bluuebunny/crossref_metadata_2025 huggingface dataset:
The Giemsa C-Banded Karyotype of Rye
Authors: Gill Bikram S. , Kimber Gordon
Published: May 2006

The chromosomes of rye have been individually identified by their distinctive heterochromatin pattern with Giemsa staining and classified on the basis of their homoeology with wheat chromosomes. The constitutive heterochromatin detected by C-banding has been shown to be identical with the classical heterochromatin as seen in the pachytene of meiosis in rye.
A Constant-Field Interrupted Resonance System for Percutaneous Electromagnetic Measurement of Blood Flow
Authors: Kolin Alexander , Steele James R. , Imai James S. , Macalpin Rex N.
Published: May 2006

A combination of deformable flow probes of negligible lateral dimensions with an electronic circuit capable of providing a prolonged plateau of
dB/dt
= 0 and of sampling the flow signal at the end of this interval permits electromagnetic measurement of blood flow with a reliable zero base line secured by switching off the magnet. An extracorporeal magnet provides the magnetic field. The flow transducer is introduced into the vascular system percutaneously through a standard angiographic catheter by conventional technique. The idea of the current generator can be described as “principle of interrupted resonance.” The current wave form can be described as a sequence of disconnected bisected sine waves joined at the apices by horizontal current plateaus where
di/dt
is
strictly
zero.
Eulerian Graphs and Polynomial Identities for Sets of Matrices
Authors: Hutchinson Joan P.
Published: May 2006

Let the standard identity of degree
m
be given by [Formula: see text] Then the minimum standard identity is determined for the set of all
n
×
n
skew-symmetric matrices over a field of characteristic 0.
Kinetic Properties of the Isoenzymes of Human Creatine Phosphokinase
Authors: Witteveen S. A. G. J. , Sobel B. E. , DeLuca M.
Published: May 2006

Studies of the three human creatine phosphokinase (EC 2.7.3.2) isoenzymes, MM, MB, and BB, show that important differences exist in substrate dependency of the reaction rates. A method was developed to study these properties in which the ATP formed in the reverse reaction was measured by means of firefly luciferase. With substrate conditions at which the isoenzymes showed substantial differences in activity the method could be used for the detection of changes in the isoenzyme pattern of the serum of patients with an acute myocardial infarction. The MB isoenzyme appearing in this condition could be detected quantitatively.
Investigation of the Composition and Formation Constant of Molecular Complexes
Authors: Sahai R. , Loper G. L. , Lin S. H. , Eyring H.
Published: May 2006

It has been the purpose of the present paper to investigate and explore the conditions under which the linear relation between Δ/

C
D

0
and Δ in the Hanna-Ashbaugh-Foster-Fyfe equation for the evaluation of equilibrium constants holds, (

C
D

0
is initial concentration of a donor and Δ is the observed chemical shift relative to the chemical shift of the acceptor) to obtain the equation representing the exact linear relation between Δ/

C
D

0
and Δ, when the linear relation between Δ/

C
D

0
and Δ holds, and to discuss how to use the Job method in nuclear magnetic resonance measurements to determine the stoichiometry of molecular complexes. We have found that the conventional belief that

C
D

0
should always be chosen to be much greater than

C
A

0
(initial concentration of acceptor) is not necessarily always true and the exact linear relation between Δ/

C
D

0
and Δ is represented by the equation Δ/

C
D

0
=
K
1
Δ
0
/(1 +
K
1

C
A

0
) -
K
1
Δ/(1 +
K
1

C
A

0
)
2
, where
K
1
is the formation constant of the complex. It is shown that in the Job method of nuclear magnetic resonance measurements one has to plot Δ

C
A

0
against the mole fraction, and the mole fraction at the maximum should give us the composition of the complex. Theoretical results have been verified experimentally on the weak interaction between naphthalene and methyl iodide.
Chemical Carcinogens as Frameshift Mutagens:
Salmonella
DNA Sequence Sensitive to Mutagenesis by Polycyclic Carcinogens
Authors: Isono Katsumi , Yourno Joseph
Published: May 2006

Other investigators have shown that several polycyclic carcinogens are frameshift mutagens in
Salmonella
. Mutagenic potency of these compounds is assessed by ability to induce reversion of histidine-requiring frameshift mutants to prototrophy. One frameshift mutation in the histidinol dehydrogenase gene,
hisD3052
, is unusually sensitive to mutagenesis by certain polycyclic carcinogens. We find that the
3052
mutation is a - 1 deletion, probably loss of a G·C pair from a DNA repeat of [unk]. The polycyclic carcinogens tested (e.g., 2-nitroso-fluorene) revert
3052
by deleting a [unk] doublet from the DNA sequence [unk], which is close to the
3052
site. This rare mispairing-prone sequence represents the carcinogen-sensitive “hotspot” in
3052
. The ICR compounds, noncarcinogenic intercalating agents, show a broader specificity of mutagenesis. Reversion with these mutagens occurs predominantly by two mechanisms: one identical to that of the polycyclic carcinogens, and the other by +1 additions in a third DNA tract narrowly separated from the
3052
site. The alkylating carcinogen
N
-methyl-
N
′-nitro-
N
-nitrosoguanidine appears to have a similar dual specificity. DNA base changes in
3052
revertants have been correlated with properties of histidinol dehydrogenase in crude extracts. This correlation of DNA base sequence with electrophoretic and other properties of the mutant proteins allows one to analyze easily the specificity of new mutagens that mutate this strain.
Pleiotropy of
hisT
Mutants Blocked in Pseudouridine Synthesis in tRNA:
Leucine
and
Isoleucine-V aline
Operons
Authors: Cortese Riccardo , Landsberg Raymond , Vonder Haar R. A. , Umbarger H. E. , Ames Bruce N.
Published: May 2006

The
hisT
gene codes for an enzyme responsible for the conversion of uridine to pseudouridine (Ψ) in the anticodon region of many tRNA species in
Salmonella typhimurium
. We have previously shown that a
hisT
mutant has tRNA
His
which lacks pseudouridine in this region and as a consequence has an altered chromatographic behavior. We show here a similar alteration in chromatographic behavior of all tRNA
Leu
and one tRNA
Ile
species from a
hisT
mutant. By contrast, tRNA
Val
, which contains no pseudouridine except for the one in the TΨCG sequence, is chromatographically unaltered in a
hisT
mutant.

