bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of 5-Methyltetrahydrofolate:Homocysteine Methyltransferase Activity by Methionine, Vitamin B
12
, and Folate in Cultured
Authors: Kamely Daphne , Littlefield John W. , Erbe Richard W.
Published: May 2006

Rapid growth of BHK cells in methioninedeficient medium required supplementation with homocysteine, B
12
, and over 40-fold greater levels of folic acid than growth in methionine-supplemented medium. The activity of the B
12
-dependent 5-methyltetrahydrofolate: homocysteine methyltransferase was studied in extracts of BHK cells grown in media containing various concentrations of the compounds of the enzyme reaction. The methyltransferase activity increased over 4-fold when B
12
-deficient deficient medium was supplemented with optimal levels of B
12
; this increase was not prevented by puromycin. Addition of homocysteine to growth medium containing methionine, B
12
, and folic acid was without effect. However, methyltransferase activity increased 2.5- to 4.0-fold further beyond the highest levels obtained in the presence of methionine, B
12
, and folic acid when homocysteine was substituted for methionine in the growth medium. This increase was blocked by puromycin and was not due to removal of feedback inhibition of activity by the product methionine. These results suggest that methyltransferase activity may be regulated in part by derepression of the enzyme's synthesis on substitution of the substrate homocysteine for the product methionine.
Correlation Between the Mobility of Inner Plasma Membrane Structure and Agglutination by Concanavalin A in Two Cell Lines of MOPC 173 Plasmocytoma Cells
Authors: Guérin Claudine , Zachowski Alain , Prigent Bernadette , Paraf Alain , Dunia Irène , Diawara Marie-Aline , Benedetti E. L.
Published: May 2006

Both the distribution of the concanavalin A-binding sites and the rearrangement of the intramembranous particles revealed by the freeze-etching technique, have been studied by means of two variants of the same cell line issued from MOPC 173 murine plasmocytoma. One variant does not agglutinate even in presence of high lectin concentration. It has been shown that the number of binding sites and affinity are almost the same in the two variants. The clustered distribution of intramembranous particles is induced by the interaction of the concanavalin A and the cell surface only in the variant which is agglutinable. From these results it became apparent that the clustered distribution of the membrane particulate components is an acquired feature of the plasma membrane accompanying cell agglutination.
Low Temperature Electronic Absorption Spectra of Oxidized and Reduced Spinach Ferredoxins. Evidence for Nonequivalent Iron(III) Sites
Authors: Rawlings Jill , Siiman Olavi , Gray Harry B.
Published: May 2006

The electronic absorption spectra of oxidized and reduced spinach ferredoxins have been measured between 1200 and 600 nm at low temperature in D
2
O/ethylene glycol glasses. Relatively weak absorption bands are observed at 720, 820, and 920 nm in oxidized ferredoxin, and at 652, 820, and 920 nm in reduced ferredoxin. The spectral results show that the two Fe(III) centers in oxidized ferredoxin are not equivalent, and that the 820- and 920-nm bands are associated with the nonreducible site. Assignment of the reducible site as tetrahedral Fe(III) is indicated. The 720-nm (13.9 kcm
-1
) band in oxidized ferredoxin is attributed to an intensity-enhanced
6
A
1
→
4
T
1
d-d
transition, whereas the 652-nm (15.3 kcm
-1
) feature of reduced ferredoxin could be due either to
5
E →
3
T
1
in tetrahedral Fe(II)S
4
or an Fe(II) → Fe(III) intervalence excitation.
The Selectivity Principle and the Question of the Bridged Structure of the 2-Norborynyl Cation
Authors: Brown Herbert C. , Peters Edward N.
Published: May 2006

Low exo/endo rate ratios in the solvolysis of certain norbornyl derivatives have been attributed to the involvement of classical (unbridged) 2-norbornyl cations. Consequently, the high exo/endo rate ratio in the parent system, 2-norbornyl arenesulfonates, has been interpreted as involving rate enhancement in the
exo
isomer arising from σ-participation. It is pointed out that this treatment involves neglect of the Selectivity Principle. Taking the relative reactivity of cyclopentyl to cyclohexyl as a representative test system, it is pointed out that those reactions which reveal low exo/endo rate ratios in norbornyI also reveal low cyclopentyl/cyclohexyl rate ratios. It is proposed that the low exo/endo rate ratios in norbornyl, observed in the above reactions, arise from the low selectivities of the test reactions. Consequently, the results cannot be utilized to support the argument that low exo/endo rate ratios reflect the absence of σ-participation and high exo/endo rate ratios reflect the presence of σ-participation.
Int-Constitutive Mutants of Bacteriophage Lambda
Authors: Shimada Kazunori , Campbell Allan
Published: May 2006

The constitutive production of small amounts of
trpB
enzyme in an
Escherichia coli
strain carrying λ
cI
857 prophage within the
trpC
gene has been examined in derivatives of this strain from which portions of the prophage have been deleted. Enzyme production requires a site (p
I
) within the prophage close to the left prophage end. Selection for mutants of this lysogen that grow on low concentrations of indole yielded two types of mutations within the prophage: (
a
)
v
2-type, in which all phage genes controlled by the major leftward operator are derepressed; and (
b
)
int-c
type, in which the only phage gene derepressed is
int
. The
int-c
mutations lie in the same part of the prophage as p
I
. All
int-c
mutants appear deficient in
xis
gene function, even when derepressed.
Highly Purified Papain-Solubilized HL-A Antigens Contain β
2
-Microglobulin
Authors: Peterson Per A. , Rask Lars , Lindblom J. Bertil
Published: May 2006

