bluuebunny/crossref_metadata_2025 huggingface dataset:
Altered promoter selection by a novel form of
Bacillus subtilis
RNA polymerase
Authors: Jaehning Judith A. , Wiggs Janey L. , Chamberlin Michael J.
Published: May 2006

Bacillus subtilis
RNA polymerase holoenzyme prepared by several standard methods utilizes bacteriophage T7 ΔD111 DNA as an efficient template. The major RNA products are specific transcripts from T7 promoters A
1
and C; these promoters are also efficiently utilized by RNA polymerases purified from a wide range of other bacterial species [Wiggs, J., Bush, J. & Chamberlin, M. (1979)
Cell
16, 97-109]. In contrast,
B. subtilis
RNA polymerase preparations purified by a modification of the method of Burgess and Jendrisak (designated fraction 5) utilize T7 ΔD111 promoters A
1
and C and an additional promoter site, J, which has been located at 90.6% on the standard T7 physical map. This promoter is not used by
B. subtilis
core RNA polymerase or by RNA polymerase from any other bacterial species we have tested. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of fraction 5 RNA polymerase shows that it contains
B. subtilis
components σ and δ and a polypeptide of
M
r
92,000 in addition to the
B. subtilis
β, β′, and α subunits. Chromatography of fraction 5 on single-stranded DNA-cellulose gives an enzyme fraction, Bs I, that is indistinguishable from
B. subtilis
RNA polymerase holoenzyme both in its peptide composition (ββ′α
2
σ) and in the selective transcription of only T7 RNAs A
1
and C. Chromatography of fraction 5 on phosphocellulose yields an enzyme fraction, Bs II, devoid of σ subunit but containing the
M
r
92,000 peptide and traces of δ. This fraction synthesizes predominantly T7 J RNA
in vitro
together with traces of T7 A
1
and C RNAs. Hence,
B. subtilis
RNA polymerase fraction Bs II appears to contain a form of RNA polymerase that can transcribe selectively without detectable amounts of
B. subtilis
σ subunit and that utilizes a promoter site not used by other known bacterial RNA polymerases. The structural basis for this specificity is not yet known.
Replication at restrictive temperatures in Escherichia coli containing a polCts mutation.
Authors: Niwa O , Bryan S K , Moses R E
Published: May 2006

Escherichia coli cells with a polCts mutation contain a temperature-sensitive DNA polymerase II and fall to replicate DNA at the restrictive temperature (43 degreees C). Mutants deficient in polymerizing activity of the other two recognized DNA polymerases in E. coli can replicate DNA. We have isolated temperature-resistant revertants from a strain containing polA-, polB-, and polCts mutations. These revertants grow at 43 degrees C, but analysis of partially purified DNA polymerase III from several such revertants shows a temperature-sensitive DNA polymerase III activity. Genetic analysis by P1 transduction confirms that such revertants can contain a polCts mutation and also a polA- mutation. We find that such revertants behave phenotypically as PolI+ cells (DNA polymerase I-containing), and extracts of such cells show a DNA polymerase I-like activity. Revertants of polA-, dnaAts and polA-, dnaBts strains do not show such a DNA polymerase activity.
Dissociation and exchange of the beta 2-microglobulin subunit of HLA-A and HLA-B antigens.
Authors: Hyafil F , Strominger J L
Published: May 2006

Human histocompatibility antigens HLA-A, HLA-B, and HLA-C are a complex of two noncovalently associated subunits: a heavy chain glycoprotein (alpha) carrying the genetic polymorphism and an invariant light chain, beta 2-microglobulin (beta 2m). Upon incubation of papain-solubilized HLA with radiolabeled urinary beta 2m, the latter is incorporated into HLA, where it substitutes for the preexisting beta 2m that has dissociated from the complex. The association-dissociation equilibrium that governs this beta 2m exchange reaction was investigated and found to be characterized by a long lifetime of the complex (half-life of 80 min at 37 degrees C) and a relatively low Kd (4 nM). The beta 2m exchange was used as the basis of a radioimmunoassay for HLA antigens with radiolabeled beta 2m as a unique label for all HLA specificities. In a similar fashion, radiolabeled beta 2m can be incorporated into HLA at the cell surface. Although the process is slower and less extensive than in solution, it can be used as a means to tag cells with specific probes for HLA antigens.
Evidence for a two-domain structure of the terminal membrane C5b-9 complex of human complement.
Authors: Bhakdi S , Tranum-Jensen J
Published: May 2006

