bluuebunny/crossref_metadata_2025 huggingface dataset:
On Some Periodic Toda Lattices
Authors: Kac M. , Van Moerbeke Pierre
Published: May 2006

A discrete version of Floquet's theory is developed and applied to a system of non-linear differential equations related to the periodic Toda lattice. A special solution previously found by Toda is thus seen to fit into the formalism of inverse scattering problems.
Purine metabolism in murine virus-induced erythroleukemic cells during differentiation in vitro.
Authors: Reem G H , Friend C
Published: May 2006

Purine metabolism was studied in murine virus-induced erythroleukemia cells stimulated to differentiate in vitro in the presence of dimethylsulfoxide. The activities of the enzymes that catalyze the synthesis of the first intermediate of the de novo purine pathway, phosphoribosyl-1-amine, were decreased while the enzymes that catalyze the conversion of purine bases to purine ribonucleotides remained unchanged at the time the cells acquired the specialized function of hemoglobin synthesis. In addition, cytidine deaminase (cytidine aminohydrolase, EC 3.5.4.5) activity increased with erythropoietic maturation, as it does during murine erythropoiesis in vivo. Stimulation of cellular proliferation of stationary erythroleukemic cells resulted in a marked increase in the activities of purine biosynthetic enzymes. These data provide a convincing example of repression and derepression of the PRA synthesizing enzymes in mammalian cells in vitro, and further evidence that the regulatory mechanisms operative in the normal development of erythrocytes can be activated by exposure of erythroleukemic cells to dimethylsulfoxide.
Production of antibodies of identical idiotype but diverse immunoglobulin classes by cells derived from a single stimulated B cell.
Authors: Gearhart P J , Sigal N H , Klinman N R
Published: May 2006

The availability of anti-phosphocholine antibody of the TEPC 15 idiotype from the clonal progeny of a single precursor cell, stimulated in vitro, permitted the demonstration of monoclonal antibodies with as many as three immunoglobulin classes with identical variable regions. This demonstration was dependent on sensitive radioimmunoassays which showed a one to one relationship between the total anti-phosphocholine antibody produced by a clone and the sum of anti-phosphocholine antibody of the different classes as well as the amount of antibody of the TEPC 15 idiotype. The class distribution was confirmed by isoelectric focusing identification of IgM, Igta, and IgGl antibodies of the TEPC 15 idiotype produced by single clones which showed characteristic pI values for each immunoglobulin class. Thus, within the generative phase of a single antibody-producing cell clone, various heavy chain constant regions can be linked to the same variable region, and single precursor cells have the capacity to generate progeny expressing at least three distinct immunoglobulin classes.
Motion of subfragment-1 in myosin and its supramolecular complexes: saturation transfer electron paramagnetic resonance.
Authors: Thomas D D , Seidel J C , Hyde J S , Gergely J
Published: May 2006

Molecular dynamics in spin-labeled muscle proteins was studied with a recently developed electron paramagnetic resonance (EPR) technique, saturation transfer spectroscopy, which is uniquely sensitive to rotational motion in the range of 10(-7)-10(-3) sec. Rotational correlation time (tau2) were determined for a spin label analog of iodoacetamide bound to the subfragment-1 (S-1) region of myosin under a variety of conditions likely to shed light on the molecular mechanism of muscle contraction. Results show that (a) the spin labels are rigidly bound to the isolated S-1 (tau2 = 2 x 10(-7) sec) and can be used to estimate values of tau2 for the S-1 region of the myosin molecule; (b) in solutions of intact myosin, S-1 has considerable mobility relative to the rest of the myosin molecule, the value of tau2 for the S-1 segment of myosin being less than twice that for isolated S-1, while the molecular weights differ by a factor of 4 to 5; (c) in myosin filaments, tau2 increases by a factor of only about 10, suggesting motion of the S-1 regions independent of the backbone of the myosin filament, but slower than that in a single molecule; (d) addition of F-actin to solutions of myosin or S-1 increases tau2 by a factor of nearly 10(3), indicating strong immobilization of S-1 upon binding to actin. Saturation transfer spectroscopy promises to provide an extremely useful tool for the study of the motions of the crossbridges and thin filaments in reconstituted systems and in glycerinated muscle fibers.
Transfer of the human gene for hypoxanthine-guanine phosphoribosyltransferase via isolated human metaphase chromosomes into mouse L-cells.
Authors: Willecke K , Ruddle F H
Published: May 2006

We have transferred the human gene for hypoxanthine-guanine phosphoribosyltransferase (HPRT, EC 2.4.2.8; IMP:pyrophosphate phosphoribosyltransferease) via isolated metaphase chromosomes from human HeLa S3 cells into murine A9 cells which lack functional murine HPRT activity, using the technique of McBride and Ozer (Proc, Nat. Acad. Sci. USA 70, 1258-1262, 1973). Three transformed clones were isolated which contained human HPRT activity as determined by electrophoretic and immunochemical assays. Twenty human isozymes other than HPRT whose genes have been assigned to 14 human chromosomes were found to be absent in our transformed clones. Moreover, the human isozymes of hlucose-6-phosphate dehydrogenase (EC 1.1.1.49; D-glucose 6-phosphate:NADP 1-oxidoreductase) and phosphoglycerate kinase (EC 2.7.2.3;ATP:3-phospho-D-glycerate 1-phosphotransferase), whose genes have been linked with the HPRT gene to the long are of the human X chromosome, were also absent. On the basis of the known linkage relationships of the three markers, we thereby suggest that the transferred piece of human genetic material is smaller than 20% of the human X chromosome or less than 1% of the human genome. This estimate assumes a normal syntenic relationship for the long arm of the X chromosome in HeLa S3 cells. In agreement with this conclusion, no human chromosomes could be detected in our transformed clones. When grown under nonselective conditions about 3% of the gene transfer cells lost the human HPRT marker per cell generation. Transformants that had lost human HPRT activity were subjected to hypoxanthine-aminopterin-thymidine selection. The frequency of revertants to the HPRT(+) phenotype was less than 1 x 10(-6), and two revertants that were obtained possessed the mouse electrophoretic phenotype. These results argue against a stable integration of the human donor genetic material into the mouse recipient genome.
Coezyme A requirement of malaria parasites: effects of coenzyme A precursors on extracellular development in vitro of Plasmodium lophurae.
Authors: Trager W , Brohn F H
Published: May 2006

