bluuebunny/crossref_metadata_2025 huggingface dataset:
Polyriboadenylate Sequences at the 3′-Termini of Ribonucleic Acid Obtained from Mammalian Leukemia and Sarcoma Viruses
Authors: Phillips Leo A. , Park James J. , Hollis Vincent W.
Published: May 2006

The location of poly(A) sequences in the RNA of mammalian RNA-tumor viruses was determined by enzymatic analyses. The 56-64S viral genomic RNAs, the 20-40S viral subunit RNAs, and the 4-5S poly(A) sequences excised from these viral RNAs were subjected to either hydrolysis with a 3′-OH specific exoribonuclease from Ehrlich ascites tumor cells or phosphorolysis from the 3′-termini with polynucleotide phosphorylase from
Micrococcus luteus
. Purified adenosine-labeled poly(A) fragments, excised from genomic viral RNAs by RNase A and T
1
digestion, were hydrolyzed with the 3′-OH specific exoribonuclease for various periods of time. Poly(U) filter binding studies of the residual poly(A) indicated that 97% of the poly(A) fragments were hydrolyzed. Adenosine-labeled genomic and subunit viral RNAs and excised poly(A) fragments were phosphorolyzed from their 3′-termini for various periods of time with polynucleotide phosphorylase. The degree of phosphorolysis was monitored by poly(U) filter binding studies, and CCl
3
COOH insolubility and solubility determinations. There was an initial preferential rate of phosphorolysis of the poly(A) sequences of genomic and subunit viral RNAs as compared to the total adenosine-labeled viral RNAs. The data from these two different enzymatic mechanisms of action indicated conclusively that the poly(A) sequences were located at the 3′-termini of genomic and subunit viral RNAs.
A Test of the Hypothesis That D
2
O Affects Circadian Oscillations by Diminishing the Apparent Temperature
Authors: Caldarola Patricia C. , Pittendrigh Colin S.
Published: May 2006

The period (τ) of a circadian pacemaker in the cockroach
Leucophaea maderae
is a nonmonotonic function of temperature. The slope of the curve (τ as a function of temperature) is negative at 20° and positive at 30°. When these insects are deuterated at 20° and 30° the period (τ) of the pacemaker lengthens in both cases, although there is a marked temperature dependence of D
2
O action. The increase in τ is nearly three times greater at 20° than 30°. This observation is a flat contradiction of a prediction made earlier that when D
2
O affects circadian pacemakers it does so by diminishing the apparent temperature of the cell. That prediction, however, involves an assumption that may well be unfounded. Unless D
2
O acts nonselectively on all the components in the system regulating τ, the prediction we sought to test is unfounded; and if D
2
O does not act nonselectively, the observed temperature dependence of D
2
O action is understandable in terms of simulating a lower temperature for those components it
does
affect.
Terminal Deoxyribonucleotidyl Transferase in Human Leukemia
Authors: Coleman Mary Sue , Hutton John J. , Simone Philip De , Bollum F. J.
Published: May 2006

Terminal deoxyribonucleotidyl transferase (EC 2.7.7.31; nucleoside triphosphate:DNA nucleotidylexotransferase) is usually found only in thymus, but has been reported in leukemic cells from children with acute lymphoblastic leukemia. In an unusual adult patient with acute myelomonocytic leukemia, terminal transferase was found at a level of 16 units per 10
8
bone marrow cells and 14 units per 10
8
circulating leukocytes (1 unit = 1 nmol of nucleotide per hr). This activity is comparable to that found in normal thymus. Assays of transferase in marrow and peripheral leukocytes from patients with typical acute and chronic myelogenous leukemias gave average values of 0.5 and 0.3 unit per 10
8
cells, respectively. Transferase activity is also found in normal bone marrow at about 0.07 unit per 10
8
cells. Terminal deoxyribonucleotidyl transferase in all samples of human marrow and peripheral blood had reaction characteristics, sedimentation, and chromatographic properties similar to the homogeneous enzyme from calf thymus.
Cleavage of Replicating Forms of Mitochondrial DNA by
Eco
RI Endonuclease
Authors: Robberson Donald L. , Clayton David A. , Morrow John F.
Published: May 2006

Digestion of mouse L cell mitochondrial DNA with
Eco
RI restriction endonuclease produces two linear duplex fragments comprising 86.3 ± 2.0% and 14.2 ± 1.0% of the circular genome length (16,000 ± 470 nucleotide pairs). Digestion of human HeLa cell mitochondrial DNA with
Eco
RI produces three linear duplex fragments comprising 49.2 ± 1.0%, 44.4 ± 0.9%, and 6.4 ± 0.4% of the circular genome length (16,590 ± 710 nucleotide pairs). These fragments are shown to be generated by cleavage in unique regions of the mouse and human mitochondrial DNAs. An electron microscopic analysis of partially replicated molecules cleaved by
Eco
RI establishes a unidirectional mode of DNA replication for L cell mitochondrial DNA. The origin for DNA replication is located on the larger
Eco
RI fragment at a position that is 1,890 ± 250 nucleotide pairs (11.8 ± 1.2% of the circular genome length) from the proximal restriction site. Replication proceeds unidirectionally away from this restriction site throughout the length of the larger
Eco
RI fragment. Analysis of L cell, D-loop mitochondrial DNA cleaved by
Eco
RI indicates that a unique sequence is synthesized in formation of the D-loop in these nonreplicating molecules. The origin of D-loop synthesis is located on the larger
Eco
RI fragment at a position 1,760 ± 180 nucleotide pairs (11.0 ± 1.1% of the circular genome length) from the proximal restriction site and is, therefore, the origin for unidirectional displacement replication.
Glucose Inhibition of Epinephrine Stimulation of Hepatic Gluconeogenesis by Blockade of the α-Receptor Function
Authors: Kneer Nancy M. , Bosch Anne L. , Clark Michael G. , Lardy Henry A.
Published: May 2006

