bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-Fertilization and Genetic Population Structure in a Colonizing Land Snail
Authors: Selander Robert K. , Kaufman Donald W.
Published: May 2006

The pulmonate land snail
Rumina decollata
in its native Mediterranean range is a complex of monogenic or weakly polygenic strains generated by a breeding system of facultative self-fertilization. One strain colonized North America and now occupies much of the southern United States and northern Mexico. No genetic variation within or among populations in the United States was detected in an electrophoretic analysis of proteins encoded by 25 loci. These findings emphasize the potential for adaptive convergence in the genetic systems of hermaphroditic animals and plants.
Proton Magnetic Resonance Study of Peptide Conformation: Effect of Trifluoroethanol on Oxytocin and 8-Lysine-Vasopressin
Authors: Walter Roderich , Glickson J. D.
Published: May 2006

The usefulness of 2,2,2-trifluoroethanol titration as a means of distinguishing between intramolecular peptide-peptide hydrogen bonding on the one hand and intermolecular peptide-peptide and peptide-solvent hydrogen bonding on the other has been investigated with neurohypophyseal hormones, and the results have been compared with those of other methods. The chemical shifts (220 MHz) of the resonances of amide N
H
and aromatic C
H
protons of oxytocin, lysine vasopressin, deamino-lysine vasopressin, and deamino-8-tosyllysine vasopressin were monitored as the solvent composition was progressively varied from 100% dimethylsulfoxide to 100% 2,2,2-trifluoroethanol. The overall backbone conformation of oxytocin appears to be retained, and possibly somewhat stabilized, during the solvent transition, while the backbone, particularly the acyclic component, of lysine vasopressin and its analogs is subject to solvent-induced perturbation.
Membrane Sealing in Frog Skeletal-Muscle Fibers
Authors: De Mello W. C.
Published: May 2006

Self-sealing, not found in frog skeletal muscle fibers immersed in Ringer's solution, can be induced by solutions rich in calcium ion. Strontium replaced calcium on the sealing process, but magnesium did not. The sealing accomplished in high-calcium media was preserved in those fibers reimmersed in normal Ringer's solution. Measurements of the rate of sealing at different temperatures indicated that self-sealing induced by calcium has a high activation energy. Phospholipase C, an enzyme that hydrolyzes membrane phospholipids, produced a marked depression on the rate of sealing. Trypsin or chymotrypsin had no influence on the sealing process.
Subunits of Human Chorionic Gonadotropin: Unbalanced Synthesis and Secretion by Clonal Cell Strains Derived from a Bronchogenic Carcinoma
Authors: Tashjian Armen H. , Weintraub Bruce D. , Barowsky Norma J. , Rabson Alan S. , Rosen Saul W.
Published: May 2006

Three clones of ectopic hormone-producing cells from a single human neoplasm (bronchogenic carcinoma) show different rates of synthesis and secretion of chorionic gonadotropin and its alpha and beta subunits. For each clone, the amount of one or the other subunit always exceeded that of the complete hormone molecule. These findings may be analogous to unbalanced immunoglobulin chain synthesis in certain forms of myeloma.
Carcinogen-Induced Chromosomal Breakage Decreased by Antioxidants
Authors: Shamberger Raymond J. , Baughman Frances F. , Kalchert Shelley L. , Willis Charles E. , Hoffman George C.
Published: May 2006

Blood leukocyte cultures were incubated with antioxidants and the carcinogens sodium cyclamate and 7,12-dimethylbenz(α)anthracene in different combinations. There were 17.4% more chromosomal breaks in the group of cells treated with dimethylbenzanthracene only than in the untreated controls. The reductions in chromosomal breaks by the antioxidants were as follows: ascorbic acid, 31.7%; butylated hydroxytoluene, 63.8%; Na
2
SeO
3
, 42.0%; and
dl
-α-tocopherol, 63.2%. Multiple chromosomal breaks were distributed equally throughout the experimental groups. Sodium cyclamate had only slightly more chromosomal breaks than the controls (11.6 compared to 10.9%). In the cyclamate groups treated with Na
2
SeO
3
, 11.2% of chromosomes were broken. More acrocentric-type chromosomal breaks (21.7%) were seen in the untreated cells than the cells treated with cyclamate (3.4%) or dimethylbenzanthracene alone (4.8%). The carcinogen-treated groups had a higher percentage of meta breaks than the untreated controls.
Biosynthesis of Reticulocyte Membrane Proteins by Membrane-Free Polyribosomes
Authors: Lodish Harvey F.
Published: May 2006

Intact rabbit reticulocyte cells synthesize two predominant species of membrane polypeptides; at least 10 reticulocyte membrane polypeptide species are not produced by the cells. Cell-free extracts of reticulocytes, free of any membranes or membrane-bound polyribosomes, synthesize large amounts of these two membrane polypeptides; one of these polypeptides appears to be modified, probably by loss of 20-40 amino acids, after it is incorporated into the membrane. Deprivation of hemin results in inhibition of synthesis by lysates of membrane proteins, globin, and all other cytoplasmic proteins.
Control of Chondrogenic Expression in Mesodermal Cells of Embryonic Chick Limb
Authors: Caplan Arnold I. , Stoolmiller Allen C.
Published: May 2006