The extracellular development in vitro of the avian malaria Plasmodium lophurae is favored by addition to the medium of coenzyme A at 0.05 mM. Coenzyme A can be replaced by dephospho-coenzyme A and to some extent by phosphopantetheine, but not by phosphopantothenoylcysteine or by phosphopantothenic acid. The activity of the two former precursors results from their conversion to coenzyme A by enzymes in the erythrocyte extract of the culture medium in the presence of ATP, also an essential ingredient of the medium. Hence, P. lophurae in its erythrocytic stage has an absolute requirement for an exogenous source of coenzyme A.
Somatic hybrid of thymus leukemia (.
Authors: Liang W , Cohen E P
Published: May 2006

A somatic hybrid of ASL-1 leukemia cells [H-2a, thymus leukemia (TL)1,2,3, Thy-1b] and LM(TK)-cells [H-2-k, TL(-), Thy-1 (-), thymidine kinase deficient] was formed with the aid of inactivated Sendai virus. The selection of hybrid cell clones was facilitated by the inability of ASL-1 cells to grow in vitro and of LM(TK)-cells to survive in hypoxanthine/amethopterin/thymidine medium. The H-2 antigens of both parental cells were formed in approximately equivalent amounts by the hybrid cells, and they possessed a hybrid karyotype. As determined by five independent experimental procedures (antibody and complement-mediated cytotoxicity tests, the reduction of specific antibody activity of antiserum of known titer, immunofluorescent tests, mixed hemagglutination tests, and their direct isolation), TL antigens but not Thy-1 antigens were formed by the hybrid cells. TL antigens of the hybrids failed to undergo modulation under conditions leading to the modulation of TL antigens of parental ASL-1 cells. Modulation was attempted with TL 1,3, TL 2, or TL 1,2,3 antisera of high titer. thybrid cells were incubated for up to 30 hr in medium with TL antisera. Both direct and indirect immune methods were attempted. These results indicate that cellular mechanisms controlling the expression of TL antigens may be distinguished from the capacity of the cells to undergo modulation.
Play: early and eternal.
Authors: Mears C E , Harlow H F
Published: May 2006

A systematic 12-week investigation of development of play behavior was conducted with eight socially reared rhesus monkey infants. A new, basic and primary play form termed self-motion play or peragration was identified and examined. This behavior follows a human model which includes a wide range of pleasurable activities involving motion of the body through space, e.g., rocking, swinging, running, leaping, and water or snow skiing. It can be argued that self-motion play is the initial primate play form and because of its persistence constitutes a reinforcing agent for maintaining many complex patterns and even pastimes. Monkey self-motion play in the present study was divided into five separate patterns in order to compare the relative importance of social and individual peragration play, the role of apparatus and the overall developmental relationships between the different individual and social self-motion play patterns. The data showed that from 90 to 180 days of age self-motion play was independent of other forms of play, that individual self-motion play appeared earlier and with significantly greater increases in frequency than did social self-motion play, and that apparatus was a necessary component for significant increases in social self-motion play. Other findings were that self-motion play existed independent of locomotion and, though initiated by exploration, was separate from it. Therapeutic implications of self-motion play were discussed.
Methylated, blocked 5 termini in HeLa cell mRNA.
Authors: Furuichi Y , Morgan M , Shatkin A J , Jelinek W , Salditt-Georgieff M , Darnell J E
Published: May 2006

Poly(A)-containing HeLa cell mRNA prepared from cells labeled with [methyl-(3)H]methionine or [(32)P]phosphate was found to contain a variety of methylated, blocked 5'-terminal structures of two general types: m(7)GpppN(7)-Np and m(7)GpppN(m)-N(m)-Np. In addition, about one-third of the [(3)H]methyl label was present in the N(6)-methyladenosine; this labeled nucleoside was not found in the 3'-terminal one-third of the mRNA chain and thus may also be in the 5' portion of the mRNA.
Changing patterns of actin localization during cell division.
Authors: Sanger J W
Published: May 2006

Changing patterns of actin localization have been studied on a light microscopic level by means of fluorescently labeled heavy meromyosin. The cellular distribution of actin is characterized by four major patterns, each of which corresponds to a particular phase of cell division. Long actin fibers are a prominent feature of the interphase cell. They disappear as the cell rounds up for mitosis and are replaced by a diffuse distribution of actin throughout the cytoplasm. During cytokinesis, the actin is localized predominantly in the cleavage furrow. The final shift of actin occurs after the completion of cytokinesis. At this time the actin becomes concentrated in the distal poles of the cell where pseudopods form to pull the daughter cells apart. When the daughter cells have separated, they flatten on the culture dish and the fibrous pattern of actin characteristic of interphase cells returns. All of these changes take place during the 1-hr period required for cell division.
Strongly Nonlinear Integral Equations of Hammerstein Type
Authors: Browder Felix E.
Published: May 2006