For isolated rat hepatocytes, glucagon, 3′:5′-cyclic AMP, 3′:5′-cyclic GMP, and epinephrine stimulate the rate of gluconeogenesis from substrates not involving pathways of mitochondrial metabolism. From estimation of the rates of glucose formation, fructose 6-phosphate phosphorylation, and lactate and pyruvate formation it is concluded that epinephrine and 3′:5′-cyclic GMP stimulate gluconeogenesis from either galactose or fructose by influencing the rate of reactions involving fructose 6-phosphate in a manner similar to that already reported for glucagon and 3′:5′-cyclic AMP. Each agent acts to inhibit flux through phosphofructokinase (EC 2.7.1.11) and enhance flux through fructose diphosphatase (EC 3.1.3.11), resulting in the re-direction of carbon from lactate and pyruvate formation to glucose synthesis. In addition to 3′:5′-cyclic GMP, dibutyryl 3′:5′-cyclic GMP, 8-bromo 3′:5′-cyclic GMP, 8-benzyl-thio 3′:5′-cyclic GMP and 8-(4-chlorophenyl)thio 3′:5′-cyclic GMP stimulate glucose formation and inhibit lactate and pyruvate formation from galactose. Guanosine monophosphate and 2′:3′-cyclic GMP are inactive. As the stimulatory effect of epinephrine is inhibited by phenoxybenzamine and not by propranolol, and is not simulated by isoproterenol, it is concluded that catecholamine activity is expressed through the α-receptor. Increased extracellular glucose concentration (>10 mM) decreases the stimulatory effect of epinephrine, 3′:5′-cyclic GMP, and partially that of 3′:5′-cyclic AMP but does not alter the efficacy of glucagon.
Biosynthesis of Tyrosine Hydroxylase in Rat Adrenal Medulla after Exposure to Cold
Authors: Chuang De-Maw , Costa E.
Published: May 2006

Exposure of rats to cold increases the content of tyrosine hydroxylase [EC 1.14.16.2; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating)] in adrenal medulla, causing a long-lasting enhancement of the enzymatic activity. We have used an antibody specific to tyrosine hydroxylase to study the molecular mechanisms involved in the trans-synaptic induction of adrenal tyrosine hydroxylase. The rate of [
3
H]-leucine incorporation into adrenal tyrosine hydroxylase was measured by specific immunoprecipitation at various times after exposure to cold (4 hr). This enhanced rate of incorporation was evident between 11 and 30 hr after the beginning of exposure to cold, but not at 7 and 50 hr. The increase of
3
H incorporation preceded the maximal enhancement of adrenal tyrosine hydroxylase activity, which occurred about 30 hr after stimulation. Neither the activity of tyrosine hydroxylase nor the rate of
3
H incorporation into tyrosine hydroxylase in cervical sympathetic ganglia was changed by 4 hr of exposure to cold. The rate of degradation of tyrosine hydroxylase was estimated at 26 and 50 hr after the beginning of cold stress, as determined by the technique of double-isotope labeling. The data indicate that the tyrosine hydroxylase degradation rate was not reduced by exposure to cold. Thus, the induction of adrenal tyrosine hydroxylase appears to be due to an increased rate of its synthesis.
Adenylate Cyclase from
Brevibacterium liquefaciens
. III.
In Situ
Regulation of Adenylate Cyclase by Pyruvate
Authors: Umezawa Kazuo , Takai Katsuji , Tsuji Shoji , Kurashina Yoshikazu , Hayaishi Osamu
Published: May 2006

In the presence of DL-alanine intracellular cyclic AMP in nonproliferating cells of
Brevibacterium liquefaciens
increased rapidly to the maximum level of approximately 180 μM, and extracellular cyclic AMP increased to 100 μM within 4 hr at 25°. Adenylate cyclase (EC 4.6.1.1) induction was not observed during this incubation. The concentration of pyruvate in the total culture increased concomitantly with that of cyclic AMP and reached approximately 20 mM after 4 hr of incubation. Since the activity of cyclic nucleotide phosphodiesterase is extremely low in this bacterium, the accumulation of cyclic AMP with DL-alanine appeared to be due to the activation of adenylate cyclase by pyruvate. D-alanine was more effective than L-alanine in producing pyruvate, and a high activity of D-alanine oxidation was detected in the cell lysate of
B. liquefaciens
.

Thus, adenylate cyclase in this bacterium appeared to be regulated
in vivo
by pyruvate which was formed, in this case, predominantly from D-alanine through the action of D-aminoacid oxidase (EC 1.4.3.3). Pyruvate, added extracellularly, also caused a rapid accumulation of intracellular cyclic AMP. Glucose did not change the level of cyclic AMP significantly. It also did not affect the intracellular accumulation of cyclic AMP with DL-alanine.
Self Assembly of Histone F
2
a
1
Authors: Sperling Ruth , Bustin Michael
Published: May 2006

Purified F
2
a
1
histone molecules assemble into organized structures observable by electron microscopy. The basic structure observed at pH 8 and ionic strength of 0.15 has the shape of a bent rod with an average width of 22 Å. The average circumferential length of the rod is 220 Å and the average distance between the tips of the rod is 150 Å. When the ionic strength is increased the rods align lengthwise into intertwined fiber-like structures. In some cases bent rods assemble “face-to-face” to give circular structures. At high protein concentrations the long fibers form paracrystalline arrays. Examination of these arrays by optical diffraction yielded a meridional reflection with a spacing of 150 Å. The main additional reflections are compatible with a structure having a repeat unit of 300 Å.