The absence of pseudouridine in the anticodon region of tRNA in
hisT
mutants has been previously shown to cause derepression of the histidine operon. We show here that in
hisT
mutants the regulation of the leucine and the isoleucine and valine operons is also affected: the enzymes of these operons are refractory to repression by the branched chain amino acids. However, there is no difference between
hisT
and wild type in the pattern of derepression caused by isoleucine or valine limitation and only a slight difference in the enzyme levels in cells grown on minimal medium.

The alteration in the regulation of branched chain amino acid operons may also explain why
hisT
mutants are resistant to inhibition of growth by the amino acid analogues 5,5,5-trifluoroleucine, β-hydroxyleucine, and norleucine and by the oligopeptides glycylglycylnorleucine and norleucylnorleucine.
Visualization of Single-Stranded Nucleic Acid of RNA Tumor Virus With The Electron Microscope
Authors: Weber G. H. , Heine U. , Cottler-Fox M. , Beaudreau G. S.
Published: May 2006

60-70S RNA of avian myeloblastosis virus was spread with the Kleinschmidt method and examined in the electron microscope after being subjected to a variety of denaturing conditions. Extension of the molecules from a collapsed configuration was seen only under stringent denaturing conditions, resulting in molecules of 1-2 μm in length. Longer strands of these extremely fragile molecules cannot be obtained with the methods presently available.
Behavior in Different Environments of Populations of
Drosophila pseudoobscura
Selected for Phototaxis and Geotaxis
Authors: Dobzhansky Theodosius , Judson Charles L. , Pavlovsky Olga
Published: May 2006

When tested in Hirsch-Hadler mazes,
Drosophila pseudoobscura
descended from natural populations is phototactically and geotactically neutral on the average. Decidedly positive and negative populations have been obtained by artificial selection. The behavior is independent of temperature (15-27°) and age (2-17 days). The flies perceive light as weak as 0.2 lux; from 7 to 3000 lux the behavior difference between positive and negative strains increases little, and perhaps decreases at 8000 lux. A remarkable transformation occurs with red light; the population that is negatively phototactic with shorter wave lengths or with white light becomes photopositive.
Cell Envelope and Shape of
Escherichia coli
K12. Crosslinking with Dimethyl Imidoesters of the Whole Cell Wall
Authors: Haller Ingo , Henning Ulf
Published: May 2006

E. coli
cells treated with the bifunctional crosslinking reagents dimethyl malonimidate, succinimidate, adipimidate, suberimidate, and sebacinimidate served for the isolation of rod-shaped “ghosts.” These ghosts proved to be crosslinked over their entire surface; i.e., a macromolecule (resistant to boiling 1% Na dodecyl sulfate) the size of the cell had been created. Also, ghosts could similarly be crosslinked. In both cases, the final “sacs” contained about 60-70% protein, and very little or no lipopolysaccharide. When ghosts from which phospholipid had been removed were crosslinked, the covalently closed ghosts were almost pure protein; 80-90% of their dry mass was accounted for by protein. Ammonolysis of the crosslinked material (whether stemming from crosslinked cells or ghosts) showed that the same four proteins (Na dodecyl sulfate gel bands) had been crosslinked that are found in normally prepared ghosts. These observations practically exclude the hypothesis that a fluid mosaic model of membrane structure can be applied to the outer membrane of the
E. coli
cell envelope; rather, extensive protein-protein interactions must exist over the whole surface of this membrane. These findings are consistent with the possibility that the ghost polypeptide chains are involved in the determination of cellular shape.
Hormonal Control of Lysosomal Enzyme Release from Human Neutrophils: Elevation of Cyclic Nucleotide Levels by Autonomic Neurohormones
Authors: Ignarro Louis J. , George William J.
Published: May 2006

The influence of autonomic neurohormones on the immunologic release of β-glucuronidase (EC 3.2.1.31) from, and the cyclic nucleotide levels in, human neutrophils was determined. Interaction of neutrophils with rheumatoid arthritic, serum-treated zymosan particles in a neutral balanced salt solution at 37° resulted in the extracellular discharge of β-glucuronidase without any loss of cell viability, as indicated by the failure of incubated cells to take up eosin Y or to release cytoplasmic lactate dehydrogenase (EC 1.1.1.27). Epinephrine reduced the release of β-glucuronidase from neutrophils in the presence of zymosan during 2-30 min of incubation and elicited a concomitant elevation of adenosine 3′:5′-monophosphate levels. Propranolol, a β-adrenergic receptor antagonist, but not phentolamine, an α-adrenergic receptor antagonist, blocked both actions of epinephrine. Acetylcholine stimulated the release of β-glucuronidase, but not lactate dehydrogenase, and provoked a concomitant elevation of guanosine 3′:5′-monophosphate levels. Atropine, a muscarinic receptor antagonist, but not hexamethonium, a ganglionic blocker, inhibited both actions of acetylcholine. Interaction of neutrophils and zymosan particles resulted in an elevation of guanosine 3′:5′-monophosphate levels within 2 min. These data suggest that intracellular guanosine 3′:5′-monophosphate may be involved in mediating the immunologic release of lysosomal enzymes from human neutrophils whereas adenosine 3′:5′-monophosphate may inhibit enzyme release. Moreover, autonomic neurohormones appear to be capable of modulating lysosomal enzyme release by virtue of their capacity to elevate neutrophil cyclic nucleotide levels.
Genetics of Somatic Mammalian Cells: Biochemical Genetics of Chinese Hamster Cell Mutants with Deviant Purine Metabolism
Authors: Patterson David , Kao Fa-Ten , Puck Theodore T.
Published: May 2006