HL-A antigens comprising 11 different antigenic specificities were isolated after papain solubilization of spleen-cell membrane constituents. During the entire purification procedure, β
2
-microglobulin appeared together with the HL-A antigens. The highly purified antigens were composed of two polypeptide chains. The large subunit carried the antigenic specificity whereas the small polypeptide chain was very similar, if not identical, to β
2
-microglobulin. The two HL-A antigen polypeptide chains were held together by noncovalent interactions only, and β
2
-microglobulin, isolated from urine, could replace the small subunit in forming a complex with the large polypeptide chain. The topographical relationship in the cell membrane between β
2
-microglobulin and the large HL-A antigen polypeptide chain is unknown. The two polypeptide chains may be fortuitously bound as a result of the solubilization procedure.
Relipidation of Phospholipid-Depleted Microsomal Particles with High Glucose 6-Phosphatase Activity
Authors: Garland Rebecca C. , Cori Carl F. , Chang Hsia-Fei Wang
Published: May 2006

Microsomal particles enriched up to 20-fold in glucose 6-phosphatase activity (as compared to crude microsomal fractions) were prepared from livers of phenobarbital-treated, normal, and diabetic rats by a method involving sucrose-density gradient centrifugation through a layer containing deoxycholate, followed by flotation of the delipidated particles in a phospholipid-detergent mixture. The flotation with phospholipid resulted in the extraction of additional protein, in a corresponding increase in specific activity, and in relipidation of the particles to their original phospholipid content. Detergents alone did not extract any additional protein. Relipidation caused a change in the properties of the microsomal membrane, as indicated by a 4-fold decrease in the
K
m
for glucose 6-phosphate and mannose 6-phosphate. The maximal rate was not affected. The crude homogenate of diabetic rat liver contained more latent enzyme than that of normal rats. The diabetic rats also yielded purified microsomal particles of specific glucose 6-phosphatase activity twice that of normal and five times that of phenobarbital-treated rats, indicating that some regulatory mechanism exists for the incorporation of different amounts of the enzyme into the endoplasmic reticulum.
Degradation of Pseudoviral DNA after Infection of Mouse Cells with Polyoma Pseudovirions
Authors: Kashmiri S. V. S. , Aposhian H. Vasken
Published: May 2006

When mouse cells are infected with [
3
H]-thymidine-labeled polyoma pseudovirions, as much as 11% of the input pseudoviral radioactivity is found in the recipient cell DNA. However, the radioactivity found in the recipient cell DNA virtually disappears when nonradioactive thymidine and deoxycytidine, or D-arabinosyl cytosine, are added to the medium. The radioactivity found in the recipient cell DNA appears to be the result of the breakdown of pseudoviral DNA to precursors of DNA and the utilization of these precursors for the synthesis of cell DNA.
Aldosterone-Induced Increase in Protein Phosphatase Activity of Toad Bladder
Authors: Liu Alice Y.-C. , Greengard Paul
Published: May 2006

A study has been carried out of the effect of aldosterone on the endogenous phosphorylation and dephosphorylation of membrane-bound and of soluble proteins from toad bladder. Membrane-bound protein D (apparent molecular weight, 49,000), a protein which may possibly be involved in the regulation of sodium transport across the mucosal epithelium of toad bladder, contained a substantial fraction of the radioactive phosphate incorporated into membrane proteins; moreover, it was the only protein to appear consistently in autoradiographs of polyacrylamide gels of phosphorylated membrane proteins. Pretreatment of toad bladder slices with aldosterone caused an increase in the endogenous dephosphorylation of membrane-bound protein D. A half-maximal increase in this dephosphorylation occurred at an aldosterone concentration of 20-40 nM. The increase in protein D phosphatase activity induced by aldosterone was prevented by inhibitors of RNA and protein synthesis as well as by spironolactone, a specific antagonist of aldosterone. The mineralocorticoid, 9α-fluorohydrocortisone, also increased protein D phosphatase activity, but testosterone did not. Aldosterone also increased the removal of [
32
P]phosphate from protein D in the cell sap. In contrast to the increase in protein D phosphatase activity, aldosterone had little effect on the phosphorylation of protein D by endogenous protein D kinase. In some experiments, effects of aldosterone and of cAMP, qualitatively similar to those found with protein D, were also observed on the phosphorylation and dephosphorylation of a protein with an apparent molecular weight of 37,000, in both the microsomal and cell sap fractions. No consistent effect of preincubation with aldosterone or of cAMP was observed on any membrane-bound or cell sap protein other than protein D and the 37,000 dalton protein.
A Limited Number of Globin Genes in Human DNA
Authors: Gambino Roberto , Kacian Daniel , O'Donnell Joyce , Ramirez Francesco , Marks Paul A. , Bank Arthur
Published: May 2006

The number of globin genes in human cells was determined by hybridizing DNA from human spleens to
3
H-labeled DNA complementary to human globin mRNA. Assuming the rates of reannealing of complementary DNA and cellular DNA are similar, the extent of hybridization of complementary DNA at various ratios of cellular DNA to complementary DNA indicate that there are fewer than 10 globin gene copies per haploid human genome. An alternative analysis of the data, which introduces no assumptions concerning the relative rates of reaction of complementary DNA and cellular DNA, indicates fewer than 20 globin gene copies are present. DNA isolated from the spleen of a patient with β
+
thalassemia contained a number of globin gene copies similar to that of normal DNA.
Stimulation of Synthesis of Free Chondroitin Sulfate Chains by β-D-Xylosides in Cultured Cells
Authors: Schwartz Nancy B. , Galligani Leonardo , Ho Pei-Lee , Dorfman Albert
Published: May 2006