We suggest that in chromatin the DNA is packed around organized periodic histone structures and that the periodicity of the histone structure may dictate the periodicity of the repeating unit in chromatin.
Glycophorin in Lipid Bilayers
Authors: Grant Chris W. M. , McConnell Harden M.
Published: May 2006

Glycophorin, the major glycoprotein of human erythrocytes, has been isolated and reincorporated into lipid vesicles. Freeze-fracture electron microscopy shows the reincorporated glycophorin to occur as small particles in vesicle fracture faces while the etch faces are smooth. The glycoprotein has a tendency to cluster into groups of several particles. Evidence is presented that, although lipids in immediate contact with glycopherin are likely somewhat immobilized, the entire lipid-protein complex has a tendency to occupy fluid regions of the bilayer. Reincorporated glycophorin assumes its proposed conformation in the intact erythrocyte in so far as it penetrates the hydrophobic membrane interior while its N-terminal end with attached carbohydrate residues is exposed to the aqueous compartment and is available as a specific recognition site.
Direct Evidence for the Presence of Epstein-Barr Virus DNA and Nuclear Antigen in Malignant Epithelial Cells from Patients with Poorly Differentiated Carcinoma of the Nasopharynx
Authors: Klein George , Giovanella Beppino C. , Lindahl Tomas , Fialkow Philip J. , Singh Surjit , Stehlin John S.
Published: May 2006

A well-differentiated squamous cell carcinoma and three poorly differentiated carcinomas of the nasopharynx were analyzed for the presence of Epstein-Barr virus DNA by hybridization with radioactive complementary RNA. The well-differentiated carcinoma contained no detectable Epstein-Barr virus DNA, whereas the three anaplastic carcinomas contained 41, 16, and 14 viral genome equivalents per cell. The anaplastic carcinomas were heavily infiltrated with lymphocytes and other non-neoplastic cells. All four tumors were successfully passaged in
nude
(thymusless) mice. Mouse cell admixture in the heterotransplanted tumors was estimated by analysis of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and varied between 25% and 80%. After two passages in
nude
mice, the carcinoma that was negative for Epstein-Barr virus DNA remained negative, while the three anaplastic carcinomas retained their viral DNA. After correction for mouse cell admixture, the latter tumors were found to contain about 80, 55, and 160 Epstein-Barr virus genome equivalents per human cell. The virus-determined nuclear antigen was localized in the large carcinoma cell clusters in all three mouse-passaged tumors positive for the viral DNA, but other virus-determined antigens were not detected, indicating the absence of virus induction. In contrast to the original tumor biopsies, the
nude
-mouse-passaged tumors showed virtually no lymphocytic infiltration. It is concluded that the Epstein-Barr virus DNA found in biopsies of human nasopharyngeal carcinomas is localized in the neoplastic cells.
The Regulation of Protein Synthesis in Mammalian Cells VI. Soluble and Polyribosome Associated Components Controlling
In Vitro
Polypeptide Initiation in HeLa Cells
Authors: Goldstein Elliott S. , Reichman Marsha E. , Penman Sheldon
Published: May 2006

The
in vitro
initiation of polypeptides on endogenous polyribosomes has been studied in extracts from HeLa cells. Regulation of the rate of initiation of polypeptides can be examined. In these experiments an assay using [
35
S]fMet-tRNA
f
Met
has been developed, and the system further characterized.

The system has been separated into a fraction containing polyribosomes with subunits and a fraction containing soluble components. The regulation of initiation has at least two distinct components.

There is one factor in the soluble fraction which develops a stimulated response after protein synthesis has been inhibited in intact cells. This stimulation does not require new RNA synthesis during the period of cell “stress.”

A second component is associated with ribosomes. This factor is necessary for the initiation of polypeptides on endogenous polyribosomes. It disappears gradually when cells are exposed to actinomycin. The disappearance is first manifested by an inability of polyribosomes to respond to stimulated supernatants. This unstable component, which decays in the presence of actinomycin, has no apparent counterpart in systems that measure initiation on exogenous mRNA.
Plasminogen Activator Production Accompanies Loss of Anchorage Regulation in Transformation of Primary Rat Embryo Cells by Simian Virus 40
Authors: Pollack R. , Risser R. , Conlon S. , Rifkin D.
Published: May 2006

We have isolated several lines of rat embryo cells transformed by simian virus 40. All these lines are fully transformed with regard to saturation density and serum sensitivity, but they differ greatly in their anchorage dependence, as assayed by efficiency of plating in methyl cellulose suspension. This set of lines reveals a consistent relation of plasminogen activator production to plating efficiency in methyl cellulose. T-antigen-positive transformed lines that synthesize activator grow in methyl cellulose suspension, while T-antigen-positive transformed lines that do not synthesize activator fail to form colonies in suspension. Normal rat embryo cells produce very little plasminogen activator and do not grow in methyl cellulose. Sera that permit high levels of plasmin formation and activity support growth in semi-solid medium better than sera whose plasminogen is activated poorly and/or sera that contain inhibitors to plasmin.
Alterations of Membrane Glycopeptides in Human Colonic Adenocarcinoma
Authors: Kim Young S. , Isaacs Richard , Perdomo Jose M.
Published: May 2006

