bluuebunny/crossref_metadata_2025 huggingface dataset:
Hemogloblin Switching in Sheep and Goats: Erythropoietin-Dependent Synthesis of Hemoglobin C in Goat Bone-Marrow Cultures
Authors: Barker Jane E. , Last Jerold A. , Adams Sherrill L. , Nienhuis Arthur W. , Anderson W. French
Published: May 2006

The anemia-induced switch from hemoglobin A (α
2
β
2
A
) to hemoglobin C (α
2
β
2
C
) synthesis occurring
in vivo
in sheep and goats has been reproduced in tissue culture of goat bone-marrow cells. Cultivation of primary cultures of goat bone marrow in the presence of erythropoietin results in the appearance of detectable amounts of β
C
globin after 48-72 hr, as well as in a decrease in β
A
globin. A population of proerythroblasts, as well as active heme and globin synthesis, are maintained for at least 3 days in erythropoietin-treated, but not in erythropoietin-deficient, cultures. These findings demonstrate (
i
) maintenance of erythropoietin-responsive cells from bone marrow
in vitro
, and (
ii
) switching
in vitro
from the synthesis of a globin chain coded by one gene to that coded by a different, nonallelic gene. Bone-marrow culture might be a useful model system for study of the mechanism of action of erythropoietin and for study of the activation (and inactivation) of specific genes
in vitro
.
Moments of the End-to-End Vector of a Chain Molecule, Its Persistence and Distribution
Authors: Flory Paul J.
Published: May 2006

The persistence vector a is defined as the configurational average of the chain vector r connecting the ends of the molecule and expressed in a reference frame fixed with respect to the first two skeletal bonds. Moments of second and higher orders in the components of r may readily be calculated for real chains in the rotational isomeric state approximation, and from them the corresponding moments of the vector ρ = r - a measured from the terminus of a. Development of the density distribution of ρ about a is proposed as an alternative to the customary treatment of the density distribution of r about
r
= 0 on the assumption that this latter distribution should be (approximately) symmetric. Past difficulties in the analysis of cyclization equilibria involving rings of moderate size, such as occur in single strands of polynucleotide chains, conceivably may be overcome by adoption of this alternative.
Induction of Lymphocyte Transformation by Sequential Treatment with Neuraminidase and Galactose Oxidase
Authors: Novogrodsky Abraham , Katchalski Ephraim
Published: May 2006

Treatment of mouse-spleen cells with galactose oxidase (EC 1.1.3.9) after incubation with neuraminidase (EC 3.2.1.18) induced extensive blastogenesis. Treatment of the cells with galactose oxidase before incubation with neuraminidase had very little stimulatory effect. Either of these enzymes alone had practically no effect on the cells. The lymphocyte transformation induced by galactose oxidase in neuraminidase-treated cells was decreased upon reacting the cells with borohydride or hydroxylamine, whereas treatment with these compounds did not affect transformation of cells by concanavalin A. It is suggested that galactosyl residues exposed by the action of neuraminidase on the cell membrane are oxidized by galactose oxidase, and the aldehyde moiety thus formed is involved in the induction of blastogenesis.
Conformations of the Li-Antamanide Complex and Na-[Phe
4
, Val
6
]Antamanide Complex in the Crystalline State
Authors: Karle Isabella L. , Karle Jerome , Wieland Th. , Burgermeister Wolfgang , Faulstich Heinz , Witkop Bernhard
Published: May 2006

Antamanide, a cyclic decapeptide isolated from the poisonous mushroom
Amanita phalloides
, preferably complexes with Na
+
, but in less polar solvents, e.g., acetonitrile, also with Li
+
or K
+
. The selectivity of complexation makes it an important model for the study of conformational requirements of ion binding. The conformations of the lithium antamanide complex and the Na-[Phe
4
, Val
6
]antamanide complex have been established by x-ray diffraction analyses of single crystals. The two compounds are isostructural, but not isomorphous. The complexes are folded into a globular shape with an approximate 2-fold axis. Two of the peptide linkages are in the
cis
conformation, Pro
2
-Pro
3
and Pro
7
-Pro
8
. There are only two intramolecular hydrogen bonds. Four C==O groups have their O atoms directed inward to form four Li-O or Na-O ligands. The fifth ligand to the metal ion is provided by a solvent molecule. The conformation found in the crystalline state is different from any of the conformations proposed for the sodium antamanide complex in solution on the basis of nuclear magnetic resonance data.
A Protein Involved in the Peptidyltransferase Activity of
Escherichia coli
Ribosomes
Authors: Nierhaus Knud H. , Montejo Vicente
Published: May 2006

Cores were prepared from 50S ribosomal subunits by incubation with 0.4 M LiCl/Mg
++
(0.4c cores); 0.8c cores and corresponding SP
0.4-0.8
split proteins were obtained from 0.4c cores. In the fragment reaction 0.4c cores were active, but 0.8c cores were not. Activity of the 0.8c cores could be restored by reconstitution with the SP
0.4-0.8
fraction. The split proteins were separated by DEAE-cellulose chromatography and Sephadex gel filtration. The peptidyltransferase activity is correlated with the amount of protein L11 added to the 0.8c core under reconstitution conditions. Whether protein L11 displays the enzymatic activity itself or is part of the enzymatic center is discussed.
Genetic Mapping of the Inversion Loop in Bacteriophage Mu DNA
Authors: Daniell Ellen , Boram William , Abelson John
Published: May 2006