Previous studies have shown that D-xylose partially overcomes the puromycin inhibition of chondroitin sulfate synthesis in cultured chick embryo chondrocytes. Likewise, D-xylose stimulates chondroitin sulfate synthesis by limb bud mesenchyme cells previously treated with BrdU or limb bud cartilage cells treated with puromycin. The studies reported here show that
p
-nitrophenyl-β-D-xylopyranoside and 4-methyl-umbelliferyl-β-D-xylopyranoside cause a much greater stimulation than does D-xylose and are active at much lower concentrations. In contrast to D-xylose, the xylosides strikingly stimulate chondroitin sulfate synthesis in predifferentiated mesenchyme cells. The xylosides stimulate synthesis of chondroitin sulfate by rat glial cell tumor cells (RC-6), a mouse neuroblastoma (C1300, NB41A), and two strains of cultured rat hepatoma cells (HTC, H
4
). These results indicate that certain types of nonconnective tissue cells contain the enzymic machinery for synthesis of chondroitin sulfate which is normally not utilized because of limited synthesis of core protein and/or xylosyltransferase. The β-xylosides may be used as a probe of the capacity of various cell types to synthesize sulfated glycosaminoglycans.
Studies on a Factor Enhancing Colicin E3 Activity
In Vitro
Authors: Ohsumi Yoshinori , Imahori Kazutomo
Published: May 2006

The mechanism of action of colicin E3 (E3) was investigated in an
in vitro
system. Purified ribosomes are less susceptible to E3 than crude or washed ribosomes. A factor was found in the supernatant fraction of normal
Escherichia coli
cells that stimulates inactivation of ribosomes by E3, and on addition of this factor, about one tenth as much E3 was required for inactivation of ribosomes. On heating a mixture of E3 and this factor above 60°, the ribosome inactivating activity of E3 increased greatly, and an amount corresponding to 0.01 μg of E3 was sufficient to inactivate 1.0
A
260
unit of ribosomes completely. By this treatment bacteriocidal activity of E3 decreased considerably, as the ratio of the two activities of E3 (ribosome inactivating activity and bacteriocidal activity) increased to 6 × 10
4
-fold. It is evident that the two activities do not run in parallel.

This heat-treated product cleaved 16S rRNA in the same way as E3. These results suggest that inactivation of ribosomes is not due to colicin molecules prepared by the standard procedure, but to a modified form of them.
Chromosome Assignment of the T-Antigen Gene of Simian Virus 40 in African Green Monkey Cells Transformed by Adeno 7-SV40 Hybrid
Authors: Croce Carlo M. , Huebner Kay , Koprowski Hilary
Published: May 2006

Somatic cell hybrids between mouse cells deficient in thymidine kinase [ATP:thymidine 5′-phosphotransferase (EC 2.7.1.75)] and two different monkey cell lines transformed by an adeno 7-SV40 hybrid have been produced using both a semiselective and a double selective procedure. Concordant segregation of the expression of SV40 T antigen with a specific monkey chromosome has been observed in all the mouse-monkey hybrid clones examined. Subcloning of three SV40 T antigen positive hybrid clones resulted in their segregation into SV40 T antigen-positive and negative subclones. Positive correlation between the SV40 T antigen and the same monkey chromosome has been observed in all the subclones examined.
Effect of Nerve Growth Factor on the Expression of Colchicine-Binding Activity and 14-3-2 Protein in an Established Line of Human Neuroblastoma
Authors: Kolber Alan R. , Goldstein Milton N. , Moore Blake W.
Published: May 2006

Purified nerve growth factor induced the outgrowth of neurites from cultured human neuroblastoma cells (NJB line) and a concomitant increase in colchicine-binding activity in extracts from these cultures. The parallel stimulation of neurite outgrowth from the cells and colchicine-binding activity of the extracts is interpreted to represent
de novo
synthesis of microtubular subunit protein in response to the challenge by nerve growth factor. The regulation of the expression of 14-3-2 protein, a protein characteristic of differentiated neuronal cells, was not affected in NJB cells by the addition of nerve growth factor to the culture medium. 14-3-2 protein is present in NJB cells at a concentration equal to that present in human brain from subculture to the stationary phase of growth of the tumor cells. It was concluded that these two gene products, characteristic of differentiated neural cells, are not coordinately regulated in NJB human neuroblastoma cells.
Alignment of the Earth's Magnetic Field with the Axis of Rotation and Reversals of Polarity: Laboratory Experiments on a Mechanism
Authors: Crane H. R.
Published: May 2006

A mechanism that can cause the earth's external magnetic field to be aligned with the axis of rotation and to reverse at random times is described. It depends upon two arbitrary assumptions: (
a
) A dipole magnetic source, of unspecified nature, deep within the core, wanders randomly in direction. (
b
) The conducting fluid at the outer boundary of the core circulates in a pattern that is symmetrical with respect to the earth's axis of rotation. It is shown that such a circulating layer will act as an anisotropic screen, which will suppress the field of the transverse component of the source dipole. The field observed outside the core will be mainly that of the axial component of the source, and it will reverse abruptly whenever the direction of the source crosses the equatorial plane. Quantitative experimental studies, made on small-scale models, of the effects and their properties are described. The only datum that even suggests a value that may be used for the angular velocity of the circulating outer layer with respect to the source is the angular velocity of the westward drift of the earth's nondipolar field. If that value is used, the anisotropic screening effect comes out to be strong enough to give alignment and reversal characteristics that are similar to those found from paleomagnetic studies.
Complex of Aspartate Carbamoyltransferase from
Escherichia coli
with Its Allosteric Inhibitor, Cytidine Triphosphate: Electron Density at 5.9-Å Resolution
Authors: Edwards Brian F. P. , Evans David R. , Warren Stephen G. , Monaco Hugo L. , Landfear Scott M. , Eisele George , Crawford James L. , Wiley Don C. , Lipscomb William N.
Published: May 2006

