely spaced particles that are smaller than the usual 80- to 90-Å particles present in other membrane types. The lattice occurs exclusively on the B-face of the postsynaptic membrane.
Inhibition of Induced Aldosterone Biosynthesis with a Specific Antagonist of Angiotensin II
Authors: Chiu Andrew T. , Peach Michael J.
Published: May 2006

The present study determined the effect of [Sar
1
-Ile
8
]-angiotensin II on steroidogenesis and induced aldosterone synthesis by the octapeptide angiotensin II, the heptapeptide des-Asp
1
-angiotensin II, and adrenocorticotropic hormone. Rabbit adrenal cells were suspended by incubation of the capsular cortical tissue with collagenase, and aldosterone levels were determined by immunoassay. Steroidogenic responses to angiotensin II and des-Asp
1
-angiotensin were essentially the same. [Sar
1
-Ile
8
]-angiotensin II (10
-7
to 5 × 10
-7
M) had no significant effect on basal aldosterone biosynthesis. However, when added with steroidogenic peptides, it completely blocked the effect of angiotensin II and des-Asp
1
-angiotensin II but not of adrenocorticotropic hormone. The dose ratio of the antagonist to angiotensin II that gave 100% inhibition was about 2:1 and to des-Asp
1
-angiotensin II, about 50:1. The data suggest that des-Asp
1
-angiotensin II has a much higher affinity for the angiotensin receptor in adrenal cortex than angiotensin II.
A Comparison of Bovine Prothrombin, Factor IX (Christmas Factor), and Factor X (Stuart Factor)
Authors: Fujikawa Kazuo , Coan Michael H. , Enfield David L. , Titani Koiti , Ericsson Lowell H. , Davie Earl W.
Published: May 2006

A comparison has been made of the electrophoretic behavior, chemical composition, amino-terminal sequence, and immunological properties of bovine prothrombin, factor IX (Christmas factor), and factor X (Stuart factor). Some immunological crossreactivity was found between the antibody to prothrombin and factor X although prothrombin and factor X differ substantially in amino-acid and carbohydrate composition. Considerable amino-acid sequence homology was found in the amino-terminal portion of prothrombin, factor IX, and the light chain of factor X. These data provide further evidence to support the hypothesis that at least three of the vitamin K-dependent clotting factors have evolved from a common ancestral gene.
Translational Diffusion Coefficient and Partition Coefficient of a Spin-Labeled Solute in Lecithin Bilayer Membranes
Authors: Dix James A. , Diamond Jared M. , Kivelson Daniel
Published: May 2006

The translational diffusion coefficient and the partition coefficient of a spin-labeled solute, di-
t
-butyl nitroxide, in an aqueous suspension of dipalmitoyl lecithin vesicles have been studied by electron spin resonance spectroscopy. When the lecithin is cooled through its phase transition temperature near 41°C, some solute is “frozen out” of the bilayer, and the standard partial molar enthalpy and entropy of partition go more positive by a factor of 8 and 6, respectively. However, the apparent diffusion constant in the lecithin phase is only slightly smaller than that in water, both above and below the transition temperature. The fraction of bilayer volume within which solute is distributed may increase with temperature, contributing to the positive enthalpy of partition. Comparison of time constants suggests that there is a permeability barrier to this solute in the periphery of the bilayer.
A Comparison of Membrane Proteins of Normal and Transformed Cells by Lactoperoxidase Labeling
Authors: Hogg Nancy M.
Published: May 2006

The enzyme lactoperoxidase (iodide:hydrogen-peroxide oxidoreductase, EC 1.11.1.8) was used to iodinate (
125
I) accessible proteins on membranes of intact virally transformed and untransformed cells. A number of labeled bands of proteins were detected by acrylamide gel electrophoresis. A heavily labeled band with a molecular weight of approximately 250,000 daltons was found in all untransformed cells but was absent from transformed cells. When Coomassie-blue-stained membrane preparations were compared, a band was seen in normal cells which co-migrated with the lactoperoxidase-labeled band. In transformed cell membranes, three discrete bands were present in the same position. Thus, the expression of this protein may be altered when cells are in the transformed state.
The Secretion of α-Ecdysone by the Prothoracic Glands of
Manduca sexta In Vitro
Authors: King D. S. , Bollenbacher W. E. , Borst D. W. , Vedeckis W. V. , O'Connor J. D. , Ittycheriah P. I. , Gilbert L. I.
Published: May 2006

Prothoracic glands of tobacco hornworm larvae cultured
in vitro
secrete into the culture medium a substance which was active in ecdysone bioassays and determined to be ecdysone-like by radioimmunoassay. The prothoracic glands appear to be the sole source of this substance. The material was identified as α-ecdysone by thin-layer, gas-liquid, and high-resolution liquid chromatography and mass spectrometry. No other active moulting principles were present in the medium. It appears that the prothoracic gland secretes a prohormone, α-ecdysone, which is subsequently converted into the active moulting hormone, β-ecdysone, in other insect tissues.
Alteration of Vein Cyclic 3′:5′ Nucleotide Concentrations During Changes in Contractility
Authors: Dunham Earl W. , Haddox Mari K. , Goldberg Nelson D.
Published: May 2006