An inversion loop seen in heteroduplex mapping of the DNA of mature Mu phage induced from a lysogen is observed also in defective λ phage carrying one end of Mu. 14% of the DNA of Mu, including this region, designated the G loop, is shown to be to the right of all known genes in the prophage map. The inhomogeneous ends of Mu are observed as a separate phenomenon and appear in all mutants investigated. The
recA
and
recBC
functions of the host are not needed for the inversion responsible for the G loop to take place. Deletions of Mu DNA in the G-loop region have been isolated and are under study.
Efficient Translation of Tobacco Mosaic Virus RNA and Rabbit Globin 9S RNA in a Cell-Free System from Commercial Wheat Germ
Authors: Roberts Bryan E. , Paterson Bruce M.
Published: May 2006

Extracts prepared from commercially available wheat germ efficiently translate messenger RNAs from either viral or eukaryotic origin. The addition of tobacco mosaic virus RNA stimulated amino-acid incorporation more than 100-times and rabbit globin 9S RNA between 20- and 30-times. The
in vitro
product directed by globin 9S RNA comigrated precisely with authentic rabbit globin on sodium dodecyl sulfate-polyacrylamide gels. Furthermore, during high voltage ionophoresis two [
35
S]methionine-labeled tryptic peptides synthesized
in vitro
comigrated in two dimensions with αT5 and βT5 tryptic peptides from authentic [
35
S]methionine-labeled rabbit globin.
Influence of Guanine Nucleotides and Elongation Factors on Interaction of Release Factors with the Ribosome
Authors: Tate W. P. , Beaudet A. L. , Caskey C. T.
Published: May 2006

Release of formylmethionine from the reticulocyte ribosomal substrate, f[
3
H]Met-tRNA·ribosome, is promoted by reticulocyte release factor (RF). The initial rate of this reaction is stimulated by GTP but inhibited by GDPCP. Formation of an RF·UA[
3
H]A
2
·ribosome complex is a measure of the binding of reticulocyte RF to the ribosome, and the recovery of this complex is increased by GDPCP and, to a lesser extent, GTP. These studies suggest that GTP is involved in the initial association of RF with the ribosome and that hydrolysis of the γ-phosphate of the guanine nucleotide is required at a subsequent rate-limiting step. The ribosomal-dependent fMet-tRNA hydrolysis and GTPase activities of reticulocyte RF are inhibited when elongation factor (EF)-2 is bound to the respective ribosomal substrate in the presence of fusidic acid and GDP. When EF-G is bound to the f[
3
H]Met-tRNA·AUG·ribosome substrate with fusidic acid and GDP, the fMet-tRNA hydrolysis activity of
Escherichia coli
RF-1 and RF-2 is also inhibited. The binding of reticulocyte RF and
E. coli
RF-1 or RF-2 to their respective ribosomes is prevented when fusidic acid·EF-2/EF-G·GDP·ribosome complexes are used.
Lambda-Chain Production in Human Lymphoblast-Mouse Fibroblast Hybrids
Authors: Orkin Stuart H. , Buchanan Philip D. , Yount William J. , Reisner Howard , Littlefield John W.
Published: May 2006

Mutant human lymphoblast cells deficient in hypoxanthine phosphoribosyltransferase (EC 2.4.2.8) activity were hybridized with thymidine kinase (EC 2.7.1.21)-deficient mouse fibroblasts. Hybrid cells were readily selected, as both parental lines were nonreverting and eliminated by hypoxanthine-amethopterinthymidine medium. Human lambda (λ) chain was the only immunoglobulin chain produced by the lymphoblast parent, as determined by immunofluorescent techniques. Two independent hybrid clones chosen for detailed study synthesized human λ chain, and continued to do so after prolonged culture.

As in both parental lines, no human immunoglobulin heavy chains, complements C3 or C4, or α
1
-antitrypsin, or mouse immunoglobulin chains or complement C5 were detectable in the hybrids. Selection against thymidine kinase-containing hybrid cells with 5-bromodeoxyuridine did not eliminate positive λ-chain reactivity, suggesting that the kinase and λ-chain loci are not linked.

The continued production of an immunoglobulin chain by human lymphoblast-mouse fibroblast hybrids contrasts with the extinction of other differentiated functions in several hybrid systems, and indicates that gene localization and linkage analysis for human immunoglobulin chains should be feasible with this system.
Guanosine 3′:5′-Cyclic Monophosphate and the Action of Insulin and Acetylcholine
Authors: Illiano Gennaro , Tell Guy P. E. , Siegel Marvin I. , Cuatrecasas Pedro
Published: May 2006

Low concentrations of insulin (120 μunits/ml) and of carbamylcholine (1 μM) increase cyclic GMP content in isolated fat cells by 350%. The maximal amount of cyclic GMP, achieved within 2 min after addition of insulin or carbamylcholine, falls rapidly for insulin and much more slowly for carbamylcholine. 10 pM Acetylcholine can also augment the content of fat-cell cyclic GMP, but by 5 min (37°) the amount falls to that of unstimulated cells. Atropine abolishes the effects of carbamylcholine and acetylcholine but does not modify that of insulin, indicating that the ability of insulin to regulate cyclic GMP levels is not mediated by cholinergic receptors. Insulin and carbamylcholine increase the concentration of cyclic GMP in rat-liver slices by 400%; the effects of both agents occur rapidly and are relatively transient. Insulin does not alter cyclic GMP concentrations in purified human peripheral lymphocytes or in rat-spleen lymphocytes, cells which possess few insulin receptors and which are insensitive to the metabolic effects of the hormone. Carbamylcholine, however, causes a substantial increase in the cyclic GMP content of these lymphocytes. The data support the view that close and reciprocal relationships may exist between the concentrations and actions of cyclic AMP and cyclic GMP, as well as between the enzymes responsible for biosynthesis and degradation of these nucleotides.
Growth Inhibition and Morphological Changes Caused by Lipophilic Acids in Mammalian Cells
Authors: Ginsburg E. , Salomon D. , Sreevalsan T. , Freese E.
Published: May 2006