This paper studies the solution of the nonlinear Hammerstein equation
u
(
x
) + ʃ
k
(
x,y
)
f
[
y,u
(
y
)]μ(
dy
) =
h
(
x
) in the singular case, i.e., where the linear operator
K
with kernel
k
(
x,y
) is not defined for all the range of the nonlinear mapping
F
given by
Fu
(
y
) =
f
[
y,u
(
y
)] over the whole class
X
of functions
u
which are potential solutions of the equation. An existence theorem is derived under relatively minimal assumptions upon
k
and
f
, namely that (
Ku,u
) ≥ 0, that
K
maps
L
1
into
L
1
loc
and is compact from
L
1
[unk]
L
∞
into
L
1
loc
, that
f
(
y,s
) has the same sign as
s
for ǀ
s
ǀ ≥
R
, and that for each constant
r
> 0, ǀ
f
(
y,s
)ǀ ≤

g
r

(
y
) for ǀ
s
ǀ ≤
r
where
g
is bounded and summable. The proof is obtained by combining
a priori
bounds, a truncation procedure, and a convergence argument using the Dunford-Pettis theorem.
Localization of the IgG effector site for monocyte receptors.
Authors: Ciccimarra F , Rosen F S , Merler E
Published: May 2006

A peptide consisting of 10 amino acids derived from the CH3 region of human IgG was shown to bind to monocytes and to inhibit rosette formation of antibody-coated erythrocytes with human monocytes. Two myeloma proteins of the IgG1 and IgG3 subclass, both with known deletions in the CH2 region of the gamma chain, showed unimpaired ability to bind to monocytes. These experiments suggest that the isolated peptide represents the primary site of attachment of IgG to monocytes.
Genetic variation as a test of natural selection.
Authors: Nevo E , Dessauer H C , Chuang K C
Published: May 2006

Allozymic variation encoded by 26 loci was analyzed electrophoretically in 507 specimens representing 12 populations of green toads, Bufo viridis, in Israel and the Vis Adriatic Island. Genetic variation in Bufo viridis is higher than in any vertebrate yet studied. Mean heterozygosity per locus per individual (H) is 0.133 (range, 0.105 to 0.159). H is higher in central populations as compared with isolates, and varies among four major protein classes, being highest in transferases and hydrolases and lowest in oxidoreductases and nonenzymatic proteins. Differential gene frequencies among polymorphisms was tested as an indicator of natural selection. Significant heterogeneity between loci in their apparent inbreeding coefficients Fe=S-2p/P(1-p) was found for all alleles and for each of the four major classes of proteins tested, which may be taken as evidence of selection. Both uniform and diversifying selection are suggested by the low and high Fe values, respectively. The general pattern of high heterozygosity in Bufo viridis is best explained as an adaptive strategy in heterogeneous environments.
Diversity of light chain variable region sequences among rabbit antibodies elicited by the same antigens.
Authors: Margolies M N , Cannon L E , Strosberg A D , Haber E
Published: May 2006

We report the complete variable region sequences of three homogeneous rabbit antibody light chains and the partial sequences of five others. Wehn these are compared to other published rabbit light chain sequences, two regions of markedly increased variability are revealed, which are homologous in position to the first and third hypervariable regions of murine and human myeloma light chains. In addition, there is increased variability among the first three residues at the aminoterminal end. A hypervariable region homologous to that identified at positions 50 to 56 in myeloma light chains is not present in these rabbit antibody light chains. The available three-dimensional models of Fab fragments based on x-ray crystallography indicate that neither the amino-terminal portion of the light chain nor the region homologous to positions 50 to 56 forms a part of the combining site. Comparison of the hypervariable regions among six light chains from antibodies to Type III pneumococcal polysaccharide and among four from antibodies to Type VIII pneumococcal polysaccharide suggests that a large number of different sequences may be found in antibodies specific for these relatively simple antigens. Certain residues outside of the hypervariable regions are invariant in the rabbit light chains and correspond to residues that are required for proper chain folding in human and murine myeloma light chains, indicating that the general conformation of myeloma light chains is the same as that of light chains of elicited antibodies.
Nuclear magnetic resonance spectrum of living tunicate blood cells and the structure of the native vanadium chromogen.
Authors: Carlson R M
Published: May 2006

The 1-H nuclear magnetic resonance spectrum of living tunicate blood cells was examined in an attempt to develop a biophysical assay for the native vanadium chromogen. The living cell spectrum was found to exhibit a broad 21 ppm downfield Gaussian signal which, however, disappears immediately upon cell disruption. Examination of the properties of this extremely low field signal revealed that it corresponds to a labile vanadium (III) aquo complex contained in the cell vacuoles, that vanadium(III) concentrations are rigidly regulated within these vacuoles, and that artifact formation does occur in the hemolysate. The living cell spectrum also indicates the number of ligand-bound vanadium(III) coordination sites in the native blood pigment. Results are discussed relation to the possible functions of the vandium chromogen.
Cloning, isolation, and characterization of replication regions of complex plasmid genomes.
Authors: Timmis K , Cabello F , Cohen S N
Published: May 2006