Following our earlier determination of the three-dimensional structure of aspartate carbamoyltransferase (EC 2.1.3.2; carbamoylphosphate: L-aspartate carbamoyltransferase) to 5.5-Å resolution [S. G. Warren, B. F. P. Edwards, D. R. Evans, D. C. Wiley & W. N. Lipscomb (1973)
Proc. Nat. Acad. Sci. USA
70, 1117-1121], we report here, from a different crystal form, the three-dimensional structure at 5.9 Å of this enzyme complexed with its allosteric inhibitor, cytidine triphosphate. Location of the major binding site of this inhibitor within each of the six regulatory chains is made secure by comparison of these results with those obtained upon binding of 5-iodocytidine triphosphate to the enzyme. Conformational changes in the aspartate carbamoyltransferase molecule when this inhibitor binds are described briefly at 5.9-Å resolution.
Conformational Studies on Arginine Vasopressin and Arginine Vasotocin by Proton Magnetic Resonance Spectroscopy
Authors: Walter Roderich , Ballardin A. , Schwartz I. L. , Gibbons W. A. , Wyssbrod H. R.
Published: May 2006

The assignments and partial conformational analysis of the 220-MHz
1
H nuclear magnetic resonance spectrum of the neurohypophyseal hormones arginine vasopressin and arginine vasotocin in uniformaly deuterated dimethylsulfoxide are reported. The chemical shifts, vicinal coupling constants, temperature coefficients of chemical shifts, and proton-deuterium exchange rates for protons of arginine vasopressin and arginine vasotocin are compared with those for the corresponding protons of the related neurohypophyseal hormones lysine vasopressin and oxytocin. Although to a first approximation the backbone conformations of the hormones exhibit conformational similarities, spectral differences are seen for protons in the amino acid residues that comprise the
20
-membered ring moieties. It is inferred that there is a gradual shift in the average conformation in going from arginine vasopressin and lysine vasopressin via arginine vasotocin to oxytocin. As judged on the basis of earlier studies, it is evident that the C-terminal acyclic tail moiety exhibits an enhanced mobility over that of the ring moiety in all of the neurohypophyseal hormones studied and, moreover, that this motion is greater in arginine vasopressin and arginine vasotocin than in oxytocin.
Utilization of Two Distinct Modes of Replication by a Hybrid Plasmid Constructed
In Vitro
from Separate Replicons
Authors: Timmis Kenneth , Cabello Felipe , Cohen Stanley N.
Published: May 2006

A hybrid plasmid, pSC134, that codes for two distinct sets of replication functions has been constructed
in vitro
by ligation of
Eco
RI endonuclease-cleaved pSC101 and Col E1 plasmid replicons, and has been introduced into
Escherichia coli
by transformation. The replication properties of the pSC134 plasmid in DNA polymerase I-defective mutants or in the presence of chloramphenicol indicate that this hybrid plasmid can utilize the functionally distinct modes of replication specified by both of its parent replicons.
Restriction Endonuclease Cleavage Maps of Animal Mitochondrial DNAs
Authors: Brown Wesley M. , Vinograd Jerome
Published: May 2006

The restriction endonuclease,
Hin
dIII, gives rise to three fragments in each of the three mitochondrial DNAs isolated from the established mammalian cell lines LA9 (mouse), HeLa (human), and BSC-1 (African green monkey). The restriction endonuclease,
Eco
RI, gives rise to three fragments in mitochondrial DNA from HeLa and to two in DNAs from LA9 and BSC-1. The sizes and the orders of the fragments in the respective genomes have been determined with data obtained from the electron microscope. The origin and the direction of replication have been designated in each of the cleavage maps. Polyacrylamide gel electrophoretic analyses demonstrated that additional fragments not detectable in the electron microscope and larger than 50 nucleotide pairs were not present.
Demographic Parameters and Natural Selection
Authors: Demetrius Lloyd
Published: May 2006

This paper introduces two new demographic parameters, the entropy and the reproductive potential of a population. The entropy of a population measures the variability of the contribution of the different age classes to the stationary age distribution. The reproductive potential measures the mean of the contribution of the different age classes to the growth rate. Using a relation between these measures and the Malthusian parameter, it is shown that in a random mating population in Hardy-Weinberg equilibrium, and under slow selection, the rate of change of entropy is equal to the genetic variance in entropy minus the genetic covariance of entropy and reproductive potential. This result is an analogue of Fisher's fundamental theorem of natural selection.
The Aldehyde Content of Luminous Bacteria and of an “Aldehydeless” Dark Mutant
Authors: Shimomura Osamu , Johnson Frank H. , Morise Hiroshi
Published: May 2006

Fatty aldehydes, present in the luminescent cells of
Photobacterium phosphoreum
and
Achromobacter fischeri
, and to a very slight extent in the cells of a visually dark, “aldehydeless” mutant of the latter species, were extracted, purified, and oxidized to the corresponding acids. The acids were analyzed by mass spectrometry. The results, in conjunction with various other lines of evidence, indicate that saturated fatty aldehydes, comprising mostly dodecanal, tetradecanal, and hexadecanal, function in the bioluminescent reaction in living cells of these luminous bacteria. The amount of these aldehydes in the cells was computed to be sufficient to sustain steady-state luminescence for a period of about 1 sec, and under such conditions the rate of oxidation of the aldehydes in the process of luminescence must be balanced by their rate of production.
Sites of Acetylation of Sickle Cell Hemoglobin by Aspirin
Authors: Shamsuddin Mir , Mason R. George , Ritchey James M. , Honig George R. , Klotz Irving M.
Published: May 2006

