bluuebunny/crossref_metadata_2025 huggingface dataset:
Acetoxycycloheximide-Induced Transient Amnesia: Protective Effects of Adrenergic Stimulants
Authors: Serota Roger G. , Roberts Richard B. , Flexner Louis B.
Published: May 2006

It has previously been shown that rats trained 5 hr after intracerebral injection of acetoxycycloheximide show a transient amnesia at 24 hr after training. We have tested the possibility that adrenergic stimulants might provide protection from the amnesia. Metaraminol, given either before or after training or before testing, prevents the drug-induced amnesia. D-Amphetamine, injected soon after training, also prevents the amnesia. A model is presented to explain the drug-induced amnesia in terms of both the assumed effect of acetoxycycloheximide on the adrenergic system and prevention of the amnesia by metaraminol and D-amphetamine.
β-Galactosidase: Immunological Activity of Ribosome-Bound, Growing Polypeptide Chains
Authors: Hamlin Joyce , Zabin Irving
Published: May 2006

Ribosomes carrying nascent chains of β-galactosidase were prepared by disruption of
Escherichia coli
in detergent-free buffer of high salt concentration, followed by purification on a discontinuous sucrose gradient. Assay by the method of immune hemolysis inhibition with anti-β-galactosidase indicated that considerable amounts of antibody were bound by the growing chains. Much of the crossreacting material could be released from the ribosomes by treatment with puromycin. The ability to bind anti-β-galactosidase was completely destroyed when ribosomes were heated at 60°C. At very early times after induction, well before the appearance of active enzyme, crossreacting material could be demonstrated on ribosomes; this finding correlated with the appearance of an amino-terminal fragment of β-galactosidase. Thus, growing chains of β-galactosidase must begin to fold before their release from the ribosome.
Cytochalasin B, Its Interaction with Actin and Actomyosin from Muscle
Authors: Spudich James A. , Lin Shin
Published: May 2006

Cytochalasin B, an alkaloid that inhibits a wide variety of cellular movements, interacts with actomyosin, the contractile protein complex of striated muscle. This interaction causes a decrease in viscosity of the actomyosin complex and an inhibition of acto-heavy meromyosin ATPase activity of at least 60%. Cytochalasin B does not affect the viscosity of myosin nor the ATPase activity of heavy meromyosin, suggesting that the drug might interact directly with the actin moiety of the actomyosin complex. Indeed, as judged by viscometry, there is a strong interaction of cytochalasin B with actin, at nearly stoichiometric concentrations. Myosin appears to compete with cytochalasin for binding to actin.
Intercellular Contact and Cell-Surface Galactosyl Transferase Activity
Authors: Roth Stephen , White Diane
Published: May 2006

Evidence is presented suggesting the presence of galactosyl transferases and galactosyl acceptors on the outer surfaces of intact Balb/c 3T3 cells. In addition, the data indicate that these transferases may only be capable of transferring galactose from uridine diphosphate galactose to galactosyl acceptors on adjacent cells after intercellular contact is made (
trans
-glycosylation). Intact Balb/c 3T12 cells, by contrast, show no requirement for intercellular contact in order to carry out this reaction suggesting that these cells, which do not exhibit contact inhibition of growth, may be able to transfer galactose to acceptors situated on the same cell as the enzyme (
cis
-glycosylation).

Electrophoretic and radioautographic assays were used to detect surface transferase activities in these two cell lines. Results of experiments on cells from sparse and dense cultures, and under conditions where intercellular contact was regulated, are consistent with the above hypothesis.
An Alternative Approach to the Study of New Enzymatic Reactions Involving DNA
Authors: Ebisuzaki K. , Behme Margaret T. , Senior Cecilia , Shannon Dale , Dunn David
Published: May 2006

Ordinarily, enzymes that catalyze bimolecular reactions involving DNA and nucleoside triphosphates are assayed in terms of the predicted changes in DNA. However, by assay of the enzymes by changes in nucleoside triphosphates, new enzymes may be sought without prior knowledge of the role of DNA in the reaction. This approach was used to isolate two new enzymes from
Escherichia coli
and one from T4 phage-infected
E. coli
. In this communication, the general application of this technique and its specific use in the isolation of two DNA-dependent ATPases from
E. coli
are described. Both enzymes catalyze a DNA-dependent cleavage of ATP to ADP and Pi. The two enzymes can be distinguished by their characteristic activities with different DNAs and synthetic polydeoxynucleotides. Neither of the enzymes shows endonuclease or exonuclease activity in conventional assays. These reactions were studied by isotope-exchange experiments. The discovery of these enzymes attests to the effectiveness of this method to seek new reactions involving nucleic acids. Moreover, our results suggest that other enzymes of nucleic acid metabolism may be found and purified by this new approach.
Photoelectron Microscopy: A New Approach to Mapping Organic and Biological Surfaces
Authors: Griffith O. H. , Lesch G. H. , Rempfer G. F. , Birrell G. B. , Burke C. A. , Schlosser D. W. , Mallon M. H. , Lee G. B. , Stafford R. G. , Jost P. C. , Marriott T. B.
Published: May 2006

A general method of imaging organic and biological surfaces based on the photoelectric effect is reported. For the experiments, a photoelectron emission microscope was constructed. It is an ultrahigh vacuum instrument using electrostatic electron lenses, microchannel plate image intensifier, cold stage, hydrogen excitation source, and magnesium fluoride optics. The organic surfaces examined were grid patterns of acridine orange, fluorescein, and benzo(a)pyrene on a Butvar surface. A biological sample, sectioned rat epididymis, was also imaged by the new photoelectron microscope. Good contrast was obtained in these initial low magnification experiments. These data demonstrate the feasibility of mapping biological surfaces according to differences in ionization potentials of exposed molecules. A number of technical difficulties, such as the intensity of the excitation source, must be solved before high resolution experiments are practical. However, it is probable that this approach can be useful, even at low magnifications, in determination of the properties of organic and biological surfaces.
Restriction of the Mobility of Lymphocyte Immunoglobulin Receptors by Concanavalin A
Authors: Yahara Ichiro , Edelman Gerald M.
Published: May 2006

