bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro
Stimulation of Sensitized Lymphocytes by Herpes Simplex Virus and Vaccinia Virus
Authors: Rosenberg Gary L. , Farber Paul A. , Notkins Abner Louis
Published: May 2006

Splenic lymphocytes from rabbits immunized with herpes simplex virus (HSV) were incubated
in vitro
with ultraviolet light-inactivated HSV, and the degree of lymphocyte transformation was determined by measurement of the incorporation of [
3
H]thymidine into acid-insoluble material. Lymphocytes from immunized rabbits were stimulated as much as 30-fold, whereas lymphocytes from control rabbits were unaffected. Lymphocyte sensitization occurred within 3 days after immunization; sensitized lymphocytes could still be detected 120 days after immunization. The antigenicity of the ultraviolet light-inactivated crude virus pool was found to reside primarily in the virion. Infectious virus, in comparison with inactivated virus, produced less lymphocyte stimulation. Studies on the interaction of the humoral and cellular immune responses showed that incubation of anti-HSV antibody with HSV antigens did not reduce the capacity of the viral antigens to stimulate sensitized lymphocytes. Other experiments revealed that lymphocytes from both the spleen and peripheral blood of animals immunized with vaccinia virus could be stimulated by vaccinia, but not by HSV. Conversely, lymphocytes from animals immunized with HSV could not be stimulated by vaccinia. The transformation of sensitized lymphocytes by viral antigens appears to be a simple, highly specific, and quantitative
in vitro
technique for the study of the cellular immune response to viral infections.
Inhibition of Collagen Secretion from Bone and Cultured Fibroblasts by Microtubular Disruptive Drugs
Authors: Diegelmann Robert F. , Peterkofsky Beverly
Published: May 2006

Collagen synthesis in chick-embryo frontal bone and 3T3 fibroblasts from mice was measured by incorporation
in vitro
of [
14
C]proline into collagenase-digestible material. About 15-25% of the collagen synthesized by the frontal bone in 60 min, and 60% of that synthesized by the fibroblasts in 2 hr, was found to be soluble in the culture medium. The microtubular disruptive drugs colchicine and vinblastine, at 10 μM, inhibited collagen secretion in both systems almost completely. Formation of collagen hydroxyproline from proline was not inhibited by these drugs. Cytochalasin B, which impairs microfilament function, had no effect on collagen secretion. Our results support the theory that collagen is transported in vesicles to the cell membrane, where it is secreted. This conclusion is based on the similarity of the collagen-secreting system to other systems in which the movement of secretory vesicles or storage granules is inhibited by microtubule disruption.
Electron Transfer to Ferricytochrome
c
: Reaction with Hydrated Electrons and Conformational Transitions Involved
Authors: Pecht Israel , Faraggi Moshe
Published: May 2006

The reaction of horse-heart cytochrome
c
with hydrated electrons has been studied by the pulseradiolysis technique. In neutral solution, the ferriheme group was reduced in a bimolecular reaction that takes place at a rate equal to that of the decay of the
e
-

aq

, and approaches the diffusion-controlled limit. This reduction is assigned mainly to a direct reaction, proceeding via the exposed edge of the porphyrin projecting into the cytochrome
c
crevice.

The reaction absorption spectrum observed 20 μsec after an electron pulse was very similar, yet blue-shifted relative to, the difference spectrum between the reduced and oxidized forms of cytochrome
c
. However, this shift vanishes in a slow monomolecular reaction, which seems to reflect the conformational relaxation of the protein to the final equilibrium state of its reduced form. In alkaline solutions, the transition of cytochrome
c
molecules into an irreducible conformation causes a proportionate decrease in the amount of ferricytochrome
c
reduced in the direct reaction. The rate of conformational transition of the protein into the reactive form is now the limiting step for a substantial part of the reduction that takes place via this slow monomolecular reaction.

Pseudomonas
cytochrome
c
551 which, in contrast to horse-heart cytochrome
c
, is a negatively charged protein at neutral pH reacts with
e
-

aq

at a rate lower than does the horse-heart protein. The reduction of the heme group follows that of the
e
-

aq

decay with a small, yet significant, delay.
Spatial Arrangement of Ribosomal Proteins: Reaction of the
Escherichia coli
30S Subunit with
bis
-Imidoesters
Authors: Bickle T. A. , Hershey J. W. B. , Traut R. R.
Published: May 2006

The 30S ribosomal subunit of
E. coli
was treated with the bifunctional reagent
bis
-(methyl)suberimidate. Crosslinked ribosomal proteins were identified as bands with increased molecular weight after electrophoresis in polyacrylamide gels containing sodium dodecyl sulphate. The pattern of crosslinked products was altered when unfolded subunits were used. Free ribosomal protein was not crosslinked. Several of the crosslinked products were cleaved by ammonolysis to form the original monomeric protein constituents. The low yields of the reactions necessitated the use of radioactive proteins and auto-radiographic procedures. The crosslinked proteins were tentatively identified by coelectrophoresis of the radioactive ammonolysis products with carrier 30S protein in sodium dodecyl sulphate, and coelectrophoresis at pH 4.5 in buffers containing urea.
Expression of Ribosomal Protein Genes as Analyzed by Bacteriophage Mu-Induced Mutations
Authors: Nomura Masayasu , Engbaek Frode
Published: May 2006