Aspirin acetylates a variety of sites on both the α and β chains of hemoglobin S. Nevertheless, the vast majority of acetyl groups become attached to three loci: βLys 59, βLys 144, and αLys 90. These observations reveal some molecular details of this transacylation reaction and suggest interesting possibilities for its extension to other acylsalicylates with a variety of different structures.
Purified Acetylcholine Receptor: Its Reconstitution to a Chemically Excitable Membrane
Authors: Michaelson Daniel M. , Raftery Michael A.
Published: May 2006

Association of purified acetylcholine receptor from
Torpedo californica
electroplax with lipids from the same organism results in a vesicular membrane system in which the receptor protein is oriented so that all neurotoxin binding sites appear to be on the outer surface. The reconstituted system is chemically excitable by acetylcholine and carbamylcholine, as measured by
22
Na
+
efflux. This excitability is specifically blocked by the antagonist α-bungarotoxin. These results demonstrate that the purified receptor macromolecule contains not only the specific neurotransmitter binding site but also the molecular elements necessary for ion translocation in order to effect postsynaptic depolarization.
Reconstruction of Objects from Radiographs and the Location of Brain Tumors
Authors: Guenther R. B. , Kerber C. W. , Killian E. K. , Smith K. T. , Wagner S. L.
Published: May 2006

The objective of this research is two-fold: (
i
) the development of a method for locating hemorrhages, blood clots, and tumors in the brain by means of ordinary hospital radiographs and without the introduction of contrast material; and (
ii
) the uncovering of new mathematical results through this point of view. The present note deals mainly with the first objective, but the mathematical setting and convergence and indeterminacy theorems are also described.
Induction of Endogenous Virus and of Thymidine Kinase by Bromodeoxyuridine in Cell Cultures Transformed by Friend Virus
Authors: Ostertag W. , Roesler G. , Krieg C. J. , Kind J. , Cole T. , Crozier T. , Gaedicke G. , Steinheider G. , Kluge N. , Dube S.
Published: May 2006

Thymidine kinase positive (TK
+
) N type cell lines that had been transformed by spleen focus-forming virus were established by transformation with NB tropic Friend virus complex. Thymidine kinase deficient (TK
-
) cell clones were isolated. Some of these cell clones release 1000- to 100,000-fold reduced amounts of Friend virus complex as compared to the TK
+
parental cell clone. TK
-
clones were grown in medium without BrdUrd. Some of these TK
-
clones can be induced to release endogenous helper virus and transforming spleen focus-forming virus on reexposure to 10
-6
-10
-4
M BrdUrd. The induced Friend virus complex is of N host range as expected with induced endogenous virus in N-type cells. Before the induction of the endogenous virus spleen focus-forming virus complex, an induction of thymidine kinase (ATP:thymidine 5′-phosphotransferase, EC 2.7.1.75) activity is observed. The latter is possibly a prerequisite for the induction of endogenous virus in TK
-
cells. Induction of thymidine kinase activity and of endogenous virus is transient and always correlated. The role of BrdUrd and another thymidine analogue, azidothymidine, in interfering with C-type virus release in virus positive cells is discussed. Azidothymidine is unable to induce endogenous virus. Induction of endogenous virus by BrdUrd and inhibition of virus release in virus positive cells is apparently not caused by the same mechanism.
Expression of Murine Leukemia Virus Structural Antigens on the Surface of Chemically Induced Murine Sarcomas
Authors: Grant John P. , Bigner Darell D. , Fischinger Peter J. , Bolognesi Dani P.
Published: May 2006

Cultured cells of different chemically-induced C57BL/6N murine sarcomas produced variable amounts of infectious murine leukemia virus (MuLV) and contained proportional amounts of MuLV structural components as determined by radioimmunoassay. Monospecific antisera directed against the major MuLV glycoprotein (gp71), the major internal antigen (p30), and the ribonucleoprotein (p10) were capable of mediating tumor cell lysis in the presence of complement, suggesting that these viral structural components were localized at least in part to the cell surface. Membrane immunofluorescence studies with MuLV p30 antiserum confirmed surface localization. Addition of MuLV p30 polypeptide to normal cells and tumor cells enhanced the cytotoxicity of MuLV p30 antiserum. Studies are presented which suggest that the presence of MuLV structural components on cell surfaces can be independent of virus production and cellular transformation.
Photon Propagation Function: A Comparison of Asymptotic Functions
Authors: Schwinger Julian
Published: May 2006

An earlier paper asserts the logarithmic asymptotic identity of various asymptotic functions associated with the photon propagation function, including the spectral weight function and the Gell-Mann-Low function. This note exhibits explicit expressions for the deviations between pairs of functions. It is emphasized that the differences are quantitatively small, and that the various functions have common qualitative characteristics. The discussion refers to a particular method for comparing the functions, which has no special physical status. When that restriction is removed, it becomes possible to prove the general existence of a transformation of variable that will produce the Gell-Mann-Low function from the spectral weight function. This supplies a physical interpretation that has otherwise been missing in the Gell-Mann-Low approach.
Inhibition of RNA-Dependent DNA Polymerase of Avian Myeloblastosis Virus by Pyran Copolymer
Authors: Papas Takis S. , Pry Thomas W. , Chirigos Michael A.
Published: May 2006