Human (HeLa, Chang liver, L-132, and Intestine 407) and other mammalian (XC, SV3T3, and chick-embryo) cells in tissue culture are at least as sensitive to inhibition by lipophilic acids and nitrite as bacteria. Some of these compounds are the most frequently used antimicrobial food additives. Short-chain fatty acids (up to hexanoate) and parabens induce, at partially inhibitory concentrations, a jagged cell shape in continuous epithelial-like cell lines, such as HeLa, Chang liver, L-132, and Intestine 407. This morphological effect is not mediated or enhanced by butyryl cyclic AMP, which specifically affects fibroblasts.
Pituitary Extracts and Steroid Hormones in the Control of 3T3 Cell Growth
Authors: Armelin Hugo A.
Published: May 2006

Results are reported showing that pituitary extracts stimulate growth of 3T3 cells, an established line of mouse fibroblast. Cells were cultured in medium containing an organic buffer (HEPES;
N
-2-hydroxyethylpiperazine-
N
′-2-ethanesulfonic acid), which increases the serum requirement for cell growth. The pituitary growth-prompting activity is (
a
) not dialyzable; (
b
) thermolabile; (
c
) protease sensitive; and (
d
) enhanced by hydrocortisone (a steroid hormone). Activity was quantitatively assayed by measurement of stimulation of cell division or [
3
H]thymidine uptake into DNA. The active species is probably different from pituitary protein hormones and it seems to be effective at concentrations observed for protein hormones
in vivo
. 3T3 cells transformed by simian virus 40 are not responsive to this activity.
Interruption of the Sequential Release of Small and Large Molecules from Tumor Cells by Low Temperature During Cytolysis Mediated by Immune T-Cells or Complement
Authors: Martz Eric , Burakoff Steven J. , Benacerraf Baruj
Published: May 2006

Specific lysis of tumor cells by thymus-derived lymphocytes from alloimmunized mice (T-effector specific lysis) was studied with target cells labeled with isotopes attached to both small (
14
C-labeled nicotinamide) and large (
51
Cr-labeled) molecules. The results confirm and extend previous reports that target cells release small molecules considerably earlier than large molecules during T-effector specific lysis. After interruption of T-effector specific lysis by specific antibody and complement directed against the
killer
cells, or by ethylenediaminetetraacetic acid, release of both isotopes continued, eventually reaching identical levels of specific release, the value of which represents the fraction of the target cell population which had been committed to die at the time these treatments were applied. On the other hand, release of both isotopes during T-effector specific lysis stops immediately when the cultures are cooled to 0°. Thus, while ethylenediaminetetraacetic acid or specific complement-mediated lysis of the killer cells merely prevents the initiation of any new damage to target cells, cooling to 0° also stops the lytic process in already-damaged target cells.

The colloid osmotic phase of target cell lysis induced by specific antibody and complement was similarly stopped at 0° in tumor cells, but not in erythrocytes. Thus, in tumor target cells, both T-effector specific lysis and complement cause a sequential release of progressively larger molecules which can be immediately stopped at any point by cooling to 0°.
Interferon Induction by Synthetic Polynucleotides: Importance of Purine N-7 and Strandwise Rearrangement
Authors: Clercq Erik de , Torrence Paul F. , Witkop Bernhard
Published: May 2006

The antiviral activity and interferon-inducing ability of single-, double-, and triple-stranded polynucleotides, modified at pyrimidine C-5 or purine N-7, were evaluated in primary rabbit kidney cells challenged with vesicular stomatitis virus. (
1
) There is a parallel increase in antiviral activity and the temperature at which double-stranded polynucleotides rearrange to inactive triple-stranded complexes. (
2
) When the purine N-7 of (A)

n

is replaced by CH, all resulting double-stranded complexes fail to provide antiviral protection or to induce interferon, even though such complexes meet all requirements previously recognized for interferon induction. (
3
) Competition experiments between inactive and active polynucleotides indicate that single-stranded polynucleotides apparently do not bind to the cellular receptor sites for interferon induction, whereas triple-stranded complexes and inactive double-stranded complexes bind to such receptor sites but, probably for conformational reasons, fail to trigger the necessary message for interferon induction.
The Length of the Terminal Repetition in Adenovirus-2 DNA
Authors: Roberts Richard J. , Arrand John R. , Keller Walter
Published: May 2006

Adenovirus-2 DNA was end-labeled by partial digestion with
Escherichia coli
exonuclease III and resynthesis with the DNA polymerase from avian myeloblastosis virus and α-
32
P-labeled deoxyribonucleoside triphosphates. This end-labeled DNA was cleaved with several specific endonucleases and the terminal fragments were characterized by gel electrophoresis and pyrimidine tract analysis. Two endonucleases gave identical fragments from both ends, presumably from cleavage within the inverted terminal repetition, while all other endonucleases gave dissimilar fragments from the two ends. From the sizes of these fragments it is estimated that the inverted terminal repetition is between 100 and 140 nucleotide pairs long.
Metallointercalation Reagents. 2-Hydroxyethanethiolato(2,2′,2″-terpyridine)-platinum(II) Monocation Binds Strongly to DNA By Intercalation
Authors: Jennette K. W. , Lippard S. J. , Vassiliades G. A. , Bauer W. R.
Published: May 2006

