bluuebunny/crossref_metadata_2025 huggingface dataset:
A Dynamic Stereochemical Reaction Mechanism for the ATP Synthesis Reaction of Mitochondrial Oxidative Phosphorylation
Authors: Korman Ephraim F. , McLick Jerome
Published: May 2006

A mechanism is presented for the ATP synthesis reaction of mitochondrial oxidative phosphorylation. This mechanism is a dynamic, stereospecific, microscopically reversible mechanism in which enzyme-bound substrates, ADP, and inorganic phosphate directly combine in a S
N
2 type of process which proceeds with retention of configuration at the phosphate phosphorus center. The mechanism involves unstable, pentacovalent trigonal bipyramidal reaction intermediates which are pseudorotationally related. The mechanism accounts for all of the observed net and equilibrium exchange reactions and their relative rates. All of the exchange reactions are directly referrable to the ATP synthesis mechanism, and are circumstantial traits of that mechanism.
Heme Biosynthesis in Intermittent Acute Porphyria: Decreased Hepatic Conversion of Porphobilinogen to Porphyrins and Increased Delta Aminolevulinic Acid Synthetase Activity
Authors: Strand L. James , Felsher Bertram F. , Redeker Allan G. , Marver Harvey S.
Published: May 2006

Hepatic conversion of porphobilinogen to porphyrins was less than 50% of control levels in human subjects with the genetic disease, intermittent acute porphyria. This relative block in heme biosynthesis may be relevant to a concomitant 6- to 10-fold elevation in δ-aminolevulinic acid synthetase activity, since this first and rate-controlling enzyme in the biosynthetic pathway is subject to negative feedback regulation by the end product, heme. A micro-radio-chemical assay of δ-aminolevulinic acid synthetase, and some of its applications, are described.
Structure and Function of Bacterial Ribosomes, XI. Dependence of 50S Ribosomal Assembly on Simultaneous Assembly of 30S Subunits
Authors: Nashimoto Hiroko , Nomura Masayasu
Published: May 2006

Some spectinomycin-resistant mutants of
Escherichia coli
are cold-sensitive. They are unable to assemble both 30S and 50S ribosomal subunits at low temperatures. They accumulate two kinds of incomplete particles, related to 30S and 50S subunits respectively. A single mutation, causing an alteration in a 30S ribosomal component, is responsible for these phenotypes. These results show that assembly of 50S subunits
in vivo
is dependent on simultaneous assembly of 30S subunits. On the other hand, the assembly of 30S subunits appears to be independent of 50S assembly.
Evidence for Transfer of Enzyme Product as the Basis of Metabolic Cooperation between Tissue Culture Fibroblasts of Lesch-Nyhan Disease and Normal Cells
Authors: Cox Rody P. , Krauss Marjorie R. , Balis M. Earl , Dancis Joseph
Published: May 2006

Tissue culture fibroblasts derived from patients with Lesch-Nyhan disease (congenital hyperuricosuria) have a reduced IMP:pyrophosphate phosphoribosyltransferase (EC 2.4.2.8) activity and therefore incorporate, as detected by radioautography, much smaller amounts of tritiated hypoxanthine or guanine into cell nuclei and cytoplasm than do normal cells. However, Lesch-Nyhan cells grown in close contact with normal fibroblasts incorporate these purines. This phenomenon, which requires cell to cell contact for correction of the mutant phenotype, has been called metabolic cooperation. After separation of Lesch-Nyhan cells from normal cells, there is a prompt reversion to the mutant phenotype although the transferase is stable under these conditions for many hours.

These results are most compatible with the transfer from normal to mutant fibroblasts of the product of the normal enzyme, a nucleotide or a nucleotide derivative, rather than the transfer of the transferase or informational macromolecules leading to the synthesis of the enzyme. Metabolic cooperation may provide a mechanism for maintaining normal cell function in the heterozygote
in vivo
. Evidence has been presented previously that selection of normal cells, presumably during embryogenesis, also provides a means for achieving normal function in the heterozygote.
Model for the Action of Hemoglobin
Authors: Saroff H. A.
Published: May 2006

A model is developed for hemoglobin which depends on six Bohr groups per tetramer of hemoglobin. These six groups are assumed to be located in six regions between the four subunits of hemoglobin. When the Bohr groups are assumed to be perturbed in an asymmetrical manner on binding oxygen, these groups then generate the cooperative interactions of hemoglobin. This approach makes it possible to explain oxygen binding, the Bohr effect, specific salt effects, and aggregation effects in a unified manner.
Mitotic Separation of Two Human X-Linked Genes in Man—Mouse Somatic Cell Hybrids
Authors: Miller O. J. , Cook P. R. , Khan P. Meera , Shin S. , Siniscalco M.
Published: May 2006

Six interspecific somatic hybrid cell lines were derived from a mouse line deficient in hypoxanthine: guanine phosphoribosyltransferase (HGPRT) and human diploid cells with normal enzyme activity. Human HGPRT was present in all six hybrids and the clones derived from them. However, in two of the six, and in some clones from another two, human glucose-6-phosphate dehydrogenase (G6PD) was absent. Since the structural loci for both these enzymes are X-linked in man, these findings suggest that these two loci have separated quite frequently through chromosome breakage and that they must be rather far apart on the X chromosome.
Epinephrine-Induced Vacuole Formation in Parotid Gland Cells and Its Independence of the Secretory Process
Authors: Batzri S. , Amsterdam A. , Selinger Z. , Ohad I. , Schramm M.
Published: May 2006