Membrane glycopeptides were examined in human colonic adenocarcinoma and normal colonic mucosa. The carbohydrates of membrane glycopeptides were found to be markedly reduced in tumor tissue and the relative proportions of the various sugars were altered. Although all of the sugars were lower in tumor tissue when compared to the adjacent normal mucosa, galactosamine, fucose, and sialic acid were more significantly reduced. Examination of the blood group activity and lectin-binding properties of membrane glycopeptides revealed that specific carbohydrate structures had changed in the tumor tissue. Most striking of these changes was the disappearance of glycoprotein-associated blood group A activity. Assay of the enzyme responsible for synthesis of the blood group A determinant showed that this glycosyltransferase activity was greatly diminished in tumor tissue. A galactosyltransferase and a fucosyltransferase were also significantly lower in the tumor tissue whereas the levels of another galactosyltransferase and a sialyltransferase were unaltered. Glycosidase activities in the normal and tumor tissues were similar. The results show that an alteration in glycoprotein biosynthesis occurred during tumorigenesis that resulted in a modified membrane glycoprotein composition and that these changes are probably a reflection of reduced levels of the enzymes responsible for glycoprotein synthesis.
An Electron-Nuclear Double Resonance (Endor) Study of the Special Pair Model for Photo-Reactive Chlorophyll in Photosynthesis
Authors: Norris J. R. , Scheer H. , Druyan M. E. , Katz J. J.
Published: May 2006

A comparison of hyperfine coupling constants obtained by electron-nuclear double resonance spectroscopy of
in vitro
monomer chlorophyll and bacteriochlorophyll free radicals with those of the photoesr (electron spin resonance) signal associated with light conversion in photosynthesis provides convincing support for the special pair model for the
in vivo
photo-reaction center.
Aberrations of Cyclic Nucleotide Metabolism in the Hearts and Vessels of Hypertensive Rats
Authors: Amer M. Samir , Gomoll Allen W. , Perhach James L. , Ferguson Hugh C. , McKinney Gordon R.
Published: May 2006

In the aortas and mesenteric arteries from spontaneous hypertensive rats and in the aortas from stress- and desoxycorticosterone-acetate-hypertensive rats, the intracellular cGMP: cAMP ratios were significantly elevated when compared to the ratios in the aortas of the respective controls. Decreases in the intracellular cAMP or cGMP levels were consistently associated with increased activity of the cyclic-nucleotide-specific low
K
m
phosphodiesterase (3′:5′-cAMP 5′ nucleotidohydrolase, EC 3.1.4.17). Increases in intracellular cGMP levels were associated with elevated guanylyl cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] activity. Furthermore, adenylyl cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activity was less sensitive to stimulation by the β-adrenergic stimulant isoproterenol in both the aortas and the hearts of the hypertensive animals. These changes could provide the biochemical basis for the (
a
) increased vascular smooth muscle tone and peripheral resistance observed in these animals, (
b
) increased reactivity to norepinephrine, and (
c
) decreased ability of aortas from hypertensive rats to relax. The presence of these same effects in different etiologic types of hypertension indicates that this aberration in cyclic nucleotide metabolism may represent a common metabolic defect basic to the hypertensive syndrome irrespective of etiology.
The 5′-Terminal Nucleotide Sequence of Galactose Messenger Ribonucleic Acid of
Escherichia coli
Authors: Musso Richard E. , De Crombrugghe Benoit , Pastan Ira , Sklar Jeffrey , Yot Pierre , Weissman Sherman
Published: May 2006

The 5′-terminal sequence of mRNA from the galactose operon of
E. coli
has been determined.
gal
RNA is synthesized
in vitro
by means of a kinetically controlled purified transcription system and is isolated by a two-step RNA·DNA hybridization scheme. The following sequence of the first 77 nucleotides has been deduced by analysis of oligonucleotides produced by digestion with T
1
, pancreatic, and carboxymethylated pancreatic ribonucleases: ppA-U-A-C-C-A-U-A-A-G-C-C-U-A-A-U-G-G-A-G-C-G-A-A-U-U-A-U-G-A-G-A-G-U-U-C-U-G-G-U-U-A-C-C-G-G-U-G-G-U-A-G-C-G-G-U-U-A-C-A-U-U-G-G-A-A-G-U-C-A-U-A-C-C-U-G-U. Residues 27-77 correspond to the amino terminal 17 amino acids of UDPgalactose 4-epimerase (EC 5.1.3.2), the protein specified by the promoter-proximal structural gene of the operon. A self-complementary sequence occurs near the 5′ terminus; 12 of 15 nucleotides between residues 4 and 18 are symmetrically located about position 11. The sequence of residues 22-33 closely resembles part of the lactose operator sequence reported previously [Gilbert, W. & Maxam, A. (1973)
Proc. Nat. Acad. Sci. USA
70, 3581-3584].
Nonhistone Proteins Control Gene Expression in Reconstituted Chromatin
Authors: Barrett T. , Maryanka D. , Hamlyn P. H. , Gould H. J.
Published: May 2006

Chromatin was reconstituted from the purified DNA and histones of chicken erythrocytes and the nonhistone proteins of either chicken reticulocytes or chicken liver. Reconstituted chromatins, native chicken reticulocyte chromatin, and free DNA were transcribed with
Escherichia coli
RNA polymerase and the concentrations of globin-specific sequences in the RNA products were measured by hybridization with [
3
H]DNA complementary to chicken globin messenger RNA. Reticulocyte, but not liver, nonhistone proteins were shown to activate the globin genes in reconstituted erythrocyte chromatin. The transcripts of native and reconstituted chromatins were indistinguishable in respect of both the total yield of the RNA and the fractional yield of globin-specific sequences.
Development of Junctions During Differentiation of Lens Fibers
Authors: Benedetti E. Lucio , Dunia Irene , Bloemendal Hans
Published: May 2006