Pyran copolymer, a known immunostimulator, was found to be a potent inhibitor of purified DNA polymerase (deoxynucleosidetriphosphate: DNA deoxynucleotidyltransferase; EC 2.7.7.7) isolated from avian myeloblastosis virus. Unlike other inhibitors, pyran showed unique features of inhibition. It interacts with the polymerase at a region other than the template site. The inhibitory effect was overcome only by excess enzyme and not affected by excess template. The degree of inhibition was not template specific for the templates tested: 70S RNA from avian myeloblastosis virus, synthetic hybrid poly(rA)·oligo(dT)
10
, synthetic copolymer poly(dA-dT), and activated calf-thymus DNA. The observed rate of inhibition by pyran was shown to vary with the different polymerases tested. Inhibition was shown with all oncornaviral polymerases and, to a lesser extent, with mammalian polymerases. However, two of the three bacterial polymerases, by contrast, showed a marked activation.
Poly(A) Polymerase and Poly(G) Polymerase in Wheat Chloroplasts
Authors: Burkard Gerard , Keller Elizabeth B.
Published: May 2006

Extracts of wheat chloroplasts contain a poly(A) polymerase which can polymerize AMP residues from ATP onto an RNA primer. Whole extracts of wheat leaves also contain another poly(A) polymerase which is present in much larger amount and is probably derived from the nuclei. Both polymerases can utilize as primer poly(A), poly(C), transfer RNA, and ribosomal RNA, but only the chloroplast polymerase can utilize poly(U) and poly(G). Both enzymes have a specific requirement for ATP. Extracts of wheat chloroplasts contain, in addition to the poly(A) polymerase, a poly(G) polymerase which can polymerize GMP residues from GTP onto primers such as poly(G), poly(A), or ribosomal RNA. The poly(G) polymerase cannot utilize ATP but can slowly polymerize CMP from CTP. When the two chloroplast polymerases are present together in an
in vitro
incubation with ATP plus GTP and poly(A), the polymerization product is a mixed poly(A,G) tract.
Magnetic Circular Dichroism Studies XXV. A Preliminary Investigation of Microsomal Cytochromes
Authors: Dolinger Peter M. , Kielczewski Michael , Trudell James R. , Barth Günter , Linder Robert E. , Bunnenberg Edward , Djerassi Carl
Published: May 2006

The application of magnetic circular dichroism as an optical probe for simultaneous identification and determination of at least two microsomal cytochromes is demonstrated. The assignments of the bands in the spectra of microsomal suspensions are made from the spectra of soluble preparations of cytochrome P-450 obtained from
Pseudomonas putida
and of cytochrome
b
5
obtained from rat livers.
In Vitro
Synthesis of Ribosomal Proteins Directed by
Escherichia coli
DNA
Authors: Kaltschmidt E. , Kahan L. , Nomura M.
Published: May 2006

In vitro
synthesis of a number of
E. coli
30S ribosomal proteins has been demonstrated in a cell-free system consisting of ribosomes, initiation factors, RNA polymerase, a fraction containing soluble enzymes and factors, and
E. coli
DNA. DNA-dependent synthesis of the following 30S proteins has been demonstrated: S4, S5, S7, S8, S9, S10, S13, S14, S16, S19, and S20.
Chick-Erythrocyte Nucleus Reactivation in Heterokaryons: Suppression by Inhibitors of Proteolytic Enzymes
Authors: Darzynkiewicz Zbigniew , Chelmicka-Szorc Ewa , Arnason Barry G. W.
Published: May 2006

Reactivation of chick-erythrocyte nuclei in heterokaryons (obtained by Sendai virus-induced fusion of chick erythrocytes with HeLa cells) is suppressed by specific inhibitors of trypsin and trypsin-like enzymes.
N
-α-tosyl-L-lysyl-chloromethane and
N
-α-tosyl-L-arginine methylester inhibit erythrocyte nuclear enlargement and suppress RNA and DNA synthesis in nuclei of erythrocytes and HeLa cells in heterokaryons at concentrations that only minimally influence individual HeLa cells or HeLa homokaryons.

Although other unknown mechanisms of action cannot be formally excluded, the data are interpreted as fitting best with an intracellular site of action of the protease inhibitors studied, and as suggesting a role for cellular proteases in reactivation of chick-erythrocyte nuclei in heterokaryons.
Human Leukemia-Associated Anti-Nuclear Reactivity
Authors: Klein George , Steiner Melita , Wiener Francis , Klein Eva
Published: May 2006

A brilliant, coarsely granular nuclear antigen was detected by anti-complement immunofluorescence in the nuclei of acute myeloid leukemia myeloblasts. Designated as LANA (leukemia-associated nuclear antigen), the reactivity differs from that of the Epstein-Barr-virus-determined nuclear antigen (EBNA) in immunological specificity and morphological appearance, although it is visualized by the same method. Serum from acute myeloid leukemia patients gave positive reactions in 73% of the cases. In acute lymphatic leukemia, chronic myeloid leukemia, chronic lymphatic leukemia, and Burkitt's lymphoma the sera were positive in 35, 14, 19, and 24%, respectively. Two of five polycythemia and two of eleven myeloma sera were also positive. Among 61 healthy controls, 58 were negative, whereas three showed a diffuse nuclear staining with a different pattern. Among 24 carcinoma patients, 18 were negative, whereas six gave a nuclear staining with a different, diffuse pattern. Sera from 20 patients who had recovered from infectious mononucleosis were all negative. In addition to the blasts of acute myeloid leukemia, a similar reactivity was seen with two Epstein-Barr virus DNA and EBNA-negative African lymphoma biopsies and in a short-lived tissue culture line derived from one of them. LANA could be a fetal or tissue-specific antigen, a virally determined antigen, or a specific form of anti-nuclear reactivity.
The Presence of the Lucké Herpesvirus Genome in Induced Tadpole Tumors and Its Oncogenicity: Koch-Henle Postulates Fulfilled
Authors: Naegele Robert F. , Granoff Allan , Darlington R. W.
Published: May 2006