The organization of ribosomal protein genes and the gene (
fus
) for a protein chain elongation factor, EF G, in
Escherichia coli
were studied with a merodiploid strain that has an episome with genetic markers,
ery
r
,
spc
r
,
str
r
, and
fus
r
, and a chromosome with markers
ery
s
,
spc
s
,
str
s
, and
fus
s
. The
ery
locus determines a 50S ribosomal protein and the
spc
and
str
loci determine 30S ribosomal proteins. The phenotype of the diploid strain is sensitive to all of the four antibiotics, erythromycin (Ery), spectinomycin (Spc), streptomycin (Str), and fusidic acid (Fus). Analysis of antibiotic-resistant mutants induced by bacteriophage Mu in the diploid strain indicates that these four genes, and probably many other ribosomal protein genes linked to them, are transcribed as a single unit, and the direction of the transcription is in the order of
ery, spc, str
, and
fus
.
Effect of Norepinephrine on Glucose Metabolism in Glioblastoma and Neuroblastoma Cells in Cell Culture
Authors: Newburgh R. W. , Rosenberg Roger N.
Published: May 2006

The addition of norepinephrine to cultured glioblastoma cells results in an inhibition of uptake of radioactivity from D-[2-
3
H]glucose, D-[1-
14
C]glucose, D-[2-
14
C]glucose, and D-[6-
14
C]glucose. In addition, if the glioblastoma cells are previously labeled with these substrates, norepinephrine causes an increase in the release of radioactivity. These effects were not observed with cultured neuroblastoma cells. It is suggested that the breakdown of glycogen is activated by norepinephrine as a result of an increase in 3′:5′-cyclic AMP.
Functional Nonequivalence of α and β Hemes in Human Adult Hemoglobin
Authors: Lindstrom Ted R. , Ho Chien
Published: May 2006

Nuclear magnetic resonance studies of the contact-shifted spectra of heme protons in deoxyhemoglobin A from human adults show conclusively that oxygen binds to the α hemes in preference to the β hemes. The preferential binding is produced in 10% hemoglobin solution at neutral pH by either a 15-fold molar excess of 2,3-diphosphoglycerate or a 5-fold molar excess of inositol hexaphosphate. Preferential binding is not observable in the absence of the organic phosphates. The results indicate that the oxygenation of hemoglobin may be described by a sequential model, or by a concerted model that allows the α hemes to bind ligand first.
2′-
O
-Methylation of Adenosine, Guanosine, Uridine, and Cytidine in RNA of Isolated Rat Liver Nuclei
Authors: Al-Arif Adhid , Sporn Michael B.
Published: May 2006

Nuclei isolated from rat liver, when incubated with methyl-labeled
S
-adenosylmethionine, incorporated label into 2′-
O
-methyladenosine, 2′-
O
-methylguanosine, 2′-
O
-methyluridine, and 2′-
O
-methylcytidine of endogenous nuclear RNA. Addition of ribosomal RNA from wheat germ to the reaction markedly stimulated 2′-
O
-methylation of total RNA. The relative incorporation of label into the four different 2′-
O
-methyl ribonucleosides was greatly changed by the addition of wheat germ RNA. There was much more 2′-
O
-methylation of the purine ribonucleosides, relative to the pyrimidine ribonucleosides, in the reaction stimulated by wheat germ RNA.
Selective Inhibition of Nuclear DNA Synthesis by 9-β-D-Arabinofuranosyl Adenine in Rat Cells Transformed by Rous Sarcoma Virus
Authors: Shipman Charles , Smith Sandra H. , Drach John C.
Published: May 2006

The drug, 9-β-D-arabinofuranosyl adenine, selectively inhibits the synthesis of nuclear DNA without affecting extrachromosomal DNA synthesis in rat cells transformed by Rous sarcoma virus (B-mix K-44/6). The inhibition was linear with respect to drug concentration over the range of 37-600 μM. Mitosis and total synthesis of DNA per cell were also depressed. DNA synthesis was determined by measurement of [
3
H]thymidine incorporation into DNA. Covalently-closed circular DNA was extracted by the Hirt procedure and separated from residual chromosomal DNA by buoyant density gradient ultracentrifugation in CsCl-propidium diiodide. On the basis of buoyant density and sedimentation velocity centrifugation, the covalently-closed circular DNA formed in the presence of the drug was indistinguishable from that formed in its absence.
Temporal Pattern of Neurogenesis in Spinal Cord: Cytoarchitecture and Directed Growth of Axons
Authors: Nornes Howard O. , Das Gopal D.
Published: May 2006

Neurogenesis was studied in rat spinal cord by correlation of the observations from [
3
H]thymidine autoradiography and Golgi techniques. The temporal pattern of the origin of neurons systematically lagged along the ventro-dorsal and rostro-caudal axes. The temporal pattern was correlated with the topographic pattern of the release and segregation of the newly formed neuroblasts from the neuroepithelium. These temporal and topographic patterns of neuroblast genesis imparted an order to the settling of the neuroblasts. Further, the emerging cytoarchitecture of the differentiating neuroblasts resulted in the formation of oriented interfaces along which the axons grew. The “pioneering” fibers grew along the interfaces formed by the regressed neuroepithelium and the assembled neuroblasts. As development progressed, the axons formed later “selectively fasciculated” along the “pioneering” fibers in a staggered pattern as a result of their differential times of origin. These temporal and topographic patterns occurred in a manner such that the preexisting structure served as an “organizing structure” or foundation upon which the axonal processes formed later in the developmental sequence were oriented and assembled.
Synthesis, Acetylation, and Phosphorylation of Histone IV and Its Binding to DNA During Spermatogenesis in Trout
Authors: Louie Andrew J. , Dixon Gordon H.
Published: May 2006

During spermatogenesis in trout testis, histone IV is extensively modified by acetylation and phosphorylation. To examine the relationship of synthesis of histone IV to its modification, histone IV labeled with [
3
H]aminoacids and inorganic [
32
P]phosphate was prepared from testis cells by acid extraction and column chromatography. Purified histone IV was resolved by starch gel electrophoresis into 10 bands, of which nine are modified by acetylation and/or phosphorylation. In the first 4 hr of labeling, the diacetyl-histone IV band showed the highest proportion of [
3
H]aminoacid label. After 12 hr of incorporation, more label was found in the triacetyl and tetraacetyl bands. A significant amount of amino-acid label in the two major bands (the unsubstituted and monoacetyl bands) of histone IV was not seen until 16 hr of incubation. From 1 to 12 days, the proportion of label in the unsubstituted and monoacetylated bands increased, while that in the tetra-, tri-, and monoacetyl bands decreased. Very little [
3
H]aminoacid was found in the phosphorylated bands of histone IV in the first 12 hr. However, after 16 hr about 20% of the total
3
H was found in the phosphorylated bands. The proportion increased to 33% and remained at this level between 1 and 8 days, but, by 16 days, had decreased to 12% of the total.