The red, cationic complex 2-hydroxy-ethanethiolato(2,2′,2″-terpyridine)platinum(II), [(terpy)-Pt(SCH
2
CH
2
OH)]
+
, binds strongly to DNA by a mechanism involving intercalation. By means of fluorescence spectroscopy, the platinum complex was shown to inhibit competitively the binding of the intercalating dye ethidium bromide to calf thymus DNA. This platinum complex increases the viscosity of calf thymus DNA, raises the melting temperature by up to 5°, and exhibits induced circular dichroism when bound to the DNA. The closed circular viral DNA from bacteriophage PM2 is unwound by the complex in a manner that is similar to that of ethidium bromide and with an unwinding angle that appears to be slightly less than that of ethidium. Studies of the related complex [(terpy)PtCl]
+
, which has a substitutionally more labile chloride ligand, suggest that it also intercalates, especially at [DNA-P]:[Pt] ratios greater than 2. The potential utility of these new metallointercalation reagents as heavy atom probes in fiber diffraction or electron microscopic studies of the interaction process is discussed.
Ferritin, a Hodgkin's Disease Associated Antigen
Authors: Eshhar Zelig , Order Stanley E. , Katz David H.
Published: May 2006

Antigens which exist in high frequency in tumor tissues of patients with Hodgkin's disease have been obtained in relatively concentrated form by gel chromatography procedures. Further purification and analysis of these antigens performed in the present study have demonstrated that the antigen of fast electrophoretic mobility (F-antigen) is normal tissue ferritin. The identification of F-antigen as ferritin has been made on the basis of comparative physicochemical and immunological analyses of purified F-antigen and normal ferritin. Thus, F-antigen was found to contain iron and to be similar to ferritin in molecular weight, amino-acid composition, electrophoretic mobility, isoelectric distribution, and immunological reactivity. Absorption of a monospecific heterologous anti-F antiserum with normal tissue ferritin completely removed all anti-F antibody activity. Moreover, the absorption of polyspecific heterologous antiserum to crude Hodgkin's extracts, which contains antibodies reacting with F-antigen, the slower migrating S-antigen, and a third specificity present in lysates of normal peripheral blood lymphocytes (PL-antigen), with ferritin, removed only anti-F activity, thus distinguishing the S- and PL-antigens from ferritin. The existence of ferritin in high quantities in serum of Hodgkin's disease patients may provide a tool of potential diagnostic and prognostic importance in the management of this disease.
Effect of Near-Ultraviolet and Visible Light on Mammalian Cells in Culture II. Formation of Toxic Photoproducts in Tissue Culture Medium by Blacklight
Authors: Stoien James D. , Wang Richard J.
Published: May 2006

Near-ultraviolet radiation was found to be lethal for mammalian cells in Dulbecco's modified Eagle's medium without serum or phenol red. Irradiation of the cells with near-ultraviolet light while the cells were in phosphate-buffered-saline abolished the lethal effect. When only the medium was irradiated followed by the addition of unirradiated cells and serum, the cells were still killed. The photoactive components of the medium for this effect were riboflavin, tryptophan, and tyrosine. When riboflavin was deleted from the medium being irradiated and added later, almost no killing was detected. Irradiation of salt solution of riboflavin and tryptophan or riboflavin and tyrosine, resulted in cell killing. Little or no killing resulted when riboflavin, tryptophan, or tyrosine was irradiated singly.

The formation of photoproducts toxic for mammalian cells appears to involve photodynamic action. Experiments utilizing Dulbecco's or similar media without proper controls may produce anomalous results from light illuminating the laboratory.
Asymptomatic Infection of Adult Volunteers with a Temperature Sensitive Mutant of
Mycoplasma pneumoniae
Authors: Greenberg Harry , Helms Charles M. , Brunner Helmut , Chanock Robert M.
Published: May 2006

Temperature sensitive mutants of
Mycoplasma pneumoniae
were developed with the expectation that their temperature sensitive defects would restrict replication
in vivo
at the temperature of the lower respiratory tract, whereas such defects would not seriously impair replication in the cooler environment of the upper respiratory passages. One such
ts
mutant,
ts-H43
, which does not replicate at a temperature of 37° or above, although noninfectious for hamsters, infected each of 16 seronegative adult volunteers when given by the intranasal route. The mutant remained genetically stable throughout the course of infection and stimulated a moderate systemic and local antibody response. The mutant was entirely avirulent for the volunteers but appeared to stimulate resistance to subsequent challenge with partially attenuated wild-type (
ts
+
)
Mycoplasma pneumoniae
.
Evidence for Somatic Generation of Antibody Diversity
Authors: Tonegawa S. , Steinberg C. , Dube S. , Bernardini A.
Published: May 2006

RNA preparations containing 70-80% mouse κ-chain mRNA have been prepared. The remainder consists of many RNA species, each of which represents a small fraction of the total RNA. The κ-chain mRNA preparation hybridizes with mouse liver DNA with bi-phasic kinetics, indicating that it consists of two fractions —“unique” and “reiterated.” Competition hybridization experiments show that the homology among the unique fractions from different mRNAs is the same as the homology among the amino acid sequences of the corresponding κ-chains. Hence, in addition to the C-region (constant-region) sequences, (most of) the V-region (variable-region) sequences are also derived from unique germ line genes. The reiterated fractions from different κ-chain mRNAs show essentially complete homology with each other. This fraction seems to consist mostly of sequences which do not code for amino-acid sequences of the secreted polypeptide chain, i.e., the “external” section of the mRNA molecule. It is concluded that the number of germ line genes is too small to account for the observed diversity of antibody molecules.
An Analytic Generalization of the Rogers-Ramanujan Identities for Odd Moduli
Authors: Andrews George E.
Published: May 2006

A (
k
- 1)-fold Eulerian series expansion is given for II(1 -
q

n

)
-1
, where the product runs over all positive integers
n
that are not congruent to 0,
i
or -
i
modulo 2
k
+ 1. The Rogers-Ramanujan identities are the cases
k
=
i
= 2 and
k
=
i
+ 1 = 2.
Correlation between Thermal Death and Membrane Fluidity in
Bacillus stearothermophilus
Authors: Esser Alfred F. , Souza Kenneth A.
Published: May 2006