The induction by anti-immunoglobulin of patch and cap formation on mouse lymphocytes was inhibited by the addition of concanavalin A. This effect was reversed by α-methyl-D-mannoside, a competitive inhibitor of the binding of concanavalin A. Concanavalin A prevented both patch and cap formation, in contrast to the metabolic inhibitor NaN
3
, which prevented only cap formation. This suggests that binding of concanavalin A induces changes on or in the lymphocyte membrane that inhibit free diffusion of immunoglobulin receptors.
Peptidyl-Puromycin Synthesis on Polyribosomes from
Escherichia coli
Authors: Pestka Sidney
Published: May 2006

Peptide bond synthesis was studied with native polyribosomes of
E. coli
. With the use of this system for transpeptidation, it was possible to show that a single K
+
activates the ribosome monomers of polyribosomes; that protonation of a single group (probably imidazole or an N-terminal amino group) with a pK
a
equal to about 7.2 inactivates the transpeptidase complex; that Mn
++
can substitute for Mg
++
, but that Ca
++
, spermidine, and putrescine do so only very poorly; and that the

K
m

for puromycin in this system is about 2.4 × 10
-6
M.
On a Theory for the Passive Transport of Solute through Semipermeable Membranes
Authors: Craig Lyman C. , Chen Hao-Chia
Published: May 2006

It has been shown that thin-film dialysis can be performed in such a way that the limiting rate is the rate of entry of the solute into the membrane from the high-concentration side. The rate of diffusion, therefore, reflects the probability of a molecule entering the pores on the surface and does not depend on the resistance to diffusion offered by the internal structure of the membrane. The good correlation, so generally found, of the order of escape times of given solutes with the order of free diffusion rates is thus explained. The data from stretching experiments with wet cellophane, in which the pore structure is distorted, are also explained.
Effects of Palmitoyl CoA on Citrate and Malate Transport by Rat Liver Mitochondria
Authors: Halperin M. L. , Robinson B. H. , Fritz I. B.
Published: May 2006

Palmitoyl CoA inhibited citrate transport from isolated rat liver mitochondria. Under conditions described, 50% inhibition was observed at about 6-8 nmol/mg of mitochondrial protein per ml. The percentage inhibition was inversely proportional to the concentration of the counter-transporting anion in the medium. Although comparable levels of palmitoyl CoA had little effect on malate exit on the dicarboxylate carrier, higher concentrations inhibited both citrate and malate transport.

The specificity of the inhibition by palmitoyl CoA was investigated by examination of the effects on the tricarboxylate transport system of fatty acids, CoASH, acetyl CoA, palmitoylcarnitine, deoxycholate, and other molecules with surface active properties. None of the above compounds, at sublytic concentrations, inhibited citrate transport appreciably. The inhibition of citrate transport by low concentrations of palmitoyl CoA was rapid and could be prevented or partially reversed by addition of albumin.
Asymmetries Generated by Diffusion and Reaction, and Their Bearing on Active Transport Through Membranes
Authors: Aris R. , Keller K. H.
Published: May 2006

A model is presented that suggests that a natural, stable asymmetry may arise on either side of a membrane, even when the bulk conditions on either side of the membrane are the same and the two faces of the membrane are indistinguishable. Equations are derived on the assumption of Michaelis-Menten kinetics with substrate inhibition to describe the properties of such a model membrane.
The Contribution of Embryo Extract to Myogenesis of Avian Striated Muscle
In Vitro
Authors: Haba Gabriel De La , Amundsen Randi
Published: May 2006

Myogenesis of avian striated muscle
in vitro
requires the presence of serum and embryo extract. The serum requirement can be satisfied by insulin. Embryo extract contributes at least two factors, one of which promotes the fusion of myoblasts, whereas the other promotes the development of myotubes.
Biologically Active Catecholamines Covalently Bound to Glass Beads
Authors: Venter J. Craig , Dixon Jack E. , Maroko Peter R. , Kaplan Nathan O.
Published: May 2006

Catecholamines bound covalently to glass beads have been found to have biological activity in several systems. Experimental evidence has been found that immobilized epinephrine and isoproterenol accelerate the heart rate in dogs, chick embryo, and chick heart cells grown in culture, whereas immobilized propranolol results in a decrease in heart rate. Isoproterenol bound to glass beads has also been shown to markedly increase the level of adenosine 3′:5′-cyclic monophosphoric acid in glial cells. The effects of the immobilized catecholamines are of longer duration than when the compounds are administered in solution. The present data indicate that the compounds are exerting their action when bound to the beads.
Sedimentation Properties of Yeast Chromosomal DNA
Authors: Petes Thomas D. , Fangman Walton L.
Published: May 2006

Sedimentation analysis of nuclear DNA released from spheroplasts of the yeast
Saccharomyces cerevisiae
indicates that it has a number average molecular weight of 6.2 × 10
8
. The chromosomal DNA molecules range in size from as small as 5 × 10
7
daltons to as large as 1.4 × 10
9
daltons. Based on these values and estimates of the total DNA content of the yeast nucleus, it is proposed that each yeast chromosome contains a single DNA duplex.
Demonstration of a Phosphopeptide Intermediate in the Mg
++
-Dependent, Na
+
- and K
+
-Stimulated Adenosine Triphosphatase Reaction of the Erythrocyte Membrane
Authors: Avruch Joseph , Fairbanks Grant
Published: May 2006