Chick-limb mesodermal cells have been maintained in tissue culture under conditions that permit development of muscle and cartilage. 3-Acetylpyridine, a nicotinamide-antagonized muscle teratogen, potentiates chondrogenic expression in cell cultures, as evidenced by histological and biochemical criteria, including the production of chondromucoprotein. Xylosyltransferase and
N
-acetylgalactosaminyltransferase are two enzymes required for chondromucoprotein synthesis; the specific activities of these enzymes were measured in differentiating mesodermal cells cultured for various periods of time in the presence and absence of 3-acetylpyridine and in intact limb tissue. The ratios of specific enzyme activities were nearly the same in both cultured cells and limb tissue, although the levels of both transferases increased severalfold during chondrogenic expression by mesodermal cells in culture. 3-Acetylpyridine causes the specific activities of xylosyl- and
N
-acetylgalactosaminyltransferases to increase 10- and 2-fold, respectively, above those of untreated cultures. Compared to the ratio of transferase activities in limb tissue and differentiating cell cultures, 3-acetylpyridine appears to increase the activity of xylosyltransferase, the initiator of chondroitin sulfate chain synthesis, more than does
N
-acetylgalactosaminyltransferase; this finding implies that the synthesis of these two enzymes may be separately regulated.
Role of an Electrical Potential in the Coupling of Metabolic Energy to Active Transport by Membrane Vesicles of
Escherichia coli
Authors: Hirata Hajime , Altendorf Karlheinz , Harold Franklin M.
Published: May 2006

Membrane vesicles from
E. coli
can oxidize D-lactate and other substrates and couple respiration to the active transport of sugars and amino acids. The present experiments bear on the nature of the link between respiration and transport.

Respiring vesicles were found to accumulate dibenzyldimethylammonium ion, a synthetic lipid-soluble cation that serves as an indicator of an electrical potential. The results suggest that oxidation of D-lactate generates a membrane potential, vesicle interior negative, of the order of -100 mV. In vesicles lacking substrate, an electrical potential was created by induction of electrogenic efflux of K
+
with the aid of the K
+
ionophores, valinomycin and monactin. These conditions induced transient accumulation by the vesicles of [
14
C]proline and other metabolites. Experiments with inhibitors and ionophores indicate that neither ATP nor the respiratory chain is involved; the electrical potential generated by K
+
efflux is coupled directly to the transport systems. The results verify two predictions derived from Mitchell's chemiosmotic hypothesis: respiring vesicles generate an electrical potential of the proper polarity and magnitude; and a membrane potential is in itself sufficient to drive the active transport of amino acids and other metabolites.
Lanthanide Ion-Induced Isotropic Shifts and Broadening for Nuclear Magnetic Resonance Structural Analysis of Model Membranes
Authors: Andrews S. Brian , Faller J. W. , Gilliam James M. , Barrnett Russell J.
Published: May 2006

The effects of a series of aquated lanthanide ions on the nuclear magnetic resonance spectrum of phospholipid bilayer suspensions are reported. The ability of these ions to provide a spectral distinction between morphologically exterior resonances and their interior counterparts was confirmed. Measurements of the relative shifting and broadening capabilities of these ions are reported, and their correlation with solid-state magnetic susceptibility anisotropies is shown to implicate a dipolar (pseudocontact) mechanism as the source of this effect. The potential for the use of dipolar shifts as structural probes is discussed and an alternative method using dipolar shifting and broadening reagents simultaneously is presented.
Rates of Induction of Specific Translatable Messenger RNAs for Ovalbumin and Avidin by Steroid Hormones
Authors: Chan Lawrence , Means Anthony R. , O'Malley Bert W.
Published: May 2006

In the chick oviduct, injections of estrogen and progesterone induce synthesis of the specific proteins ovalbumin and avidin, respectively. We have studied the rate of induction of the specific messenger RNA molecules for these proteins after a single injection of estrogen or progesterone. The mRNAs were extracted, partially purified, and quantified
in vitro
in a heterologous protein-synthesizing system. Single injections of estrogen in chicks previously withdrawn from all steroid hormones for 2 weeks led to rapid increases in ovalbumin mRNA with 3 hr, which coincided with increases in the rate of ovalbumin synthesis. Maximal ovalbumin mRNA activity occurred by 18-20 hr. The half-life of the mRNA was estimated to be 8-10 hr and corresponded to the half-life for cessation of intracellular ovalbumin synthesis after a single injection of an estrogen. Similarly, after an injection of progesterone into chicks first treated with estrogen, appearance of avidin mRNA preceded demonstrable accumulation of this specific protein in oviduct cells. The mRNA for avidin was first apparent at 6 hr, and reached maximal concentrations between 18 and 24 hr after injection. These data confirm that both estrogen and progesterone act on oviduct to induce rapid accumulation of specific mRNAs before and coincident with the appearance of the cell-specific induced proteins. The overall results of these experiments are compatible with the hypothesis that the production of mRNA is a rate-limiting step in the steroid hormone-mediated induction of protein synthesis.
Collagen and Procollagen Production by a Clonal Line of Schwann Cells
Authors: Church R. L. , Tanzer M. L. , Pfeiffer S. E.
Published: May 2006