These data suggest that an “obligatory” acetylation of recently synthesized histone IV is involved in the correct binding of newly synthesized histone IV to DNA. We propose that ε-amino acetylation of lysyl residues 5, 8, 12, and 16 neutralizes their positive charges and allows the NH
2
-terminal region of histone IV to assume the correct conformation (in this case, an α-helix), and fit into the major groove of DNA. Deacetylation then “locks” histone IV to DNA by ionic linkages. The biological significance of phosphorylation of histone IV is not known.
A Novel Mechanism for the NIH-Shift
Authors: Yagi Haruhiko , Jerina Donald M. , Kasperek George J. , Bruice Thomas C.
Published: May 2006

Kinetics of aromatization of 1,4-dimethylbenzene oxide (
I
) to 2,5-dimethylphenol (
II
) and 2,4-dimethylphenol (
III
), the latter arising by an NIH-Shift of a methyl group, as measured in the pH range 1-12, follow the equation -
d
[
I
]/
dt
= [
I
][
k
0
+ (
k
[unk] +
k
[unk])
a
H], where
k
0
= 4.8 × 10
-3
sec
-1
,
k
[unk] = 7.3 × 10
2
M
-1
sec
-1
, and
k
[unk] = 5.3 × 10
2
M
-1
sec
-1
. The ratio of products
II
to
III
at pH ≥ 6 in the
spontaneous
rearrangement (
k
0
) is 13 to 87, and changes to 54 to 46 in the
acid-catalyzed
rearrangement (
k
[unk] and
k
[unk]). While no intermediate is detectable in the acid-catalyzed rearrangement of the arene oxide by pathway
k
[unk], simultaneous addition of water (and other nucleophiles) by pathway
k
[unk] leads,
via
the intermediate 1,4-dimethyl-2,5-cyclohexadiene-1,4-diol (
IV
), to the phenols
II
and
III
. This new mechanism for the NIH-Shift serves as a model for the ease of nucleophilic addition to other arene oxides, such as those of the polycyclic aromatic hydrocarbons recently implicated in mechanisms of carcinogenesis.
Association by Hydrogen Bonding of Mononucleotides in Aqueous Solution
Authors: Raszka Matthew , Kaplan Nathan O.
Published: May 2006

Evidence for hydrogen bonding between 5′-ribonucleotides in water has been obtained from a 220-MHz proton magnetic resonance study of nitrogenous protons. The amino groups of GMP, AMP, and CMP exhibit proton resonance lines which are somewhat broadened by proton exchange with the solvent at 0°; their downfield Shifts in mixtures of mononucleotides provide the basis for the following order of base-pairing tendencies: GMP·CMP > AMP·UMP. Hydrogen bonding is also observed in other pairs of mononucleotides, notably GMP·UMP, AMP·CMP, and CMP·UMP, to a lesser extent in GMP·IMP, CMP·XMP, and possibly in CMP·IMP. In agreement with previous reports, hydrophobic interactions of mononucleotides have also been observed; base pairing occurs in addition to vertical stacking of these bases, their hydrogen bonding to water, or self-association. Only CMP shows clear evidence of self-association via hydrogen bonding in water; the evidence for GMP is less direct, and that for AMP is negative. This lack of observable self-association may occur as a result of competition from strong stacking interactions. Only CMP shows restricted rotation of the amino group at 0° and neutral pH. As expected, higher temperatures increase the rate of rotation of the amino group for CMP, as well as accelerate the rate of proton exchange between water and the amino protons of mononucleotides.

High-resolution proton magnetic resonance spectroscopy could prove to be a valuable tool in mapping out the specificities conferred by hydrogen bonding between biomolecules in aqueous solution.
Microgeographical Variation in Allozyme Frequencies in
Avena barbata
Authors: Hamrick J. L. , Allard R. W.
Published: May 2006

Microgeographical distribution of alleles of five enzyme loci and one morphological variant has been determined within populations of
A. barbata
occupying sites that are transitional between different vegetational zones. The results show that the spatial distribution of alleles is nonrandom and highly correlated with habitat in patterns that parallel the distribution of the same alleles in major climatic zones in California. It is concluded that the observed patterns of variation are best explained by Neo-Darwinian evolutionary models, in which selection plays a predominant role.
Nonchromosomal Antibiotic Resistance in Bacteria: Genetic Transformation of
Escherichia coli
by R-Factor DNA
Authors: Cohen Stanley N. , Chang Annie C. Y. , Hsu Leslie
Published: May 2006

Transformation of
E. coli
cells treated with CaCl
2
to multiple antibiotic resistance by purified R-factor DNA is reported. Drug resistance is expressed in a small fraction of the recipient bacterial population almost immediately after uptake of DNA, but full genetic expression of resistance requires subsequent incubation in drugfree medium before antibiotic challenge. Transformed bacteria acquire a closed circular, transferable DNA species having the resistance, fertility, and sedimentation characteristics of the parent R factor. Covalently-closed, catenated, and open (nicked) circular forms of R-factor DNA are all effective in transformation, but denaturation and sonication abolish the transforming ability of R-factor DNA in this system.
Dopamine-sensitive adenylate cyclase in caudate nucleus of rat brain, and its similarity to the “dopamine receptor”
Authors: Kebabian John W. , Petzold Gary L. , Greengard Paul
Published: May 2006