Human erythrocyte membranes are phosphorylated by [γ-
32
P]ATP in association with the Mg
++
-dependent, Na
+
and K
+
-stimulated ATPase (EC 3.1.6.3) reaction. To delineate the membrane species involved, phosphorylated membranes were analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate, under conditions that minimize hydrolysis of acyl phosphate linkages. Three radioactive components were detected, of which only one was a phosphopeptide, of apparent molecular weight 105,000. The phosphate bound to this peptide undergoes rapid turnover and is discharged by hydroxylamine. In the presence of Mg
++
, the phosphorylation of this peptide is specifically stimulated by Na
+
and blocked by ethylene diamine tetraacetate; its dephosphorylation is stimulated by K
+
and blocked by ouabain. We conclude that this phosphopeptide is an intermediate in the Mg
++
-dependent, Na
+
- and K
+
-stimulated ATPase reaction of the erythrocyte membrane.
Formation of a Mammalian Initiation Complex with Reovirus Messenger RNA, Methionyl-tRNA
F
, and Ribosomal Subunits
Authors: Levin Daniel H. , Kyner David , Acs George
Published: May 2006

Previous data demonstrated that reovirus mRNA, synthesized
in vitro
with the particulate RNA transcriptase of reovirus cores, efficiently directs the synthesis of polypeptides
in vitro
. The present studies indicate that all of the three size classes of reovirus mRNA produced
in vitro
can form protein initiation complexes with rat liver [
36
S]Met-tRNA
F
and incubated 40S and 60S ribosomal subunits, which had been washed in 0.5 M KCl of mouse fibroblast L-929 cells. Mild prior treatment of the mRNA with HCHO was required to expose the initiator region. The initiation complex reacted quantitatively with puromycin to form a puromycin peptide, whose electrophoretic properties were identical to methionyl-puromycin formed in response to poly(A,G,U) or the initiator codon AUG. The complex was relatively stable and specific for [
35
S]Met-tRNA
F
; rat liver [
35
S]Met-tRNA
M
was unreactive unless the supernatant factors EF T
1
and EF T
2
were also present. However, the addition of fusidic acid, at a concentration that did not affect complex formation with [
35
S]Met-tRNA
F
, completely inhibited Met-tRNA
M
utilization. Exogenous ribosomal factors and GTP were not required unless the separated 40S and 60S subunits were further treated with 1 M KCl. The data suggest that reovirus mRNA contains AUG initiator codons that form a complex with Met-tRNA
F
at a puromycin-reactive site on ribosomes.
Neuronal Dynamics and Axonal Flow: Axonal Peristalsis
Authors: Weiss Paul A.
Published: May 2006

By time-lapse, phase-contrast cinemicrography of sensory nerve fibers of young mice, isolated with their originating spinal ganglia in nutrient solution, the postulated peristaltic surface drive of the cellulifugal propulsion of the semisolid axonal column at a rate of the order of 1 mm/day (1 μm/min) could be verified and quantitatively analyzed. The pulse waves follow each other at about 30-min intervals, regardless of whether the continuity of the axon is preserved or disrupted by degenerative fragmentation. Even when the axonal flow is obstructed, surface peristalsis continues.
Characterization of Yolk DNA from
Xenopus laevis
Oocytes Ovulated
In Vitro
Authors: Hanocq F. , Kirsch-Volders M. , Hanocq-Quertier J. , Baltus E. , Steinert G.
Published: May 2006

High molecular weight DNA was isolated from the yolk platelets of
Xenopus laevis
oocytes ovulated
in vitro
. Yolk DNA has the same buoyant density in CsCl gradients as mitochondrial and nuclear DNAs, and, like them, it is double-stranded. Yolk DNA behaves like nuclear DNA, and not like mitochondrial DNA, upon renaturation after denaturation. The molecules are always linear. Cytochemical and biochemical controls preclude the possibility that the yolk DNA might be contaminated by nuclear or mitochondrial DNA. We conclude that the yolk DNA is an endogenous component of the yolk platelets.
Chemical Characterization and Surface Orientation of the Major Glycoprotein of the Human Erythrocyte Membrane
Authors: Marchesi V. T. , Tillack T. W. , Jackson R. L. , Segrest J. P. , Scott R. E.
Published: May 2006

The major glycoprotein of the human erythrocyte membrane has been isolated by treatment with lithium di-iodosalicylate and found to be a single polypeptide chain with a molecular weight of about 50,000. This molecule, which is 60% carbohydrate and 40% protein, carries multiple blood-group antigens, the receptors for influenza viruses, and various plant agglutinins. Four unique carbohydrate-containing peptides (α-1, α-2, α-3, and β) are produced by tryptic digestion of the isolated glycoprotein; their order in the molecule has been determined by sequential tryptic digestion of intact erythrocyte membranes and partially digested glycoprotein fragments. Cleavage of the native protein with cyanogen bromide produces five fragments; two of these (C-5 and C-1) contain most of the carbohydrate in the molecule and are derived from the N-terminal half of the polypeptide chain. The nonpolar amino acids of this glycoprotein are located predominantly in the C-terminal fragment (C-2).