EcoRI endonuclease-generated DNA fragments carrying replication regions of the F'lac and R6-5 plasmids have been cloned and isolated, using as a selection vehicle a nonreplicating ampicillin-resistance DNA fragment derived from a Staphylococcus aureus plasmid. Heteroduplex analysis of the constructed plasmid chimeras and the parent replicons has localized the cloned R6-5 replication region to a DNA segment between kilobase pair coordinates 1.0 and 88.0 on the R6-5 map. Physical proximity between the plasmid replication functions and the locus governing plasmid incompatibility has been shown for both parent replicons. The cloning method reported appears to be generally applicable for the identification and isolation of replication regions of a variety of complex genomes.
Effect of growth conditions on DNA-membrane attachment in Escherichia coli.
Authors: Parker D L , Glaser D A
Published: May 2006

DNA-membrane attachment in cultures of E. coli B/r is found to depend on the pattern of DNA synthesis, (a) When the number of replication points increases, the fraction of the DNA that is membrane bound also increases. The relationship between the amount of DNA-membrane attachment and the number of replication points is most consistent with attachment of all replication points and attachment of at least one other chromosomal site; it is inconsistent with attachment of the replication points only, the chromosomal origin only, or the chromosomal terminus only. (b) When repair DNA synthesis is stimulated by irradiation with ultraviolet light, the DNA-membrane attachment remains unchanged.
Separation of "estrogen-induced" protein from phosphoprotein phosphatase activity of immature rat uterus.
Authors: Kaye A M , Walker M D , Sömjen D
Published: May 2006

Preparations of the "induced protein" which appears in the rat uterus within 40 min of estradiol administration have recently been reported to contain phosphoprotein phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) activity. We found that these two proteins distribute differently on ammonium sulfate fractionation of uterine cytosol. Preparative cellulose acetate electrophoresis afforded complete (greater than 99.9%) separation of phosphoprotein phosphatase activity from the induced protein. The specific activity of phosphoprotein phosphatase in uterine cytosol was unchanged 1, 4, 12, or 24 hr after estradiol administration. These results are incompatible with the view that the induced protein mediates estrogen action by virtue of an inherent phosphoprotein phosphatase activity.
Association of mouse liver adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels with histocompatibility-2 genotype.
Authors: Meruelo D , Edidin M
Published: May 2006

When the content of cyclic AMP (cAMP) was compared in livers of a series of congenic mouse strains differing at the H-2 locus, significant variation in concentration of cAMP per unit wet weight was found among strains, and also for animals of a given strain with increasing age. For a given age, from 8 to 22 weeks, cAMP levels in liver of H-2a and H-2b genotype animals were significantly higher than that in liver of H-2k type animals. This difference was seen whether the H-2 gene was on the genetic background of strain C57BL/10, C3H, or A. Levels of cAMP in livers of H-2d animals were between those of H-2a and H-2k animals.
Lysis of leukemia cells by spleen cells of normal mice.
Authors: Zarling J M , Nowinski R C , Bach F H
Published: May 2006

Spleen cells from 2- to 3-month-old normal mice of some strains having a low incidence of spontaneous leukemia were found to lyse cells of the spontaneous AKR leukemia K36 in the 51Cr release assay. Incubation of 51Cr-labeled ADR K36 cells with spleen cells from normal C57BL/6, C57L, C57BL/10, and RF mice resulted in the release of significantly more 51Cr than that released in the presence of medium alone. In contrast, 51Cr released from AKR K36 cells after incubation with spleen cells from mice of the high leukemic strains AKR and C58 was less than that released spontaneously. The results of competitive inhibition tests when C57BL/6 spleen cells were incubated simultaneously with 51Cr-labeled AKR K36 target cells and varying numbers of nonlabeled cells demonstrated that the cytotoxic activity of normal C57BL/6 spleen cells was directed against an antigen(s) associated with several leukemias, but that was undetectable on normal thymocytes. Pretreatment of C57BL/6 spleen cells with carbonyl iron and a magnet, which removed phagocytic macrophages, did not decrease the cytotoxic acitivity for AKR K36 cells.
Synthetic analogs of active sites of iron-sulfur proteins: bis (o-xylyldithiolato) ferrate (III) monoanion, a structurally unconstrained model for the rubredoxin Fe-S4 unit.
Authors: Lane R W , Ibers J A , Frankel R B , Holm R H
Published: May 2006

To complete the set of synthetic analogs of the three recognized types of active sites in iron-sulfur redox proteins, the compound (Et4N)[Fe((SCH2)2C6H4)2], derived from o-xylyl-alpha,alpha'-dithiol, has been prepared and its structure has been determined by x-ray diffraction. The bischelate anion contains a near-tetrahedral Fe(III)-S4 coordination unit with small rhombic distortions and all Fe-S bond distances in the range 2.252-2.279 A. Its electronic properties have been partially characterized by measurement of electronic absorption, paramagnetic resonance, Mössbauer spectra, and magnetic susceptibility. The analog, as the protein, exhibits the Fe(III)/Fe(II) redox couple. These results substantiate designation of [Fe((SCH2)2C6H4)2]- as a synthetic analog of the Fe(III)(S-Cys)4 center in oxidized rubredoxin proteins. Comparison of the analog structure with that of the Clostridium pasteurianum rubredoxin active site shows that the former is substantially less distorted from idealized tetrahedral symmetry, and is considered to represent an essentially unconstrained structural model of the latter. Provided the grossly distorted tetrahedral stereochemistry of the protein site persists through final structural refinement, the analog-protein structural comparison supports an entatic state description of oxidized rubredoxin.
Increased frequency of initiation of RNA synthesis due to a protein factor from chicken myeloblastosis nuclei.
Authors: Chuang R Y , Chuang L F
Published: May 2006