An adenylate cyclase that is activated specifically by low concentrations of dopamine has been demonstrated in homogenates of caudate nucleus of rat brain. A half-maximal increase in the activity of the enzyme occurred in the presence of 4 μM dopamine. Concentrations of dopamine as low as 0.3 μM stimulated the activity of the enzyme. The adenylate cyclase activity of the homogenates was also stimulated by low concentrations of apomorphine, a substance known to mimic the physiological and pharmacological effects of dopamine. The stimulatory effect of dopamine was blocked by low concentrations of either haloperidol or chlorpromazine, agents known to block the actions of dopamine in mammalian brain. The results suggest that dopamine-sensitive adenylate cyclase may be the receptor for dopamine in mammalian brain. The isolation of this enzyme from caudate nucleus should facilitate the search for new therapeutic agents useful in the treatment of extrapyramidal diseases.
Coupling of Replication to Transcription
In Vitro
Authors: Karkas John D.
Published: May 2006

In a coupled system consisting of RNA polymerase and DNA polymerase I of
Escherichia coli
, the four deoxyribo- and the four ribonucleoside triphosphates, and DNA of bacteriophage f1 as template, DNA synthesis depends on the concomitant synthesis of RNA. Over a wide range of concentrations of the two polymerases, RNA synthesis was unaffected by the simultaneous synthesis of DNA, whereas the rate of DNA synthesis depended on the level of RNA synthesis. In the coupled reaction, RNA synthesis starts immediately at a high rate, which subsequently decreases, whereas DNA synthesis starts after a lag and its rate increases as the reaction proceeds. Upon addition of rifampicin, the rate of RNA synthesis falls abruptly, while that of DNA declines only gradually. The base composition of the DNA synthesized in the coupled reaction is complementary to that of f1 DNA template. It is suggested that the RNA synthesized by the RNA polymerase serves as a primer rather than as a template for the DNA polymerase.
Homing in Pigeons with Impaired Vision
Authors: Schmidt-Koenig K. , Schlichte H. J.
Published: May 2006

In order to test the importance of vision in homing pigeons, their vision was impaired by frosted contact lenses. Pigeons wearing such lenses seemed unable to recognize artificial landmarks at 6-m distance. Nevertheless, most birds homed from distances of 15 km, and some even from 130-km distance. This result indicates that, contrary to common expectation, vision need not play an essential role in homing.
Modulation of Cell Behavior
In Vitro
by the Substratum in Fibroblastic and Leukemic Mouse Cell Lines
Authors: Macieira-Coelho Alvaro , Avrameas Stratis
Published: May 2006

Fibroblastic and leukemic mouse cell lines were cultivated on a bovine serum albumin polymer covered with basic or acidic substances. Contact inhibition of fibroblast movement (cell overlapping) and division varied depending on prior treatment of the albumin polymer. The leukemic cells, which normally grow in suspension, attached and spread out on the polymers and could be carried as a monolayer. Preparation of surfaces capable of modulating different parameters of cell behavior
in vitro
is thus possible.
Antigen-Binding Specificity of Isolated Cell-Surface Immunoglobulin from Thymus Cells Activated to Histocompatibility Antigens
Authors: Cone Robert E. , Sprent Jon , Marchalonis John J.
Published: May 2006

Lactoperoxidase-catalyzed radioiodination of cell-surface proteins was used in the isolation of cell-surface immunoglobulin from thymus-derived thoracic duct lymphocytes activated to histocompatibility-2 antigens. Immunoglobulin was identified by specific precipitation with antiserum to mouse immunoglobulin. Polyacrylamide gel electrophoresis of reduced and alkylated precipitates showed that the immunoglobulin molecules possessed μ-type heavy chains and light chains. Cell-surface immunoglobulin isolated from thymus-derived cells activated to histocompatibility-2 antigens possessed binding specificity for the activating antigens.
Localization of Antibody-Combining Sites within the Variable Portions of Heavy and Light Chains
Authors: Inbar Dan , Hochman Jacob , Givol David
Published: May 2006

The Fab′-fragment of a mouse IgA-myeloma (protein-315) was split by pepsin to yield a smaller fragment that retained the anti-2,4-dinitrophenyl activity of the intact protein. This fragment, which we call Fv, has a molecular weight of about 30,000 (half that of Fab′), and is composed of two polypeptide chains (molecular weight 14,000) held together by noncovalent bonds. The N-terminal sequence of Fv suggests that it is composed of the N-terminal half of Fab′, and consists of the variable portions of the heavy and light chains. Since Fv has about one binding site with the same association constant as Fab′, this experiment provides direct evidence that the antibody site in this protein is contained entirely in the variable portion, and is independent of the constant portion, of the molecule.
Translational Control of Specific Uterine Protein Synthesis After Estrogen Induction
Authors: DeAngelo Anthony B. , Fujimoto George I.
Published: May 2006

The rate of leucine incorporation into a specific estrogen-induced protein of immature rat isolated by gel electrophoresis declines rapidly between 2-4 hr after estrogen stimulation
in vivo
followed by incubation
in vitro
. Actinomycin D present during the
in vitro
phase prevents this decline, and elicits a “superinduction” effect at 2 hr. Labeled induced protein remains stable during this time period, indicating that its decline is due to a reduction in synthesis capacity for the inducible protein, rather than to its degradation. A second injection of hormone at 3 hr has no effect on the reduced level of synthesis capacity for induced protein noted at 4 hr in the rat uterus.
Induction of Cytolysis of Cultured Lymphoma Cells by Adenosine 3′:5′-Cyclic Monophosphate and the Isolation of Resistant Variants
Authors: Daniel Violet , Litwack Gerald , Tomkins Gordon M.
Published: May 2006