Lipid vesicles carrying the purified membrane C5b-9 complex [C5b-9(m)] of complement were analyzed immunochemically and in the electron microscope after treatment with a combination of trypsin and alpha-chymotrypsin. Under reducing conditions, the externally oriented annulus was removed. The remaining part of the C5b-9(m), representing approximately half of the total mass of the macromolecular complex, was visualized in the electron microscope as a hollow cylindrical structure with walls of 1-nm thickness. This structure remained tenaciously attached to the lipid bilayer, projecting 8-9 nm from the external membrane surface into the aqueous environment. Cleavage of C5b-9(m) by proteolysis and reduction resulted in a sharp reduction of tis antigenic determinants. One hydrophilic protease-resistant C5 derivative was released from the membrane and recovered in the fluid phase. The membrane-bound residue almost totally lacked antigens precipitable with antisera to C5, C6, C9, and C5b-9(m).
Enhancement of hexose uptake in human polymorphonuclear leukocytes by activated complement component C5a
Authors: McCall Charles E. , Bass David A. , Cousart Sue , DeChatelet Lawrence R.
Published: May 2006

The polymorphonuclear leukocyte (PMNL) depends on glucose as a source of energy for motility, chemotaxis, phagocytosis, and bactericidal activity. Activated complement (C5a) at low concentrations stimulates carrier-mediated carbohydrate transport in PMNLs as measured by the uptake of 2-deoxy-D-[
3
H]glucose. Human PMNLs were preincubated at 37°C for 15 min with zymosan-activated human serum or various purified preparations of human C5a. A concentration-dependent increase in deoxyglucose transport (>700% of control) into PMNLs occurred with all test substances. Reaction was linear for 30 min, and uptake of deoxyglucose followed saturation kinetics. C5a caused a decrease in the
K
m
for deoxyglucose, from 0.53 to 0.11 mM, without altering the
V
max
(44 nmol/30 min per 5 × 10
6
PMNLs in control and 46.6 with C5a). The optimal concentration of C5a for enhanced carrier-mediated transport of deoxyglucose was similar to that which promoted optimal chemotaxis. Activated serum from C5-deficient mice had little or no effect on deoxyglucose transport whereas that from normal syngeneic mice enhanced deoxyglucose transport. C5a did not enhance deoxyglucose transport into isolated erythrocytes, platelets, or lymphocytes. The deoxyglucose within the cell was primarily in the phosphorylated form, and hexokinase activity was not increased in PMNLs stimulated with C5a, indicating that hexokinase was not rate limiting and that enhanced transport was the mechanism of the C5a activity. Insulin at physiologic concentration (10 ng/ml) had no effect on deoxyglucose transport in PMNL and did not act as a competitive inhibitor of C5a. This insulin-like bioactivity could be detected with the amount of C5a that would be present after activation of 0.1-0.5% of the C5 in 1 ml of serum. This suggests that uptake of [
3
H]deoxyglucose by PMNLs might serve as a highly sensitive test for activation of the fifth component of complement.
Internal organization of long repetitive DNA sequences in sea urchin genomes.
Authors: Chaudhari N , Craig S P
Published: May 2006

In keeping with earlier reports, we have found that reassociated long repeat DNA from sea urchins is thermostable, indicating the absence of evolutionarily diverged families of repeated sequences. However, we found that when fragments of radiolabeled long repeat DNA were denatured and reassociated with intact long repeat driver DNA, then sheared to 350 basepairs and assayed for thermal stability, the level of mismatch found in the duplexes varied inversely with the length of the starting fragments. This effect was shown to be due directly to the physical size of the molecules involved in reassociation. These results are consistent with, and support a model for, long repeat DNA in which short units of repetition are arranged in precise arrays. The significance of this arrangement of sequence units within long repeat DNA is discussed.
Identification of chorion protein precursors and the mRNAs that encode them in Drosophila melanogaster.
Authors: Thireos G , Shea R G , Kafatos F C
Published: May 2006

Specific antisera were generated for major size classes of Drosophila chorion proteins. These antisera were used in conjunction with cell-free translation of follicular RNA to identify precursors, containing signal peptides, for chorion components A1, A2, B1, and B2. An additional precursor cross-reacts with anti-B antisera, although its product appears to correspond to a protein distinct from authenic B proteins. The size classes of mRNA encoding A and B protein precursors have been identified by cell-free translations.
The delta subunit of Escherichia coli DNA polymerase III holoenzyme is the dnaX gene product.
Authors: Hübscher U , Kornberg A
Published: May 2006