Throughout the differentiation of eye lens epithelium into fibers, an extensive system of intercellular junctions develops. The junctional assembly is initially characterized by the accumulation of 9.0-nm intramembranous particles, forming linear rows in the matching plasma membranes of adjoining fibers. At the final stage of the fiber differentiation, the junctional particles are assembled in geometrically packed arrays. The formation of linear rows and bidimensional lattices of intramembranous particles probably favors reciprocal recognition of cell surfaces and specific cell-to-cell interlocking. Moreover, the existence of a rather rigid lipid core of the plasma membrane of eye lens fiber may promote the clustered distribution of intramembranous particles and facilitate the junctional assembly.
Function of Individual 30S Subunit Proteins of
Escherichia coli
. Effect of Specific Immunoglobulin Fragments (Fab) on Activities of Ribosomal Decoding Sites
Authors: Lelong J. C. , Gros D. , Gros F. , Bollen A. , Maschler R. , Stöffler G.
Published: May 2006

Specific anti-30S protein immunoglobulin G fragments (Fab) were used to determine the contribution of each of the 30S ribosomal proteins to: (
1
) polyphenylalanine synthesis, (
2
) initiation factor-dependent binding of fMet-tRNA, (
3
) T-factor-dependent binding of phenylalanyl-tRNA, and (
4
) fixation of radioactive dihydrostreptomycin. Twenty of the 21 possible antibodies (antibody against S17 excepted) were used. In conditions where all the 30S proteins were accessible to Fabs, all of these monovalent antibodies strongly inhibited polyphenylalanine synthesis
in vitro
. Antibodies against S4, S6, S7, S12, S15, and S16, however, showed a weaker effect.

30S proteins can be classified into four categories by their contributions to the function of sites “A” and “P”: class I appears nonessential for tRNA positioning at either site (S4, S7, S15, and S16); class II includes proteins whose role in initiation is critical (S2, S5, S6, S12, and S13); class III (S8, S9, S11, and S18) corresponds to proteins whose blockade prevents internal (elongation factor Tudependent) positioning; and class IV includes entities that are essential for activities of both “A” and “P” sites (S1, S3, S10, S14, S19, S20, and S21). Dihydrostreptomycin fixation to the 30S or 70S ribosomes was inhibited by antibodies against S1, S10, S11, S18, S19, S20, and S21, but only weakly by the anti-S12 (Str A protein) Fab.

The significance of these results is discussed in relation to 30S protein function, heterogeneity, and topography.
The Crystal and Molecular Structure of Ethyl Chlorophyllide
a
·2H
2
O and Its Relationship to the Structure and Aggregation of Chlorophyll
a
Authors: Strouse Charles E.
Published: May 2006

Determination of the crystal structure of ethyl chlorophyllide
a
·2H
2
O by single crystal x-ray diffraction techniques has provided the first detailed molecular structural data available for a magnesium-containing derivative of chlorophyll. At the same time the aggregation observed in this structure serves as the basis for a model of chlorophyll aggregation
in vitro
and
in vivo
. The magnesium atom in ethyl chlorophyllide is displaced 0.4 Å from the plane of the chlorin ring in the same direction as the methyl ester substituent. A water molecule occupies the fifth coordination site. A second water molecule is hydrogen bonded to the coordinated water molecule and also to the carbonyl oxygen atom of the methyl ester. Hydrogen bonds between the water molecules and carbonyl oxygen atoms link the chlorophyllide molecules into a two-dimensional aggregate of crosslinked one-dimensional polymers. The relationship of this aggregate to aggregates of chlorophyll both
in vitro
and
in vivo
is discussed, as is the efficiency of exciton transport within the polymer.
Calcium-Induced Extrusion of Secretory Granules (Exocytosis) in Mast Cells Exposed to 48/80 or the Ionophores A-23187 and X-537A
Authors: Cochrane D. E. , Douglas W. W.
Published: May 2006

Isolated peritoneal mast cells from rats were observed, by phase contrast microscopy, to extrude secretory granules when exposed to 48/80 or the ionophores A-23187 and X-537A, which are known to facilitate transmembrane fluxes of calcium. These effects were abolished when the cells were treated with EDTA and suspended in a Ca-free environment. Ca-deprived cells exposed to any one of the three drugs promptly extruded granules when calcium, but not magnesium, was added to the incubation medium. Such Ca-evoked or Ca-dependent responses persisted when Na was omitted from the incubation medium and replaced with sucrose, choline, or K. The responses thus seem independent of possible shifts in the alkali metal ions. The results are considered support for the view that Ca influx mediates stimulus-secretion coupling and does so by initiating exocytosis.
Mode of Action of a Supernatant Activity from T-Cell Cultures that Nonspecifically Stimulates the Humoral Immune Response
Authors: Hunter Philippa , Kettman J. R.
Published: May 2006

The mode of action of “allogeneic supernatant” (the culture supernatant of a 24-hr mixedlymphocyte reaction), has been studied. This factor stimulates the response of spleen cell cultures depleted in thymus-derived lymphoid cells (T-cells) to antigens that elicit a thymus-dependent response. We used a limiting dilution analysis, in which the frequency and size of response of individual bone-marrow-derived lymphoid cells (B-cells) could be measured. In confirmation of other reports, the occurrence of B-cells responding to antigen under different conditions was shown to follow a Poisson distribution in mouse spleen cell suspensions. Allogeneic supernatant increased responses to thymus-dependent antigens, both by increasing the frequency of B-cells whose response is initiated and by increasing the numbers of antibody-forming cells obtained from each responding B-cell. Two fractions were obtained by dialysis of the supernatant. The nondialyzable fraction contained factors able to increase both the frequency of B-cells responding to sheep erythrocytes, and the size of the responding unit. The dialysate contained factors that were only able to increase the numbers of antibody-forming cells obtained per responding B-cell from B-cells whose response had already been initiated by antigen-specific T-cells.