Studies are presented on the biochemical genetics of 30 adenine-requiring mutants of the Chinese hamster ovary cell which were induced by mutagenesis and selected by the BrdU-visible light technique. Representative experiments conducted with these mutants include: hybridization with each other; hybridization with normal human cells; nutritional analysis; biochemical analysis with radioactively labeled intermediates; and measurement of reversion frequencies to wild-type phenotype occurring spontaneously and under the influence of selected mutagens. All mutants behave as if having point mutations. These experiments provide information relevant to the determination of dominant-recessive relationships, resolution into different complementation classes, localization of the human chromosomes which carry human genes required by the individual mutants, determination of the point of metabolic block for different mutants, and elucidation of the nature of the underlying DNA changes. These experiments illustrate the range of biochemical-genetic studies now possible with such a family of somatic mammalian cell mutants
in vitro
. Possible application to problems of human genetic disease are indicated.
Pattern of Immunoglobulin Synthesis and Assembly in a Human-Mouse Somatic Cell Hybrid Clone
Authors: Schwaber Jerrold , Cohen Edward P.
Published: May 2006

Fusion of human peripheral blood lymphocytes, not forming detectable immunoglobulins, with mouse myeloma cells (TEPC-15), secreting mouse immunoglobulin A with known antibody activity, yielded a somatic cell hybrid clone that secreted both human and mouse immunoglobulins. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that human gamma, alpha, and light chains, as well as mouse alpha and light chains, were formed by the hybrid cells. To determine whether individual antibody molecules with both human and mouse components were secreted, medium from the hybrid cells was precipitated first with antibody against mouse immunoglobulin produced in rabbit, reduced, and alkylated, and then reprecipitated with antibody against human immunoglobulin produced in rabbit. Human gamma, alpha, and light chains were detected after electrophoresis of the immunoprecipitates on sodium dodecyl sulfate-polyacrylamide gels, indicating that antibody molecules containing both human and mouse components were secreted by the hybrid cells. These data indicate that this somatic cell hybrid clone synthesized human gamma and alpha heavy chains and human light chains, as well as mouse alpha heavy chains and mouse light chains. Some of these immunoglobulin components were assembled as hybrid antibody molecules.
Lipid Binding to the Amphipathic Membrane Protein Cytochrome
b
5
Authors: Dehlinger Peter J. , Jost Patricia C. , Griffith O. Hayes
Published: May 2006

The lipid binding properties of the membrane protein cytochrome
b
5
(detergent-extracted from calf liver microsomal preparations) were characterized by studying the interaction of spin-labeled lipids (5-, 12-, and 16-doxylstearic acid and 5- and 16-doxylphosphatidyl-choline, where doxyl refers to the nitroxide moiety) with cytochrome
b
5
, using electron spin resonance spectroscopy. The intact cytochrome
b
5
molecule immobilizes all of the lipid spin labels, while the segment of cytochrome
b
5
released by trypsin does not affect lipid mobility. The immobilization of lipid spin labels on the hydrophobic surface of intact cytochrome
b
5
is not appreciably altered by associating the protein with liposomes. Differences in polarity of the lipid binding sites between cytochrome
b
5
and phospholipid vesicles were also observed. The lipid binding sites on cytochrome
b
5
are hydrophobic by conventional criteria, but are more polar than the interior of fluid phospholipid bilayers.
Nerve Growth Factor in Rat Glioma Cells
Authors: Longo Angela M. , Penhoet Edward E.
Published: May 2006

We have shown that rat glioma tumors contain a protein that crossreacts with antibody against mouse 2.5S nerve growth factor prepared in rabbit in microcomplement fixation assays and has analogous isoelectric points to all the hybrids of 2.5S nerve growth factor (a dimer). Partially purified protein preparations from gliomas cause chick dorsal root ganglia to extend neurites in the nerve growth factor assay and cause morphological differentiation of mouse neuroblastoma cells. We conclude that the rat glioma protein is homologous to mouse salivary nerve growth factor and suggest the possibility that glial nerve growth factor plays a role in neuronal development and regeneration.
Oxaziridines as Possible Intermediates in Flavin Monooxygenases
Authors: Orf H. W. , Dolphin D.
Published: May 2006

The enzymatic hydroxylation reactions of flavin monooxygenases are suggested to involve an oxaziridine as the active oxygenating agent. The chemistry of these monooxygenases and their nonenzymatic model systems are consistent with an oxaziridine intermediate. Several advantages of the oxaziridine model over the previously proposed “carbonyl oxide” and flavin peroxide models are discussed.
The Role of Cytoplasmic Membranes in Controlling the Transport of Nuclear Messenger RNA and Initiation of Protein Synthesis
Authors: Shiokawa K. , Pogo A. O.
Published: May 2006

Three different classes of poly(A)-containing RNA have been identified in the yeast system. They have been characterized by their kinetics of labeling, by their localization in the nuclear, membranous, and soluble cytoplasmic fractions, and by their size. The evidence indicates that the membrane-bound poly(A)-containing RNA is a product of the nuclear poly(A)-containing RNA and is the precursor of the polysomal poly(A)-containing RNA. In addition, it has been demonstrated that transport of mRNA is coupled with protein synthesis.
Granulocyte Colonies Derived from Lymphocyte Fractions of Normal Human Peripheral Blood
Authors: Zucker-Franklin D. , Grusky G. , L'esperance P.
Published: May 2006