The delta subunit of DNA polymerase III holoenzyme has been purified extensively with an assay for phi X174 DNA synthesis using core (pol III) and beta and gamma subunits. Either the purified delta subunit or the purified DNA polymerase III holoenzyme can complement a defective enzyme fraction from the conditional replication mutant SG133 described by Sevastopoulos et al. [Sevastopoulas, C.G., Wehr, C.T. & Glaser, D. A. (1977) Proc. Natl. Acad. Sci. USA 74, 3485-3489]. It has been established by Henson et al. [Henson, J.M., Chu, H., Irwin, C.A. & Walker, J.R. (1979) Genetics 92, 1,41-1059] that SG133 has two temperature-sensitive mutations, called dnaX and dnaY. The crude enzyme source from dnaX can be complemented by the delta subunit and by DNA polymerase III holoenzyme. By contrast, the core DNA polymerase III and the beta and gamma subunits are unable to complement this defective enzyme fraction. Thus, the delta subunit of DNA polymerase III holoenzyme appears to be the dnaX gene product of Escherichia coli.
Genetic and biochemical analysis of the a1 cell-surface antigen associated with human chromosome 11.
Authors: Jones C , Moore E E , Lehman D W
Published: May 2006

A highly versatile system for genetic, biochemical, and immunological analysis of human cell surface components has been developed using a human-Chinese hamster somatic cell hybrid containing chromosome 11 as its only human chromosome. This system lends itself to studies such as identification of human cell surface antigens and other genetic markers, regional gene mapping of these markers on chromosome 11, mutational analysis of these markers, and exploration of distribution of these antigens in normal and pathological human tissues. Genetic analysis of a1, one of the human antigens expressed by this hybrid, has been accomplished by subjecting a series of a1- variants to complementation analysis. These experiments have shown that the a1- variants behave in a recessive manner and that at least four genes, including three Chinese hamster genes, are needed for a1 antigen expression. Biochemical analysis has shown that a macroglycolipid isolated from human erythrocytes contains the a1 antigenic activity, so that genes coding for glycosyltransferases are required for its biosynthesis and may correspond to the complementation groups identified. The power of combined genetic, biochemical, and immunological approaches to understanding cell membrane molecules is demonstrated.
Mitochondrial DNA clones and matriarchal phylogeny within and among geographic populations of the pocket gopher, Geomys pinetis.
Authors: Avise J C , Giblin-Davidson C , Laerm J , Patton J C , Lansman R A
Published: May 2006

Restriction endonuclease assay of mitochondria DNA (mtDNA) and standard starch-gel electrophoresis of proteins encoded by nuclear genes have been used to analyze phylogenetic relatedness among a large number of pocket gophers (Geomys pinetis) collected throughout the range of the species. The restriction analysis clearly distinguishes two populations within the species, an eastern and a western form, which differ by at least 3% in mtDNA sequence. Qualitative comparisons of the restriction phenotypes can also be used to identify mtDNA "clones" within each form. The mtDNA clones interconnect in a phylogenetic network which represents an estimate of matriarchal phylogeny for G. pinetis. Although the protein electrophoretic data also differentiate the eastern and western forms, the data are of limited usefulness in establishing relationships among more local subpopulations. The comparison between these two data sets suggests that restriction analysis of mtDNA is probably unequalled by other techniques currently available for determining phylogenetic relationships among conspecific organisms.
A general method for maximizing the expression of a cloned gene.
Authors: Roberts T M , Kacich R , Ptashne M
Published: May 2006

We present a method, utilizing a combination of restriction endonuclease cleavage and digestion with Escherichia coli exonuclease III and Aspergillus orizae nuclease S1, that allows us to position a restriction fragment bearing the promoter of the lacZ gene of E. coli at virtually any distance in front of any cloned gene. In particular, we have used this method to examine the effect on protein production of gene-promoter separation for the cro gene of phage lambda and to produce plasmids that, upon transformation into appropriate E. coli hosts, direct the synthesis of up to 190,000 cro protein monomers per cell.
Lack of experimental evidence for frequency-dependent selection at the alcohol dehydrogenase locus in Drosophila melanogaster.
Authors: Yoshimaru H , Mukai T
Published: May 2006