Paramagnetic resonance spectra of spin labels partitioned into spheroplast membranes of
Bacillus stearothermophilus
indicate lateral lipid phase separations. Cells adjust their lipid composition in response to temperature changes so that the same change of state in membrane phospholipids is achieved at the respective growth temperature. A temperature-sensitive mutant that fails to change its lipid composition above a certain temperature can survive only up to the higher temperature boundary for lateral phase separation. These data are interpreted to indicate that the maximal and minimal growth temperatures of thermophiles are regulated by the onset and conclusion of phase separations of the particular lipid composition they synthesize. It is suggested that isolated lipid domains are required for functional membrane assembly.
Dissection of Chromosome Structure with Trypsin and Nucleases
Authors: Weintraub Harold , Lente Frederick Van
Published: May 2006

Exhaustive digestion of chromatin with trypsin leads to the cleavage of only 20-30 amino acids from each of histones III (f3), IV (f2a1), IIb2 (f2b), and IIb1 (f2a1), the remainder of these chains being resistant. This resistance is not altered by removing the histones from the DNA with 2 M NaCl, but is dramatically reduced in 6 M urea. Histones III, IV, IIb2, and possibly IIb1 are cleaved at their N-termini. Histones I and V and the nonhistone proteins are the first to be attacked by trypsin and have no detectable trypsin-resistant fragments. The arginine rich histones, III and IV, are then cleaved as a pair, followed by most of IIb2 and IIb1, also as a pair. This data is consistent with a model in which basic N-terminal “arms” extend from a trypsin-resistant histone complex. The structural arrangement of these arms relative to the trypsin-resistant histone complex may define the spatial coordinates of DNA binding sites and, consequently, the folding of the DNA fiber in the chromosome.

Accompanying the tryptic digestion of the N-terminals of histones III, IV, IIb2, and possibly IIb1, is an increased sensitivity of chromatin to staphylococcal nuclease. As analyzed by electrophoresis, untrypsinized chromatin is digested into eight discrete limit-digest fragments by nuclease. Trypsinization results in the nuclease digestion of some, but not all, of these DNA bands. Together with the information on the way trypsin cleaves histones in chromatin, the analysis of the resistant DNA suggests that histone N-terminals are associated with some DNA bands and histone C-terminals with other DNA bands. We propose that histones fold the chromosome by crosslinking the DNA corresponding to these bands.
Piezoelectric Theory of Enzymic Catalysis as Inferred from the Electromechanochemical Principles of Bioenergetics
Authors: Caserta Giuseppe , Cervigni Tommaso
Published: May 2006

Starting from the electromechanochemical principles of bioenergetics formulated by Green and Ji, a theory is proposed which describes enzymic catalysis in terms of piezoelectricity in semiconductors. The choice of this particular physical effect for describing catalytic processes is founded on the following experimental observations: most of the amino-acid residues of enzymes, as well as a large number of other biologically important molecules, exhibit piezoelectric resonances; besides, enzymes can behave like semiconductors. In the proposed theory the catalysis is assumed to be accomplished by means of three fundamental processes: (
a
) the lowering of the substrate-product energy barrier; (
b
) the electron-induced selective amplification of the low-frequency vibrational waves present in thermal background in the enzyme structure; and (
c
) the channeling into the substrate of the energy associated with the amplified waves and utilization of this energy for generating electrical or mechanical fields inside a susceptible region of the substrate. A mathematical description of the theory is outlined, and a rough estimate of some quantities involved in the process of wave amplification is also reported.
On the Mechanism of Oscillations in the “Beating Mercury Heart”
Authors: Lin Shu-Wai , Keizer Joel , Rock Peter A. , Stenschke Herbert
Published: May 2006

The discovery of a class of electrochemical-mechanical oscillators—similar to the beating mercury heart -are reported and characterized. Chemical and physical effects on the voltage-time oscillations in these systems have been measured and a mechanism consistent with these effects is given. Interesting cross-catalytic effects involving the electrocapillarity of mercury are proposed to be the origin of the oscillations in these systems.
Magnetic Circular Dichroism Studies XXXV. A Comparison of Cytochromes
P
-450 and
P
-448
Authors: Dawson John H. , Dolinger Peter M. , Trudell James R. , Barth Günter , Linder Robert E. , Bunnenberg Edward , Djerassi Carl
Published: May 2006

Cytochromes
P
-450 and
P
-448 in microsomal suspensions have been shown to be spectrally distinct by magnetic circular dichroism spectroscopy. Furthermore, this technique can be used to measure induction of these two cytochromes by phenobarbital and 3-methyl-cholanthrene. Magnetic circular dichroism spectroscopy is thus at least as useful as difference spectroscopy for the investigation of
P
-450 and
P
-448 and more informative because the presence of cytochrome
b
5
and hemoglobin can be detected concurrently. We have also shown that the molar magnetic ellipticity for reduced + CO treated cytochrome
P
-450 of
Pseudomonas
grown on camphor is of similar value to that of reduced + CO treated microsomal
P
-450 and
P
-448.
Coexistence of Several Putative Neurotransmitters in Single Identified Neurosn of
Aplysia
Authors: Brownstein Michael J. , Saavedra Juan M. , Axelrod Julius , Zeman Gary H. , Carpenter David O.
Published: May 2006