Granulocyte colonies can be grown from leukocyte-rich plasma obtained from normal human peripheral blood. Purification of lymphocytes by the Ficoll-Hypaque gradient method and subsequent removal of monocytes achieved a 10-fold increase in the number of colonies formed, suggesting that the colony-forming cell is nonadherent, nonphagocytic, and morphologically difficult to distinguish from a lymphocyte. Ultrastructural analysis of intact colonies by a new method developed for this purpose showed orderly differentiation and maturation. Only undifferentiated cells were seen in colonies on day 5, promyelocytes with developing primary lysosomes were present on day 9, whereas myelocytes and metamyelocytes were most prevalent on days 15 and 21, respectively. The studies suggest where further concentration of precursor cells may be attempted, and where further functional and histochemical analysis of colonies on the ultrastructural level will be possible.
New Phage-SPO1-Induced Polypeptides Associated with
Bacillus subtilis
RNA Polymerase
Authors: Fox Thomas D. , Pero Janice
Published: May 2006

RNA polymerase was precipitated from extracts of
Bacillus subtilis
infected with phage SP01 by antiserum prepared against core RNA polymerase. As shown by sodium dodecyl sulfate gel electrophoresis, the precipitates contained at least five new polypeptides not present in uninfected bacteria, in addition to the known subunits of RNA polymerase. The molecular weights of these polypeptides are (1) 85,000; (II) 40,000; (III) 28,000; (IV) 25,000; and (V) 23,000. Four of the polypeptides (I, III, IV, and V) co-purified with RNA polymerase through gel filtration and phosphocellulose chromatography. A pulse-chase experiment indicated that all five polypeptides are synthesized
de novo
after infection. The synthesis of polypeptides II, III, and IV commences almost immediately after infection, while polypeptides I and V first appear several minutes later. A
sus
mutant blocked early in transcription,
susF21
[Fujita,
et al.
(1971)
J. Mol. Biol.
57, 301-317] failed to induce polypeptides I, IV, and V, while two other mutants,
susF4
and
susF14
, blocked late in transcription both failed only to induce polypeptide V.
Lung Collagen Heterogeneity
Authors: Bradley Kathryn , McConnell-Breul Sally , Crystal Ronald G.
Published: May 2006

The structural heterogeneity of rabbit lung collagen was examined by extracting labeled collagen from short-term cultures of lung minces with 1 M NaCl-50 mM Tris·HCl (pH 7.4), 0.5 M acetic acid, or 0.4 ionic strength phosphate buffer. The extracted collagens were purified by carboxymethyl-cellulose chromatography, and their cyanogen bromide peptides were mapped by ion exchange chromatography and acrylamide gels. Rabbit skin α1(I) and α2 chains and rabbit sternal cartilage α1(II) chains were used as markers.

The peripheral lung, containing alveoli, small blood vessels, and small airways, synthesized α1(I) and α2 chains. The trachea and the bronchial tree (first through seventh order branches) both synthesized α1(II) chains. Lung α1(I), α2, and α1(II) chains all have a molecular weight of about 100,000 and are all sensitive to Clostridial collagenase.

The extraction and purification methods used isolate only 50% of the collagen synthesized by these structures
in vitro
. Once all collagen types in lung can be described and quantitated, it should be possible to utilize lung collagen types as biochemical markers to study normal lung development and to define the lung fibrotic diseases.
Regulation of Nuclear DNA Replication by the Chloroplast in
Chlamydomonas
Authors: Blamire John , Flechtner Valerie R. , Sager Ruth
Published: May 2006

The experiments described in this paper implicate chloroplast protein synthesis in the regulation of nuclear DNA replication. The inhibition of nuclear DNA replication in the lower eukaryote,
Chlamydomonas reinhardi
strain
21gr
, was examined after growth of cells with a series of antibiotics (streptomycin, neamine, spectinomycin, cleocin, chloramphenicol, and rifampicin) each of which has a known effect upon chloroplast RNA or protein synthesis in this organism. Each antibiotic inhibited nuclear DNA replication at drug concentrations at which there was little or no inhibition of adenine incorporation into chloroplast DNA. That chloroplast DNA was replicating under these conditions rather than merely being repaired, was shown first by the high incorporation rates and second by a
14
N-
15
N density transfer experiment in which chloroplast DNA doubled in the presence of streptomycin, while no incorporation into nuclear DNA was detected. A small DNA peak, Component III, located between nuclear and chloroplast DNA's in CsCl gradients, possibly mitochondrial, was more pronounced in DNA from antibiotic-inhibited cultures than from controls.
Isolation of DNA Strand-Specific Early Messenger RNA Species in Cells Infected by Human Adenovirus 2
Authors: Büttner Werner , Veres-Molnár Zsuzsanna , Green Maurice
Published: May 2006

Hybridization to the separated light (L) and heavy (H) strands of adenovirus 2 DNA in 50% formamide at 37° was used to isolate undegraded virus-specific RNA molecules from the polyribosomes of cycloheximide-treated human KB cells early after infection with adenovirus 2. About 20% of polyribosomal RNA labeled with [
3
H]uridine from 4 to 7 hr after infection was virus-specific. Twice as much labeled RNA was homologous to the L strand as to the H strand. Polyacrylamide gel electrophoresis of RNA selected with unfractionated adenovirus DNA resolved a major component of virus-specific RNA in the 19-20 S region of the gel and smaller amounts of viral RNA in two heterogeneous fractions migrating at 15-18 S and 21-26 S. Selection with individual DNA strands showed that the 19-20 S main size class of early mRNA consists of two homogeneous RNA species with slightly different mobilities, the transcripts from the L and H strand having molecular weights of 7.4 × 10
5
and 7.7 × 10
5
, respectively. The 15-18 S RNA hybridized with the L strand and the 21-26 S RNA with the H strand.
Nucleotide Sequence in the Promoter Region of the
Escherichia coli
Tyrosine tRNA Gene
Authors: Sekiya Takao , Khorana H. Gobind
Published: May 2006