Catecholamines cause rapid release of K
+
and formation of vacuoles in acinar gland cells. A high K
+
concentration in the medium bathing parotid gland slices prevents vacuole formation by epinephrine and facilitates the secretion of most of the exportable amylase.
N
6
-monobutyryl 3′:5′-cyclic AMP does not cause K
+
release and vacuole formation although it efficiently induces amylase secretion. It is suggested that the secretory process is independent of vacuole formation.
Interconvertible Forms of
Escherichia coli
RNA Polymerase
Authors: Chelala César A. , Hirschbein Luisa , Torres Héctor N.
Published: May 2006

Escherichia coli
RNA polymerase exists in two different forms, one less active than the other under standard assay conditions. Conversion of the active to the inactive form requires ATP-Mg
++
. The reverse, inactive to active enzyme conversion, requires Mg
++
. Covalently bound adenylic acid residue(s) are contained in the inactive form.
A Model for Protein Synthesis Involving the Intermediate Formation of Peptidyl-5S RNA
Authors: Raacke Ilse Dorothea
Published: May 2006

A model for protein synthesis is proposed in which the donor for the peptide elongation reaction is peptidyl-5S RNA. Space-filling models show that peptide bond formation between peptidyl-5S RNA and aminoacyl-tRNA is eminently feasible from a stereochemical point of view. The peptide is transferred to 5S RNA, while at the same time the deacylated tRNA is exchanged by a new aminoacyl-tRNA acceptor. Two peptidyl transferases are required by the model, both of which have sites for binding the termini of both aminoacyl-tRNA and peptidyl-5S RNA. The model makes detailed predictions about the properties of the transferases.
Helper Activity of Human Leukemic Tissue Extracts for Leukemia Virus Expression in Mice
Authors: Steeves Richard A. , Fjelde Audrey , Mirand Edwin A.
Published: May 2006

Extracts of cultured human leukemic tissues increased the spleen focus-forming activity of Friend leukemia virus preparations in BALB/c and other partially resistant mice. Such mice carry the

Fv-1
b

gene, which inhibits the expression of helper virus indigenous to the Friend virus complex, and allows co-infecting leukemia viruses of mice, cats, or chickens to substitute for the inhibited helper virus and increase the expression of the spleen focus-forming virus. The helper activity of extracts from human leukemic tissues shared several important properties with that associated with known leukemogenic viruses of animals.
Mutant Strains of
Escherichia coli
K12 That Use D-Amino Acids
Authors: Kuhn Jonathan , Somerville Ronald L.
Published: May 2006

A series of mutations has been isolated that confer upon amino-acid auxotrophs of
Escherichia coli
K-12 the ability to grow when fed various D-amino acids. Several distinct systems, mediating cellular use of the D-isomers of leucine, histidine, phenylalanine, tyrosine, tryptophan, isoleucine, and valine, can be mutationally activated. Mutations leading to D-tryptophan use (
dadR
) all map near
purB
. They result in high activities of an enzyme that deaminates D-amino acids. Neither the enzymes of the tryptophan biosynthetic pathway nor tryptophanase (EC 4.2.1.e) are involved in D-tryptophan utilization.
Beta Thalassemia and Translation of Globin Messenger RNA
Authors: Nathan David G. , Lodish Harvey F. , Kan Yuet W. , Housman David
Published: May 2006

To define the quality and relative quantity of beta and alpha messenger RNA in human nonthalassemic and thalassemic reticulocytes, intact cells were incubated with [
35
S]methionine. The relative amounts of beta- and alpha-nascent chains on polysomes of different sizes were measured by tryptic digestion of pooled polysomes and by determination of the specific activities of beta and alpha peptides that contain methionine. Betachain synthesis predominated on heavy polysomes in nonthalassemic, as well as in thalassemic cells. Since beta chains in thalassemia are made on normal-size polyribosomes, we conclude that the defect in thalassemia does not involve reduction in the rate of initiation of translation due to the production of an abnormal beta message. Such would lead to beta-chain synthesis on very small polysomes. We therefore suggest that the decreased production of beta-globin chains results from a decreased amount of functional beta-globin messenger RNA.
The Order of the Antipode of Finite-dimensional Hopf Algebra
Authors: Taft Earl J.
Published: May 2006

Examples of finite-dimensional Hopf algebras over a field, whose antipodes have arbitrary even orders ≥4 as mappings, are furnished. The dimension of the Hopf algebra is
q

n
+1

, where the antipode has order 2
q
,
q
≥ 2, and
n
is an arbitrary positive integer. The algebras are not semisimple, and neither they nor their dual algebras are unimodular.
A Specific Metabolic Activity on the Surface Membrane in Malignant Cell-Transformation
Authors: Inbar Michael , Ben-Bassat Hannah , Sachs Leo
Published: May 2006

The carbohydrate-binding protein, Concanavalin A (Con A), binds to glucose- or mannose-like sites on the cell-surface membrane. Unless the cells are treated with trypsin, this protein agglutinates malignantly transformed cells, but not normal cells. The transformed cells were agglutinated at 24°C but not at 4°C. Transformed and normal cells treated with trypsin were agglutinated at both 24°C and 4°C with high concentrations of Con A (500 μg/ml), but only at 24°C with low concentrations (5 μg/ml). The same number of Con A molecules were bound to normal and transformed cells at both temperatures. The results indicate that the site for Con A on the surface membrane contains two activities, a component that binds Con A molecules (
B
) and a component that determines agglutination (
A
).
B
is not temperature sensitive and is active in normal and transformed cells, whereas
A
, which is temperature sensitive, is in an active form only in transformed cells.
A
can be activated by trypsin, and the increased activity per cell allows agglutination at 4°C with a high, but not with a low, concentration of Con A. Agglutination of transformed cells by wheat-germ agglutinin, which binds to
N
-acetyl-D-glucosamine-like sites, and by soybean agglutinin, which binds to
N
-acetyl-D-galactosamine-like sites, was not temperature sensitive. Thus, the temperature-sensitive component
A
is specific for Con A, and malignant transformation of normal cells, which results in agglutinability by Con A, is associated with the activation of a specific temperature-sensitive activity on the surface membrane.
Increased Survival of Sickle-Cell Erythrocytes after Treatment
In Vitro
with Sodium Cyanate
Authors: Gillette Peter N. , Manning James M. , Cerami Anthony
Published: May 2006