By sensitive enzymatic micromethods several putative neurotransmitters were measured in four identifiable neurons of
Aplysia californica
(R-2, R-14, L-11, and C-1). Serotonin was found in all of these neurons, and octopamine in all but C-1. Acetylcholine has been previously reported to be present in R-2 and L-11. The catecholamines, norepinephrine and dopamine, were not detected in the four cells examined. The possible biological consequence of the presence of several putative transmitters in single identifiable neurons is discussed.
Actin Is the Naturally Occurring Inhibitor of Deoxyribonuclease I
Authors: Lazarides Elias , Lindberg Uno
Published: May 2006

Various tissues and cells in culture contain a specific inhibitor of DNase I (EC 3.1.4.5). In this paper evidence is presented that this inhibitor is actin, one of the major structural proteins of muscle and nonmuscle cells. (
a
) The inhibitor is a major cellular component constituting 5-10% of the soluble protein. (
b
) It migrates with actin on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, having a characteristic molecular weight of 42,000. (
c
) It has an amino-acid composition closely similar to that of actin. (
d
) The peptide maps of the two proteins are nearly identical. (
e
) Skeletal muscle actin inhibits the enzymatic activity of DNase I. (
f
) DNase I-agarose affinity chromatography quantitatively retains purified skeletal muscle actin, and actin, specifically, from high-speed supernatants of whole cell extracts. (
g
) An antibody to purified inhibitor protein from calf thymus, used in indirect immunofluorescence on cells grown in culture, stains a two-dimensional network of fibers similar to that seen with an actin-specific antibody.

The observation that actin can be isolated by DNase-agarose affinity chromatography provides a useful tool for the biochemical study of actin under different physiological conditions.
Biosynthesis of Collagen Crosslinks: Increased Activity of Purified Lysyl Oxidase with Reconstituted Collagen Fibrils
Authors: Siegel Robert C.
Published: May 2006

Lysyl oxidase catalyzes the formation of crosslinking aldehydes in collagen and elastin. This report demonstrates that the enzyme has high activity with collagen precipitated as native fibrils, an apparent

K
m

of 0.95 μM, and low activity toward either soluble forms such as denatured collagen, isolated α chain, or isolated α1-CBl peptide, or precipitated collagen fibrils after pepsin treatment. These results indicate that the biosynthesis of the aldehyde crosslink intermediate probably occurs primarily after the onset of fibril formation
in vivo
. Biosynthesis of aldehydes and subsequent crosslinks may be related to the rate of fibril formation as well as to the concentration of lysyl oxidase
in vivo
.
Synthesis of a Pentekontapeptide with High Lipolytic Activity Corresponding to the Carboxyl-Terminal Fifty Amino Acids of Ovine β-Lipotropin
Authors: Yamashiro Donald , Li Choh Hao
Published: May 2006

The synthesis of a peptide, composed of fifty amino-acid residues, corresponding to positions 42-91 in ovine β-lipotropin has been accomplished by the solidphase method. The preformed symmetrical anhydride and active ester coupling methods were used exclusively. The synthetic product was purified by gel filtration, carboxymethylcellulose chromatography, and partition chromatography on Sephadex G-50. Its lipolytic activity in isolated rabbit fat cells was about six times that of β-lipotropin on a weight basis.
The General Structure of Transfer RNA Molecules
Authors: Kim S. H. , Sussman J. L. , Suddath F. L. , Quigley G. J. , McPherson A. , Wang A. H. J. , Seeman N. C. , Rich Alexander
Published: May 2006

The three-dimensional structure of yeast phenylalanine tRNA serves as a useful basis for understanding the tertiary structure of all tRNAs. A large number of tRNA sequences have been surveyed and some general conclusions are drawn. There are only a few regions in the molecule in which there are differences in the number of nucleotides; and the structure of yeast phenylalanine tRNA can accommodate these differences by forming or enlarging protuberances on the surface of the basic framework molecule. The nature and distribution of the differences in number of nucleotides are surveyed and possible hydrogen bonding interactions are discussed for a number of tRNA classes. The two most significant features of the molecule are the large number of stacking interactions which are seen to include most of the nucleotides in the molecule and the system of specific hydrogen bonding interactions. It is likely that these stabilizing elements are preserved in all tRNA structures.
The Presence of I-Region-Associated Antigens on B Cells in Molecules Distinct from Immunoglobulin and H-2K and H-2D
Authors: Unanue Emil R. , Dorf Martin E. , David Chella S. , Benacerraf Baruj
Published: May 2006

The distribution of I-region-associated antigenic specificities in murine lymphoid cells was studied by immunofluorescence. The antigens were mostly represented in B cells and in macrophages. The complexes of I-anti-I-region-associated antigens were found to be distributed throughout the lymphocyte surface both at 4° and 37°. In about two-thirds of the lymphocytes the complexes redistributed into caps after incubation with a second ligand (an anti-mouse immunoglobulin). The I-region specificities were in molecules distinct from immunoglobulin or from the molecules coded by the H-2K and H-2D regions.
Determination of the Absolute Number of
Escherichia coli
Membrane Vesicles That Catalyze Active Transport
Authors: Short S. A. , Kaback H. R. , Kaczorowski G. , Fisher J. , Walsh C. T. , Silverstein S. C.
Published: May 2006

Transport of vinylglycolate (2-hydroxy-3-butenoic acid) via the lactate transport system is the limiting step for covalent labeling of membrane vesicles prepared from
E. coli
ML 308-225. Thus, the rate and extent of vinylglycolate labeling is stimulated about 10-fold by ascorbate-phenazine methosulfate, and stimulation is abolished by 2,4-dinitrophenol and by phospholipase treatment, neither of which affect the rate of vinylglycolate oxidation. [
3
H]Vinylglycolate of high specific activity has been prepared, and vesicles have been labeled with this compound in the presence of ascorbate-phenazine methosulfate. Examination of these preparations by high resolution radioautography in the electron microscope demonstrates that virtually all of the vesicles are labeled. The experiments provide a strong indication that most, if not all, of the membrane vesicles in these preparations catalyze active transport.
The Organization and Diversity of Immunoglobulin Genes
Authors: Leder Philip , Honjo Tasuku , Packman Seymour , Swan David , Nau Marion , Norman Barbara
Published: May 2006