The relative changes in vascular tissue levels of cyclic 3′:5′-guanosine monophosphate (cGMP) and cyclic 3′:5′-adenosine monophosphate (cAMP) were determined in bovine and canine vein strips that were quickfrozen during changes in contractility elicited by prostaglandins (PG) or isoproterenol. Prostaglandin F
2α
-induced venoconstriction was associated with increased vascular tissue levels of cGMP and increased ratios of cGMP to cAMP concentrations, but no consistent qualitative change in cAMP levels. In contrast, vein cAMP concentrations were increased during administration of the vasodilators PGE
2
and isoproterenol. The results suggest possible opposing roles for the two cyclic nucleotides in vasomotion.
The Cation Radicals of Free Base and Zinc Bacteriochlorin, Bacteriochlorophyll, and Bacteriopheophytin
Authors: Fajer J. , Borg D. C. , Forman A. , Felton R. H. , Dolphin D. , Vegh L.
Published: May 2006

One-electron oxidation of zinc tetraphenylbacteriochlorin and its metal-free base yielded stable cation radicals. Electron spin resonance hyperfine splittings were assigned by selective deuterations. These results indicate that the protons of the saturated rings of the bacteriochlorins carry large spin densities, in accord with molecular orbital calculations. Comparison
in vitro
of the optical spectra of bacteriochlorins and their cation radicals with those of bacteriochlorophyll show close correspondence and suggest that the electron spin resonance data from the former may also prove a guide to the biological molecule. The surprising similarity in properties between the radicals of free base and zinc bacteriochlorins is maintained in the chlorophylls: cation radicals of bacteriopheophytin and methyl pheophorbide (the free bases of bacteriochlorophyll and methyl chlorophyllide, respectively) exhibit electron spin resonance properties similar to those of their magnesium-containing derivatives. The possibility that metal-free chlorophylls participate in photosynthesis is discussed.
Genetic Control of Melanization: Isolation and Analysis of Amelanotic Variants from Cultured Melanotic Melanoma Cells
Authors: Pawelek John , Sansone Marilyn , Morowitz Joshua , Moellmann Gisela , Godawska Elizabeth
Published: May 2006

Melanoma cells express a phenotype that is easy to recognize: the synthesis of melanin. We used this marker to isolate clones of amelanotic variants from large populations of wild-type melanotic clones. Cloudman mouse melanoma (S91, clone M-3, CCL 53.1) was chosen as the parental line because the cells are highly pigmented, grow well as clones in soft agar, and fuse readily with Sendai virus. Subclones (10
7
) of this line were screened without prior mutagenesis, and nine amelanotic variants were isolated. The mutagen ethylmethanesulfonate increased the frequency of variants by three to four orders of magnitude. Wild-type cells had both basal and melanocyte stimulating hormone-inducible tyrosinase activities. The four amelanotic variants that we have examined to date all behaved similarly: they lost basal tyrosinase (EC 1.14.18.1; monophenol monooxygenase) activity but retained melanocyte stimulating hormone-inducible activity; they contained Stage-II melanosomes but no melanized melanosomes; they exhibited growth characteristics similar to those of wild-type cells in culture but produced fewer tumors in mice.
Translational Control Induced by Bacteriophage T7
Authors: Herrlich P. , Rahmsdorf H. J. , Pai S. H. , Schweiger M.
Published: May 2006

Phage T7 discontinues host gene expression by translational and transcriptional control mechanisms. Translational control is exerted by the T7 translational-repressor. This protein inhibits the synthesis of β-galactosidase (EC 3.2.1.23)
in vivo
and
in vitro
and the synthesis of the T3 enzyme
S
-adenosylmethioninehydrolase (EC 3.3.1.-). The translational-repressor does not interfere with T7-specific enzyme synthesis. The T7 translational-repressor purifies with the initiation factors. The repressor interacts with the initiation of translation of host enzymes. The translational-repressor gene is close to the promotor for RNA polymerase of
Escherichia coli
.
Virus-Specific Messenger RNA on Free and Membrane-Bound Polyribosomes from Cells Infected with Rauscher Leukemia Virus
Authors: Gielkens A. L. J. , Salden M. H. L. , Bloemendal H.
Published: May 2006

Cells infected by Rauscher leukemia virus synthesize virus-specific RNA which can be detected by hybridization to the single-stranded DNA copy of the viral RNA. Evidence is provided that virus-specific RNA is present in free and membrane-bound polyribosomes of these cells. The relative content of virus-specific RNA, as measured by hybridization, is 6-10 times less on free polyribosomes than on membrane-bound polyribosomes. The messenger RNA associated with both classes of polyribosomes was characterized by density gradient centrifugation. In addition to a major RNA species identified as 36S RNA, at least 2 minor components in the 14S and 21S region have also been found. There is a striking difference in the distribution of these RNA species between free and membrane-bound polyribosomes.
Endogenous Guinea Pig Virus: Equability of Virus-Specific DNA in Normal, Leukemic, and Virus-Producing Cells
Authors: Nayak D. P.
Published: May 2006