Cyanate reacts with the amino-terminal valine residues of hemoglobin S and prevents the sickling
in vitro
of 50-80% of the erythrocytes from patients with sickle-cell disease. The purpose of the studies reported here was to determine whether this anti-sickling effect would increase the survival of cyanate-treated cells that were returned to the patient. In seven subjects with sickle-cell disease, the mean 50% survival of
51
Cr-labeled sickle erythrocytes was increased from 9.9 to 20.7 days (normal 25-35 days) after treatment of the cells
in vitro
with sodium cyanate. These results provide evidence that the antisickling effect of cyanate observed
in vitro
is retained
in vivo
, and strengthen the rationale for further investigation of cyanate as a possible therapeutic agent in sickle-cell disease.
Gaucher's Disease: Deficiency of “cid”β-Glucosidase and Reconstitution of Enzyme Activity
In Vitro
Authors: Ho Mae Wan , O'Brien John S.
Published: May 2006

The spleen from a patient with adult Gaucher's disease was shown to be deficient in a β-glucosidase (EC 3.2.1.21) isoenzyme that has optimal activity at pH 4.0-4.3, and is stimulated by 0.02% Triton X-100. A mixture of spleen homogenates from a control and from the patient contained β-glucosidase activity equivalent to 2-3 times the theoretical expected activity. The increase in enzyme activity occurred at pH 4.0-4.3; the magnitude of the increase was proportional to the amount of each homogenate added. Two factors, one called factor P from the patient's spleen, the other called factor C from the control spleen, were responsible for a reconstitution of β-glucosidase activity
in vitro
. Factor P is tentatively identified as an acid glycoprotein.
Salmonellosis Pacifarin Activity of Enterobactin
Authors: Wawszkiewicz E. J. , Schneider H. A. , Starcher B. , Pollack J. , Neilands J. B.
Published: May 2006

Salmonellosis pacifarin activity is detected by an increased survivorship of mice, doubly infected with avirulent and virulent
Salmonella typhimurium
, when heretofore unknown agents, found in certain natural foodstuffs and in the supernatants of certain bacterial cultures, are fed to the infected animals as dietary supplements. We now announce the identity of one of these agents: it is
enterobactin
, a cyclic trimer of 2,3-dihydroxy-
N
-benzoyl-L-serine. Basal diets enriched with as little as 2 mg of crystalline trimer per kg of diet show pacifarin activity to a statistically significant degree. Diets supplemented with as much as 100 mg of the monomer per kg of diet show no such activity.
Enzymatic Conversion of 5-Oxo-L-Proline (L-Pyrrolidone Carboxylate) to L-Glutamate Coupled with Cleavage of Adenosine Triphosphate to Adenosine Diphosphate, a Reaction in the γ-Glutamyl Cycle
Authors: Werf Paul Van Der , Orlowski Marian , Meister Alton
Published: May 2006

A new enzyme, 5-oxoprolinase, was found in rat kidney and in several other tissues; it catalyzes the conversion of 5-oxo-L-proline (L-5-oxo-pyrrolidine-2-carboxylic acid, L-2-pyrrolidone-5-carboxylic acid, L-pyroglutamic acid) to L-glutamic acid, with concomitant stoichiometric cleavage of ATP to ADP and orthophosphate. The reaction catalyzed by 5-oxoprolinase, in which 5-oxoproline formed from γ-glutamyl amino acids by the action of γ-glutamylcyclotransferase is converted to glutamate, appears to function in the γ-glutamyl cycle. 5-Oxoprolinase requires Mg
++
(or Mn
++
) and K
+
(or NH
4
+
) for activity. The equilibrium is markedly in favor of glutamate formation at pH 7.8.
Reconstitution of Horse Heart Cytochrome
c
: Interaction of the Components Obtained upon Cleavage of the Peptide Bond following Methionine Residue 65
Authors: Corradin Giampietro , Harbury Henry A.
Published: May 2006

Horse heart cytochrome
c
can be divided into a heme peptide of 65 residues (H65CNBr) and a nonheme peptide of 39 residues (N39CNBr) by treatment of the molecule with cyanogen bromide. Upon mixture of the two peptides in aqueous solution, a 1: 1 complex with properties closely resembling those of the parent heme protein can be formed. The reaction can conveniently be effected in sodium acetate buffer of pH 4.7, with the H65CNBr in the reduced form. The heme peptide is predominantly in the high-spin state under these conditions, and, upon the addition of N39CNBr, is converted to a complex with absorption and circular dichroism spectra which correspond closely to those of ferrocytochrome
c
. If N39CNBr is added to the oxidized form of H65CNBr, the spectral properties of the product differ appreciably from those of the parent protein. A complex with absorption and circular dichroism spectra comparable to those of ferricytochrome
c
can readily be obtained, however, through oxidation of the product of the reaction of N39CNBr with H65CNBr in the reduced state. The complex formed in this manner has an absorption band at 695 nm, exhibits no tryptophan or tyrosine fluorescence, and is active in the succinate oxidase system.
Melatonin Metabolism: Neural Regulation of Pineal Serotonin: Acetyl Coenzyme A
N
-Acetyltransferase Activity
Authors: Klein David C. , Weller Joan L. , Moore Robert Y.
Published: May 2006