A well-characterized line of rat Schwann cells has been examined for its ability to produce collagen. About 14% of the [
3
H]proline in the proteins that were secreted into the culture medium by the cells was hydroxylated, while only 1% of the labeled proteins in the cell layer contained [
3
H]hydroxyproline. Three sizes of procollagen polypeptides, of molecular weights about 105,000, 120,000, and 155,000, were present in the medium, as well as tropocollagen molecules that contained the usual α1 and α2 chains. Subsequently, the Schwann cells ceased producing the smaller collagenous polypeptides, although the total [
3
H]hydroxyproline content of the medium was unchanged. The [
3
H]hydroxyproline was almost entirely accounted for by the polypeptide of 155,000 daltons; this peptide was rapidly digested by collagenase or pepsin or chymotrypsin. The destruction by pepsin and chymotrypsin indicates that the large polypeptide, in contrast to procollagen and tropocollagen, is not in the collagenous (helical) conformation. Possibly, this substance is a very early form of procollagen that does not fold into the collagen conformation. The data show that cells of neuroectodermal origin can synthesize collagen, and also suggest that Schwann cells may be responsible for a large proportion of the collagen seen in peripheral neurinomas
in vivo
.
Heat Exchnage in the Black Skipjack, and the Blood-Gas Relationship of Warm-Bodied Fishes
Authors: Graham Jeffrey B.
Published: May 2006

The black skipjack,
Euthynnus lineatus,
uses a centrally located vascular heat exchanger to maintain core body temperatures warmer than ambient sea water. The heat exchanger is composed of the dorsal aorta, the posterior cardinal vein, and a large vertical rete. The dorsal aorta is embedded in the posterior cardinal vein and is completely bathed in venous blood. Skipjack hemoglobin appears similar to that of the bluefin tuna in that oxygen capacity is unaffected by changing temperature. Temperature-insensitive hemoglobin may function in warm-bodied fishes to prevent the premature dissociation of oxygen from hemoglobin as blood is warmed en route to the muscles.
Optimality of Profit-Including Prices Under Ideal Planning
Authors: Samuelson Paul A.
Published: May 2006

Although prices calculated by a constant percentage markup on all costs (nonlabor as well as direct-labor) are usually admitted to be more realistic for a competitive capitalistic model, the view is often expressed that, for optimal planning purposes, the “values” model of Marx's
Capital
, Volume I, is to be preferred. It is shown here that an optimal-control model that maximizes discounted social utility of consumption per capita and that ultimately approaches a steady state must ultimately have optimal pricing that involves equal rates of steady-state profit in all industries; and such optimal pricing will necessarily deviate from Marx's model of equal rates of surplus value (markups on direct-labor only) in all industries.
Purification and Properties of the γ-Protein Specified by Bacteriophage λ: An Inhibitor of the Host RecBC Recombination Enzyme
Authors: Sakaki Yoshiyuki , Karu Alexander E. , Linn Stuart , Echols Harrison
Published: May 2006

Previous experiments have indicated that the
gam
gene of bacteriophage λ is responsible for an inhibition of the RecBC DNase—an enzyme that is essential for the major host pathway of genetic recombination. We report here experiments that define the inhibitor as the protein product of the
gam
gene (“γ-protein”) and that characterize the inhibition reaction with highly purified preparations of γ-protein and RecBC DNase. Genetic characterization was performed with partially purified fractions prepared from cells infected with various λ mutants. An activity that inhibits RecBC DNase was absent in extracts prepared after infection by phage that carry nonsense or deletion mutations in the
gam
gene; this activity was highly thermolabile in an extract prepared after infection by phage that carry a temperature-sensitive mutation in the
gam
gene. For biochemical characterization, the γ-protein has been purified more than 800-fold. This highly purified preparation inhibited all of the known catalytic activities associated with the RecBC enzyme, but exhibited no detectable DNase or ATPase activities by itself. These findings are discussed in terms of their implications for regulation of genetic recombination and bacteriophage λ development.
Dopamine-β-Hydroxylase: A Tetrameric Glycoprotein
Authors: Wallace Ellen F. , Krantz Mark J. , Lovenberg Walter
Published: May 2006

Dopamine-β-hydroxylase (EC 1.14.2.1) has been isolated as a pure protein from bovine-adrenal glands. Although the molecular weight of the native protein is well established (290,000), sodium dodecyl sulfate-gel electrophoresis under dissociating conditions gave a single band with a molecular weight of about 75,000. The enzyme contains about 4% carbohydrate, which consists of residues of mannose, glucosamine, galactose, glucose, fucose, and sialic acid. The pure enzyme also contains about 4 atoms of copper per molecule. It is concluded that dopamine-β-hydroxylase is a tetrameric glycoprotein.
Presynaptic Inhibition at Inhibitory Nerve Terminals. A New Synapse in the Crayfish Stretch Receptor
Authors: Nakajima Yasuko , Tisdale Ann D. , Henkart Maryanna P.
Published: May 2006

Previous physiological evidence has shown that the receptor neuron of the slowly adapting stretch receptor organ of crayfish receives synapses from three inhibitory axons, while the receptor muscle is innervated by both excitatory and inhibitory axons. Fine structural studies have indicated that after certain preparative procedures synaptic vesicles in the inhibitory terminals on dendrites of the receptor neuron appear small and elongate, while those in the excitatory terminals on the receptor muscle are round and larger. This study describes a new synapse between two inhibitory nerve endings on the receptor neuron. One axon, containing small elongate vesicles, forms a presynaptic chemical contact with another morphologically similar axon that, itself, presumably releases inhibitory transmitter onto the receptor neuron. A second type of presynaptic axo-axonic synapse, analogous to one previously described in another crustacean muscle, was also found between presumed inhibitory and excitatory nerve terminals on the receptor muscle. Thus, the stretch receptor has a relatively complex organization with a morphological basis for two types of presynaptic inhibition: one on excitatory terminals and the other on inhibitory terminals.
Synthesis and Aminoacylation of 3′-Amino-3′-deoxy Transfer RNA and Its Activity in Ribosomal Protein Synthesis
Authors: Fraser Thomas H. , Rich Alexander
Published: May 2006