Cultured mouse lymphosarcoma cells are killed on exposure to 0.1 mM
N
6
,
O
2′
-dibutyryl-adenosine 3′:5′-cyclic monophosphate. A population of cells resistant to the killing effect of dibutyryl cyclic AMP at concentrations as high as 1 mM was selected. The growth characteristics of the resistant cells were similar to those of the sensitive parental line. However, the resistant cells contain less cytoplasmic cyclic AMP-binding proteins and decreased cyclic AMP-stimulated protein kinase activity. It is proposed that transition from sensitivity to resistance to dibutyryl cyclic AMP in lymphoma cells is connected with a modification of the cyclic AMP-binding protein, which appears to be the regulatory subunit of the cyclic AMP-activated protein kinase.
RNA-Linked DNA Fragments
In Vitro
Authors: Sugino Akio , Okazaki Reiji
Published: May 2006

RNA-linked DNA fragments are intermediates in DNA replication in
Escherichia coli
cells made permeable to nucleoside triphosphates by treatment with toluene. Covalent linkage of a short RNA stretch to the 5′ end of the DNA is proved by transfer of
32
P from [α-
32
P]dNTP to ribonucleotides upon digestion with alkali or pancreatic RNase, and by a small decrease in the molecular size upon alkaline hydrolysis. The
32
P transfer experiments reveal a unique structure...p(rPy)p(rA)p(rU or rC)p(dC)p... at the RNA-DNA junction.
Acetylcholine-Like Molecular Arrangement in Psychomimetic Anticholinergic Drugs
Authors: Maayani Saul , Weinstein Harel , Cohen Sasson , Sokolovsky Mordechai
Published: May 2006

A study of the relation between the psychotropic activity and the antagonism to acetylcholine observed for some heterocyclic amino esters and compounds of the phencyclidine series suggests some common molecular structural requirements for their properties.

Criteria obtained from quantum mechanical calculations of acetylcholine-like molecules indicate that their molecular reactivity with the cholinergic receptor site follows a certain dynamic interaction pattern. This pattern suggests a certain molecular arrangement essential for the interaction, which is based on the electronic properties of the molecules and therefore remains valid for the evaluation of compounds which lack any apparent similarity to acetylcholine. This type of molecular arrangement is shown to be shared by both activators and inhibitors of the acetylcholine receptor discussed here, thus supporting the hypothesis of their binding to a common receptor. The differences in biological activity are attributed to the effect of molecular structural factors which are not commonly included in the molecular arrangement based on the active groups of acetylcholine. The role of such factors is revealed by a study of the observed differences in the cholinergic and psychomimetic activities of related pairs of isomers and enantiomers of the molecules investigated. Structural factors which interfere with the conformational changes occurring in the receptor protein induced by an activator are characterized through differences obtained by the comparative investigation of the activities of the agonist acetate and the antagonist benzilate amino esters of quinuclidine, tropine, and pseudotropine. The same factors are shown in studies of the phencyclidine series to contribute to the antagonism to acetylcholine activity that is closely related to the psychomimetic activity of these drugs in the central nervous system. Similarly, phencyclidine derivatives in which the characteristic acetylcholine-like molecular arrangement is modified by various substitutions are shown to loose both anticholinergic and psychotropic behavior. This close correlation is supported by the identification of molecular regions which will generate the proper molecular arrangement in local anesthetics and morphine, compounds which are known to be involved in cholinergic mechanisms.
Microfluorometric Detection of Deoxyribonucleic Acid Replication in Human Metaphase Chromosomes
Authors: Latt Samuel A.
Published: May 2006

Fluorescence of the dye 33258 Hoechst bound to chromosomes is partially quenched by the introduction of BrdU into chromosomal DNA. This finding has allowed microfluorometric detection of DNA synthesis in human metaphase chromosomes. Incorporation, shortly before cell harvest, of a pulse of thymidine into chromosomes otherwise substituted with BrdU results in sharply defined foci of bright 33258 Hoechst fluorescence, corresponding to regions of late DNA replication. The latereplicating X chromosome can thereby be clearly identified, and the time course of appearance of its fluorescent bands can be compared with that of its earlier replicating homologue. Growth of cells in medium containing BrdU for two generations allows fluorometric documentation of the semiconservative distribution of newly replicated DNA between sister chromatids, and regions of sister chromated exchange are demarcated. This approach should constitute, in many instances, a convenient, high-resolution fluorometric alternative to autoradiography.
Nonheuristic Computer Determination of Molecular Structure Based Upon Carbon-13 Nuclear Magnetic Resonance Data. Branched Alkanes
Authors: Burlingame A. L. , Mcpherron R. V. , Wilson D. M.
Published: May 2006

A computer-based system for elucidation of molecular structure is described for the branched alkanes, based upon
13
C nuclear magnetic resonance data. All possible structures of a given carbon content are exhaustively generated in a DENDRAL-like manner, and scored according to the fit of their predicted spectral characteristics to those of the “unknown” alkane. The technique may be generalized to any class of organic compounds for which
13
C chemical-shift additivity parameters are reliable, and shows promise for stereochemical elucidation.
Size and Base Composition of RNA in Supercoiled Plasmid DNA
Authors: Williams Peter H. , Boyer Herbert W. , Helinski Donald R.
Published: May 2006

The average size and base composition of the covalently integrated RNA segment in supercoiled ColE
1
DNA synthesized in
Escherichia coli
in the presence of chloramphenicol (CM-ColE
1
DNA) have been determined by two independent methods. The two approaches yielded similar results, indicating that the RNA segment in CM-ColE
1
DNA contains GMP at the 5′ end and comprises on the average 25 to 26 ribonucleotides with a base composition of 10-11 G, 3 A, 5-6 C, and 6-7 U.
Effects of Bradykinin and Indomethacin on Cyclic GMP and Cyclic AMP in Lung Slices
Authors: Stoner J. , Manganiello V. C. , Vaughan M.
Published: May 2006