The mechanism of the effect of an RNA polymerase II (RNA nucleotidyltransferase II) stimulation factor isolated from the nuclei of chicken myeloblastosis cells was studied. The stimulation requires the presence of all four nucleoside triphosphates and depends upon an exogenous DNA template. In the absence of the factor, RNA synthesis ceases after 20-30 min, but in the presence of the factor, synthesis continues up to 60-80 min. Addition of the factor at 35 min after incubation causes resumption of RNA synthesis. The factor greatly stimulates the activity of RNA polymerase II at low enzyme concentrations. The RNA polymerase activity is more sensitive to alpha-amanitin inhibition when the factor is present. Experiments of [gamma-32P]ATP incorporation reveal that the factor provides for an increased frequency of initiation of RNA chains, both of the primary initiation events and re-initiation after previous ones were completed. A slightly higher rate of RNA chain growth was also observed with this factor but the ultimate size of RNA synthesized was not affected, as determined by formaldehyde/sucrose gradient centrifugation. These data suggest that the factor functions at the initiation stages of the RNA polymerase reaction.
Surface ruffles as markers for studies of cell transformation by Rous sarcoma virus.
Authors: Ambros V R , Chen L B , Buchanan J M
Published: May 2006

Confluent chick embryo fibroblasts infected with the Ts68 mutant of Rous sarcoma virus were examined by scanning electron microscopy at the permissive (36 degrees) and nonpermissive (41 degrees) temperatures for transformation. Infected cells shifted from 41 degrees to 36 degrees undergo a change in shape from elongated to rounded. This process is preceded by the appearance of surface ruffles on the cell. These surface ruffles are not observed on cells maintained at 41 degrees, appear as early as 0.5 hr after a shift to 36 degrees, and are common on cells maintained at 36 degrees. By 3.5 hr after the shift from 41 degrees to 36 degrees, cultures appear fully transformed by the criteria of cell roundedness and the presence of surface ruffles. This surface alteration of cells is the earliest event of those so far reported during the transformation process and is not dependent upon protein synthesis and extracellular plasminogen during the period of temperature shift.
Omega-aminoalkyl agaroses in the resolution of enzymes involved in regulation of glutamine metabolism.
Authors: Shaltiel S , Adler S P , Purich D , Caban C , Senior P , Stadtman E R
Published: May 2006

Systematic examination of a homologous series of omega-aminoalkyl agaroses showed that the pentyl derivative (Seph-C5-NH2) was best suited for the retention and subsequent separation of several proteins involved in the regulation of glutamine metabolism in Escherichia coli, including: glutamine synthetase [EC 6.3.1.2; L-glutamate:ammonia ligase (ADP-forming)], ATP:glutamine synthetase adenylyltransferase (EC 2.7.7.42), the PII regulatory protein which regulates the adenylylation and deadenylylation activities of the adenylyltransferase, the UTP:PII protein uridylyltransferase, and the uridylyl removing enzyme which catalyzes the removal of uridylyl groups from uridylylated PII protein. Resolution of these proteins was achieved by gradually increasing the concentration of KCl in the eluant, which resulted in consecutive detachment of the proteins from the column. Proteins that co-elute from a DEAE-cellulose column can be resolved and further purified on epsilon-aminopentyl agarose, probably due to the fact that with the homologous series it is possible to adjust the contribution of hydrophobic interactions for optimal resolution.
Headgroup conformation and lipid--cholesterol association in phosphatidylcholine vesicles: a 31P(1H) nuclear Overhauser effect study.
Authors: Yeagle P L , Hutton W C , Huang C H , Martin R B
Published: May 2006

The nuclear Overhauser effect has been observed in the nuclear magnetic resonance spectra of 31P. The information content of the nuclear Overhauser effect has been applied to the structure and dynamic properties of phosphatidylcholine vesicles. In the vesicles only 1/3 of the theoretical maximum nuclear Overhauser effect enhancement is observed. This result is accounted for by dipolar interactions between the N-methyl protons and the phosphate of phosphatidylcholine, and a correlation time for internal motion of 1.4 X 10(-9) sec. Addition of up to 30% cholesterol does not change the nuclear Overhauser effect enhancement or spin-lattice relaxation time of the vesicles. It is argued that the OH group of cholesterol is hydrogen bonded to the ester carbonyl oxygen of the phosphatidylcholine molecules.
Subunit structure of a naturally occurring chromatin lacking histones F1 and F3.
Authors: Gorovsky M A , Keevert J B
Published: May 2006

Macronuclei of the ciliated protozoan Tetrahymena pyriformis contain at least five classes of histones, including two with properties like those of histones F3 and F1 of higher eukaryotes. Micronuclei isolated under identical conditions contain little or no detectable F3 or F1. Digestion of both macronuclei and micronuclei with staphylococcal nuclease results in DNA fragments of discrete sizes. The electrophoretic mobilities of the larger fragments suggest that they are oligomers of the smallest ones. These results indicate that the periodic subunit structure observed in the chromatin of higher organisms also occurs in protozoans, and that this structure does not depend on the presence of either histone F1 or F3, even in an organism which has the genetic information for synthesizing these proteins.
Cell surface species-specific high affinity receptors for discoidin: developmental regulation in Dictyostelium discoideum.
Authors: Reitherman R W , Rosen S D , Frasier W A , Barondes S H
Published: May 2006