3′-amino-3′-deoxy adenosine was enzymatically converted into 3′-amino-3′-deoxy ATP. This ATP analogue was incorporated into the 3′-terminal adenosine position of
Escherichia coli
tRNA. The modified tRNA was aminoacylated with phenylalanine by use of
E. coli
phenylalanyl tRNA synthetase. The phenylalanine was attached to the 3′-amino group of the tRNA, as shown by its high resistance to base-catalyzed hydrolysis in contrast with the normal lability of phenylalanyl-tRNA. Aminoacyl tRNA synthetases charge the 3′-amino-3′-deoxy tRNA with kinetics that are similar to those of the charging reaction in which normal tRNA is the substrate. When phenylalanyl-3′-amino-3′-deoxy tRNA is used in a protein-synthesizing system directed by poly(U)
in vitro
, this molecule is capable of receiving an acetyl-phenylalanine from the donor site of the ribosome. However, the ribosome is unable to cleave the amide bond connecting phenylalanine to the tRNA molecule; hence, the phenylalanyl-3′-amino-3′-deoxy tRNA has acceptor but not donor activity in protein synthesis. Failure of the ribosome to cleave the amide bond may be due to its greater stability relative to the normal ester bond. However, it may also be due to the fact that the isomerization of the peptidyl chain between the 2′ and 3′ positions of adenosine is prevented due to the amide bond at the 3′ position, and cleavage may normally occur with the peptidyl chain on the 2′ position of adenosine.
Electrostatic Effects on Lipid Phase Transitions: Membrane Structure and Ionic Environment
Authors: Träuble Hermann , Eibl Hansjörg
Published: May 2006

Ordered → fluid phase transitions in bilayers of charged lipids are accompanied by a decrease in electrostatic free energy mainly as a result of bilayer expansion. For uniform charge distribution the Gouy-Chapman theory of the electrical double layer predicts a decrease of the transition temperature with increasing charge density. We studied the effects of pH and mono- and divalent cations on the phase transition of lecithin, cephalin, phosphatidylserine, and phosphatidic acid bilayers. Phosphatidic acid with two ionizable protons was selected for a systematic investigation. A change in pH from 7 to 9 increases the charge per polar group from one to two elementary charges. This lowers the transition temperature by about 20°C in agreement with the theory. In this pH region rather small changes in pH suffice to induce the phase transition at constant temperature. Divalent cations (Mg
++
and Ca
++
) increase the transition temperature by charge neutralization and thus can be used to induce the fluid → ordered transition at constant temperature. In contrast, monovalent cations (Li
+
, Na
+
, K
+
) lower the transition temperature, or fluidize the bilayer structure at a given temperature. Rather small changes in ionic environment can induce gross alterations in bilayer structure; divalent and monovalent cations have antagonistic effects. This result parallels current theories on nerve excitation and sensory transduction where cation-induced structural changes in biomembranes are invoked.
Assignment of the Gene for Adenine Phosphoribosyltransferase to Human Chromosome 16 by Mouse-Human Somatic Cell Hybridization
Authors: Tischfield Jay A. , Ruddle Frank H.
Published: May 2006

A series of mouse-human hybrids was prepared from mouse cells deficient in adenine phosphoribosyltransferase (EC 2.4.2.7) and normal human cells. The hybrids were made in medium containing adenine and alanosine, an antimetabolite known to inhibit
de novo
adenylic acid biosynthesis. The mouse cells, unable to utilize exogenous adenine, were killed in this medium, but the hybrids proliferated as a consequence of their retaining the human
aprt
gene. The hybrids were then exposed to the adenine analogs 2,6-diaminopurine and 2-fluoroadenine to select for cells that had lost this gene. Before exposure to the adenine analogs, the expression of human adenine phosphoribosyltransferase by the hybrids was strongly associated only with the presence of human chromosome 16, and afterwards this was the only human chromosome consistently lost. This observation suggests that the human
aprt
gene can be assigned to chromosome 16.
A Protonmotive Force Drives ATP Synthesis in Bacteria
Authors: Maloney Peter C. , Kashket E. R. , Wilson T. Hastings
Published: May 2006

When cells of
Streptococcus lactis
or
Escherichia coli
were suspended in a potassium-free medium, a membrane potential (negative inside) could be artificially generated by the addition of the potassium ionophore, valinomycin. In response to this inward directed protonmotive force, ATP synthesis catalyzed by the membrane-bound ATPase (EC 3.6.1.3) was observed. The formation of ATP was not found in
S. lactis
that had been treated with the ATPase inhibitor,
N,N′
-dicyclohexylcarbodiimide, nor was it observed in a mutant of
E. coli
lacking the ATPase. Inhibition of ATP synthesis in
S. lactis
was also observed when the membrane potential was reduced by the presence of external potassium, or when cells were first incubated with the proton conductor, carbonylcyanidefluoromethoxyphenylhydrazone. These results are in agreement with predictions made by the chemiosmotic hypothesis of Mitchell.
Differences Between Laboratory Strains of Epstein-Barr Virus Based on Immortalization, Abortive Infection, and Interference
Authors: Miller George , Robinson James , Heston Lee , Lipman Muriel
Published: May 2006

Biologic activities of extracellular Epstein-Barr virus (EB virus) from two laboratory strains, namely, P
3
J-HR-1 (P-H) from Burkitt lymphoma and B95-8 (B95) from infectious mononucleosis, were compared. Virus stocks from both sources contained approximately the same number of virions. Virus from the P-H line induced “early antigen” in six nonproducer EB virus genome carrier cell lines; virus from B95 did not induce “early antigen.” Extracellular virus from B95 regularly caused lymphocytes from human umbilical cords to form continuous lines (immortalization); P-H virus did not cause primary cultures of human lymphocytes to grow continuously. B95 virus stimulated DNA synthesis as determined by rate of incorporation of [
3
H]thymidine into acid-insoluble material; P-H virus did not stimulate DNA synthesis. Pretreatment of lymphocytes with undiluted P-H virus inhibited immortalization and stimulation of DNA synthesis by B95 virus. The inhibitory properties of the P-H virus were sedimented at 100,000 ×
g
and inactivated by heat and UV irradiation; interference by the P-H virus was neutralized by human serum with antibody to EB virus and not by antibody-negative human serum.