Bradykinin, 1-100 μg/ml, produced a rapid rise in the concentration of 3′:5′-guanosine monophosphate (cyclic GMP) and 3′:5′-adenosine monophosphate (cyclic AMP) in slices of guinea pig lung. Concentrations of both nucleotides reached a maximum in about 2 min, then declined to a basal levels in 6-12 min. The transient nature of the effect was presumbaly due to the rapid destruction of bradykinin as evidenced by (
1
) reaccumulation of nucleotides when bradykinin was added a second time, and (
2
) potentiation of the bradykinin effects by pyroGlu-Lys-Trp-Ala-Pro, a peptide that inhibits inactivation of bradykinin by kininase. It has been reported elsewhere that histamine, prostaglandins E
1
and E
2
, and β-adrenergic stimulation can cause accumulation of cyclic AMP in lung slices without affecting cyclic GMP concentration, whereas acetylcholine increases the concentrations of both cyclic GMP and cyclic AMP. Thus it was possible that the effects of bradykinin were indirect, i.e., secondary to release of one or more of these compounds. Promethazine (an antihistamine), propranolol (a β-adrenergic blocking agent) and atropine (an anticholinergic agent) did not alter basal cyclic nucleotide concentrations or the effects of bradykinin. Two inhibitors of prostaglandin synthesis, indomethacin and aspirin, which alone were without effect, in the presence of bradykinin completely prevented the rise in cyclic AMP but did not interfere with cyclic GMP accumulation. Similarly, the effect of acetylcholine on cyclic AMP was abolished by indomethacin while that on cyclic GMP was unaltered. We suggest that in lung and probably in other tissues, bradykinin, acetylcholine, and perhaps other stimuli enhance the synthesis and release of prostaglandins as one of the consequences of their effects on cyclic GMP metabolism.
The Importance of Calcium Ions for the Regulation of Guanosine 3′:5′-Cyclic Monophosphate Levels
Authors: Schultz G. , Hardman J. G. , Schultz K. , Baird C. E. , Sutherland E. W.
Published: May 2006

Guanosine 3′:5′-cyclic monosphosphate (cyclic GMP) levels in the ductus deferens of the rat were increased 2- to 3-fold by acetylcholine (10-1000 μM) or by 125 mM KCl, while adenosine 3′:5′-cyclic monophosphate (cyclic AMP) levels were not changed. After incubation for 30 min in the absence of Ca
++
, cyclic GMP control levels were decreased by 85% and were not affected by acetylcholine or KCl. The readdition of Ca
++
(1.8 mM) for 3 min to Ca
++
-deprived tissue partially restored basal cyclic GMP levels and the effects of acetylcholine and KCl. The addition of Sr
++
(3.6 mM) or of Ba
++
(1.8 or 10 mM) also caused an increase in basal cyclic GMP in Ca
++
-deprived tissue. Cyclic AMP levels were not significantly changed under any of these conditions. The addition of the phosphodiesterase inhibitor, 1-methyl-3-isobutylxanthine (0.1 mM), to ductus deferentes increased the amount of cyclic AMP about 50% and that of cyclic GMP about 2-fold. The later effect also depended on the presence of Ca
++
. 1-Methyl-3-isobutylxanthine (0.1 mM) increased cyclic GMP and cyclic AMP levels in slices of rat submaxillary glands. Methacholine increased cyclic GMP if added in the presence of methyl isobutylxanthine. Cyclic GMP control levels and the effect of methyl isobutylxanthine were unchanged by Ca
++
omission, but the effect of methacholine was abolished.

These findings indicate that calcium ions are important for the control of cyclic GMP levels in these tissues.
Stereochemical Trigger for Initiating Cooperative Interaction of the Subunits During the Oxygenation of Cobaltohemoglobin
Authors: Hoard J. L. , Scheidt W. R.
Published: May 2006

Relative to the standard provided by an unconstrained five-coordinate imidazoleiron(II) porphyrin, the axial separation (N
ε
...P
μ
) in deoxyhemoglobin of the complexed histidine-nitrogen (N
ε
) atom from the mean plane (P
μ
) of the protoporphyrin is stretched by [unk] 0.30 Å. Retention of the same globin framework (quaternary structure) in deoxycobaltohemoglobin implies an axial connection with the cobalt protoporphyrin that carries enhanced tension, but a somewhat smaller value of N
ε
...P
μ
than the 2.90 Å observed in deoxyhemoglobin. Structural constraints imposed on and by the globin in support of tension in the axial linkage are conducive to doming of the entire 24-atom porphine skeleton of the protoporphyrin toward the metal (M) atom. Furthermore, the presence of an odd electron in the 3

d
z

2
orbital of the metal atom is responsible for an easily stretched M-N
ε
bond. It then appears that moderate doming of the porphinato core in combination with modest stretch in the Co-N
ε
bond can readily lead to an N
ε
...P
μ
distance approaching 2.90 Å in deoxycobaltohemoglobin and, consequently, to compatibility with Perutz's postulated trigger for the initiation of cooperative interaction of the subunits during the reversible oxygenation of hemoglobin.
Activation of a Proteolytic System by a Membrane Lipoprotein: Mechanism of Action of Tissue Factor
Authors: Nemerson Yale , Esnouf M. P.
Published: May 2006