Vegetative (noncohesive) D. discoideum cells and cells at several stages during the development of cohesiveness were fixed with glutaraldehyde, and their agglutinability by purified carbohydrate-binding proteins (lectins) from slime molds and plants was determined. The two purified lectins from D. discoideum, called discoidin I and II, were poor agglutinins of fixed vegetative D. discoideum cells and potent agglutinins of fixed cohesive D. discoideum cells. The increased agglutinability of D. discoideum cells by discoidin I or discoidin II with differentiation paralleled discoidin appearance in cell extracts and development of cohesiveness. The lectin of another slime mold, Polysphondylium pallidum (pallidin) and the lectin of Ricinus communis (RCA-I) were also more potent agglutinins of fixed differentiated D. discoideum cells than of fixed vegetative D. discoideum cells. However, wheat germ agglutinin was much more potent with fixed vegetative cells. The association constant (Ka) of discoidin I and discoidin II for fixed differentiated D. discoideum cells was in the range of 10(9) M-1, more than twenty-fold higher than the Ka of these lectins for fixed vegetative cells. The Ka of discoidin I and discoidin II for fixed differentiated P. pallidum cells was an order of magnitude lower than for fixed differentiated D. discoideum cells. The Ka of pallidin for fixed differentiated P. pallidum cells was about 4 X 10(9) M-1 and was an order of magnitude lower for fixed differentiated D. discoideum cells. Since previous studies showed that the lectin of each of these slime mold species is detectable on the surface of cohesive cells, the observation of species-specific receptors on the surface of cohesive cells suggests a basis for species-specific cohesion.
Receptor synapses without synaptic ribbons in the cochlea of the cat.
Authors: Dunn R A , Morest D K
Published: May 2006

This report describes recepto-neural junctions thought to be chemical synapses without synaptic ribbons or vesicle aggregates. Such synapses occur in the cat between the outer hair cells of the cochlea and auditory nerve fibers. These synapses are formed by flat or indented junctions having symmetric membrane complexes associated with smooth endoplasmic reticulum and coated vesicles in the outer hair cell cytoplasm. Inner hair cells have receptoneural junctions with asymmetric membrane complexes; synaptic ribbons and vesicles gather at one type of junction, while the other type associates with endoplasmic reticulum. Gap junctions are not seen at cochlear synapses but do link supporting cells. The results suggest that inner and outer hair cell synapses have different properties and raise questions about the role of synaptic vesicles and endoplasmic reticulum in the storage and release of transmitters.
Nucleotide sequences of the 3'-terminal untranslated region of messenger RNA for human beta globin chain.
Authors: Forget B G , Marotta C A , Weissman S M , Cohen-Solal M
Published: May 2006

In normal messenger RNA for the human beta-globin chain, nucleotide sequences have been identified which can be matched to the amino-acid sequence of the abnormally long segment of the beta-chain of hemoglobin Cranston. The finding of these sequences strengthens the hypothesis that the betaCranston chain arose by a frameshift mutation allowing the "readthrough" of the normal termination codon and translation of usually untranslated portions of the messenger RNA for the beta-globin chain. The oligonucleotides which match the amino-acid sequence of hemoglobin Cranston provide a sequence of 36 nucleotides which follows the normal beta-chain termination codon UAA.
Transposition of R factor genes to bacteriophage lambda.
Authors: Berg D E , Davies J , Allet B , Rochaix J D
Published: May 2006

Transpositions of segments of R factor (antibiotic resistance plasmids) to bacteriophage lambda have been selected and characterized. Cells of Escherichia coli harboring R factors that determine kanamycin resistance were infected with phage lambda, and lambdakan transducing lines were obtained. Each of the three examined is unusual when compared to lambda transducing phages containing E. coli chromosomal genes: the kan insertions (a) occur at several sites, each well removed from the integration region POP', (b) are not associated with deletion of lambda phage DNA, and (c) are separable from the lambda genome during transduction or during lytic growth. Two insertions from the same R factor contain 1.5 kilobase sequences repeated in inverted order. The properties of the lambdakan phage suggest that R factors contain systems capable of mediating genetic exchange in the absence of extensive DNA homology. It is suggested that such systems of exchange may have played important roles in R factor evolution.
Tumor regression at an untreated site during immunotherapy of an identical distant tumor.
Authors: Schlager S I , Dray S
Published: May 2006

The effects of two immunotherapy regimens on the development of an untreated, uniformly lethal transplantable line-10 hepatoma in strain 2 guinea pigs were monitored during treatment of an identical tumor 10 cm away. Line-10 cells were injected intradermally simultaneously at each of two sites. When one site was treated 6 and 16 days later with rabbit antibody against guinea pig fibrin fragment E, the complete regression of the treated tumor, a 25--30% depression in the development of the untreated tumor, and an increased survival time were observed. In another group of animals, when one site was treated 5 days after tumor challenge with syngeneic or xenogeneic "tumor-immune" RNA in a regimen including syngeneic nonsensitive lymphoid cells and tumor-specific antigen, all animals survived after complete and apparently specific regression of the tumors at both the treated and untreated sites. For the RNA regimen, we have shown that immunotherapy of an intradermally established line-10 tumor results in complete abrogation of both the treated and a distant untreated tumor; i.e., demonstrating a systemic effect.
[13C]Valine metabolism in methylmalonicacidemia using nuclear magnetic resonance: propinonate as an obligate intermediate.
Authors: Tanaka K , Armitage I M , Ramsdell H S , Hsia Y E , Lipsky S R , Rosenberg L E
Published: May 2006