The sequence of 29 nucleotides immediately preceding the starting point of transcription of the
E. coli
tyrosine tRNA gene has been determined. This is: [Formula: see text] The sequence contains regions of 2-fold symmetry. Transcription of the gene begins at the first nucleotide to the left of nucleotide 1 and is leftward.
Stimulation of the Hydrolytic Activity and Decrease of the Transpeptidase Activity of γ-Glutamyl Transpeptidase by Maleate; Identity of a Rat Kidney Maleate-Stimulated Glutaminase and γ-Glutamyl Transpeptidase
Authors: Tate Suresh S. , Meister Alton
Published: May 2006

γ-Glutamyl transpeptidase catalyzes transfer of the γ-glutamyl moiety of glutathione (and other γ-glutamyl compounds) to amino acid and peptide acceptors; this reaction probably involves (
a
) formation of a γ-glutamyl enzyme and (
b
) reaction of the γ-glutamyl-enzyme with an acceptor. Maleate decreases the latter reaction and markedly increases hydrolysis of the γ-glutamyl donor, apparently by affecting the enzyme so as to facilitate reaction of the γglutamyl enzyme with water. Transpeptidase catalyzes γ-glutamyl hydroxamate formation from many γ-glutamyl compounds and hydroxylamine; this reaction is stimulated 4- to 5-fold by maleate. Glutamine, a poor substrate for transpeptidation as compared to glutathione, is slowly hydrolyzed and converted to γ-glutamyl-glutamine by the transpeptidase; in the presence of maleate, hydrolysis of glutamine is markedly (>10-fold) increased, as is also its conversion to γ-glutamyl hydroxamate in the presence of hydroxylamine. The findings suggest that the previously described “maleate-stimulated phosphate-independent glutaminase” is a catalytic function of γ-glutamyl transpeptidase. Transpeptidase-catalyzed glutaminase activity may play a role in renal ammoniagenesis. The ability of maleate to decrease transpeptidation of γ-glutamyl compounds (and to increase their hydrolysis to glutamate), when considered in the light of earlier findings that treatment of animals with maleate produces aminoaciduria, is consistent with function of transpeptidase and the γ-glutamyl cycle in amino-acid transport.
Purification of Naked Intranuclear Particles from Human Liver Infected by Hepatitis B Virus
Authors: Hirschman Shalom Z. , Gerber Michael , Garfinkel Esther
Published: May 2006

The isolation and purification of the naked intranuclear particles of a human liver infected with hepatitis B virus is described. The particles had a diameter of 27-28 nm, were hexagonal, and showed the presence of capsomeres and spikes with lengths of 7-10 nm projecting from the surfaces. The particles formed cubic arrays with center-to-center distances of 40-42 nm. The overall particle symmetry was icosahedral. The ultraviolet absorption spectrum of the particles showed a peak at 264 nm with a shoulder at 280 nm. Endogenous DNA polymerase activity was not detected in fractions containing particles. DNA polymerase activity was present when activated DNA or d(A-T)
n
was used as exogenous template.
On the Mechanism of Action of Choline Acetyltransferase
Authors: Currier Stephen F. , Mautner Henry G.
Published: May 2006

The substrate specificity of choline acetyltransferase (EC 2.3.1.6) isolated from squid ganglia was investigated. The enzyme catalyzed the acetylation of choline and aminocholine but not of homocholine. In D
2
O solution there was considerable slowing of the transacetylation reaction. Photo-oxidation in the presence of methylene blue or rose bengal rapidly inactivated the enzyme, suggesting involvement of a histidine residue in the catalytic site. It seems likely that general-base catalysis by imidazole enhances the ability of enzyme-bound choline (or ammoniumcholine) to react with a thiolester group. Attempts to isolate an acetylthio-enzyme intermediate after incubation with [
14
C]acetylcoenzyme A were unsuccessful. A possible mechanism for the action of choline acetyltransferase is proposed.
Prostaglandin Endoperoxides. Novel Transformations of Arachidonic Acid in Human Platelets
Authors: Hamberg Mats , Samuelsson Bengt
Published: May 2006

Arachidonic acid incubated with human platelets was converted into three compounds, 12L-hydroxy-5,8,10,14-eicosatetraenoic acid, 12L-hydroxy-5,8,10-heptadecatrienoic acid, and the hemiacetal derivative of 8-(1-hydroxy-3-oxopropyl)-9,12L-dihydroxy-5,10-heptadecadienoic acid. The formation of the two latter compounds from arachidonic acid proceeded by pathways involving the enzyme, fatty acid cyclo-oxygenase, in the initial step and with the prostaglandin endoperoxide, PGG
2
, as an intermediate. The first mentioned compound was formed from 12L-hydroperoxy-5,8,10,14-eicosatetraenoic acid, which in turn was formed from arachidonic acid by the action of a novel lipoxygenase. Aspirin and indomethacin inhibited the fatty acid cyclo-oxygenase but not the lipoxygenase, whereas 5,8,11,14-eicosatetraynoic acid inhibited both enzymes. The almost exclusive transformation of the endoperoxide structure into non-prostaglandin derivatives supports the hypothesis that the endoperoxides can participate directly and not by way of the classical prostaglandins in regulation of cell functions. The observed transformations of arachidonic acid in platelets also explain the aggregating effect of this acid.
Purification and Separation of Pyridine Nucleotide-Linked Dehydrogenases by Affinity Chromatography Techniques
Authors: Kaplan Nathan O. , Everse Johannes , Dixon Jack E. , Stolzenbach Francis E. , Lee Chi-Yu , Lee Ching-Lun T. , Taylor Susan S. , Mosbach Klaus
Published: May 2006