Since the nondialyzable factors were active in the absence of detectable functional T-cells, it was concluded that these factors, produced by T-cells, might represent one mechanism whereby T-cells cooperate with B-cells in the initiation or development of a humoral immune response.
31
P Nuclear Magnetic Resonance Spectroscopy of Native and Recombined Lipoproteins
Authors: Assmann Gerd , Sokoloski Edward A. , Brewer H. Bryan
Published: May 2006

Native and recombined lipoproteins have been studied by
31
P nuclear magnetic resonance spectroscopy. Very low-, low-, and high-density lipoproteins exhibited characteristic spectra. The main resonances were assigned to phosphatidylcholine and sphingomyelin. Relaxation times for these phospholipids were separately measured in low-density lipoproteins and high-density lipoproteins. The effect of paramagnetic ions (Eu
+++
) on the nuclear magnetic resonance spectrum of high-density lipoproteins is reported.
Protein Kinase Induction in
Escherichia coli
by Bacteriophage T7
Authors: Rahmsdorf H. J. , Pai S. H. , Ponta P. , Herrlich P. , Roskoski R. , Schweiger M. , Studier F. W.
Published: May 2006

After bacteriophage T7 infection, a protein kinase (EC 2.7.1.37; ATP:protein phosphotransferase) activity can be demonstrated in
E. coli in vivo
by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Cell-free extracts catalyzed the transfer of the terminal phosphoryl group of [
γ
-
32
P]ATP to endogenous protein acceptor or to added histone. The bond between phosphate and protein shows the characteristics of serine phosphate: it is stable in 1 N HCl (100°) and cleaved by 1 N KOH (37°) and by alkaline phosphatase treatment. Moreover, after partial acid hydrolysis, radiophosphate migrates with marker
O
-phosphoserine on polyethyleneimine-cellulose thin-layer chromatograms. Enzyme activity in uninfected cells is negligible. Ultraviolet irradiation of the phage genome prevents the appearance of the protein kinase; irradiation of the host genome does not. The enzyme activity occurs 4 min after infection and its gene maps in the early region (promoter proximal to gene
1
). Ribosomal proteins are phosphorylated
in vivo
and are substrates
in vitro
. Enzyme activity
in vitro
is not changed by addition of cyclic AMP or cyclic GMP.
A Distinct Class of Inducible Murine Type-C Viruses that Replicates in the Rabbit SIRC Cell Line
Authors: Benveniste Raoul E. , Lieber Michael M. , Todaro George J.
Published: May 2006

The existence of the selectively permissive rabbit cell line SIRC allows definition of a new class of endogenous murine type-C virus. Continuous clonal lines of transformed cells derived from the BALB/c mouse-embryo cell line BALB/3T3 contain at least two distinct classes of endogenous type-C viral genomes. Spontaneously released endogenous viruses grow well on the mouse cell line NIH/3T3 (N-tropic viruses) but not on the rabbit cell line SIRC. Type-C viruses induced by treatment with BrdU grow well on SIRC (S-tropic viruses) but not in NIH/3T3 or BALB/3T3. BrdU-treated AKR mouse-embryo cells also release an S-tropic virus. N-tropic and S-tropic viruses both have the mouse intraspecies gs-1 and viral RNA-directed DNA polymerase antigenic determinants. DNA·RNA hybridization techniques reveal that the two host-range classes of endogenous viruses are only partially related to each other. Cell transformation facilitates the spontaneous release of the N-tropic viruses; treatment with thymidine analogues induces the production of the S-tropic viruses. Thus, the two classes of viral genomes appear to be subject to different cellular controls.
Isolation of a Peptidyl-Pantetheine-Protein from Tyrocidine-Synthesizing Polyenzymes
Authors: Lee Sung G. , Lipmann Fritz
Published: May 2006

The polyenzyme complex responsible for the synthesis of tyrocidine in
Bacillus brevis
(ATCC 8185) was found to contain 4′-phosphopantetheine, which appeared to be connected with the production of growing peptide chains. Confirmation of this assumption has now been obtained by purifying from bacterial lysates a polyenzyme-dissociation product; this was labeled with [
14
C]pantothenic acid and peptide chains containing tritiated amino acids, and had a molecular weight of 17,000. To obtain these results, organisms were grown udner conditions favorable for incorporation of radioactive pantothenic acid into tyrocidine-synthesizing enzymes. A crude lysate of the [
14
C]pantothenic acid-labeled organisms was preincubated with the tritiated amino acids to form enzyme-bound growing peptide chains. The doubly labeled fragments were purified from the polyenzyme-dissociation products produced by prolonged lysis. In a second set of experiments, the three enzymes responsible for tyrocidine synthesis, including the two polyenzymes containing pantetheine, were purified and incubated with radioactive amino acids and ATP to form polyenzyme-bound peptide chains. Thereupon, a Triton X-100 extract of the 20,000 ×
g
fraction of crude homogenate was added to dissociate the purified polyenzymes. The dissociation products were purified and yielded, on dodecyl sulfate gel electrophoresis, peptidyl-marked products ranging in molecular weight from 90,000 to 17,000, the latter being most abundant. Electrophoresis of analogous preparations after preincubation with higher concentrations of dodecyl sulfate and dithiothreitol at 100° yielded a single product of 17,000 molecular weight, indicating that the larger molecular weight fractions were aggregates thereof.
Coordinate Inhibition of Elongation Factor G Function and Ribosomal Subunit Association by Antibodies to Several Ribosomal Proteins
Authors: Highland Joseph H. , Ochsner Erika , Gordon Julian , Bodley James W. , Hasenbank Renate , Stöffler Georg
Published: May 2006