Herpesvirus extracted from a naturally occurring frog renal carcinoma (Lucké tumor) induced virus-free Lucké tumors in developing frogs. Herpesvirus recovered from an induced tumor after incubation at low temperature of tumor fragments cultured
in vitro
was oncogenic when injected into developing frog embryos. With the exception of the “pure culture” requirement, this experiment fulfills Koch-Henle postulates for the identification of the causative agent of the Lucké tumor.
Cleavage by RNase III Converts T3 and T7 Early Precursor RNA into Translatable Message
Authors: Hercules Kathleen , Schweiger Manfred , Sauerbier Walter
Published: May 2006

The processing of the early T3 and T7 high-molecular-weight precursor messenger RNA by RNase III is necessary for its efficient translation both
in vivo
and
in vitro
.
A Human Leukemia Cell with Both B and T Cell Surface Receptors
Authors: Shevach E. , Edelson R. , Frank M. , Lutzner M. , Green I.
Published: May 2006

Bone-marrow-derived (B) and thymus-derived (T) lymphocytes can be distinguished by the presence of a number of receptors and differentiation antigens. The presence of these markers has facilitated the identification and characterization of the mononuclear cells in a number of animal and human lymphoid malignancies. We describe here the immunological properties of human leukemia cells that are highly unusual, since they simultaneously bear the receptor for sheep erythrocytes characteristic of human T lymphocytes and the receptor for antigen-antibody-complement complexes characteristic of human B lymphocytes. A small number (about 2%) of normal human lymphocytes bearing both of these receptors was also identified.
Effect of Transfer Factor Therapy on Mixed Lymphocyte Culture Reactivity
Authors: Dupont Bo , Ballow Mark , Hansen John A. , Quick Cedric , Yunis Edmond J. , Good Robert A.
Published: May 2006

We have studied the effect of dialyzable transfer factor therapy on three patients with immunodeficiency disease and in one patient who demonstrated no evidence of deficiency of either humoral or cellular immunity. We found evidence for nonspecificity in the effect of transfer factor on mixed lymphocyte culture reactivity. The data suggest that in patients with immunodeficiency disease a maturation of lymphocytes may lead to a generalized increased immune responsiveness. More profoundly, our data show that transfer factor may induce changes in the expression of histocompatibility determinants. We observed changes in the expression of determinants capable of stimulating in the mixed lymphocyte culture reaction as well as an increase in the capacity of lymphocytes to respond.
Electron Spin Resonance Studies of Erythrocytes from Patients with Myotonic Muscular Dystrophy
Authors: Butterfield D. A. , Chesnut D. B. , Roses A. D. , Appel S. H.
Published: May 2006

Electron magnetic resonance experiments have demonstrated that spin-labeled myotonic erythrocyte membranes have spectra that are recognizably different from those of normal erythrocytes. The spin label incorporated in the erythrocyte membranes of patients having myotonic muscular dystrophy is apparently located in a less polar and somewhat more fluid region than the label in a normal membrane. Although the mechanisms of molecular interaction and their relationship to enzymatic differences is unclear, the results lend confirmation to the suggestion that myotonic muscular dystrophy may be a disease resulting from a basic membrane abnormality.
Hybrid Antibody-Induced Topographical Redistribution of Surface Immunoglobulins, Alloantigens, and Concanavalin A Receptors on Mouse Lymphoid Cells
Authors: Stackpole Christopher W. , De Milio Lawrence T. , Hämmerling Ulrich , Jacobson Janet B. , Lardis Michael P.
Published: May 2006

Redistribution of surface immunoglobulins, H-2
b
, Thy-1.2, and TL.1,2,3 alloantigens, and concanavalin A receptors on mouse lymphoid cells induced by hybrid rabbit F(ab′)
2
antibody (anti-mouse immunoglobulin/anti-visual marker or anti-concanavalin A/anti-visual marker) was studied by immunofluorescence. When used directly to label surface immunoglobulin, and indirectly to label alloantigens and concanavalin A receptors, hybrid antibodies induced similar displacement of all surface components from a uniform distribution into “patches” and “caps” at 37°. One hybrid antibody preparation, antimouse immunoglobulin/anti-ferritin, contained negligible amounts of bivalent anti-mouse immunoglobulin antibody, and was therefore “monovalent” for the antimouse immunoglobulin specificity. This observation suggests that factors other than multivalent crosslinking are responsible for hybrid antibody-induced redistribution of cell-surface components. Cap formation induced by hybrid antibody was enhanced markedly by attachment of the visual marker, either ferritin or southern bean mosaic virus, at 37°. At -5°, hybrid antibody does not displace uniformly distributed H-2
b
alloantigen-alloantibody complexes, but patches of label develop when ferritin attaches to the hybrid antibody. These results explain the patchy distribution of cell-surface components, which is a temperature-independent characteristic of labeling with hybrid antibodies and visual markers for electron microscopy.
The Isolation of Simian Virus 40 Variants with Specifically Altered Genomes
Authors: Brockman William W. , Nathans Daniel
Published: May 2006

Serial passage of simian virus 40 (SV40) at high multiplicity of infection leads to the emergence of variants with deleted, substituted, and/or duplicated DNA. Individual variants have been cloned by selective complementation with temperature sensitive SV40 mutants, or nonselectively by coinfection of cells with wild-type helper virus. In each case, the presence of variants was detected by the appearance of discrete short viral genomes in infected cell lysates. Such short genomes, isolated by agarose gel electrophoresis, were shown to be specifically altered by comparing the electrophoretic pattern of their DNA fragments produced by
Haemophilus influenzae
restriction endonuclease with the pattern of fragments from parental DNA. In addition to defective variants, one infectious variant that had an additional segment of DNA within its genome was isolated.
Photochemical Attachment of
lac
Repressor to Bromodeoxyuridine-Substituted
lac
Operator by Ultraviolet Radiation
Authors: Lin Syr-Yaung , Riggs Arthur D.
Published: May 2006