Two experiments were conducted for testing frequency-dependent selection at the alcohol dehydrogenase locus (Adh; map position, 2--50.1), where two types of alleles, AdhF and AdhS, have been found to be polymorphic in natural populations. First, a competition experiment was carried out between inversion-free AdhF/AdhF and AdhS/AdhS genotypes at five gene frequency levels (those of AdhF = 0.83, 0.67, 0.5, 0.33, and 0.17). First-instar larvae of the two homozygous types in various ratios were placed in a vial, and the frequency of adult flies of each genotype was determined. However, the relative viabilities of these two types did not change with the change in the frequencies of genotypes or genes. The second test was performed by using the results of viability tests with the Cy method of Wallace, using the results of inversion-free crosses only. Although there was variation in the gene frequencies among the vials in testing the viability of individuals consistng of random combinations of two second chromosomes, no difference was found in average viabilities among the vials in which the gene frequencies were different. Thus, no evidence for frequency-dependent selection was obtained.
Insertion of Ia and H-2 alloantigens into model membranes.
Authors: Littman D R , Cullen S E , Schwartz B D
Published: May 2006

The study of immune phenomena dependent on the major histocompatibility complex (MHC) would be greatly simplified by the use of MHC antigen-containing liposomes in various functional systems. Towards this end, we have constructed unilamellar phosphatidylcholine liposomes containing H-2 and Ia antigens. These molecules were not simply trapped within the aqueous compartment of the liposome as assessed by their accessibility to papain digestion. They were shown to be integrally inserted in the liposome bilayer because they could not be dissociated from the liposome with high salt and EDTA concentrations but could be solubilized by detergent. A sensitive radioimmunoassay showed that the Ia molecules were antigenically active in the liposome environment. Both Ia and H-2 antigens could be immunoprecipitated from detergent-solubilized liposomes. By comparing liposome-associated Ia activity in the presence and absence of detergent and by showing accessibility of the Ia antigens to papain, it was concluded that the majority of Ia antigens were exposed on the external surface of the liposome. These results suggest that the orientation of MHC antigens in liposomes closely parallels their natural orientation in the cell membrane.
Interaction of papain with derivatives of phenylalanylglycinal: fluorescence studies.
Authors: Henes J B , Mattis J A , Fruton J S
Published: May 2006

Fluorescence studies have been performed on the interaction of papain with active-site-directed inhibitors of the type mansyl-(Gly)n-Phe-glycinal, where n = 0, 1, 2. It has been found that whereas the mansyl [6-(N-methylantilino)-2-naphthalene sulfonyl] fluorescence of mansyl-Phe-glycinal is greatly enhanced, that of the two longer mansyl compounds is not, although all three are equally effective as inhibitors of papain action. Measurements of fluorescence polarization and rotational relaxation time support the conclusion that the fluorescent probe group of the two longer mansyl compounds protrudes into the solvent to a greater degree than that of mansyl-Phe-glycinal. Considerable energy transfer from papain tryptophan to the mansyl group is evident for all three inhibitors, however, although it is most marked with mansyl-Phe-glycinal. Stopped-flow fluorescence measurements have shown that, after initial rapid interaction, the first-order conformational changes in the active-site region of papain in the complex with mansyl-Phe-glycinal are approximately 1/10(4) those observed with comparable mansyl oligopeptide substrates, and approximately 1/10(2) those with acetyl-Phe-glycinal.
Inducers of mammalian cell differentiation stimulate dome formation in a differentiated kidney epithelial cell line (MDCK).
Authors: Lever J E
Published: May 2006

Cell cultures of a differentiated kidney epithelial cell line, MDCK, spontaneously form fluid-filled domes or hemicysts composed of numbers of cells as a manifestation of specialized epithelial transport phenomena. Addition to MDCK cells of a broad spectrum of compounds that are known as potent inducers of mammalian cell differentiation in cell culture caused a striking increase in the frequency of dome formation. Polar compounds such as N,N-dimethylformamide, dimethyl sulfoxide, or hexamethylene bisacetamide stimulated increased dome formation 15--30 hr after addition. Induction of domes by these compounds was prevented either by inhibitors of protein synthesis or by ouabain, cytochalasin B, or vinblastine. Inhibition of DNA synthesis did not block chemical induction of domes. Other inducers were compounds of physiological occurrence such as n-butyrate or adenosine. Furthermore, a variety of conditions expected to elevate intracellular levels of cyclic AMP also stimulated dome formation. These findings suggest the hypothesis that domes are formed in cell culture by a form of cell differentiation that is under positive control by cyclic AMP.
Strand exchange in site-specific recombination.
Authors: Enquist L W , Nash H , Weisberg R A
Published: May 2006