The kinetics of hybrid formation between the RNA of BrdU-activated endogenous guinea pig virus and the DNA of leukemic, normal, or BrdU-activated guinea pig cells were measured by the technique of RNA·DNA hybridization in DNA excess. The results suggest that virus-specific sequences representing some 60-70% of the viral genome are unique (2-3 copies per haploid cell genome), while the remainder (30-40%) are reiterated (147 copies), and that the reiterated virus-specific DNA may be composed of more than one species, each having a different reiteration frequency. No difference was found in the quantity of viral DNA sequences contained in normal, leukemic, or bromodeoxyuridine-activated guinea pig cells. These data are considerably different from those reported for exogenous (infectious) oncornaviruses, where cells infected or transformed by exogenous RNA tumor viruses have been shown to contain increased amounts of virus-specific DNA. The data reported here are consistent with the contention that preexisting viral genes are activated by bromodeoxyuridine treatment. Results of hybridization experiments done at different DNA/RNA ratios suggest that although the virus-specific DNA is partly unique and partly reiterated, the viral RNA does not contain any detectable internal reiteration. Total mass of the viral RNA sequences is around 0.7 to 1 × 10
7
daltons.
Recombinant Rabbit Secretory Immunoglobulin Molecules: Alpha Chains with Maternal (Paternal) Variable-Region Allotypes and Paternal (Maternal) Constant-Region Allotypes
Authors: Knight Katherine L. , Malek Thomas R. , Hanly W. Carey
Published: May 2006

A population of IgA molecules having heavy chains coded by two parental chromosomes in
trans
position has been identified in rabbits heterozygous at both the V
H
a
locus, which controls allotypic specificities on the variable part of heavy chains, and the C
α
g
locus, which controls allotypic specificities on the constant part of alpha chains. These recombinant molecules have alpha-chain allotypic specificities controlled by both the maternal V
H
a
gene and the paternal C
α
g
gene or conversely, the paternal V
H
a
gene and the maternal C
α
g
gene. These recombinant molecules were found in F(ab)
2α
fractions obtained after passage of F(ab)
2α
preparations through immunosorbent columns designed to remove one population of F(ab)
2α
molecules, i.e., g74- or g75-type molecules. The effluent F(ab)
2α
fractions were then examined by radioprecipitation methods for allotypic specificities controlled by the V
H
a
and C
α
g
loci. About 40% of the g75 F(ab)
2α
molecules from each of three rabbits with the
a
1
g
74
and
a
2
g
75
allogroups were alg75 recombinants. These alg75 recombinant molecules represented from 2.5-5.6% of the total unfractionated F(ab)
2α
sample. The F(ab)
2α
fractions from two rabbits with the
a
1
g
75
and
a
3
g
74
allogroups had from 1.8-8.2% recombinant molecules: some were alg74 recombinants and some were a3g75 recombinants. Somatic recombination as a mechanism responsible for the synthesis of polypeptide chains in which part of the information is obtained from one chromosome and part from the homologous chromosome is discussed.
Epstein-Barr Virus-Associated Membrane-Reactive Antibodies During Long Term Survival After Burkitt's Lymphoma
Authors: Gunvén Peter , Klein George , Clifford Peter , Singh Surjit
Published: May 2006

Antibodies to Epstein-Barr virus associated cell membrane antigens persisted or slowly decreased during prolonged uncomplicated survival of patients with Burkitt's lymphoma in remission. Serum was sampled from four patients within 6 months before recurrence occurring after the first year and preceded by remission during more than 6 months. Rapid and significant decreases of the antibodies before clinical recognition of the recurrences were found in three patients. The fourth patient had slowly increasing titers before relapse. Immune stimulant treatment during remission, with BCG (Bacille Calmette Guérin vaccine) or BCG +
Bordetella pertussis
, temporarily increased the antibody levels. Possible mechanisms for the observed titer changes before recurrence are discussed.
Regulation of Melanocyte Stimulating Hormone Action at the Receptor Level: Discontinuous Binding of Hormone to Synchronized Mouse Melanoma Cells During the Cell Cycle
Authors: Varga J. M. , Dipasquale A. , Pawelek J. , McGuire J. S. , Lerner A. B.
Published: May 2006

Melanocyte stimulating hormone coupled to Sepharose effects an increase in tryosinase (EC 1.14.18.1; monophenol monoxygenase) activity of cultivated mouse melanoma cells. Synchronized cells are found to respond to melanocyte stimulating hormone only in the G2 phase of the cell cycle, although their response to cyclic AMP is independent of position in the cell cycle. The binding of
125
I-labeled melanocyte stimulating hormone occurs predominantly in G2. These observations are satisfied by a model in which the hormone can activate adenylate cyclase (EC 4.6.1.1) by binding to a melanocyte stimulating hormone receptor only in G2; the events distal to cyclic AMP production can occur throughout the cell cycle.