We have used purified mouse immunoglobulin light chain mRNA and synthetic DNA which is complementary to it to assess the reiteration frequency of gene sequences corresponding to the κ constant region of the mouse immunoglobulin light chain. These studies indicate that the constant region sequence is represented only two to three times per haploid mouse genome, a finding that rules out a simple stringent germ line mechanism which would require the constant region sequence to be represented hundreds if not thousands of times. Hybridization studies involving
125
I-labeled myeloma light chain mRNA yield interesting results which may eventually permit us to distinguish between the remaining somatic mutation and recombinational germ line hypotheses. These results reveal a major component of relatively unique frequency and a minor component with a reiteration frequency of approximately 30 to 50 copies per haploid genome. As discussed, these results do not permit us to distinguish unambiguously between a germ line model and a type of somatic mutation model that permits germ line genes corresponding to each κ subgroup. The results do, however, clearly rule out the existence of thousands of variable region sequences so closely related to the MOPC-41 V-region as to permit extensive stable cross-hybridization.
Two Eukaryotic Initiation Factors (IF-I and IF-II) of Protein Synthesis that Are Required to Form an Initiation Complex with Rabbit Reticulocyte Ribosomes
Authors: Cashion Linda M. , Stanley Wendell M.
Published: May 2006

The formation of an initiation complex with rabbit reticulocyte ribosomes and certain templates is dependent upon the action of two initiation factors (IF-I and IF-II) of protein synthesis isolated from 0.5 M KCl extracts of rabbit reticulocyte polysomes. IF-I mediates the GTP-dependent, but template-independent, binding of the cytoplasmic initiator transfer RNA (rabbit liver) to a 40S ribosomal subunit. In the presence of a 60S ribosomal subunit and of AUG, AUG(U)
25
, or rabbit-globin messenger ribonucleoproteins (but not of rabbit-globin messenger RNAs), IF-II causes the transfer of the initiator transfer RNA to an initiation complex containing an 80S ribosome. Although 5′-guanylylmethylenediphosphonate can replace GTP as the cofactor used in binding the initiator transfer RNA to IF-I or to a 40S ribosomal subunit, the subsequent transfer of the initiator transfer RNA to an initiation complex requires GTP and cannot take place in the presence of 5′-guanylylmethylenediphosphonate. After the formation of this initiation complex, the initiator transfer RNA is bound in the P site of the 80S ribosome since exposure of the complex to puromycin releases the methionine residue from the initiator transfer RNA as methionyl-puromycin.

IF-I and IF-II are dissociated from polysomes by 0.5 M KCl as a complex having a molecular weight of about 370,000, and they remain in this form during and after gel filtration. However, the two factors can be separated by appropriate step elutions from DEAE-cellulose. After separation of the two activities, the molecular weights of IF-I and IF-II are about 150,000 and 220,000, respectively.
Homeoviscous Adaptation—A Homeostatic Process that Regulates the Viscosity of Membrane Lipids in
Escherichia coli
Authors: Sinensky Michael
Published: May 2006

E. coli
incorporates increasing proportions of saturated and long-chain fatty acids into phospholipids as growth temperature is increased. It was found that this compositional variation results in the biosynthesis of phospholipids that have identical viscosities at the temperature of growth of the cells. This “homeoviscous adaptation” can also be observed in
E. coli
membrane preparations. Viscosities were determined by use of the electron spin resonance spin-label technique.
Regulation of Mammalian Fatty-Acid Synthetase. The Roles of Carbohydrate and Insulin
Authors: Volpe Joseph J. , Vagelos P. Roy
Published: May 2006

The regulation of fatty-acid synthetase has been studied in liver, adipose tissue, and brain of diabetic and normal rats in relation to insulin administration and glucose or fructose feeding. The data indicate that: (
1
) insulin is not necessary for regulation of synthetase activity in liver but may be necessary in adipose tissue; (
2
) synthetase of liver can be regulated by carbohydrate, which can enter the glycolytic scheme in the absence of insulin (e.g., fructose), suggesting the possibility that regulation of synthetase may depend on the concentration of certain intermediates of the glycolytic pathway or beyond; (
3
) fructose feeding affects the synthetase by causing an increase in the rate of synthesis of fatty-acid synthetase; and (
4
) unlike fatty-acid synthetase of liver and adipose tissue, the enzyme of brain is unaffected by the diabetic state or by glucose or fructose feeding.
“Alpha Chain Disease” Protein Def: Internal Deletion of a Human Immunoglobulin A
1
Heavy Chain
Authors: Wolfenstein-Todel Carlota , Mihaesco Edith , Frangione Blas
Published: May 2006

Protein Def is a human alpha chain disease protein related to α1 immunoglobulin heavy chain. The molecular weight of the polypeptide portion of the monomeric molecule is 29,300, which is a little greater than half of a normal α1 chain. The NH
2
-terminal of the polypeptide is heterogenous and, after a short segment corresponding to the variable region, displays a gap which comprises the C
H
1 constant domain. Normal synthesis resumes at a valine residue in the hinge region just before a segment which contains a partially duplicated fragment and the interheavy disulfide bonds. From there on, the molecule is apparently normal. Protein Def is therefore synthesized as an internally deleted α1 heavy chain, followed by postsynthetic amino-terminal proteolysis. It is postulated that codon(s) specifying valine at the hinge region may be a recognition site for reinitiating synthesis after internal gaps equivalent to position 216 in gamma chain disease proteins.
Role of 1,25-Dihydroxyvitamin D
3
in Maintaining Serum Phosphorus and Curing Rickets
Authors: Tanaka Y. , Deluca H. F.
Published: May 2006