There is a diurnal rhythm in the activity of serotonin
N
-acetyltransferase in the rat pineal gland. In the normal rat, the nocturnal enzyme activities are 15-to 30-fold greater than are daytime activities. This rhythm is abolished by decentralization or removal of the superior cervical ganglia, procedures that interrupt the only source of central neural input to the pineal gland. This effect of superior cervical sympathectomy on the
N
-acetyltransferase rhythm cannot be attributed to changes occurring in the denervated pineal parenchymal cells. When chronically denervated glands are placed in organ culture with norepinephrine, the neurotransmitter normally located in sympathetic terminals in the gland,
N
-acetyltransferase activity increases 10- to 20-fold. These data indicate that superior cervical sympathectomy abolishes the
N
-acetyltransferase rhythm by elimination of the input of central signals to the gland. These signals appear to regulate the
N
-acetyltransferase rhythm in the normal rat by regulation of the release of norepinephrine from the sympathetic terminals within the pineal gland.
Van der Waals Interactions and Exciton Condensation
Authors: Handel P. H. , Kittel C.
Published: May 2006

It is shown that the van der Waals interaction can lead at low temperatures to a condensed state of excitons with properties in qualitative agreement with the observations of exciton droplets. Our calculation gives a binding energy of the correct sign and magnitude for the exciton condensate. In a diclectric medium, the strong enhancement of the exciton polarizability leads to a giant van der Waals interaction, and this interaction appears to make possible a condensed exciton phase.
Albumin Evolution in Frogs: A Test of the Evolutionary Clock Hypothesis
Authors: Wallace Donald G. , Maxson Linda R. , Wilson Allan C.
Published: May 2006

Frogs are an ancient group compared to placental mammals. Yet, although there are about as many species of frogs as there are of mammals, zoologists consider that frogs have undergone only limited morphological divergence, while placental mammals have diversified greatly in morphology and way of life. The serum albumins of numerous frog species were compared by the quantitative microcomplement fixation technique. Frogs that are morphologically similar enough to merit taxonomic distinction at only the species level often exhibit differences in the serological properties of their albumins larger than those usually seen between mammals placed in distinct families or suborders. Thus, there seems to be a contrast between albumin evolution and evolution at the organismal level. The large differences between albumins among frogs can be explained by the hypothesis that albumin evolution has proceeded at the same rate in frogs as in mammals.
The Population Variance of the Proportion of Genetic Admixture in Human Intergroup Hybrids
Authors: Reed T. Edward
Published: May 2006

For each individual in a human hybrid population there is a proportion μ
i
, whose value is usually unknown, that expresses the fraction of his genes deriving from a specified parental population. The distribution of these individual proportions about the mean proportion μ is not known for any large hybrid population in man. It is of interest to know whether the population variance of individual proportions (μ
i
) can be estimated from the variation between different, independent estimates of the mean proportion (μ).

This possibility was tested with data on Negroes of the Oakland, California area, by the use of some of the principles of analysis of variance. Even with a large sample and the useful Duffy blood-group system to indicate admixture, almost no information about the population variance of individual proportions is provided by between-sample variation in estimates of μ. It is concluded that group data on admixture proportions usually do not give useful information about the population variance. It is further concluded that a recent estimate of this variance by Shockley is in error.
The Molecular Organization of Lipids in the Membrane of
Escherichia coli:
Phase Transitions
Authors: Esfahani M. , Limbrick A. R. , Knutton S. , Oka T. , Wakil S. J.
Published: May 2006

X-ray diffraction techniques have been used to investigate the physical state of the lipids in the membrane of an unsaturated fatty acid auxotroph of
Escherichia coli
. Thermotropic phase transitions have been detected in membranes prepared from cells grown on various fatty acid supplements. Below the transition temperature, the X-ray diffraction pattern features a sharp ring at 420 pm (4.2 Å) due to the close hexagonal packing of the apolar groups of the lipids; above the transition temperature the lipids are in a less organized liquid-crystalline state that gives rise to a diffuse band centered at a Bragg spacing of 460 pm (4.6 Å). This transition occurs at or below the temperature at which the cells were grown. Disparities between this transition temperature and the temperature of discontinuities in the Arrhenius plots for proline transport and succinic dehydrogenase activity lead us to conclude that the distribution of lipids within the membrane is heterogeneous.
Detection of Human and Chick Nuclear Antigens in Nuclei of Chick Erythrocytes during Reactivation in Heterokaryons with HeLa Cells
Authors: Ringertz Nils R. , Carlsson Sten-Anders , Ege Thorfinn , Bolund Lars
Published: May 2006

Inactive nuclei of chick erythrocyte resume RNA synthesis and increase in volume and dry mass in heterokaryons made by virus-induced fusion of human tumor cells (HeLa) with chick erythrocytes. Nuclear growth is due primarily to migration of human macromolecules into the chick nucleus. Human nucleoplasmic antigens were detected in the nucleoplasm and human nucleolar antigens were detected in the nucleoli of reactivated chick erythrocyte nuclei. After some time, chick-specific nucleolar antigens appear in the nucleoli of both the reactivated chick nuclei and the HeLa cellnuclei. The results suggest that human nuclear proteins play an important part in the reactivation of the chick genome.
Temperature-Dependent Surface Changes in Cells Infected or Transformed by a Thermosensitive Mutant of Polyoma Virus
Authors: Eckhart Walter , Dulbecco Renato , Burger Max M.
Published: May 2006