Phytohemagglutinin conjugated to ferritin has been used to map the distribution of glycoprotein receptors over the surfaces of intact erythrocytes by freeze-etching and electron microscopy. This label localizes to sites on the membrane that overlie the intramembranous particles. These findings suggest that the glycoprotein is oriented at the cell surface with its oligosaccharide-rich N-terminal end exposed to the exterior, while its C-terminal segment interacts with other components in the interior of the membrane to form intramembranous particles.
X-Ray Diffraction Studies of Lecithin Bimolecular Leaflets with Incorporated Fluorescent Probes
Authors: Lesslauer W. , Cain J. E. , Blasie J. K.
Published: May 2006

X-ray diffraction studies on dispersions and oriented multilayers of dipalmitoyllecithin and different fluorescent probe molecules are reported. Analysis of the diffraction data provides the electron density profile for the different bilayers to 6- to 8-Angstrom resolution. The location of the probe molecules in the bilayer structure and the perturbation of the lecithin bilayer produced by the probes are discussed.
Endogenous RNA-Directed DNA Polymerase Activity in Uninfected Chicken Embryos
Authors: Kang Chil-Yong , Temin Howard M.
Published: May 2006

Early chicken embryos that are either positive or negative for group-specific antigens of avian leukosis viruses contained endogenous RNA-directed DNA polymerase activity. This endogenous DNA polymerase activity was not increased after mixture of soluble DNA polymerases isolated from chicken embryos with disrupted chicken embryo cells. The endogenous activity was resistant to treatment with deoxyribonuclease, and the initial rate of DNA synthesis was partially resistant to actinomycin D. In contrast, over 90% of the endogenous polymerase activity was destroyed by ribonuclease in medium with high salt concentration. The DNA product of the endogenous DNA polymerase activity from chicken embryos did not hybridize with RNA of Rous sarcoma virus or reticuloendotheliosis virus, whereas about 40% of this DNA product hybridized with the RNA from the same chicken-cell fraction. Antibody against DNA polymerase of avian myeloblastosis virus did not neutralize the chicken endogenous DNA polymerase activity. These results demonstrate that uninfected chicken embryo cells contain endogenous RNA-directed DNA polymerase activity that is not derived from avian leukosis or reticuloendotheliosis viruses.
Fractionation of Antigen Reactive Cells on a Cellular Immunoadsorbent: Factors Determining Recognition of Antigens by T-Lymphocytes
Authors: Wekerle H. , Lonai P. , Feldman M.
Published: May 2006

Monolayers of mouse fibroblasts were used as cellular immunoadsorbents to separate rat lymphocytes that recognize specific mouse histocompatibility antigens. Normal lymphocytes were incubated on fibroblasts of strain C3H/eb, and nonadherent cells were separated from adherent cells, then transferred for sensitization onto fresh monolayers of C3H. When tested on
51
Cr-labeled target monolayers the nonadherent cells manifested significantly lower cytotoxicity than the adherent cells. However, the nonadherent cells could be sensitized against mouse fibroblasts of an unrelated H-2 phenotype (strain Balb/c). The immune specificity of the adherence was further demonstrated by a stepwise adsorption, which resulted in complete loss of the capacity to acquire specific lytic activity towards C3H antigens. Lymphocytes recognizing strain-specific antigens of the mouse were separated at 37° (not at 0° or 4°); separation was inhibited after treatment with dinitrophenol, sodium azide, or trypsin. Prior treatment with neuraminidase rendered the lymphocytes suceptible to separation at 0°.
Viral-Related RNA in Hodgkins' Disease and Other Human Lymphomas
Authors: Hehlmann R. , Kufe D. , Spiegelman S.
Published: May 2006

Molecular hybridization with radioactively labeled DNA complementary to the RNA of the Rauscher leukemia virus was used to probe for homologous RNA in human lymphomas. 22 of 32 specimens contained RNA possessing homology to the RNA of the mouse leukemia virus, but not to that of the unrelated viruses causing mammary tumors in mice or myeloblastosis in chickens. Normal adult and fetal tissues failed to show significant levels of the leukemia-specific RNA. It appears that human lymphomas contain RNA sequences homologous to those found in a viral agent known to cause leukemia and lymphomas in an experimental animal. The fact that human leukemias and sarcomas also contain this type of RNA further emphasizes a remarkable similarity between the corresponding neoplasias of murine and human origin.
Relaxation Study of Complex Formation between Monovalent Cations and Cyclic Polyethers
Authors: Chock P. B.
Published: May 2006

Equilibrium quotients for the 1:1 complexes of dibenzo-30-crown-10 with Na
+
, K
+
, Rb
+
, Cs
+
, NH
4
+
, and T1
+
in methanol solution have been determined spectrophotometrically. The observed selectivity pattern is discussed in terms of the hydration energy of the cations and the cation-ligand binding energy. The rate of complex formation is diffusion-controlled. Relaxation amplitude data are consistent with a mechanism that involves conformational change of the crown compound.
Isolation and Partial Characterization of a Mutant of
Escherichia coli
Deficient in DNA Polymerase II
Authors: Campbell Judith L. , Soll Larry , Richardson Charles C.
Published: May 2006

A mutant of
Escherichia coli
deficient in DNA polymerase II has been isolated from
E. coli polA1
by mutagenesis with
N
-methyl-
N
′-nitro-
N
-nitrosoguanidine and assay of polymerase activity in extracts of survivors. The
polA1
mutation was suppressed during mutagenesis by introduction of the suppressor, su7
+
, into the parental strain. The mutant, HMS83
polA1 polB1
, contains less than 0.5% of the normal levels of DNA polymerase II. The only polymerase activity detected in the mutant is DNA polymerase III.
E. coli
HMS83 grows normally at both 25 and 42°, and supports the growth of bacteriophages T4, T7, lambda, ϕX174, 186, P2, and fd. The
polB
mutation does not affect sensitivity to ultraviolet irradiation or recombination frequencies.
Translation of Messenger RNA for Histones from HeLa Cells by a Cell-Free Extract from Mouse Ascites Tumor
Authors: Jacobs-Lorena M. , Baglioni C. , Borun T. W.
Published: May 2006