The transducing phage λh80
dlac
carries the
lac
operator, whereas wild-type λh80 does not. We find that in high salt (0.18 M KCl), ultraviolet radiation causes the formation of a very stable complex between repressor and 5-bromodeoxyuridine (BrdU)-substituted λh80
dlac
but not to BrdU-λh80 DNA. Studies with inducers of the
lac
operon confirm the specificity of attachment. In low slat (0.01 M KCl), ultraviolet radiation will also attach repressor nonspecifically to BrdU-λh80 DNA. The stability of the complex suggests that covalent bonds are formed. We also report that another regulatory protein, the catabolite gene activator protein, can be attached similarly to DNA.
Human Antigen and Enzyme Markers in Man-Chinese Hamster Somatic Cell Hybrids: Evidence for Synteny Between the
HL-A, PGM
3
,
ME
1
, and
IPO-B
Loci
Authors: Someren H. Van , Westerveld A. , Hagemeijer A. , Mees J. R. , Khan P. Meera , Zaalberg O. B.
Published: May 2006

In man-Chinese hamster somatic cell hybrids the segregation of the loci for 27 human enzyme markers and the species-specific surface antigens, including the HL-A histocompatibility antigens, was studied. The results show a synteny of the human loci for phosphoglucomutase 3, cytoplasmic malic enzyme, tetrameric indophenol oxidase, and HL-A. Furthermore, evidence is presented that the loci for the human species-specific antigens are distributed over several chromosomes.
Purification and Characterization of the Hormone Initiating Sexual Morphogenesis in
Volvox carteri
f.
nagariensis
Iyengar
Authors: Starr Richard C. , Jaenicke Lothar
Published: May 2006

In
Volvox carteri
f.
nagariensis
male spheroids secrete into the medium a sexual hormone which controls the initiation of the developmental pathway leading to the formation of sexual embryos. In the absence of the hormone asexual embryos are formed. Analysis of the highly purified hormone indicates that it is a glycoprotein of 27,500-30,000 daltons, composed of one peptide chain, which has a typical composition except for a relatively low content of tryptophan. The glycosidic moiety, which accounts for about 45% of the weight of the molecule, consists of pentoses, hexoses, and amino hexoses. In the bioassay the highly purified hormone stimulates 100% formation of sexual embryos at a concentration of 10
-10
g/liter and 14.4% sexual embryos at 10
-11
g/liter (3 × 10
-16
M). The activity is remarkably thermostable and resistant to different denaturing procedures.
Polyadenylylation and Transcription Following Fertilization
Authors: Slater Isabel , Slater D. W.
Published: May 2006

Polyadenylylated RNA from sea urchin embryos concomitantly labeled with [
3
H]adenosine and [
14
C]uridine between fertilization and the four-cell stage was used to determine whether the RNA primers prerequisite to the massive polyadenylylation known to occur after fertilization are synthesized during oogenesis or subsequent to fertilization. Characterization of this RNA and unlabeled RNA via retention on nitrocellulose membranes and poly(U)-impregnated filters, molecular hybridization with [
3
H]poly(U), RNase resistance, oligo(dT)-cellulose chromatography, and size-distribution studies indicates that the poly(A) tracts synthesized after fertilization are predominantly appended to preexisting cytoplasmic primers of oogenic origin. Hence, if polyadenylylation is involved in the selective editing of presumptive genetic messages, this process is not confined to the nucleus unless a given codogenic transcript can undergo more than one cycle of adenylylation.
Interspersion of Repetitive and Single-Copy Sequences in Nuclear Ribonucleic Acid of High Molecular Weight
Authors: Holmes David S. , Bonner James
Published: May 2006

Nuclear RNA of high molecular weight, approximately 15 to 30 × 10
3
nucleotides long, isolated from rat ascites cells, has been shown previously to contain both middle repetitive and single-copy sequences. However, it was not known whether these sequences were located on separate molecules or whether they were interspersed within the same molecule. The present communication distinguishes between these possibilities and shows that a large proportion of nuclear RNA of high molecular weight consists of interspersed middle repetitive and single-copy sequences.
Dopamine-Sensitive Adenylate Cyclase in Mammalian Brain: A Possible Site of Action of Antipsychotic Drugs
Authors: Clement-Cormier Yvonne C. , Kebabian John W. , Petzold Gary L. , Greengard Paul
Published: May 2006

Adenylate cyclase (EC 4.6.1.1), selectively stimulated by low concentrations of dopamine, has been found in the olfactory tubercle, the nucleus accumbens, and the caudate nucleus of several mammalian species. Several different classes of drugs effective in the treatment of schizophrenia (antipsychotic drugs) were potent inhibitors of the stimulation by dopamine of the enzyme from these various regions. The drugs studied included representatives of the phenothiazine, butyrophenone, and dibenzodiazepine classes. The inhibition by these antipsychotic drugs was competitive with respect to dopamine. The most potent of the antipsychotic agents tested was fluphenazine, which had a calculated inhibition constant (
K
i
) of about 5 × 10
-9
M. For each of several drugs tested, the
K
i
for the enzyme from the olfactory tubercle was similar to that for the enzyme from the caudate nucleus. Several compounds closely related structurally to the psychoactive phenothiazines, but which have little or no antipsychotic or extrapyramidal actions clinically, had low relative potencies as inhibitors of dopamine-stimulated adenylate cyclase activity. The results, considered together with other data, raise the possibility that the therapeutic effects, as well as the extrapyramidal side effects, of these antipsychotic agents may be attributable, at least in part, to their ability to block the activation by dopamine of specific dopamine-sensitive adenylate cyclases in the human brain.