The hypothesis most consistent with these results is that the P-H virus is defective in gene(s) needed for initiation of immortalization. We speculate that the absence of this gene allows early antigen to be expressed upon super-infection of nonproducer cell lines. The availability of two laboratory strains of EB virus which differ in biologic behavior provides starting material for analysis of the mechanism of lymphocyte immortalization by EB virus and of virus structural differences which affect immortalization.
Evidence for Mitotic Recombination in the Cellular Slime Mold
Dictyostelium discoideum
Authors: Katz E. R. , Kao Vivien
Published: May 2006

A mutant resistant to methanol was isolated and the mutation was shown to be located on the same linkage group with two other previously identified markers, white spore color and temperature sensitivity. In the course of analyzing methanol-resistant haploid segregants, four classes of methanol-resistant diploids were found. It is proposed that these represent mitotic recombinants, and a map of the chromosome is suggested. Segregation analysis of the diploids shows the genotypes of the diploids to be in perfect agreement with the mitotic recombination model.
Threshold Excitations, Relaxation Oscillations, and Effect of Noise in an Enzyme Reaction
Authors: Hahn H.-S. , Nitzan A. , Ortoleva P. , Ross J.
Published: May 2006

We study a deprotonation reaction by an enzyme with activity dependent on pH. The rate and transport equations are simplified with a number of assumptions, are analyzed according to the presence of different time scales, and are solved numerically to show relaxation oscillation and threshold excitation, for different choices of parameters. The imposition of fluctuations (noise) on the deterministic equations for threshold excitation conditions leads to random occurrence of an excitation and return to steady state at low noise level and to large, random variations in concentrations at high noise level. At intermediate noise levels (of the order of the threshold excitation), however, we find quasi-periodic concentration oscillations. Thus, critical values of external constraints necessary for oscillations are altered by the presence of noise.
Conformation of Fibrinogen: Calorimetric Evidence for a Three-Nodular Structure
Authors: Donovan John W. , Mihalyi Elemer
Published: May 2006

Solutions of fibrinogen show two endothermal (denaturing) transitions, at 61° and at 100°, when heated in a differential scanning calorimeter. Similar transitions are observed for a mixture of the fragments D and E obtained by limited proteolysis of fibrinogen. Isolated fragment E shows only a single transition, at 97°. The independent thermal denaturation of these portions of fibrinogen supports the three-nodular model proposed for fibrinogen. The D and E subunits retain their characteristic denaturation behavior when fibrinogen is clotted by thrombin addition, but over a period of about one hundred times the clotting time, the denaturation temperature of the D subunit increases by 9° and its enthalpy of denaturation by one-third. Since this change takes place in the absence of Factor XIII activity, and its rate is proportional to thrombin concentration, it is presumed to be mediated by a proteolytic cleavage distinct from those which liberate the A and B fibrinopeptides.
The Nutritional Teamwork Approach: Prevention and Regression of Cataracts in Rats
Authors: Heffley James D. , Williams Roger J.
Published: May 2006

We have taken advantage of a newly assimilated principle in nutrition: no nutrient by itself should be expected to prevent or cure any disease; nutrients as such always work cooperatively in metabolism as a team.

By feeding galactose-containing diets to young rats, cataracts are regularly produced. When, however, we furnished galactose-fed animals with what may be considered a well balanced, full team of nutrients, cataract prevention was accomplished. On four galactose-containing diets supplied with a full team of nutrients, not a single cataract developed in 24 rats (48 eyes). On four diets using the same dietary galactose challenge, accompanied with inadequate nutritional teams, 47 out of 48 eyes developed cataracts. Diets of intermediate quality induced the development of intermediate numbers of cataracts. Cataracts once formed were regressed slowly and incompletely by shifting the animals to a diet similar to that which had previously been found to protect against cataract formation.

The significance of these findings for nutritional research and for attacks on the problems of human cataracts and other ailments is discussed.
The Compression Hypothesis and Temporal Resource Partitioning
Authors: Schoener Thomas W.
Published: May 2006

Contingency models of feeding compare the energy per unit time gained from utilizing a resource unit of a particular kind (food types, habitat patches, time periods) against that energy/time expected if the unit is skipped. Optimally, an animal should reject the particular unit if and only if the former energy/time is less than the latter. Consequently, food or habitat types should be excluded if the prospect of finding and consuming better types is sufficiently high. In contrast, feeding periods should be skipped only if it is less
costly
to wait than to feed.

In situations of high food abundance, contingency models imply that animals should be maximally specialized with respect to food or habitat type, but maximally generalized with respect to time period. As food decreases in abundance, food and habitat types should be added to the diet or itinerary, but time periods should be omitted from feeding activity. In contrast, animals with fixed caloric intake should broaden diet, habitat, and feeding times as abundance decreases.