7-9S RNA has been isolated from polyribosomes of HeLa S-3 cells in S phase. These RNA species direct the synthesis
in vitro
of all five classes of human histones when they are added to a protein-synthesizing system derived from mouse ascites tumor cells. The histones synthesized
in vitro
have been identified by two kinds of acrylamide gel electrophoresis, and by paper electrophoresis of tryptic digests. By use of the ratio of tyrosine to tryptophan incorporation as an index of contamination, it was determined that less than 10% of the 7-9S RNA is translated into proteins other than histones.
Phytochrome and Photosystem I Interaction in a High-Energy Photoresponse
Authors: Schneider Michael , Stimson William
Published: May 2006

At least two photoreactions can be demonstrated in plant developmental responses: the low-energy requiring phytochrome system and the high energy reaction. The action of these photoreactions on the formation of anthocyanin by turnip seedlings is discussed. The synthesis of small amounts of anthocyanin can be controlled solely by phytochrome, as evidenced by the red-far-red photoreversible effect of brief irradiations. Appreciable synthesis requires prolonged irradiations, the duration of irradiation being more important than intensity. The data presented suggest that the energy dependence of anthocyanin synthesis arises through photosynthesis. A mechanism for the interaction between photosynthesis and phytochrome is suggested. Under conditions of natural illumination of plants, the concentration of the species of phytochrome that absorbs far-red light may be lower than previously realized.
Hemoglobin Switching in Sheep and Goats: Change in Functional Globin Messenger RNA in Reticulocytes and Bone Marrow Cells
Authors: Nienhuis Arthur W. , Anderson W. French
Published: May 2006

Anemia causes a change in the type of circulating hemoglobin in goats and certain sheep: HbA (α
2
β
2
A
) is replaced by HbC (α
2
β
2
C
). We have isolated globin mRNA from erythroid cells of anemic and nonanemic animals to investigate the mechanism whereby anemia causes this switch. To study several stages in transition from β
A
to β
C
synthesis, active globin mRNA was isolated from bone marrow cells, as well as from reticulocytes. By assaying these globin mRNAs in a rabbit reticulocyte cell-free system, we have demonstrated that the switch from β
A
to β
C
globin synthesis is mediated via a change in functional globin mRNA.
Simulation of Genetic Mucopolysaccharidoses in Normal Human Fibroblasts by Alteration of pH of the Medium
Authors: Lie Sverre O. , McKusick Victor A. , Neufeld Elizabeth F.
Published: May 2006

Catabolism of sulfated mucopolysaccharide by normal human fibroblasts in culture is progressively inhibited as the pH of the growth medium is raised from 6.8 to 8.0. The final cell density increases with the change in pH. The capacity to degrade mucopolysaccharide is rapidly restored by lowering the pH, and this reactivation does not require protein synthesis. Such pH dependence is not observed in cells from patients with genetic impairment of mucopolysaccharide degradation, such as the Hurler or Hunter syndromes. These results may have relevance not only to studies of mucopolysaccharide metabolism in cell culture, but also to the use of metachromasia as a genetic marker and to the observation that normal fibroblasts are released from contact inhibition of growth as the pH of the growth medium is raised.
Molecular Basis of Maternal Inheritance
Authors: Sager Ruth , Lane Dorothy
Published: May 2006

The mechanism of preferential transmission (i.e., maternal inheritance) of cytoplasmic genes was investigated with chloroplast DNA of
Chlamydomonas
as a model system. The behavior of nuclear and chloroplast DNAs were compared in the sexual cycle; DNAs from male and female parents were distinguished by labeling with
14
N- or
15
NH
4
Cl and then by making the crosses:
14
N (female) ×
15
N (male) and the reciprocal. Chloroplast DNAs from the two parents followed different paths in the zygote, but nuclear DNAs showed no differences. Chloroplast DNA from the female parent persists in the zygote, but undergoes a density shift of 0.003-0.005 g/cm
3
to a lighter buoyant density, whereas that from the male disappears soon after zygote formation. The possibility is discussed that a modification-restriction system may be involved.
Hydrostatic Pressure and Ionic Strength Effects on the Kinetics of Lysozyme
Authors: Neville Walter M. , Eyring Henry
Published: May 2006

The kinetics of the reaction catalyzed by egg-white lysozyme from hen eggs (EC 3.2.1.17) was investigated by measurement of the decrease in turbidity of suspensions of dried
Micrococcus luteus
cells. The substrate and NaCl concentration were varied, as well as the hydrostatic pressure (1-476 atm). A plot of the initial velocity against the reciprocal of the substrate concentration gave straight lines. From these plots values for the maximum velocity,
V
, and the apparent Michaelis constant,

K
m

, as well as the effect of NaCl concentration were determined. The maximum velocity showed a pronounced maximum when plotted over a range of NaCl concentration from 0-0.208 M. The volume change of activation, Δ
V
[unk]
, calculated from
V
, was negative, and decreased in absolute value from -8 to about 0 cm
3
/mol as the NaCl molarity was increased over the above range. This effect is explained as due to a different number of salt molecules being built into activated complexes with each of these activated complexes reacting at its own characteristic rate. Strong pressure-dependence of enzyme catalysis indicates appreciable conformational changes of the enzyme as it is incorporated into the activated complex. The volume change causing the pressure effect arises principally from changes in the number of ionized species with the accompanying electrostriction.
Genetic Variation in Activity of Enzymes Involved in Synthesis of Catecholamines
Authors: Kessler S. , Ciaranello R. D. , Shire J. G. M. , Barchas J. D.
Published: May 2006