We previously showed that treatment of
Escherichia coli
ribosomes with antibodies specific for proteins L7 and L12 inhibits both EF-G·GDP binding and ribosome-dependent GTP hydrolysis (Highland
et al.
(1973)
Proc. Nat. Acad. Sci. USA 70
, 142-150; and Kischa
et al.
(1971)
Nature New Biol. 233
, 62-63). We now report that antibodies to six additional proteins also inhibit GTP hydrolysis, but do not inhibit EF-G·GDP binding. Moreover, inhibition by these antibodies is dependent on the state of association of the treated ribosomes. When 70S couples are treated, only antibodies to proteins L14 and L23 are inhibitory and then only partially. However, when separated ribosomal subunits are treated individually and then mixed with the complementary untreated subunits, inhibition by antibodies L14 and L23 is complete, and antibodies to proteins L19, L27, S9, and S11 now show an inhibitory effect. In addition, treatment of subunits with any of these six antibodies (but not those to L7 or L12) results in inhibition of reassociation, which is presumably responsible for the inhibition of hydrolysis. These data suggest that the area of interaction between EF-G and the ribosome is restricted to proteins L7 and L12, and that antibodies to proteins L14, L19, L23, L27, S9, and S11, but not L7 and L12, block the physical association of the subunits.
Independent Regulation of the Nuclear RNA Polymerases I and II During the Yeast Cell Cycle
Authors: Sebastian Jesus , Takano Isamu , Halvorson Harlyn O.
Published: May 2006

The activities of the nuclear RNA polymerases I and II have been investigated in cells of
Sacharomyces cerevisiae
at G
1
, S, early G
2
, and late G
2
stages of the cell cycle. The results show that the ratio of the activities of the two enzymes is different at these four stages, indicating that the two RNA polymerases are regulated independently during the cell cycle. The specific activity of the RNA polymerase I remains constant but that of RNA polymerase II increases sharply in cells at the beginning of the G
2
phase. These results are compatible with a pattern of continuous synthesis of the RNA polymerase I and step-wise synthesis of the RNA polymerase II during the yeast cell cycle.
Serotonin-Sensitive Adenylate Cyclase in Neural Tissue and Its Similarity to the Serotonin Receptor: A Possible Site of Action of Lysergic Acid Diethylamide
Authors: Nathanson James A. , Greengard Paul
Published: May 2006

An adenylate cyclase (EC 4.6.1.1) that is activated specifically by low concentrations of serotonin has been identified in homogenates of the thoracic ganglia of an insect nervous system. The activation of this enzyme by serotonin was selectively inhibited by extremely low concentrations of D-lysergic acid diethylamide (LSD), 2-bromo-LSD, and cyproheptadine, agents which are known to block certain serotonin receptors
in vivo
. The inhibition was competitive with respect to serotonin, and the calculated inhibitory constant of LSD for this serotonin-sensitive adenylate cyclase was 5 nM. The data are consistent with a model in which the serotonin receptor of neural tissue is intimately associated with a serotonin-sensitive adenylate cyclase which mediates serotonergic neurotransmission. The results are also compatible with the possibility that some of the physiological effects of LSD may be mediated through interaction with serotonin-sensitive adenylate cyclase.
Localization of the Stringent Protein of
Escherichia coli
on the 50S Ribosomal Subunit
Authors: Ramagopal S. , Davis Bernard D.
Published: May 2006

The “stringent” protein of the ribosome, required for its synthesis of (p)ppGpp, is readily lost during zonal centrifugation. However, enough can be retained to permit its qualitative localization. It is found in native 50S subunits, runoff 70S ribosomes, and polysomes, but not in native 30S subunits. This protein, therefore, appears to be attached to the 50S moiety of the ribosome, and it may be a constant (though easily removed) component of that structure rather than a factor that joins and leaves during the ribosome cycle.
Comparison of Human Serum Dopamine-β-Hydroxylase Levels by Radioimmunoassay and Enzymatic Assay
Authors: Rush Robert A. , Thomas Paul E. , Nagatsu Toshiharu , Udenfriend Sidney
Published: May 2006

Human serum dopamine-β-hydroxylase (3,4-dihydroxyphenylethylamine, ascorbate:oxygen oxidoreductase, EC 1.14.17.1) has been measured in a normal adult population by both enzymatic assay and by radioimmunoassay. The levels of enzymatic activity varied over a very wide range from 0.6 units/ml to 85 units/ml. In contrast, the amount of total dopamine-β-hydroxylase protein present in these samples, as measured by radioimmunoassay, varied only over a 3-fold range: from 11.7 μg/ml to 34.4 μg/ml. From an analysis of the purified enzyme, the percentage of serum dopamine-β-hydroxylase that was catalytically active was estimated to be small and variable.
Migration Enhancement Factor: A New Lymphokine
Authors: Weisbart Richard H. , Bluestone Rodney , Goldberg Leonard S. , Pearson Carl M.
Published: May 2006

Production of human migration inhibitory factor by lymphocytes exposed to antigen was studied at intervals over a 7-day period. Migration inhibitory factor was measured by an agarose gel method, with buffycoat leukocytes as indicator cells. Lymphocyte supernatants from 7-day cultures consistently showed migration inhibitory factor activity; by contrast, enhancement of migration was frequently noted when effector cells were exposed to supernatants from 2- to 5-day cultures. Enhancement activity was manifested either by enhanced migration or by a sequential reduction in inhibitory activity consistent with a factor opposing the action of migration inhibitory factor. When supernatants were subjected to polyacrylamide gel electrophoresis, enhancement activity was regularly found in the beta-globulin region and migration inhibitory factor in the albumin fraction of the gel. The enhancement activity was heat-stable and nondialyzable. These findings characterize a hitherto unreported lymphokine, migration enhancement factor.
Evolution and the Distribution of Glutaminyl and Asparaginyl Residues in Proteins
Authors: Robinson Arthur B.
Published: May 2006

Recent experiments on the deamidation of glutaminyl and asparaginyl residues in peptides and proteins support the hypothesis that these residues may serve as molecular clocks that control biological processes. A hypothesis is now offered that suggests that these molecular clocks are set by rejection or accumulation of appropriate sequences of residues including a glutaminyl or asparaginyl residue during evolution.
Induction of Nucleolar and Mitochondrial DNA Replication in
Tetrahymena pyriformis
Authors: Engberg Jan , Nilsson Jytte R. , Pearlman Ronald E. , Leick Vagn
Published: May 2006

Selective induction of replication of nucleolar and mitochondrial DNA has been demonstrated in starved-refed cultures of
Tetrahymena pyriformis
by different techniques.