Infection of BALB/3T3 cells by polyoma virus causes an alteration in the cell surface, characterized by enhanced agglutination of the cells by wheat germ agglutinin or concanavalin A. Infection by the thermosensitive mutant of polyoma, ts-3, causes the cell surface alteration at the permissive temperature, but not at the nonpermissive temperature. The cell surface alteration requires cellular DNA synthesis, but not viral DNA synthesis. BHK cells transformed by ts-3 show the surface alteration when grown at the permissive temperature, but not when grown at the nonpermissive temperature. It is concluded that the surface alteration in transformed cells is under the control of a viral gene.
Loss of Feedback Control of Hydroxymethylglutaryl Coenzyme A Reductase in Hepatomas
Authors: Siperstein Marvin D. , Gyde Ann M. , Morris Harold P.
Published: May 2006

The feedback response of mevalonate: NADP oxidoreductase (acylating CoA; EC 1.1.1.34) in two varieties of hepatoma has been examined. In marked contrast to the feedback inhibition of this enzyme that is regularly observed in normal liver, the feedback control is completely lost in minimal-deviation hepatomas 9121 and 3924A. This finding provides the first specific biochemical localization of the defect in cholesterol feedback control, which has been shown previously to be a characteristic of all hepatomas.
Rapid and Complete Purification of Acetylcholinesterases of Electric Eel and Erythrocyte by Affinity Chromatography
Authors: Berman Jonathan Dembitz , Young Michael
Published: May 2006

Affinity chromatography has been used to purify acetylcholinesterase both from the electric tissue of
Electrophorus electricus
and from bovine erythrocyte membranes. For this purpose, several specific enzymic inhibitors of each protein were synthesized and joined covalently to an insoluble support resin. AchE is selectively retained by such inhibitor-resins when highly impure solutions are chromatographed upon them. After removal from the resin, both enzymes are electrophoretically homogeneous and they may be recovered in yields of 75% or more.
The Characters of the Symmetric Group
Authors: Murnaghan Francis D.
Published: May 2006

A short and simple derivation of the formula of Frobenius, which gives the dimensions of the irreducible representations of

S
n

, the symmetric group on any number,
n
, of symbols, is given. These dimensions are the characters of the identity element of the group, i.e., of the element all of whose cycles are unary. It is shown how a slight modification of Frobenius' formula yields, when
n
= 2
p
is even, the characters of an element of

S
n

all of whose cycles are binary and, when
n
= 3
p
is a multiple of 3, the characters of an element of

S
n

all of whose cycles are ternary and, generally, when
n = kp
is a multiple of any positive integer
k
, the characters of an element of

S
n

all of whose cycles are of length
k
. It is noteworthy that the calculations become simpler, rather than more complicated, as
k
increases. Finally, this paper shows how to derive from Frobenius' formula the characters of an element of

S
n

which has at least one unary cycle and, from the present modifications of Frobenius' formula, the characters of an element of

S
n

which has at least one cycle of length
k, k
= 2, 3,...,
n
.
Putrescine and Spermidine Biosynthesis in the Development of Normal and Anucleolate Mutants of
Xenopus laevis
Authors: Russell Diane H.
Published: May 2006

Ornithine decarboxylase (EC 4.1.1.17), the enzyme that catalyzes the synthesis of putrescine from ornithine, increases dramatically in developing
Xenopus
embryos. Between the 2-cell stage and early blastula stage, activity increases 10-fold, and in swimming tadpoles, the enzyme activity is 100-fold higher than that present in either unfertilized eggs or 2-cell embryos.
S
-adenosyl-L-methionine decarboxylase, an enzyme that catalyzes spermidine synthesis from putrescine and
S
-adenosyl-L-methionine, increases 40-fold in activity during the development of
Xenopus
, but does not increase in activity prior to gastrulation. Concomitant with these enzyme changes, putrescine and spermidine concentrations are elevated during the development of
Xenopus
embryos. Maximal accumulations are present in the swimming tadpole and correspond to maximal enzyme activities. Anucleolate-mutant embryos of
Xenopus
, which do not synthesize new ribosomes, have no detectable
S
-adenosyl-L-methionine decarboxylase activity and do not accumulate spermidine after gastrulation. Ornithine decarboxylase activity is depressed in these mutants and putrescine accumulation is decreased also. The activity of some dehydrogenases that increase in
Xenopus
embryos after gastrulation show normal increases in the anucleolate mutants. Thus, the synthesis of putrescine and spermidine in embryos correlates with the onset of ribosomal-RNA synthesis and the formation of a viable nucleolus in the embryonic cell.
Expression of H-2 and Moloney Leukemia Virus-Determined Cell-Surface Antigens in Synchronized Cultures of a Mouse Cell Line
Authors: Cikes Matko , Friberg Sten
Published: May 2006

A mouse cell line derived from bone marrow (JLS-V9) was infected
in vitro
with Moloney leukemia virus. After the cell-surface antigens specified by this virus appeared, cells were synchronized in mitosis by a short treatment with colcemid. The expression of H-2- and virus-determined surface antigens was monitored during one cell cycle by an indirect membrane-immunofluorescence test. The highest proportion of antigen-positive cells was found during the G1 period; the proportion dropped as the cells entered the S period, and remained low until they entered the G1 period of the next cycle. The H-2- and virus-determined surface antigens were temporally coexpressed.
A Mechanochemical Mechanism for Muscle Contraction
Authors: Harrington William F.
Published: May 2006