A genetic analysis of differences in adrenal phenylethanolamine
N
-methyltransferase (EC 2.1.1.X) and tyrosine hydroxylase (EC 1.99.1.X.) and brain tyrosine hydroxylase was performed in three inbred mouse strains. In adrenal glands, the pattern of inheritance of both enzymes was similar; genes carried by the CBA/J strain appeared to be dominant to those of the other strains. The pattern of inheritance of tyrosine hydroxylase activity in adrenals differed from that in the brain. In both tissues, dominant genes appeared to determine intermediate, rather than extreme, levels of enzyme activities.
An Active Derivative of Rabbit Antibody Light Chain Composed of the Constant and the Variable Domains Held Together Only by a Native Disulfide Bond
Authors: Poulsen Knud , Fraser Kevin J. , Haber Edgar
Published: May 2006

The immunoglobulin light chain is thought to be organized into two structural domains, the constant and the variable regions, linked by a switch region of lesser tertiary organization. Light chains of homogeneous rabbit antibodies to pneumococcal polysaccharides labeled with
125
I were subjected to trypsin digestion at different temperatures. At 43° molecular size (as determined by gel filtration) remained unchanged until the chain was subjected to full reduction and alkylation, when half molecules were demonstrated. One light chain resisted tryptic digestion at 43°. At 50° extensive digestion to small peptides occurred. These experiments confirm the susceptibility of the switch region to enzymatic attack as well as the relative resistance of the constant and variable region domains. They also demonstrate that the third disulfide bridge in rabbit light chain extends between the two structural domains and maintains the integrity of the molecule even when a peptide bond in the switch region is cleaved. When the light chain was subjected to dilute acid hydrolysis [10% acetic acid-pyridine (pH 2.5) in 7 M guanidine-HCl for 24-90 hr] selective cleavage at the switch region was demonstrated in yields up to 90%. The site of cleavage was shown to be the acid labile Asp 109-Pro 110 bond by automated Edman degradation. After cleavage the molecule remained intact until full reduction and alkylation, when half molecules were again demonstrated. A light chain cleaved in this way with its interdomain disulfide bond intact, was able to recombine with a homologous heavy chain and restore antigen binding. This indicates that an intact switch region is not needed for antibody activity. The availability of a functional variable region now allows for planning an examination of the antibody combining site by the technique of peptide synthesis.
On Coupled Rate Equations with Quadratic Nonlinearities
Authors: Montroll Elliott W.
Published: May 2006

Rate equations with quadratic nonlinearities appear in many fields, such as chemical kinetics, population dynamics, transport theory, hydrodynamics, etc. Such equations, which may arise from basic principles or which may be phenomenological, are generally solved by linearization and application of perturbation theory. Here, a somewhat different strategy is emphasized. Alternative nonlinear models that can be solved exactly and whose solutions have the qualitative character expected from the original equations are first searched for. Then, the original equations are treated as perturbations of those of the solvable model. Hence, the function of the perturbation theory is to improve numerical accuracy of solutions, rather than to furnish the basic qualitative behavior of the solutions of the equations.
Detection of Maternal Esterase in Mouse Embryonic Tissues
Authors: Sherman Michael I. , Chew Nancy J.
Published: May 2006

A genetic variant of esterase in mice is used to demonstrate for the first time that an enzyme of maternal origin is taken up intracellularly by two mid-gestation tissues dervied from the embryo: trophoblast and yolk sac (visceral endoderm). Although other alternatives are still possible, it is likely that the esterase is transported from the mother to the trophoblast via the serum. If so, the phenomenon is selective, since at least one other prominent serum esterase is not found in trophoblast or yolk sac cells. The enzyme has not been detected in the embryo proper, even at very late stages of pregnancy.

Trophoblast cells-developing from blastocysts implanted under the kidney capsule of a male mouse also appear to have the ability to take up host esterase. Efforts to demonstrate uptake of the enzyme by trophoblast cells in blastocyst cultures have been unsuccessful.
Identity of the Ribosomal Proteins Involved in the Interaction with Elongation Factor G
Authors: Highland Joseph H. , Bodley James W. , Gordon Julian , Hasenbank Renate , Stöffler Georg
Published: May 2006

Rabbit antibodies produced against 50 of the 55 individually purified ribosomal proteins of
Escherichia coli
were tested for their ability to interfere with the formation of the ribosome·EF-G·GDP complex. Only antibodies produced against proteins L7 and L12 inhibited complex formation, and they did so completely. These two proteins were previously shown to be immunologically indistinguishable and necessary for the interaction between ribosomes and EF-G. The present data are consistent with the view that the interaction between ribosomes and EF-G that results in GTP hydrolysis occurs on, and is limited to, proteins L7 and L12 on the surface of the 50S ribosomal subunit.
Transfer RNA Synthesis
In Vitro
Authors: Nierlich Donald P. , Lamfrom Hildegard , Sarabhai Anand , Abelson John
Published: May 2006

During infection of
Escherichia coli
, bacteriophage T4 directs the synthesis of at least eight transfer RNAs and of two stable RNA species of low molecular weight, of unknown function. When T4 DNA is incubated with purified RNA polymerase and the appropriate substrates, a high molecular weight RNA is produced. This RNA, on further incubation with a supernatant fraction prepared from
E. coli
, is cleaved to several species of RNA. These cleaved RNAs were analyzed by gel electrophoresis and fingerprint techniques, and were found to be similar or identical to those made
in vivo
. The fingerprint analysis of one of these, a tRNA
Gly
, is presented. The molecule made
in vitro
, except for the absence of modified bases, appears to be identical to the RNA made by T4-infected cells. Therefore, in this system the tRNA genes are transcribed with fidelity, the transcript is cleaved correctly, and the tRNAs are made in good yield.
In Vitro
Assembly of Bacteriophage Lambda Heads
Authors: Kaiser Dale , Masuda Terrie
Published: May 2006