[Alpha-13C]- and [alpha,beta-13C]valine were administered sequentially to a patient with methylmalonicacidemia to clarify the metabolic pathway of valine from methylmalonic acid semialdehyde to methylmalonyl-CoA. Methylmalonic acid was isolated from multiple urine samples, purified, and analyzed by 13C nuclear magnetic resonance spectroscopy. Contrary to the widely accepted view, the results show unequivocally that methylmalonic acid semialdehyde is decarboxylated to propionate before conversion to methylmalonyl CoA.
Bounds for a joint distribution function with fixed sub-distribution functions: Application to competing risks
Authors: Peterson Arthur V.
Published: May 2006

This paper gives sharp bounds for the joint survival function
G
(
t
1
,
t
2
,...,

t
r

) ≡
P
(
X
1
>
t
1
,
X
2
>
t
2
,...,

X
r

>

t
r

), and for the marginal survival functions

S
j

(
t
) ≡
P
(

X
j

>
t
),
j
= 1,2,...,
r
, when the sub-survival functions

S
j

*
(
t
) ≡
P
(

X
j

>
t
,

X
j

= min

k
=1,2

,...,

r
X
k

) are fixed. Theorem 1 gives the bounds for
r
= 2, and Theorem 2 gives the bounds for general
r
. Theorem 3 applies the result to the competing risks problem, and presents empirical bounds based on the observations. Finally, an example illustrates the bounds.
Prevention of viral-chemical co-carcinogenesis in vitro by type-specific anti-viral antibody.
Authors: Price P J , Bellew T M , King M P , Freeman A E , Gilden R V , Huebner R J
Published: May 2006

Low passage Fischer rat embryo cultures, which are normally very resistant to transformation by 3-methylcholanthrene but are highly susceptible when chronically infected with the Rauscher murine leukemia virus, were completely protected from transformation by methylcholanthrene when treated with neutralizing antibody specific for the leukemia virus prior to and during treatment with methylcholanthrene. Sister cultures were not protected by neutralizing antibody specific for the B-tropic radiation leukemia virus. This demonstrates clearly a definite type specific role for Rauscher murine leukemia virus in the 2-methylcholanthrene transformation system in rat cells.
Mutual potentiation by magnesium and calcium of growth in animal cells.
Authors: Rubin H , Koide T
Published: May 2006

The effects on DNA synthesis of various combinations of Mg2+ and Ca2+ in cultures of chick embryo cells have been studied. When [Mg2+] larger than or equal to 0.24 mM, reduction of Ca2+ from the standard concentration of 1.72 mM to 0.01 mM had no effect on the incorporation of [3H]thymidine ([3H]dThd) into DNA over a 16-hr period. When Mg2+ was reduced to 0.04 mM, [3H]dThd incorporation into DNA decreased directly with [Ca2+] below 1.72 mM and increased slightly up to [Ca2+] = 5.02 mM, where cell damage began to occur. The change in [Ca2+] necessary to maintain a half-maximal rate of [3H]dThd incorporation was found to depend inversely on the fourth power of the change in [Mg2+]. Chelation of Ca2+ with approximately equimolar ethylene glycol-bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) in the presence of [Mg2+] larger than or equal to 0.24 mM reduced [3H]dThd incorporation about 10-fold, and large excesses of EGTA did not further reduce it. The amount of EGTA required to produce a detectable inhibition of [3H]dThd incorporation was independent of [Mg2+] larger than or equal to 0.24 mM, as was the level of residual incorporation in excess EGTA. When [Mg2+] was reduced to 0.04 mM, however, [3H]dThd incorporation declined even when [EGTA] less than [Ca2+], and vanished when EGTA was in large excess. The results are discussed within the framework of a model for the regulation of cell metabolism and growth in which the availability of free Mg2+ is the central coordinating factor. The metabolic effects of Mg2+ depend on its distribution between elements such as ATP and binding sites on membranes. We propose that the major metabolic effects of varying [Ca2+] are produced indirectly through its competition with Mg2+ for membrane sites, thereby making more or less Mg2+ available for rate-limiting transphosphorylation reactions.
Mutability of different genetic loci in mammalian cells by metabolically activated carcinogenic polycyclic hydrocarbons.
Authors: Huberman E , Sachs L
Published: May 2006

The relationship between carcinogenesis and mutagenesis in mammalian cells has been determined with 10 polycyclic hydrocarbons with different degrees of carcinogenicity. Mutagenesis was determined in Chinese hamster cells with genetic markers that affect the surface membrane, nucleic-acid synthesis, and protein synthesis. The mutations were characterized by resistance to ouabain, 8-azaguanine, and temperature. Mutagenesis by the carcinogens required metabolic activation and this was provided by the presence of lethally irradiated metabolizing cells. The degree of carcinogenicity was related to the degree of mutagenicity for all three genetic markers. The most potent carcinogen, 7,12-dimethylbenz[a]anthracene, gave the highest mutagenicity and mutagenicity was obtained with 0.01 mug/ml. Treatment of the cells with aminophylline, which increases polycyclic hydrocarbon metabolism, increased mutagenesis by the carcinogens. It is suggested that such an experimental system with these and other mammalian cells should be useful as a sensitive assay for hazardous environmental chemicals.
Magnetic circular dichroism of ferrous carbonyl adducts of cytochromes P-450 and P-420 and their synthetic models: further evidence for mercaptide as the fifth ligand to iron.
Authors: Collman J P , Sorrell T N , Dawson J H , Trudell J R , Bunnenberg E , Djerassi C
Published: May 2006