A mechanism for contraction in skeletal muscle is proposed in which the tension-generating site is located within the core of the thick (myosin) filament, specifically within the trypsin-sensitive hinge region of the myosin rod. The force-developing mechanism is thought to be the transfer of energy from ATP splitting in the globular head of one molecule directly to the hinge region of an adjoining molecule, resulting in a phase transition from crystalline to amorphous within the hinge segment of the second molecule. Binding of MgATP at the actinmyosin interface is considered to be a release mechanism. The model leads to out-of-phase oscillating movement of the cross bridges.
Neutral Sites for Calcium Ion Binding to Elastin and Collagen: A Charge Neutralization Theory for Calcification and Its Relationship to Atherosclerosis
Authors: Urry D. W.
Published: May 2006

Neutral, uncharged binding sites for calcium ions are proposed for elastin and collagen. The sites utilize, particularly from a conformational viewpoint, the most striking feature of the amino acid composition, that is, the high glycine content. Glycines favor the formation of β-turns and associated conformations that are known, from studies on ion-transporting antibiotics, to interact with cations. By analogy with certain antibiotics, which are uncharged polypeptides and depsipeptides that bind cations by coordination with neutral acyl oxygens, it is proposed that calcium-ion binding also utilizes uncharged coordinating groups, i.e., neutral sites, in the protein matrix. The protein matrix, which becomes positively charged by virtue of the bound calcium ions, attracts neutralizing phosphate and carbonate ions, which then allow further calcium ion binding. The driving force is, therefore, the affinity of calcium ions for the neutral nucleation sites.

The charge neutralization theory of calcification suggests a fundamental role of organic anions, for example sulfated mucopolysaccharides, in regulating bone formation and in retardation of atherosclerosis. The proposed mechanism contains elements that tend to unify several theories on the pathogenesis of atherosclerosis.
Linkage Disequilibrium in a Local Population of
Drosophila melanogaster
Authors: Mukai Terumi , Mettler L. E. , Chigusa Sadao I.
Published: May 2006

461 second chromosomes of
Drosophila melanogaster
were extracted from a Raleigh, N.C. population and four enzymes controlled by the genes located in this chromosome (alcohol dehydrogenase (EC 1.1.1.1.), malate dehydrogenase-1 (EC 1.1.1.37), glycerol-3-phosphate dehydrogenase-1 (EC 1.1.1.8), and α-amylase (EC 3.2.1.1), were assayed electrophoretically and cytologically (salivary-gland chromosomes). Linkage disequilibrium could not be detected among any pair of isozyme genes, except in one case that is best explained as due to a chance error in estimation. Some disequilibria were detected, however, between isozyme genes and polymorphic inversions. The relative viabilities of homozygous and heterozygous combinations of these chromosomes were estimated with respect to the alcohol dehydrogenase alleles and the glycerol-3-phosphate dehydrogenase alleles; no significant difference could be detected. The role of epistasis in natural populations is discussed on the basis of these results.
Allotypy of High Density Lipoprotein of Rabbit Serum
Authors: Berg Kåre , Boman Helge , Torsvik Harald , Walker Suzanne M.
Published: May 2006

A common antigenic polymorphism of high density lipoprotein (HDL) in rabbit serum is described. The presence or absence of an antigen termed Hl 1 appears to be controlled by autosomal dominant inheritance. The polymorphism should be a useful tool in the study of serum lipoproteins, particularly since genetic polymorphisms within the low density lipoprotein are already known in several species. The Hl polymorphism may make the rabbit more useful for model studies of serum lipoproteins in health and disease.
Specific Inactivation of 16S Ribosomal RNA Induced by Colicin E3
In Vivo
Authors: Bowman C. M. , Dahlberg J. E. , Ikemura T. , Konisky J. , Nomura M.
Published: May 2006

Treatment of sensitive
Escherichia coli
cells with colicin E3 leads to inactivation of 30S ribosomal subunits.
In vitro
reconstitution of 30S subunits indicates that the E3-induced defect lies solely in the 16S RNA. 16S RNA from E3-treated cells lacks several T
1
RNase oligonucleotides of normal 16S RNA, including the one from the 3′-end of the 16S RNA, as analyzed by the fingerprint technique of Sanger. An RNA fragment about 50 nucleotides long has been isolated from E3-treated cells. This RNA contains the original 3′-terminal oligonucleotide and other oligonucleotides missing in the E3-16S RNA. The results show that colicin E3 treatment causes the cleavage of 16S RNA at a specific position near the 3′-terminus.
Antibody Formation: Reduced Responses After Administration of Excessive Amounts of Nonspecific Stimulators
Authors: Braun Werner , Ishizuka Masaaki
Published: May 2006

Enhancement of antibody formation
in vitro
and
in vivo
by poly(A·U), cyclic AMP, dibutyryl cyclic AMP, or any one of these agents in combination with theophylline or caffeine, is usually limited to certain dose ranges. High doses of these nonspecific stimulators can produce less or no enhancement, or may actually inhibit antibody formation. Such dose-response relationships may be pertinent to an understanding of phenomena of specific immunological nonresponsiveness and certain types of antigenic competition.
Sympathetic Reinnervation of the Rat Iris in Organ Culture
Authors: Silberstein Stephen D. , Johnson David G. , Jacobowitz David M. , Kopin Irwin J.
Published: May 2006

Reinnervation of sympathetically denervated rat iris by superior cervical ganglion cells has been demonstrated to occur
in vitro
. Return of [
3
H]norepinephrine uptake by irises incubated in contact with ganglia was associated with the reappearance of nerve fibers containing catecholamines that were demonstrable by fluorescent histochemistry. The reinnervating neurons appeared to follow the same general pattern of innervation seen in the normal iris, but the density of the neural plexus was much greater. Nerve growth factor influenced the rate and extent of innervation of the iris but not of neuronal growth within the ganglion.
The Crystal and Molecular Structure of an Intermolecular Complex between Riboflavin and an Adenosine Derivative
Authors: Voet Donald , Rich Alexander
Published: May 2006