The assembly of plaque-forming particles in cell-free extracts of induced lambda lysogens was observed two ways. (
i
) DNA isolated from a λ-related phage, 434 for example, is added to an extract of an induced λ lysogen, and plaque-formers with the genotype of the added DNA are detected. (
ii
) One extract from an induced λ lysogen that carries an amber mutation in one of the head genes (
A, B, C, D
, or
E
) is mixed with one carrying an amber mutation in a different head gene; an increase in the number of λ plaque-formers is found over that in either extract alone. These plaque-forming particles have the properties of normal phage particles. They are resistant to DNase, although DNase added to an extract before addition of DNA prevents their appearance; they have a sensitivity to neutralizing antibody and a specificity of adsorption to bacteria characteristic of the source of the extract, but they have the genotype of the added DNA; and they have about the same bouyant density as phage particles.

Mutants in genes
B, C
, or
D
can donate DNA to the phage formed by complementation between extracts of different mutants, but mutants in genes
A
or
E
cannot. Complementation occurs between a pair of extracts only if one (or both) is a DNA donor. This observation suggests a tentative pathway for head assembly: that the products of genes
A
and
E
act before those of
B, C
, and
D
.
Identification of 50S Proteins at the Peptidyl-tRNA Binding Site of
Escherichia coli
Ribosomes
Authors: Oen Helen , Pellegrini Maria , Eilat Dan , Cantor Charles R.
Published: May 2006

Bromoacetyl-phenylalanyl-tRNA
phe
bound to 70S
E. coli
ribosomes reacts covalently with proteins of the 50S subunit. The major reactions are with proteins L2 and L27. In the presence of poly(U), 70S-bound bromoacetyl-phenylalanyl-tRNA
phe
can participate in peptidebond formation with phenylalanyl-tRNA
phe
or puromycin. Most of the products of these reactions are also found covalently attached to L2 and L27. Chloramphenicol and sparsomycin markedly inhibit the peptide-bond formation. These results strongly suggest that bromoacetylphenylalanyl-tRNA
phe
can function as a normal peptidyl-tRNA and that the 50S proteins, L2 and L27, are located in the peptidyl-tRNA binding site. The side reactions of bromoacetyl-phenylalanyl-tRNA
phe
are with one or more 50S proteins from the set L14-17, L6 and/or L11, and L26. These occur to a much less extent than the reactions with L2 and L27. Any functional significance of the side reactions is unknown.
Structural Comparison of Ectopic and Normal Placental Alkaline Phosphatase
Authors: Greene Patricia J. , Sussman Howard H.
Published: May 2006

An alkaline phosphatase immunochemically similar to placental alkaline phosphatase (EC 3.1.3.1) was purified from liver metastases of a giant-cell carcinoma of the lung. Some properties of its physical and chemical structure were determined and compared to those of purified placental alkaline phosphatase. The purified tumor phosphatase and the placental phosphatase were similar with regard to the following properties: (
1
) NH
2
-terminal sequence, (
2
) peptide map, (
3
) subunit molecular weight, and (
4
) isoelectric point. The physical properties and NH
2
-terminal sequence of alkaline phosphatase isoenzyme of liver differed from the placental and the tumor enzyme. The data from the present study strongly support the hypothesis that the tumor and the placental alkaline phosphatases are products of the same gene.
Characterization of RNA from Noninfectious Virions Produced by Sarcoma Positive-Leukemia Negative Transformed 3T3 Cells
Authors: Phillips Leo A. , Hollis Vincent W. , Bassin Robert H. , Fischinger Peter J.
Published: May 2006

RNA from noninfectious virions produced by two established clonal lines of sarcoma positive-leukemia negative (S+L-)-transformed 3T3 cells has been characterized. RNA from virions or nucleoids of S+L--(C243) cells consisted of three to four sizes: ±44 S (6%), 28 S (17%), 18 S (38%), and <18 S (39%). 28S virion RNA contained some virus-specific information demonstrable by RNA·DNA hybridization with a DNA probe derived from the RNA-directed DNA polymerase product of murine sarcoma-leukemia virus, while parallel studies indicated that 28S ribosomal RNA from ribosomal subunits of transformed and nontransformed 3T3 cells did not contain virus-specific information. In contrast to the S+L-(C243) virions, RNA from virions or nucleoids of S+L-(D56) cells consisted of five sizes: 80 S (6%), 68 S (8%), 56 S (5%), 28 S (28%), and <28 S (53%). Thermal dissociation studies suggested that this S+L- genome is comprised of 28S RNA subunits. From these studies we postulate that the 28S viral RNA is most probably the monomeric genome of S+L- virions.
Auxin-Induced Hydrogen Ion Excretion from
Avena
Coleoptiles
Authors: Cleland Robert
Published: May 2006

Avena
coleoptiles excrete hydrogen ions in response to the hormone auxin. Both auxin-induced cell elongation and hydrogen ion excretion occur after only a short lag, and both are prevented by either carbonyl cyanide
m
-chlorophenylhydrazone or cycloheximide. These results support the idea that hydrogen ions act as a second messenger in auxin-induced cell elongation and can be the wall-loosening factor.
A Mammalian Cell Mutant with a Temperature-Sensitive Leucyl-Transfer RNA Synthetase
Authors: Thompson L. H. , Harkins J. L. , Stanners C. P.
Published: May 2006