One pathway of blood coagulation, the extrinsic system, is initiated by a specific interaction between tissue factor, which is a membrane lipoprotein, and factor VII, one of the plasma coagulation factors. Factor VII was prepared from bovine plasma by adsorption onto and elution from BaSO
4
. The eluate was chromatographed on DEAE-Sephadex and purified by preparative disc-gel electrophoresis. Factor VII complexed with purified bovine-brain tissue factor and, when eluted from the complex, factor VII had a greater mobility in acrylamide-gel electrophoresis in the presence of sodium dodecyl sulfate, i.e., it had a reduced molecular weight. Factor VII was also cleaved in the presence of orthophenanthroline, an inhibitor of the peptidase activity of tissue factor. Prior treatment of factor VII with diisopropylphosphorofluoridate, however, completely blocked its cleavage and the development of coagulant activity, although factor VII treated with diisopropylphosphorofluoridates complexed equally well as the native protein with tissue factor. Factor VII in whole bovine plasma was also inhibited by the drug. Factor VII labeled with [
32
P]diisopropylphosphorofluoridate and radioautographed after electrophoresis in gels showed two major components, only one of which was labeled. We conclude that tissue factor initiates blood coagulation by facilitating a proteolytic attack within the factor VII “complex.” The most likely mechanism is proteolysis of one form of factor VII by the diisopropylphosphorofluoridate-sensitive enzyme, although additional intramolecular proteolysis may be involved.
Appearance in Trypsinized Normal Cells of Reactivity with Antibody Presumably Specific for Malignant Cells
Authors: Tarro Giulio
Published: May 2006

Trypsinization of normal human diploid cells (WI-38 and MRC 5) resulted in the appearance of complement-fixing reactivity with an immunoglobulin (anti-HeLa G globulin), prepared against a purified HeLa (malignant human) cell antigen (G), which reacts with various malignant human cell lines and tumors but not with certain normal human cells. The presence of receptors in the nonreacting, untrypsinized normal human cells and the specificity of the reactive groups that appeared after trypsinization was established by the fact that the antibody could be completely absorbed with large quantities of packed, untrypsinized human cells
but not
with similar quantities of either rabbit or guinea-pig kidney tissue-culture cells, which did not react with this antibody either before or after treatment with trypsin. The change produced by trypsinization is thus similar to the previously demonstrated appearance of reactive groups with the same anti-HeLa G globulin in normal human cells at certain times after infection with herpes simplex and vaccinia viruses.

The fact that the trypsinized WI-38 cells absorbed more antibody than the same number of cells before trypsinization indicated that trypsinization resulted not only in the appearance of reactivity with antibody but also in a greater concentration of combining receptors, which is unlike the situation with lectins producing agglutinability without an increase in the number of receptors. Moreover, the fact that absorption with trypsinized normal cells removed larger amounts not only of the antibody reacting with the trypsin-treated WI-38 cells but also of antibody that reacts with WI-38 cells infected with herpes simplex virus and with the malignant HEp-2 cells, suggests that the combining groups that emerge after trypsinization of the normal human cells are the same or similar to those present in malignant human cells (HEp 2) and to those that emerge after infection of the normal human cells with herpes simplex virus.
A Factor from a Transformed Cell Line That Affects Cell Migration
Authors: Bürk R. R.
Published: May 2006

When a monolayer culture of normal Balb/c3T3 cells is wounded by scraping away part of the cell sheet, the cells do not migrate into the cleared area unless there is serum in the culture medium. By contrast, SV40-transformed Balb/c3T3 cells do migrate into the wound area without serum. A quantitative assay for the migration of Balb/c3T3 cells into wounds is described. This assay is used in the partial purification of a migration factor released into serum-free medium by SV28 cells. SV28 is a line of BHK21/13 hamster cells transformed by SV40 chosen for its malignancy. The most purified fractions have about 1500 times the specific activity of whole calf serum. These fractions have an activity that promotes overgrowth of Balb/c3T3 cells to high density and an activity that prolongs cell survival without serum. The SV28 migration factor is not extractable from the medium of untransformed BHK21/13 cells or from serum. This migration factor might contribute to the malignancy of SV28 cells.
Biological Activities of Synthetic Peptides Corresponding to Fragments of and to the Entire Sequence of the Vasoactive Intestinal Peptide
Authors: Bodanszky Miklos , Klausner Yakir S. , Said Sami I.
Published: May 2006

An octacosapeptide with the entire sequence proposed for the newly isolated vasoactive intestinal polypeptide was synthesized and had the expected biological properties. Synthetic peptides corresponding to the C-terminal hendeca-, tetradeca-, pentadeca-, and docosapeptide sequences of the vasoactive intestinal polypeptide showed activities that increased with increasing chain length.
Adenosine 3′:5′-Cyclic Monophosphate as a Regulator of Bacterial Transformation
Authors: Wise Edmund M. , Alexander Susan P. , Powers Marilyn
Published: May 2006

Adenosine 3′:5′-cyclic monophosphate added to exponentially growing cells of
Hemophilus influenzae
strain Rd increases competence for transformation 100- to 10,000-fold. Cyclic AMP added to near-stationary or stationary cells does not increase competence over the high level normally found in the early stationary phase.
Terminal Deoxynucleotidyl Transferase in a Case of Childhood Acute Lymphoblastic Leukemia
Authors: McCaffrey Ronald , Smoler Donna F. , Baltimore David
Published: May 2006

Cells from a patient with childhood acute lymphoblastic leukemia contain an apparent DNA polymerase activity that was not found in any other cells except thymus cells. The enzyme has the properties of terminal transferase, an enzyme known to be found in thymocytes. The cells also contain the three major DNA polymerases found in growing cells. The results suggest that these tumor cells arose from a block in the differentiation of thymocytes. Terminal transferase may be a marker for the origin of leukemic cells.
Ethylene in Plant Growth
Authors: Burg Stanley P.
Published: May 2006