Riboflavin and the adenosine derivative 5′-bromo-5′-deoxyadenosine form a crystalline 1:1 intermolecular complex, the structure of which has been solved by x-ray diffraction analysis. The adenine ring is found to be joined by two hydrogen bonds to the uracillike end of the riboflavin isoalloxazine ring. In addition, the riboflavin and the adenosine molecules associate through the formation of stacks of alternating parallel adenine and isoalloxazine rings. These intermolecular associations are considered to be models for intramolecular association in the coenzyme flavin adenine dinucleotide (FAD), which contains both adenosine and riboflavin.
Approximate Treatment of the Conformational Characteristics of a Cyclic Nonapeptide, Cyclolinopeptide A
Authors: Tonelli A. E.
Published: May 2006

Possible conformations for a cyclic nonapeptide that are consistent with conformation-dependent information obtained from an NMR investigation of the peptide in solution are presented. These several conformations are deduced from the myriad of possible conformations by eliminating from consideration all cyclic species having one or more residues in a conformation that does not correspond to the vicinal coupling constants observed by NMR between the amide and α-protons. A Karplus-like relation connecting the dihedral angle [unk]′ and the vicinal coupling J
Nα
between N—H and C
α
—H
α
is used to test this correspondence. A further reduction in the number of cyclic conformations under consideration is made possible by rejecting the conformations that have a high intramolecular conformational energy. The intramolecular conformational energy of the cyclic nonapeptide is estimated by summing the independent residue energies. These have been calculated by others with approximate potential functions to account for the intrinsic torsional potentials and the nonbonded steric (6-12 potential) and electrostatic (monopole-monopole) interactions solely dependent upon one or both of the residue rotations, [unk] and Ψ, about the N—C
α
and C
α
—C bonds, respectively.
Interconnected Patterns of Biogeography and Evolution
Authors: Darlington Philip J.
Published: May 2006

Analysis of the fauna of the carabid beetles of New Guinea reveals both a broad dispersal pattern and a local turnover pattern that together fit into a world-wide pattern of successive dispersals and replacements that run from large to small areas and from more to less favorable climates. This pattern coincides broadly with a world-wide pattern of species numbers. Evolution by group selection, proceeding most rapidly and effectively where species are most numerous, connects the patterns and can supply the force that gives direction to the dispersal pattern. Directional change at any level of complexity involves
movement
that results in the formation of diverse
groups
of units (which are themselves groups of smaller units) and
differential survival
. This process—generalized group selection—has been continuous from chemical evolution on the earth's surface, through the origin of life, and into successive interacting levels of organic evolution. A corollary is that evolution should make situations favorable to itself, by group selection, and has probably done so in (for example) tropical rain forest, where new information about group evolution may be sought.
A Polynucleotide Segment Rich in Adenylic Acid in the Rapidly-Labeled Polyribosomal RNA Component of Mouse Sarcoma 180 Ascites Cells
Authors: Lee Se Yong , Mendecki Jozef , Brawerman George
Published: May 2006

The rapidly-labeled polyribosomal RNA component from mouse sarcoma 180 cells is retained on nitrocellulose (Millipore) membrane-filters at high ionic strength. This property is due to the presence of a polynucleotide sequence rich in adenylic acid that resists both T
1
and pancreatic RNase digestion. The resistant material shows sedimentation characteristics close to those of transfer RNA. The RNA molecules that contain this material can be separated from the rest of the polysomal RNA by differential phenol extraction with neutral and alkaline Tris buffers. Synthetic poly(A) exhibits the same behavior as the rapidly-labeled polysomal RNA with respect to Millipore binding and phenol fractionation. The characteristics of the rapidly-labeled polysomal RNA component permit its isolation free of ribosomal RNA.
Transplantation of Nuclei in
Drosophila melanogaster
Authors: Zalokar Marko
Published: May 2006

Nuclei surrounded by ooplasm of the syncytial stage of developing eggs of wild-type
Drosophila melanogaster
were implanted into freshly laid fertilized eggs of females of a
y w
stock. More than half of the recipient eggs produced larvae, but few of the larvae hatched or developed further. The best sets of experiments gave about twelve percent of imagos, mostly
y w
in appearance. Several larvae were mosaics with yellow Malpighian tubes, and two flies had part of the abdominal segments of the wild type. Half of the flies were fertile, but they produced only
y w
offspring, except for two males that had
y w
appearance, but wild-type gonads. When crossed with
y w
females, they gave wild-type females and
y w
males.
Immunological Tolerance: “Forbidden Clones” Allowed in Tetraparental Mice
Authors: Wegmann T. G. , Hellström I. , Hellström K. E.
Published: May 2006

Tetraparental (allophenic) mice, made chimeric at the eight-cell stage by joining two embryos from histoincompatible parental strains, were examined by a microcytotoxicity test. The results indicate that parental-strain fibroblasts are more effectively destroyed
in vitro
by lymph node cells from the tetraparental mice than by lymph node cells from the F
1
hybrid or either parental stain. The destruction by tetraparental lymph node cells is indistinguishable from that mediated by lymph node cells from previously immunized allogeneic animals. It can be prevented by serum from the tetraparental mice, but not by sera from the F
1
hybrid or the parental strain animals. The results suggest that a concomitant immunity and serum blocking effect, rather than a central failure of the immune response, may mediate some aspects of normal tolerance.
Gene Activation in WI-38 Fibroblasts Stimulated to Proliferate: Requirement for Protein Synthesis
Authors: Rovera Giovanni , Farber John , Baserga Renato
Published: May 2006