According to contingency models, competitors cannot cause item kinds to be dropped from the diet, but because they can affect the values of patches once found, can cause habitat kinds to be dropped from the itinerary. Competitors also reduct the value of feeding during particular time periods, but ordinarily fairly severe depletion must occur before it is optimal to feed no longer in a period frequented by competitors.

These arguments imply that temporal resource partitioning on a diel basis should be relatively rare. In fact, specialization according to feeding period should differentially occur in animals of limited abilities to use or process available food, whereas that need not be the case for food-type or habitat specialization. It should also occur in animals sensitive to and found in variable climates.
The Identification of Collagen Messenger RNA
Authors: Boedtker Helga , Crkvenjakov Radomir B. , Last Jerold A. , Doty Paul
Published: May 2006

RNA isolated from calvaria of 16- to 18- day-old chick embryos, assayed in rabbit reticulocyte lysates, programs the synthesis of a collagenase-sensitive protein with the molecular weight of collagen pro-α-chains. When RNA labeled with [
3
H]uridine for 2 hr and chased for 1 or 2 hr was electrophoresed on aqueous polyacrylamide gels, most of the radioactivity not in 28S or 18S rRNA migrated with an apparent molecular weight of about 1,800,000. After oligo(dT)-cellulose chromotography and analysis in 99% formamide gels, this nonribosomal, rapidly labeled calvaria RNA species migrates at 28S-30S and thus has a molecular weight of at least 1,600,000.

Both the ability to program the synthesis of collagenase-sensitive protein in reticulocyte lysates and the presence of a single prominent rapidly labeled 30S peak in acrylamide gels strongly support the deduction that there is only one major mRNA species in calvaria and that this species is collagen messenger RNA.
Stereospecific Binding of Propranolol and Catecholamines to the β-Adrenergic Receptor
Authors: Atlas Daphne , Steer Michael L. , Levitzki Alexander
Published: May 2006

The stereospecificity of the β-adrenergic receptor of turkey erythrocyte ghosts was studied. Binding of the specific β-adrenergic antagonist, propranolol, was found to occur exclusively with the
l
-stereoisomer. The stereospecificity of catecholamine binding was determined by assaying the ability of the catecholamines to displace [
3
H]propranolol. Binding of the catecholamines was also found to be stereospecific for the
l
-stereoisomers. Furthermore, the
d
-stereoisomers do not compete with the
l
form for binding. Using this displacement technique, we were able to calculate the dissociation constants for
l
-epinephrine,
l
-norepinephrine, and
l
-isoproterenol from the β-receptor and compare these values to the
apparent
dissociation constants obtained from the direct activation of adenylate cyclase (EC 4.6.1.1) by these catecholamines.
Evidence for Crossing-Over Between Avian Tumor Viruses Based on Analysis of Viral RNAs
Authors: Beemon Karen , Duesberg Peter , Vogt Peter
Published: May 2006

The RNAs of several avian tumor virus recombinants that had inherited their focus-forming ability from a sarcoma virus and their host range marker from a leukosis virus were investigated. Electrophoretic analyses showed that the cloned sarcoma virus recombinants contained only size class
a
RNA, although they had acquired a marker that resided on class
b
RNA in the leukosis virus parent. Class
a
RNA of different recombinant clones, derived from the same pair of parental viruses and selected for the same biological markers, differed slightly in electrophoretic mobility from each other and from the parental sarcoma virus. They were also found to have different fingerprints of RNase T1-resistant oligonucleotides.

The average complexity of the 60-70S RNA prepared from Prague Rous sarcoma virus of subgroup B was estimated to be 3.5 × 10
6
daltons from the size of 20 RNase T1-resistant oligonucleotides, which represented 3.9% of the RNA and that of a recombinant to be 3.3 × 10
6
daltons from 23 oligonucleotides, which represented 4.7% of the RNA. This result suggests that the genome of wild-type and of recombinant RNA tumor viruses is polyploid.

The sum of these observations led us to propose that recombination among avian tumor viruses occurred by crossing-over between homologous pieces of nucleic acid.
Ovalbumin Messenger RNA: Evidence That the Initial Product of Transcription Is the Same Size as Polysomal Ovalbumin Messenger
Authors: McKnight G. Stanley , Schimke Robert T.
Published: May 2006

The messenger RNA for ovalbumin, the major secretory protein of the chick oviduct, appears not to be made as a high-molecular-weight precursor when artifacts due to aggregation are eliminated. No ovalbumin messenger RNA sequences that will hybridize to complementary DNA made against ovalbumin mRNA are found in concentrated samples of hen oviduct RNA larger than 28 S. The sensitivity of the hybridization assay is sufficient to detect less than one molecule of ovalbumin mRNA precursor per tubular gland cell. Newly synthesized ovalbumin messenger RNA isolated from immature chicks stimulated briefly by estrogen is the same size as that found in hen polyribosomes. We conclude that ovalbumin messenger RNA does not undergo any significant change in molecular weight from its initial transcription to its incorporation into polyribosomes.
Tunable Laser Resonance Raman Spectroscopy of Bacteriorhodopsin
Authors: Lewis Aaron , Spoonhower John , Bogomolni Roberto A. , Lozier Richard H. , Stoeckenius Walther
Published: May 2006