Absorption and magnetic circular dichroism (MCD) spectra have been obtained for the ferrous carbonyl adducts of cytochromes P-450 and P-420 as well as synthetic model systems. Ferrous porphyrins with sodium methyl mercaptide and CO in benzene give MCD and absorption spectra which are almost identical to those of the natural enzyme, indicating that in P-450 a mercaptide serves as the fifth ligand in the ferrous carbonyl adduct. MCD spectra of models with either propyl mercaptan or N-methylimidazole as the axial ligand are identical with that of P-420. Thus, no unambiguous assignment of the axial ligand can be made in this case. The infrared stretching frequencies of ferrous porphyrin carbonyl complexes and the absorption spectrum of the CO adduct of Na[Fe1(meso-tetraphenylporphyrin dianion)] are consistent with the concept that in P-450 considerable electron density is transferred to the iron by the mercaptide ligand.
Modifications of purified glucose-6-phosphate dehydrogenase and other enzymes by a factor of low molecular weight abundant in some leukemic cells.
Authors: Kahn A , Boivin P , Rubinson H , Cottreau D , Marie J , Dreyfus J C
Published: May 2006

Highly purified platelet glucose-6-phosphate dehydrogenase (G6PD; D-glucose-6-phosphate:NADP+ 1-oxidoreductase, EC 1.1.1.49) can be modified in its isoelectric point and its molecular specific activity by extracts of some leukemic granulocytes. The "G6PD modifying factors" are relatively small molecules (molecular weight slightly under 5000), thermostable, dialyzable, and ultrafilterable. These molecules are destroyed by various endo- and exopeptidases and by serine enzymes present in crude extracts of leukocytes and commercial preparations of ribonuclease. The alterations of platelet G6PD due to the "G6PD modifying factors" are stable and not reversible by dialysis or further chromatography. The leukemic extracts which are able to modify G6PD also can modify the electrophoretic mobility and (or) the enzymatic activity of purified leukocyte pyruvate kinase, 6-phosphogluconate dehydrogenase, and glucosephosphate isomerase. The chemical nature of such modifications and their relationships with post-translational modifications which occur in leukemic or normal cells are discussed.
A relation between automorphic forms on
GL
(2) and
GL
(3)
Authors: Gelbart Stephen , Jacquet Hervé
Published: May 2006

Let ρ

n

denote the standard n-dimensional representation of
GL(n
,C) and ρ

n

2
its symmetric square. For each automorphic cuspidal representation π of
GL
(2,A) we introduce an Euler product
L
(
s
,π,ρ
2
2
) of degree 3 which we prove is entire. We also prove that there exists an automorphic representation II of
GL
(3)—“the lift of π”—with the property that
L
(
s
,II,ρ
3
) =
L
(
s
,π,ρ
2
2
). Our results confirm conjectures described in a more general context by R. P. Langlands [(1970)
Lecture Notes in Mathematics
, no. 170 (Springer-Verlag, Berlin-Heidelberg-New York)].
Catecholamine-stimulated cyclic GMP accumulation in the rat pineal: apparent presynaptic site of action.
Authors: O'Dea R F , Zatz M
Published: May 2006

Guanosine 3':5'-cyclic monophosphate (cGMP) increased 7-fold in rat pineal glands incubated in the presence of l-norepinephrine. This response consisted of two components-one was stereospecific and inhibited by alpha-adrenergic antagonists while the other was not stereospecific and not readily inhibited by antagonists. Although l-isoproterenol was more potent than l-norepinephrine it had less intrinsic activity and its action was not stereospecifc. The increase in cGMP caused by these catecholamines, unlike that of adenosine 3':5'-cyclic monophosphate (cAMP), was dependent upon extracellular calcium. Ouabain and high levels of potassium produced a marked, calcium-dependent increase in pineal cGMP, without affecting cAMP. There was no effect of cholinergic agonists on cGMP. Surgical denervation markedly reduced the cGMP response to stimulation by l-norepinephrine, potassium, or ouabain. This was in contrast to the enhanced response of cAMP in denervated glands. The nonspecific increase in cGMP caused by l-isoproterenol, however, was not affected by denervation. These data demonstrate the existence of a calcium-dependent presynaptic mechanism for the generation of cGMP which may be mediated by an alpha-adrenergic-like receptor. In addition, the mechanisms regulating pineal cGMP appear to be physiologically distinct from those regulating cAMP.
Catabolite modulator factor: a possible mediator of catabolite repression in bacteria.
Authors: Ullmann A , Tillier F , Monod J
Published: May 2006

Water soluble extracts of Escherichia coli cells have been found to exert an extremely strong repressive effect upon the expression of catabolite sensitive operons. The compound responsible for this activity has been partially purified and proves to be of low molecular weight and heat stable. The effect of this compound, hereafter designated as catabolite modulator factor, is only partially antagonized by adenosine 3':5'-cyclic monophosphate. The possible role of catabolite modulator factor in the physiological regulation of catabolite repression is discussed.
Absence of low-molecular-weight alpha crystallin in nuclear region of old human lenses.
Authors: Roy D , Spector A
Published: May 2006

Examination of old human lenses indicates that low-molecular-weight alpha crystallin is not present in the inner 30-40%, the nucleus, of the lens. The remainder of such lenses, the periphery, contains normal levels of this protein. This finding is in marked contrast to observations in young lenses, where a large quantity of this protein is found throughout the tissue.