A number of different dehydrogenases have been shown to bind to Sepharose-bound
N
6
-(6-aminohexyl)-AMP. These dehydrogenases can be specifically eluted by binary adducts of NAD
+
or with cofactor gradients. In such manner pure enzymes can be obtained from crude extracts, as demonstrated in the purification on a preparative scale of lactate dehydrogenase from dogfish muscle. The data presented indicate the usefulness of general ligands as affinity agents. The techniques are particularly adaptable for the isolation of human mutant enzymes in blood or in the purification and concentration of enzymes present at low levels in fluids or tissues, as shown in the extensive purification of serum lactate dehydrogenase and glucose 6-phosphate dehydrogenase from hemolysate. lsoenzymes with different affinities for co-enzymes can be separated by affinity techniques. Application of affinity techniques may lead to the separation of isoenzymes or mutant enzymes that are not separable by electrophoretic methods.
Three Flies and Three Islands: Parallel Evolution in Drosophila
Authors: Carson Hampton L.
Published: May 2006

Most organisms are evolutionary conservatives; they may subdivide their niches but tend to remain within them. Yet the fossil record shows many cases of breakthrough to a new mode of life. How may such evolutionary innovation be recognized at this time level? Three species of Drosophila have accomplished an innovation in that they breed as obligate commensals on tropical land crabs. This could be dismissed as a curious aberration were it not for the fact that the three flies concerned represent three different phyletic lines of the family. Although Drosophila is abundant on the continents, these three parallel innovative evolutions have occurred on islands. The proposal is made that the genetic systems of many conservative groups of organisms carry variability that would permit them to evolve in a novel direction. The realization of this capacity, however, is possible only under special environmental conditions.
Distribution of 5-Bromodeoxyuridine in the DNA of Rat Embryo Cells
Authors: Schwartz Stephen A. , Kirsten Werner H.
Published: May 2006

Rat embryo cells were treated with
3
H-labeled 5-bromodeoxyuridine (BrdU) in order to determine the nature of substitution and distribution of the analog in DNA. At optimal oncornavirus-inducing doses of BrdU (10
-4
M), density gradient centrifugation and DNA·DNA reassociation experiments revealed extensive (>90%) and uniform base substitution in repetitive, intermediate, and unique DNA sequences. Suboptimal doses (10
-7
M) of [
3
H]BrdU resulted in less than 5% thymine replacement and nonrandom labeling of DNA. Treatment of cells with 10
-7
M [
3
H]dT resulted in relatively uniform labeling throughout all DNA sequences. At low concentrations, BrdU was incorporated predominantly within the repetitive and intermediate DNA of rat embryo cells. Moreover, the single-copy DNA sequences were lightly substituted and reassociated extensively only in the presence of excess unlabeled DNA. Such specificity of base substitution may be related to the unusually selective nature of BrdU effects on animal cells.
Agrobacterium tumefaciens
DNA and PS8 Bacteriophage DNA Not Detected in Crown Gall Tumors
Authors: Chilton Mary-Dell , Currier Thomas C. , Farrand Stephen K. , Bendich Arnold J. , Gordon Milton P. , Nester Eugene W.
Published: May 2006

Renaturation kinetics of labeled
Agrobacterium tumefaciens
DNA are not influenced by addition of 10
4
-fold excess of crown gall tumor DNA. Reconstruction experiments demonstrated that 0.01% added bacterial DNA produces a detectable increase in rate of renaturation of labeled DNA. Crown gall tumor DNA therefore cannot contain as much as 0.01%
A. tumefaciens
DNA (one entire bacterial genome per three diploid tumor cells).

By the same technique, PS8 bacteriophage DNA is not detected in crown gall tumor DNA under conditions that allow detection of 0.0007-0.001% added phage DNA. Crown gall tumor DNA cannot contain as much as one entire phage genome per diploid tumor cell. The presence of a small fraction of either genome (less than 5%), even if present as multiple copies, would escape detection by this method.
Source Theory Viewpoints in Deep Inelastic Scattering
Authors: Schwinger Julian
Published: May 2006

The phenomena of deep inelastic electron scattering on single nucleons, viewed as virtual photon absorption, are reexamined with the nonspeculative, phenomenological attitude of source theory. The use of a double spectral representation for forward scattering, and of experimental inputs from the low energy resonance region and the high energy real photon diffraction region, lead naturally to the general observed characteristics of deep inelastic scattering. A reasonably successful description of deviations from simple scaling behavior is also presented.
Xeroderma pigmentosum cells contain low levels of photoreactivating enzyme.
Authors: Sutherland B M , Rice M , Wagner E K
Published: May 2006

Fibroblasts from patients with xeroderma pigmentosum contain low levels of photoreactivating enzyme in comparison to normal cells. Levels vary from 0 (line 1199) to 50 (line 1259) percent of normal. The depressed enzyme levels are not an artifact of low growth rate, age of cell donor, cell culture conditions, assay conditions, the presence of inhibitors, or mycoplasma contamination. We show that human fibroblasts can monomerize pyrimidine dimers in vivo.
Cyclic AMP-dependent endogenous phosphorylation of a microtubule-associated protein.
Authors: Sloboda R D , Rudolph S A , Rosenbaum J L , Greengard P
Published: May 2006