Labeling of starved cells with [
3
H]thymidine during a nutritional shift-up and analysis of the DNA in isopycnic CsCl gradients shows that the two initially labeled species of DNA are two species banding on the heavy and light side of the bulk macronuclear DNA. In isolated macronuclei the radioactivity is found only in the high density fraction, which has been shown to be of nucleolar origin. In sucrose gradients the newly replicated mitochondrial and nucleolar DNAs sediment considerably slower than the bulk DNA, as one discrete band corresponding to a molecular weight of about 3 to 4 × 10
7
.

Electron microscope autoradiography of cells labeled with [
3
H]thymidine as above shows that the peripheral nucleoli of the macronucleus as well as the mitochondria are labeled before any radioactivity is found in the chromatin granules of the macronucleus.

The results clearly indicate that nucleolar and mitochondrial DNA replication are under a control independent of that for the replication of bulk DNA.
Conditions for Using DNA Polymerase I as an RNA-Dependent DNA Polymerase
Authors: Gulati S. C. , Kacian D. L. , Spiegelman S.
Published: May 2006

Conditions are described for using
Escherichia coli
DNA polymerase I for synthesizing complementary DNA copies of natural RNA molecules, which are suitable for use in hybridization experiments. The molar ratio of enzyme to template is critical; below a certain level, synthesis is not observed. Hybrids formed with the complementary DNA are of comparable specificity and stability to those formed with complementary DNAs synthesized by viral RNA-directed DNA polymerase. Synthesis of dA-dT polymers, a common occurrence with this enzyme, can be eliminated by including distamycin in the reaction mixture.
Octopamine- and Serotonin-Stimulated Phosphorylation of Specific Protein in the Abdominal Ganglion of
Aplysia california
Authors: Levitan Irwin B. , Barondes Samuel H.
Published: May 2006

Phosphorylation of a protein (or proteins) of molecular weight 120,000 in the
Aplysia
abdominal ganglion, as measured by incorporation of [
32
P] or [
33
P]sodium phosphate
in vitro
followed by separation of the phosphoproteins on sodium dodecyl sulfate-polyacrylamide gels, was specifically stimulated by incubation in the presence of the putative neurotransmitters octopamine or serotonin. The stimulatory effect of octopamine and serotonin was inhibited by phentolamine and methysergide, respectively, and was mimicked by incubation in the presence of dibutyryl cyclic AMP. Label-chase experiments indicated that the difference between control and octopamine-treated ganglia persists for several hours after removal of the drug from the incubation medium. This result suggests that neurotransmitters may produce relatively long-lasting changes in a phosphoprotein in the ganglion, perhaps in postsynaptic cells.
Purification and Properties of Two RNA Polymerases from
Physarum polycephalum
Authors: Burgess Ann Baker , Burgess Richard R.
Published: May 2006

Two RNA polymerases have been purified from the slime mold
Physarum polycephalum
, one sensitive and one resistant to α-amanitin. Both enzymes are more active with denatured DNA than native DNA as a template and prefer Mn
++
rather than Mg
++
as a divalent cation. The α-amanitin-sensitive enzyme shows maximum activity at 0.15 M KCl, whereas the resistant enzyme is most active at very low ionic strength. Analysis of the resistant enzyme on polyacrylamide gels containing sodium dodecyl sulfate shows two subunits present in a 1:1 ratio with molecular weights of 205,000 and 125,000.
In Vivo
Release of Glycoprotein I from the Ha Subline of TA
3
Murine Tumor into Ascites Fluid and Serum
Authors: Cooper Amiel G. , Codington John F. , Brown Michael C.
Published: May 2006

Previous studies have demonstrated that a unique glycoprotein can be cleaved by trypsin from the plasma membrane of the Ha, but not the St, subline of the TA
3
murine mammary adenocarcinoma. Using an automated quantitative method for measurement of trypsincleaved fragments (glycoprotein fraction I) by inhibition of
Vicia graminea
lectin hemagglutination, we find evidence that glycoprotein fraction I-like molecules appear in the ascites fluid and serum of the Ha-bearing, but not the St-bearing, syngeneic mice. These molecules were shown by gel filtration to be larger than the trypsincleaved glycoprotein fraction I but have a carbohydrate composition very similar to glycoprotein fraction I. It is likely that these ascites and serum glycoproteins have been released
in vivo
from the membranes of the viable Ha tumor cells. In view of the ability of the Ha, but not the St, cells to grow in allogeneic recipients, it is possible that these circulating membrane-derived molecules may be playing a blocking role in the immune response to the tumor.
Cholinergic Augmentation of Lymphocyte-Mediated Cytotoxicity. A Study of the Cholinergic Receptor of Cytotoxic T Lymphocytes
Authors: Strom Terry B. , Sytkowski Arthur J. , Carpenter Charles B. , Merrill John P.
Published: May 2006

Cholinergic agonists have previously been shown to augment the ability of sensitized lymphocytes to injure cells bearing the sensitizing alleantigens. The cholinergic receptor of the attacking lymphocyte population has been studied with pharmacological manipulation of an
in vitro
system that quantitates the injury mediated by sensitized attacking cells upon target cells. The data reveal that muscarinic ligands are several orders of magnitude more potent than nicotinic agents in altering cytotoxicity.