A cell mutant of the Chinese hamster ovary line, which is temperature sensitive for protein synthesis, is specifically defective
in vivo
in its ability to charge tRNA with leucine. Cytoplasmic extracts exhibited temperature-sensitive leucyl-tRNA synthetase activity. It is, therefore, highly likely that the mutant has a structural alteration in leucyl-tRNA synthetase. The low leakiness and low reversion rate of this mutant, combined with the specificity of the defect in its protein-synthesizing machinery, make it an appealing tool for investigating regulatory mechanisms in animal cells.
Phosphorylation of Human Platelet Myosin
Authors: Adelstein Robert S. , Conti Mary Anne , Anderson William
Published: May 2006

A preparation extracted from human blood platelets, which incorporates
32
P from γ-labeled AT
32
P into one of the two light chains of platelet myosin and platelet myosin head is described. This phosphorylation, which appears to be due to an endogenous kinase, is specific for the myosin light chain in that no other protein extracted in 0.6 M KCl-15 mM Tris·HCl (pH 7.5) is phosphorylated. The phosphorylated light chain, which has been purified by gel filtration, releases the covalently bound phosphate after incubation in alkali and not after incubation in acid.
Role of Allophycocyanin as Light-Harvesting Pigment in Cyanobacteria
Authors: Lemasson C. , Marsac N. Tandeau De , Cohen-Bazire G.
Published: May 2006

Photosynthetic action spectra of several cyanobacteria show a peak at about 650 nm, the height of which is correlated with allophycocyanin content in the strains examined. Allophycocyanin harvests light more efficiently than do phycocyanin and phycoerythrin. The contribution of chlorophyll
a
absorption to photosynthetic activity is barely detectable in cells of normal pigment composition. Chlorophyll
a
becomes the major light-harvesting pigment in cells that have been physiologically depleted of phycobiliproteins.
Heme Proteins: Quantum Yield Determined by the Pulse Method
Authors: Brunori Maurizio , Giacometti Giorgio M. , Antonini Eraldo , Wyman Jeffries
Published: May 2006

We report results of the application of the “pulse method” to the study of photodissociation of various ligands from several heme proteins. By use of this technique, which allows the determination of the quantum yield of photodissociation accurately and rapidly, several ligands (CO, O
2
, isocyanides) have been investigated for sperm-whale myoglobin and trout hemoglobin I. In agreement with previous results, the new data lead to the conclusion that no simple relationship exists between the quantum yield and the affinity constant in the ground state. For trout hemoglobin I, the experiments were extended to measure the quantum yield of the CO photodissociation as a function of the initial degree of saturation, from fully saturated down to the initial values of about 1.5%. The results yield additional information to that obtained by the “steady-state” method, and in particular exclude the idea that the photochemical yield is in any way dependent on the fractional saturation of the molecule with carbon monoxide.
Quantitation of Membrane Sites in Aggregating
Dictyostelium
Cells by Use of Tritiated Univalent Antibody
Authors: Beug H. , Katz F. E. , Stein A. , Gerisch G.
Published: May 2006

Cell-to-cell adhesion during aggregation of
Dictyostelium discoideum
cells is completely blocked by univalent antibody (Fab) directed against two classes of target sites: surface structures characteristic for aggregation-competent cells (“contact sites A”) and others present also on growth-phase cells (“contact sites B”). 3 × 10
5
Fab molecules bound per cell are sufficient to block contact sites A completely, although the Fab fragments cover not more than 2% of the total cell surface. Up to 8-fold this value can be bound per cell when Fab fragments of another specificity are used, without affecting activity of contact sites A. Blockage of cell-to-cell adhesion therefore depends on the binding of Fab fragments to specific target sites, rather than on the total number of Fab molecules bound per cell. This conclusion is also valid for cell adhesion attributed to contact sites B. Contact sites therefore represent a special class of cell-surface sites which, in cell homogenates as well as
in vivo
, can be traced by Fab, and which are not identical with the bulk of cell-surface antigens present on aggregating cells.
Early Stimulation of RNA Synthesis by Erythropoietin in Cultures of Erythroid Precursor Cells
Authors: Maniatis George M. , Rifkind Richard A. , Bank Arthur , Marks Paul A.
Published: May 2006

The effect of erythropoietin on cultured erythroid precursor cells from 13-day mouse-fetal livers was examined. Within 1 hr, erythropoietin causes a 2- to 3-fold stimulation of uridine incorporation into RNA by these cells. The types of RNA preferentially stimulated by erythropoietin during the first hour of exposure of the cells to the hormone include ribosomal RNAs and their precursors, as well as 4-5S RNA. No unique RNA species, not present in control cells, could be detected by sucrose gradient sedimentation or gel electrophoresis. Inhibition of protein synthesis for up to 1 hr does not abolish the stimulatory effect of erythropoietin on RNA synthesis, suggesting that the effect of the hormone on RNA synthesis is not mediated by a newly synthesized protein.
Regulatory Properties of Myocardial Myosin
Authors: Fenner Claudia , Mason Dean T. , Zelis Robert , Wikman-Coffelt Joan
Published: May 2006

The ATPase activity of purified myocardial myosin was activated by either K
+
or Ca
++
; the addition of one in the presence of the other caused inhibition. According to Hill-plot analyses the K
+
-saturation curves were sigmoidal (
n
= 2.92), while the Ca
++
-saturation curves were hyperbolic (
n
= 1.25). Ca
++
-saturation curves in the presence of K
+
were inhibitory with sigmoidicity (
n
= 4.11), while K
+
-saturation curves in the presence of Ca
++
followed the Michaelis-Menten inhibition kinetics (
n
= 1.11). Substrate saturation curves were hyperbolic for both Ca
++
and K
+
systems. There was no enzymatic activity when Na
+
was used as the activating metal; furthermore, Na
+
inhibited in the presence of either K
+
or Ca
++
. Both Na
+
curves of inhibition followed the Michaelis-Menten relationship.