Bacteriorhodopsin is a rhodopsin-like protein found in the cell membrane of
Halobacterium halobium
. It shows an absorption maximum at 570 nm and, in the light, undergoes cyclic spectral changes which include a relatively long-lived complex absorbing maximally at 412 nm. Excitation profiles have been obtained with several laser frequencies for two vibrations in the resonance Raman spectrum of bacteriorhodopsin. The results show that the Schiff base retinylidene lysine linkage is protonated in the 570 nm complex and that in the 412 nm complex it is unprotonated. The 412 nm complex must be present at appreciable concentrations when bacteriorhodopsin is exposed to high-energy argon ion laser light of the Raman spectrophotometer at room temperature. We conclude that the observed C=N stretch at 1622 cm
-1
in the room temperature spectra, which in an earlier study by Mendelsohn was interpreted as evidence for an unprotonated linkage in bacteriorhodopsin, results from the presence of the 412 nm complex.
Non-specific DNA Binding of Genome Regulating Proteins as a Biological Control Mechanism: 1. The
lac
Operon: Equilibrium Aspects
Authors: Hippel Peter H. Von , Revzin Arnold , Gross Carol A. , Wang Amy C.
Published: May 2006

The regulatory system of the lactose operon has been “modeled” by a set of mass action equations and conservation constraints which describe the system at equilibrium. A “base-set” of values of binding constants and total component concentrations has been assembled from the available experimental data, and the simultaneous equations solved by computer procedures, to yield equilibrium concentrations of all the relevant molecular species. Considering the operator-repressor-inducer system alone, it is shown that the
in vivo
basal and induced (derepressed) levels of
lac
enzyme synthesis in both wild-type and certain mutant
Escherichia coli
can be accounted for only if binding of repressor and repressor-inducer complexes to non-specific DNA sites is included in the calculations as an integral component of the ovrall control system. A similar approach was applied to the RNA polymerase-promoter system to show that sigma factor may modulate the general level of transcription in the cell by “inducing” polymerase off non-specific DNA binding sites, thus making it available to promoters. Competitive and non-competitive models for the interaction of repressor and polymerase at the
lac
operon can, in principle, be distinguished by these computational procedures, though data sufficient to permit unambiguous differentiation between the models are not available at this time. However, for any competitive binding model the results show that repression in the entire (operator-repressor-RNA polymerase-
lac
promoter) system can occur only because non-specific binding of the regulatory proteins reduces the concentration of free polymerase, relative to that of repressor, to appropriate levels.
Heterogeneity of Membrane Vesicles from
Escherichia coli
and Their Subfractionation with Antibody to ATPase
Authors: Hare James F. , Olden Kenneth , Kennedy Eugene P.
Published: May 2006

The energy-transducing, Mg-Ca activated ATPase (ATP phosphohydrolase, EC 3.6.1.3) of
E. coli
is located on the inner surface of the cytoplasmic membrane. Antibody to purified ATPase has now been used to demonstrate that membrane vesicles as ordinarily prepared by the lysozyme-EDTA method consist of two distinct populations. About half the vesicles are everted, and thus readily agglutinated by antibody to ATPase, while half are right-side out. NADH oxidase (reduced NAD:O
2
oxidoreductase EC 1.6.99.3) activity is associated almost entirely with everted vesicles, while the ability to concentrate proline is a property of the right-side out vesicles. The results explain the failure of previous workers to observe the energization of membrane vesicles by oxidation of NADH.
Kirromycin, an Inhibitor of Protein Biosynthesis that Acts on Elongation Factor Tu
Authors: Wolf Heinz , Chinali Gianni , Parmeggiani Andrea
Published: May 2006

Kirromycin, a new inhibitor of protein synthesis, is shown to interfere with the peptide transfer reaction by acting on elongation factor Tu (EF-Tu). All the reactions associated with this elongation factor are affected. Formation of the EF-Tu·GTP complex is strongly stimulated. Peptide bond formation is prevented only when Phe-tRNA
Phe
is bound enzymatically to ribosomes, presumably because GTP hydrolysis associated with enzymatic binding of Phe-tRNA
Phe
is not followed by release of EF-Tu·GDP from the ribosome. This antibiotic also enables EF-Tu to catalyze the binding of Phe-tRNA
Phe
to the poly(U)·ribosome complex even in the absence of GTP. EF-Tu activity in the GTPase reaction is dramatically affected by kirromycin: GTP hydrolysis, which normally requires ribosomes and aminoacyl-tRNA, takes place with the elongation factor alone. This GTPase shows the same
K
m
for GTP as the one dependent on Phe-tRNA
Phe
and ribosomes in the absence of the antibiotic. Ribosomes and Phe-tRNA
Phe
, but not tRNA
Phe
or Ac-Phe-tRNA
Phe
, stimulate the kirromycin-induced EF-Tu GTPase. These results indicate that the catalytic center of EF-Tu GTPase that is dependent upon aminoacyl-tRNA and ribosomes is primarily located on the elongation factor. In conclusion, kirromycin can substitute for GTP, aminoacyl-tRNA, or ribosomes in various reactions involving EF-Tu, apparently by affecting the allosteric controls between the sites on the EF-Tu molecule interacting with these components.
Synthesis and Processing of Nuclear Precursor-Messenger RNA in Avian Erythroblasts and HeLa Cells
Authors: Spohr Georges , Imaizumi Tereza , Scherrer Klaus
Published: May 2006