Ethylene inhibits cell division, DNA synthesis, and growth in the meristems of roots, shoots, and axillary buds, without influencing RNA synthesis. Apical dominance often is broken when ethylene is removed, apparently because the gas inhibits polar auxin transport irreversibly, thereby reducing the shoot's auxin content just as if the apex had been removed. A similar mechanism may underly ethylene-induced release from dormancy of buds, tubers, root initials, and seeds. Often ethylene inhibits cell expansion within 15 min, but delays differentiation so that previously expanding cells eventually grow to enormous size. These cells grow isodiametrically rather than longitudinally because their newly deposited cellulose microfibrils are laid down longitudinally rather than radially. Tropistic responses are inhibited when ethylene reversibly and rapidly prevents lateral auxin transport. In most of these cases, as well as certain other instances, ethylene action is mimicked by application of an auxin, since auxins induce ethylene formation. Regulation by ethylene extends to abscission, to flower formation and fading, and to fruit growth and ripening. Production of ethylene is controlled by auxin and by red light, auxin acting to induce a labile enzyme needed for ethylene synthesis and red light to repress ethylene production. Numerous cases in which a response to red light requires an intervening step dependent upon inhibition of ethylene production have been identified. Ethylene action requires noncovalent binding of the gas to a metal-containing receptor having limited access, and produces no lasting product. The action is competitively inhibited by CO
2
, and requires O
2
. Ethylene is biosynthesized from carbons 3 and 4 of methionine, apparently by a copper-containing enzyme in a reaction dependent upon an oxygen-requiring step with a

K
m

= 0.2% O
2
. The oxidative step appears to be preceded by an energy-requiring step subsequent to methionine formation.
An Improved Bacterial Test System for the Detection and Classification of Mutagens and Carcinogens
Authors: Ames Bruce N. , Lee Frank D. , Durston William E.
Published: May 2006

We previously described a set of four strains of
Salmonella typhimurium
designed for detecting the various types of mutagens, and showed their utility in detecting a wide variety of carcinogens as mutagens. The lipopolysaccharide that normally coats these bacteria is a barrier to penetration of mutagens to the cell membrane. The set of tester strains has been improved by adding a mutation (
rfa:
deep rough) that results in a deficient lipopolysaccharide. The techniques for using these strains for detecting mutagens are presented and the tests are shown to be extremely sensitive and convenient. The specificity of frameshift mutagenesis is clarified. As adjuncts to the test with the four strains, we describe a test that compares mutagenic killing in deep rough strains with and without DNA excision repair, and a test using forward mutagenesis in a deep rough strain lacking excision repair.
Ultraviolet Patterns on Rear of Flowers: Basis of Disparity of Buds and Blossoms
Authors: Eisner Thomas , Eisner Maria , Aneshansley D.
Published: May 2006

Flowers of
Jasminium primulinum
and
Hypericum
spp. have ultraviolet patterns on the reverse surface of the corolla. Those areas of the surface that are exposed to the outside in the bud are ultraviolet absorbent, whereas the portions that come into view at maturity in the open blossom are ultraviolet reflectant. Buds and blossoms, as a result, appear different in color to insects sensitive to ultraviolet light. Experimental evidence indicates that the ultraviolet-absorbent quality of the outer surface of the bud is a consequence of exposure itself, attributable possibly to a “sun tanning” effect.
Neurophysiology of Flight in Wild-Type and a Mutant
Drosophila
Authors: Levine Jon D. , Wyman Robert J.
Published: May 2006

We report the flight motor output pattern in
Drosophila melanogaster
and the neural network responsible for it, and describe the bursting motor output pattern in a mutant. There are 26 singly-innervated muscle fibers. There are two basic firing patterns: phase progression, shown by units that receive a common input but have no cross-connections, and phase stability, in which synergic units, receiving a common input and inhibiting each other, fire in a repeating sequence.

Flies carrying the mutation
stripe
cannot fly. Their motor output is reduced to a short duration, high-frequency burst, but the patterning within bursts shows many of the characteristics of the wild type. The mutation is restricted in its effect, as the nervous system has normal morphology by light microscopy and other behaviors of the mutant are normal.
Mechanism of Action of 1-β-D-Ribofuranosyl-1,2,4-Triazole-3-Carboxamide (Virazole), A New Broad-Spectrum Antiviral Agent
Authors: Streeter David G. , Witkowski J. T. , Khare Gyaneshwar P. , Sidwell Robert W. , Bauer Randy J. , Robins Roland K. , Simon Lionel N.
Published: May 2006

The antiviral activity of the synthetic nucleoside, Virazole (1-β-D-ribofuranosyl-1,2,4-triazole-3-carboxamide), against measles virus in Vero cell cultures was substantially reversed by xanthosine, guanosine, and to a slightly lesser extent by inosine. Virazole 5′-phosphate was subsequently found to be a potent competitive inhibitor of inosine 5′-phosphate dehydrogenase (IMP:NAD
+
oxidoreductase, EC 1.2.1.14) isolated from
Escherichia coli
(

K
m

= 1.8 × 10
-5
M) with a

K
i

of 2.7 × 10
-7
M. Guanosine 5′-phosphate (GMP) was a competitive inhibitor of this enzyme with a

K
i

of 7.7 × 10
-5
M. Virazole 5′-phosphate was similarly active against IMP dehydrogenase isolated from Ehrlich ascites tumor cells, with a

K
i

of 2.5 × 10
-7
M. The

K
m

for this enzyme was 1.8 × 10
-5
M, and the

K
i

for GMP was 2.2 × 10
-4
M. These results suggest that the antiviral activity of Virazole might be due to the inhibition of GMP biosynthesis in the infected cell at the step involving the conversion of IMP to xanthosine 5′-phosphate. This inhibition would consequently result in inhibition of the synthesis of vital viral nucleic acid.