Microtubules prepared from chick brain homogenates by successive cycles of assembly-disassembly were found to contain two high-molecular-weight proteins, designated microtubule-associated protein1 and microtubule-associated protein2. Microtubule-associated protein2 (apparent molecular weight 300,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) was the preferred substrate for an endogenous cyclic AMP-dependent protein kinase which appeared to be an integral component of the microtubules. The initial rate of phosphorylation of microtubule-associated protein2 was enhanced 4- to 6-fold by cyclic AMP, with half-maximal stimulation occurring at 2 times 10-7 M cyclic AMP. Under optimal conditions, a total of 1.0 and 1.9 mol of phosphate was incorporated per mole of microtubule-associated protein2, in the absence and presence of cyclic AMP, respectively. Cyclic AMP also stimulated the phosphorylation of tubulin, but the rate of phosphate incorporation per mol of tubulin was only 0.15% that of microtubule-associated protein2. The data raise the possibility that the cyclic AMP-dependent phosphorylation of microtubule-associated protein 2 may play a role in microtubule assembly or function.
The Acid-Base Properties, Hydrolytic Mechanism, and Susceptibility to O
2
Oxidation of Fe
4
S
4
(SR)
4
-2
Clusters
Authors: Bruice Thomas C. , Maskiewicz Richard , Job Robert
Published: May 2006

The iron-sulfur cluster compounds Fe
4
S
4
(SR)
4
-2
[where —SR = —SCH
3
, —S—C(CH
3
)
3
, and —S— CH
2
—CH(CH
3
)
2
] have been found to represent the base species of weak acids of pK
a
comparable to that of carboxylic acids. The acid species Fe
4
S
4
(SR)
4
H
-
is most subject to reaction with O
2
and to acid-catalyzed solvolysis, while the base species Fe
4
S
4
(SR)
4
-2
most readily undergoes ligand exchange. The kinetics for hydrolysis of the isobutyl mercaptide cluster salt has been investigated in detail and a mechanism involving the stepwise process [Formula: see text] has been proposed. The importance of the acid-base equilibria in determining the reactivity of the iron-sulfur clusters and its possible importance as a factor in the determination of the potentials of ferredoxins and high potential iron protein are discussed.
A mechanism to activate branch migration between homologous DNA molecules in genetic recombination.
Authors: Sobell H M
Published: May 2006

A mechanism to activate branch migration between homologous DNA molecules is described that leads to synapsis in genetic recombination. The model involves a restriction-like endonucleolytic enzyme that first nicks DNA (to produce single-strand breaks) on strands of opposite polarity at symmetrically arranged nucleotide sequences (located at ends of genes or operons). This is followed by local denaturation of the region, promoted by a single-strand-specific DNA binding protein (i.e., an unwinding protein). Hydrogen-bounding between homologous DNA molecules can then be initiated and this allows for subsequent propagation of hybrid DNA in the pathway to formation of the synapton structure.
Evidence for adenosine diphosphate ribosylation of Ca2+, Mg2+-dependent endonuclease.
Authors: Yoshihara K , Tanigawa Y , Burzio L , Koide S S
Published: May 2006

The molecular basis for the inhibition of the Ca2+,Mg2+-dependent endonuclease resulting from the formation of poly(adenosine diphosphate ribose) (ADP-Rib) was studies in a simplified system containing purified rat liver or bull semen endonuclease, purified rat liver poly(ADP-Rib) synthetase, [3H]NAD+, and DNA. Poly-(adp-rib) synthetase activity was stimulated when Ca2+, Mg2+-dependent endonuclease was added to the reaction mixture in place of histones, suggesting that the endonuclease can act as an acceptor for ADP-Rib. Evidence was presented to show that the ADP-Rib moiety of [3H]NAD+ was incorporated in the endonuclease fraction. The [3H]ADP-Rib bound to the endonuclease was in the form of monomers and oligomers and not long chain polymers. The present results suggest that the Ca2+,Mg2+-dependent endonuclease was ADP-ribosylated when the endonuclease was incubated with poly(ADP-Rib) synthetase and NAD+.
A kinetic study in vitro of the reoxidation of interchain disulfide bonds in a human immunoglobulin IgGLk. Correlation between sulfhydryl disappearance and intermediates in covalent assembly of H2L2.
Authors: Sears D W , Mohrer J , Beychok S
Published: May 2006

After reduction by dithiothreitol and removal of the reductant by molecular sieve chromatography, the four interchain disulfide bonds of the human IgGlk protein Fro reoxidize in the presence of oxygen and trace metal ions. The six molecular components of the reoxidation--L (light chain), H (heavy chain), HL, H2, H2L, H2L2--are quantitatively determined from polyacrylamide gels containing sodium dodecyl sulfate and the time-dependent sulfhydryl titer is measured with 5,5'-dithiobis-(2-nitrobenzoic acid). The rates of H2L2 covalent assembly depend on pH in an unexpected way: If the reduced protein is chromatographed at pH 3.2 and then adjusted to pH 7.5 (25 degrees, ionic strength equals 0.14), H2L2 formation proceeds rapidly, with half-times ranging between 20 and 40 min. In contrast, if chromatography is carried out at pH 5.5 before adjusting to the same final conditions, the half-times for H2L2 formation are considerably longer (120-180 min). The half-times in the former case approach the somewhat faster rates of H2L2 assembly observed in pulse-chase experiments with various types of mouse, IgG-producing cells [Baumal, et al. (1971) J. Exp. Med. 134, 1316-1334]. To facilitate comparison of experiments and models, we plot the concentrations of the six components against the corresponding number of sulfhydryl equivalents per mole of Fro. The respective plots for the pH 3.2 leads to 7.5 and 5.5 leads to 7.5 experiments are very similar despite the rate differences. Moreover, these plots differ significantly from the calculated plot for a hypothetical random reoxidation in which the intrinsic probability for formation of each correct HL and H2 disulfide bond is assumed equal and independent. It is concluded that the in vitro reoxidation of Fro (i) is other than random; (ii) involved a pathway of pathways with HL, H2, and H2L precursors; and (iii) involves at least some kinetic cooperativity in bond formation, since no model bases solely on independent bond formation adequately accounts for the results. The models were used also to examine the cellular assembly pathways of mouse IgG proteins.
Changes of tissue water proton relaxation rates during early phases of chemical carcinogenesis.
Authors: Floyd R A , Yoshida T , Leigh J S
Published: May 2006