The intravenous injection of a single dose of 650 pmoles of 1,25-dihydroxyvitamin D
3
to rats fed a vitamin D-deficient, low-phosphorus diet caused an elevation of serum phosphorus within 5 hours which reached a maximum in about 10-12 hours. This elevated serum phosphorus returned to deficiency levels 2-3 days later. On the other hand, a single injection of 650 pmoles of 25-hydroxyvitamin D
3
produced a significant rise at 12 hours, reached a maximum in 24-36 hours, and was maintained for at least 7 days. The single dose of 1,25-dihydroxyvitamin D
3
supported little calcification of bone, whereas the 25-hydroxyvitamin D
3
produced marked calcification. Six-hundred and fifty pmoles of 24,25-dihydroxyvitamin D
3
increased serum phosphorus only slightly and induced no calcification. When 1,25-dihydroxyvitamin D
3
was given each day, a sustained increase in serum phosphorus and marked bone calcification resulted. In contrast to the serum phosphorus responses, intestinal calcium transport remained high 5 days after administration of a single dose of 1,25-dihydroxyvitamin D
3
. Serum calcium was not changed appreciably by any of the metabolites.

Thyroparathyroidectomized rats or rats fed a diet extremely deficient in phosphate still exhibited a marked elevation of serum phosphorus in response to 1,25-dihydroxyvitamin D
3
. The effect of 1,25-dihydroxyvitamin D
3
on serum phosphorus was greatly reduced in nephrectomized rats, suggesting that the serum phosphorus response to 1,25-dihydroxyvitamin D
3
may arise from an enhancement of phosphate reabsorption in the renal tubules.

It is suggested that 1,25-dihydroxyvitamin D
3
cures rickets in rats by increasing the concentration of serum phosphorus rather than by increasing serum calcium concentration and calcium absorption.
Interfacial Photoreactions and Chemical Capacitance in Lipid Bilayers
Authors: Hong Felix T. , Mauzerall David
Published: May 2006

The electrical response of a pigmented lipid bilayer to a short laser pulse is measured by a
tunable voltage clamp method
. In this method, a variable access impedance permits “tuning” of the observed relaxations for optimal measurements. Analysis of the data so obtained leads to an equivalent circuit that contains a novel
chemical capacitance
charged by the specific photoreaction across a single membrane-water interface. This chemical capacitance is distinct from the ordinary membrane capacitance. The intrinsic chemical rate constant obtained from the equivalent circuit analysis is shown to be the pseudo-first-order rate constant of the reverse dark reaction of the reduced acceptor and the oxidized pigment. The tunable voltage clamp method of measurement and analysis allows unambiguous separation of this rate constant into resistive and capacitative elements, which are interpreted in molecular terms.
Effects of Epinephrine, Adrenocorticotrophic Hormone, and Theophylline on Adenosine 3′,5′-Monophosphate Phosphodiesterase Activity in Fat Cells
Authors: Pawlson L. G. , Lovell-Smith C. J. , Manganiello V. C. , Vaughan M.
Published: May 2006

When rat fat cells were incubated with ACTH, epinephrine, or theophylline for 2 to 10 min, cyclic AMP phosphodiesterase (3′:5′-cyclic-AMP 5′-nucleotidohydrolase, E.C. 3.1.4.17) activity (
K
m
about 0.39 μM) in the 100,000 ×
g
sediment fraction of homogenates was increased 35 to 50%. The effects of epinephrine and ACTH were concentration dependent and maximal increases were produced with concentrations similar to those that maximally stimulate lipolysis. Theophylline (0.5 mM) similarly increased phosphodiesterase activity but did not enhance the effects of maximally effective concentrations of the hormones. The changes in phosphodiesterase activity following addition of ACTH or theophylline paralleled changes in cell cyclic AMP content; both reached a maximum within 5 min and then declined, approaching basal levels after 20 or 30 min. The increased phosphodiesterase activity in cells incubated for 5 min with epinephrine reverted to basal levels within 2.5 min after the addition of propranolol. Our data are consistent with the view that there is a component of the fat-cell phosphodiesterase, perhaps localized in the plasma membrane, whose activity can be acutely modified by the concentration of its substrate, cyclic AMP.

As previously reported (
J. Biol. Chem.
248
, 7164-7170, 1973), exposure of fat cells to insulin increases the activity of a low
K
m
phosphodiesterase also localized in the 100,000 ×
g
sediment fraction of fat cell homogenates. In the presence of insulin, however, phosphodiesterase remained elevated for at least 40 min and there was no significant change in fat-cell cyclic AMP content. When phosphodiesterase activity was elevated and cyclic AMP content maintained at a high level by incubation of cells with ACTH plus theophylline, insulin produced a further increase in enzyme activity. Whether or not insulin and ACTH (or epinephrine or theophylline) affect the same phosphodiesterase, there seems little doubt that the underlying mechanisms are different.
The Effect of Erythropoietin on Colonial Growth of Erythroid Precursor Cells
In Vitro
Authors: Cooper Marvin C. , Levy Joseph , Cantor Linda N. , Marks Paul A. , Rifkind Richard A.
Published: May 2006

A method is described for the colonial growth, in semi-solid medium, of erythropoietin-responsive erythroid cell precursors. The erythroid cell precursors were isolated by immune hemolysis from fetal mouse liver. Both the number of precursor cells triggered to proliferate and differentiate, and the size of the erythropoietic colonies formed, are directly dependent upon the concentration of erythropoietin included in the culture.