The kinetics of synthesis and turnover of animal cell nuclear precursor-mRNA fractions all of which, in the case of avian erythroblast RNA, are shown by specific complementary DNA hybridization to contain globin mRNA sequences, were analyzed by exponential polyacrylamide gel electrophoresis. Three metabolically distinct size-fractions were characterized: (
1
)
nascent
precursor-mRNA (apparent molecular weight 5 to 20 × 10
6
, approximate half-life 30 min), (
2
)
intermediate-size
precursor-mRNA (molecular weight 1 to 5 × 10
6
, approximate half-life 3 hr), (
3
)
small
precursor-mRNA (molecular weight 0.5 to 1.5 × 10
6
, half-life more than 15 hr). Nascent precursor-mRNA behaves kinetically as a precursor to the smaller precursor-mRNAs that accumulate in the nucleus, as well as to cytoplasmic mRNA; however, no stringent proof can be given that the two smaller nuclear precursor-mRNA fractions are
direct
physical precursors of functional mRNA. In terms of total mass, more precursor-mRNA accumulates in the nucleus than there is translated mRNA in the cytoplasm. Globin mRNA of final size (9 S) does not accumulate in the nuclei of avian erythroblasts.
Active Transport of Calcium in Inverted Membrane Vesicles of
Escherichia coli
Authors: Rosen Barry P. , McClees John S.
Published: May 2006

Accumulation of
45
Ca
++
was found to occur in membrane vesicles of
E. coli
prepared by lysis with a French pressure cell. The uptake occurs by active transport, requiring an energy source. Substrates of the electron transport chain, including D-lactate, reduced phenazine methosulfate, and NADH, stimulated accumulation, but this effect was blocked by the addition of cyanide. ATP could also stimulate accumulation, and this effect was blocked by dicyclohexylcarbodiimide. Uncouplers of oxidative phosphorylation inhibited the accumulation driven by either type of energy source.

Accumulation of calcium is rapid, reaching the steady-state plateau within 1 min. Addition of phosphate to the assay buffer results in a prolongation of the reaction, allowing for the time-dependent accumulation of calcium for as long as 30 min.

Vesicles prepared by lysis with a French pressure cell exhibit almost no ability to accumulate proline, while vesicles prepared by the method of Kaback transport proline but exhibit little energy-dependent transport of calcium. It is suggested that the accumulation of calcium in these vesicles, which are believed to be inverted, reflects a system that
in vivo
is responsible for the active extrusion of calcium from the cells.
Developing Social Indicators
Authors: Duncan Otis Dudley
Published: May 2006

Recent progress in developing social indicators is described in terms of six activities. In regard to social bookkeeping, we are expanding the number of domains covered by population surveys, and survey data are being more widely disseminated. In social accounting, demographic stock-flow schemes show promise of integrating systems of social statistics. Social science theories have provided models of achievement and other social processes. Social forecasting is potentially an important component of work on social indicators, but a new definition of the purpose of forecasting is needed. The practice of social reporting is best exemplified in the work of recent commissions. Social advising, while it draws upon social indicators, involves functions that cannot be performed by any system of indicators alone. The most worthy aspiration of the social indicators movement would be to contribute to the enlightenment of a changing society.
The Amino-Acid Sequence of the Amino-Terminal 37 Residues of Human Parathyroid Hormone
Authors: Niall H. D. , Sauer R. T. , Jacobs J. W. , Keutmann H. T. , Segre G. V. , O'Riordan J. L. H. , Aurbach G. D. , Potts J. T.
Published: May 2006

The sequence of the amino-terminal 37 residues of human parathyroid hormone has been established. The hormone used in these studies was isolated in highly purified form from parathyroid adenomata and was subjected to automated degradation in a Beckman sequencer. A high-sensitivity sequencing procedure employing
35
S-labeled phenylisothiocyanate of high specific activity as the coupling agent was used. The sequence obtained differs from that of bovine parathyroid hormone in three of the first 37 positions, and from that of porcine parathyroid hormone in two positions. A single human-specific residue was found (asparagine 16). The sequence obtained differs at three positions (22, 28, and 30) from the structure for human parathyroid hormone reported recently by Brewer
et al
. [(1972)
Proc. Nat. Acad. Sci. USA
69, 3585-3588] and synthesized by Andreatta
et al
. [(1973)
Helv. Chim. Acta
, 56, 470-473] We have carefully reviewed our data, reported here in detail, on the sequence positions in dispute. We must conclude, on the basis of all available data, that the structure that we propose is the correct structure. The objective resolution of these discrepancies in structural analysis through further chemical and immunochemical studies is important, since synthesis of human parathyroid hormone, in which there is widespread interest for physiological and clinical studies, must be based on the correct sequence of the human hormone if the peptide is to be genuinely useful.
Effects of Phagocytosis and Colchicine on the Distribution of Lectin-Binding Sites on Cell Surfaces
Authors: Oliver J. M. , Ukena T. E. , Berlin R. D.
Published: May 2006

The effect of phagocytosis on lectin binding to plasma membranes of polymorphonuclear leukocytes was examined. The specific activities of binding sites of concanavalin A and
Ricinus communis
agglutinin (defined as μg of lectin bound per 100 μg of membrane protein) were measured on isolated membranes; they decreased in parallel with phagocytosis. Our data suggest that this removal occurs by concentration of binding sites into internalized membrane. Colchicine and vinblastine, which did not inhibit phagocytosis, prevented the selective removal of lectin-binding sites from the surface. It was also shown that at 37° lectins induce their own internalization. This property was used to define operationally three classes of lectin receptors, one of which is most extensively removed from plasma membrane during phagocytosis. Based on other morphological studies in which it is shown that before phagocytosis the surface distribution of concanavalin-binding sites is random, it is inferred that phagocytosis alters surface topography by inducing the selective movement of binding sites into membrane undergoing internalization and that colchicine-sensitive proteins are essential for this imposed topographical reorganization.