Water proton spin lattice relaxation rate (T1) was determined on tissues of rats experiencing early phases of chemical carcinogenesis. Rats were fed a fast acting carcinogen, 3'-methyldimethylaminoazobenzene, and a slower acting carcinogen, 2-acetylaminofluorene, for up to 4 weeks. T1 of blood serum and liver tissue was significantly higher than those of controls after 4 weeks of 3'-methyldimethylaminoazobenzene feeding. This was not the case for 2-acetylaminofluorene. The blood serum T1 increase reflected the onset of liver nodulation (assumed to be preneoplastic). Liver T1 values increased as the degree of nodulation increased. Blood serum T1 correlated inversely with protein content and directly with water content. Liver T1 values correlated with water content, but this was not true for spleen T1 values. Spleen T1 values were significantly lower than controls at the earliest sampling date for each carcinogen: one week for 3'-methyldimethylaminoazobenzene and 4 weeks for 2-acetylaminofluorene. The spleen T1 decrease paralleled an increase of iron detectable by electron spin resonance in this tissue. Spleen T1 decreases are probably not unique to chemical carcinogenesis.
Sulfhydryl dependence in primary explant hematopoietic cells. Inhibition of growth in vitro with vitamin B12 compounds.
Authors: Toohey J I
Published: May 2006

Primary explants of P388, EL-4, and L1210 murine leukemia cells and of normal mouse bone marrow are shown to require sulfhydryl compounds for proliferation in vitro. Nine extablished cell lines show no stimulation by these compounds. Leukemia cells can lose the sulfhydryl dependence after various periods of adaptation to in vitro culture. Various sulfhydryl compounds have widely differing potencies in promoting in vitro proliferation of dependent cells. The effect appears to be specific for sulfhydryl groups in the reduced form. Vitamin B12 compounds inhibit the growth of sulfhydryl-requiring cells, apparently by catalyzing the oxidation of the sulfhydryl groups.
A general method for the introduction of enzymes, by means of immunoglobulin-coated liposomes, into lysosomes of deficient cells.
Authors: Weissmann G , Bloomgarden D , Kaplan R , Cohen C , Hoffstein S , Collins T , Gotlieb A , Nagle D
Published: May 2006

Phagocytes of the smooth dogfish (Mustelus canis) contain no endogenous peroxidase within their lysosomes and constitute models for cells genetically deficient in lysosomal enzymes such as myeloperoxidase. We have obtained uptake of over 50% of exogenous horseradish peroxidase, provided the enzyme is exhibited to cells after incorporation into liposomes coated with heat-aggregated (62 degrees, 10 min), isologous IgM. Trapping of horseradish peroxidase (EC 1.11.1.7) by liposomes was established by chromatographic resolution (Sephadex G-200; Sepharose 2B and 4B) of free enzyme from that associated with liposomes; liposome-associated horseradish peroxidase, together with trapped markers of the aqueous compartment (glucose, CrO4 equals), were excluded, and free enzyme and markers were retained. Enzyme and marker trapping was not electrostatic, varied with the molar ratio of charged membrane components, and was reversed by detergent lysis (Triton X-100) of liposomes. Uptake at 30 degrees of aggregated IgM-coated liposomes containing trapped horseradish peroxidase exceeded that of free enzyme of 100-fold, and was more efficient than uptake of horseradish peroxidase presented in uncoated liposomes or in liposomes coated with native IgM. After phagocytosis, peroxidase-rich liposomes were localized exclusively in lysosomes of the phagocytes by ultrastructural histochemistry; the enzyme displayed over 50% latency to osmotic lysis. This method may prove to be of general use in the provision of exogenous enzymes to phagocytic cells genetically deficient in lysosomal hydrolases.
Restriction endonuclease analysis of mitochondrial DNA from grande and genetically characterized cytoplasmic petite clones of Saccharomyces cerevisiae.
Authors: Morimoto R , Lewin A , Hsu H J , Rabinowitz M , Fukuhara H
Published: May 2006

Digestion of grande mitochondrial DNA (mtDNA) BY EcoRI restriction endonuclease gives rise to nine fragments with a total molecular weight of 51.8 x 10(6). HindIII digestion yields six fragments with a similar total molecular weight. Specific restriction fragments can be detected despite the fact that yeast mtDNA consists of a heterogeneous distribution of randomly broken molecules. Digestion patterns of 10 genetically characterized petite clones containing various combinations of five antiobiotic resistance markers indicate that the petite mtDNA predominantly represents deletion of the grande genome. The petite mtDNAs contained up to seven EcoRI restriction fragments which comigrate with grande restriction fragments, and at least one fragment that did not correspond to any in the grande. Some strains contained multiple fragments with mobility different from that of grande; these fragments were usually present in less than molar concentrations. The genetic markers were associated with individual sets of restriction fragments. However, several internal inconsistencies prevent the construction of a definitive genetic fragment map. These anomalies, together with the digestion patterns, provide strong evidence that, in addition to single contiguous deletion, other changes such as multiple deletion and heterogeneity of mtDNA populations are present in some of the petite mtDNAs.