Confluent monolayers of WI-38 human diploid fibroblasts can be stimulated to divide by fresh medium containing 30% fetal-calf serum. Up to 80% of the cells are stimulated to divide, with a peak of DNA synthesis between 15 and 21 hr. 1 hr after the change of medium there is a 70% rise in chromatin template activity. Cycloheximide inhibited the increase in chromatin template activity. A requirement for RNA synthesis was investigated by incubating stimulated and unstimulated cells with 10 μg/ml of actinomycin D. In spite of a 95% inhibition of RNA synthesis in whole cells, purified chromatin from stimulated cells showed the usual increase in template activity. These experiments implicate a requirement for protein synthesis in template activation, and imply that the synthesis of this (or these) protein(s) is independent of RNA synthesis and regulated by a purely translational mechanism.
Symmetrical
In Vivo
Transcription of Mitochondrial DNA in HeLa Cells
Authors: Aloni Y. , Attardi G.
Published: May 2006

RNA·DNA hybridization experiments utilizing separated strands of HeLa mitochondrial DNA and mit-RNA from HeLa cells exposed to short pulses of [5-
3
H]uridine have shown that the labeled RNA hybridizes with both the light (L) and the heavy (H) strand, though to a different relative extent depending upon the labeling time. Thus, hybridization of pulse-labeled RNA is about equal with the two strands when the pulse is very short (1-5 min), and becomes more and more predominant with the H strand with increasing pulse length. Pulse-labeled fast-sedimenting mit-RNA forms RNase-resistant double-stranded structures up to more than 5 μm long when self-annealed or annealed with an excess of unlabeled mit-RNA. These observations and the previous evidence of complete transcription of the H strand strongly suggest that mit-DNA is transcribed in HeLa cells symmetrically over a considerable portion of its length, with the transcript of the L strand being rapidly degraded or otherwise removed from the mitochondrial fraction.
Conformational Transition in Oligopeptides: An NMR Spectroscopic Study
Authors: Temussi Piero A. , Goodman Murray
Published: May 2006

We examined the 220-MHz NMR spectra for a series of oligopeptides derived from γ-ethyl L-glutamate, an octapeptide based on β-methyl L-aspartate, and a low molecular weight L-glutamate polymer ([unk]DP = 20) in deuterochloroform-trichloroacetic acid. A definite transition from folded to nonhelical forms was established for the glutamate systems. The aspartate behavior is explained by a progressive solvation of a peptide chain in a disordered conformation. In all the solvent systems studied, separate peaks for each N-H are observed for the glutamate and aspartate oligomers. Thus, end effects and polydispersity are important in interpreting NMR spectra of partially helical polypeptides. Slow exchange between NH groups on the same chain does not appear to play a significant role in the helix-coil transition.
Photochromic Activators of the Acetylcholine Receptor
Authors: Bartels Eva , Wassermann Norbert H. , Erlanger Bernard F.
Published: May 2006

Two photochromic activators of the electrogenic membrane of the electroplax of
Electrophorus electricus
are described.
Trans
-3,3′-bis[α-(trimethylammonium)methyl]azobenzene dibromide (Bis-Q), one of the most potent ever reported, is active at concentrations of less than 10
-7
M. Its
cis
isomer, which is obtained from the
trans
by exposure to light of 330 nm, is practically devoid of activity. Photoregulation of the potential of the membrane takes place in the presence of Bis-Q, presumably because of the conversion of the active
trans
isomer to the inactive
cis
isomer in the single-cell electroplax system. The second activator, 3-(α-bromomethyl)-3′-[α-(trimethylammonium)methyl]azobenzene bromide (QBr) can be covalently attached to the electroplax membrane after reduction of the membrane with dithiothreitol. Activation of the membrane is induced by the covalently linked reagent. Its
cis
isomer, obtained from the
trans
by exposure to light of 330 nm, is, like
cis
-Bis-Q, of very low activity. Both isomers of Bis-Q are equally active as inhibitors of acetylcholinesterase, 50% inhibition occurring at a concentration of 10
-5
M. The possibility of using
trans
-Bis-Q and
trans
-QBr to characterize and isolate the receptor protein is discussed.
Evidence for and Localization of Vegetative Viral DNA Replication by Autoradiographic Detection of RNA·DNA Hybrids in Sections of Tumors Induced by Shope Papilloma Virus
Authors: Orth Gérard , Jeanteur Philippe , Croissant Odile
Published: May 2006

The occurrence and localization of vegetative viral DNA replication was studied in sections of tumors induced by the rabbit Shope papilloma virus, in cottontail and domestic rabbit papillomas, in primary domestic rabbit carcinoma, and in transplantable VX2 carcinoma, by
in situ
hybridization of radioactive RNA complementary to viral DNA. Vegetative viral DNA replication and viral protein synthesis were compared by means of cytological hybridization and immunofluorescence techniques on adjacent frozen sections.

Vegetative viral DNA replication is completely repressed in the proliferating cellular layers of these tumors, which suggests a provirus state of the viral genome, as in other cells transformed by oncogenic DNA viruses. Vegetative viral DNA replication is induced, after initiation of the keratinization, in cells of cottonail rabbit papillomas, where it is usually followed by viral protein synthesis; this illustrates the influence of the physiological state of the host cell on the control of viral functions. Vegetative viral DNA replication is deteced only in a few cells of domestic rabbit papillomas, at the end of the keratinization process; this observation provides indirect evidence that the DNA synthesis specifically induced in these tumors after the onset of keratinization reflects mostly the induction of cellular DNA synthesis.