The site-specific recombination system of phage lambda promotes crossovers at its attachment site (att). In this report we show that when phage are crossed in conditions where only the site-specific recombination system is active, a low frequency of crossovers can also be detected in a region that is close to but does not contain att. These crossovers require the phage int gene, the host hip gene, and the integrity of att. They are not detected if one of the parents carries a substitution of a heterologous attachment site (attB instead of attP). To explain these findings we suggest that site-specific recombination can proceed by exchange of single strands between the participating chromosomes at att and migration of the resulting junction outside of att.
Model nebulae and determination of the chemical composition of the Magellanic Clouds
Authors: Aller L. H. , Keyes C. D. , Czyzak S. J.
Published: May 2006

An analysis of previously presented photoelectric spectrophotometry of HII regions (emission-line diffuse nebulae) in the two Magellanic Clouds is carried out with the aid of theoretical nebular models, which are used primarily as interpolation devices. Some advantages and limitations of such theoretical models are discussed. A comparison of the finally obtained chemical compositions with those found by other observers shows generally a good agreement, suggesting that it is possible to obtain reliable chemical compositions from low excitation gaseous nebulae in our own galaxy as well as in distant stellar systems.
Specificity of memory cells raised against trinitrophenyl-conjugated syngeneic cells
Authors: Maeda Toyozo , McConnell Harden M.
Published: May 2006

Exogenous lipid analogues can be incorporated into purified plasma membranes of EL4 tumor cells. When EL4 membranes are incubated with sonicated lipid vesicles containing spin-labeled phosphatidylcholine and then purified, they exhibit paramagnetic resonance spectra characteristic of spin labels dilutely dispersed in the lipid bilayer. Also, when EL4 membranes are incubated with vesicles of fluorescent lipid (
N
-4-nitrobenzo-2-oxa-1,3-diazole phosphatidylethanolamine), the fluorescence intensity of the mixture gradually increases and the labeled membranes are strongly fluorescent under a microscope, whereas the original lipid vesicles are much less fluorescent because of self-quenching at the high relative concentration of the fluorophore in the vesicles (33%, wt/wt). Thus, lipid analogues can be integrated into the bilayers of EL4 plasma membranes. The ability of the EL4 membranes containing trinitrophenyl phosphatidylethanolamine to induce a secondary proliferation of C57BL/6 mouse spleen lymphocytes primarily stimulated by trinitrophenyl-modified autologous cells was investigated. Although trinitrophenyl-modified plasma membranes as well as trinitrophenyl-modified lymphocytes or EL4 cells caused a specific, H-2 restricted response, membranes containing trinitrophenyl phosphatidylethanolamine did not induce a secondary proliferative response. Because of the strong likelihood that all three lipid analogues mentioned above are similar to one another in having a high lateral mobility and in not being strongly associated with H-2 cell-surface molecules, these results can be viewed, with caution, as being consistent with a “modified self” model rather than a dual recognition model for H-2 restriction in the cell-mediated immune response to chemically modified syngeneic cells.
Identification of the messenger RNAs coding for the
gag
and
env
gene products of the murine mammary tumor virus
Authors: Sen Ganes C. , Smith Steven W. , Marcus Stuart L. , Sarkar Nurul H.
Published: May 2006

Full-length (35S) genomic RNA from murine mammary tumor virus (MuMTV) was translated
in vitro
, using a reticulocyte lysate system, into proteins of 105,000, 75,000, 65,000, 35,000, and 27,000 daltons. These proteins were all immunoprecipitable with a monospecific antiserum to the major viral core protein, p27, but not with antiserum to the major viral envelope glycoprotein, gp47. Translation
in vitro
of RNA of about 24S size extracted from MuMTV yielded proteins similar in size and immunoreactivity to the products of the 35S RNA translation. Polyadenylylated RNA isolated from an MuMTV-producing cell line was fractionated according to size by velocity sedimentation and subsequently hybridized to MuMTV complementary DNA probes. These studies identified at least three size classes (35S, 24S, and 14-18S) of intracellular MuMTV-specific RNA. The 35S intracellular RNA was translated into MuMTV-specific proteins identical in size and immunoreactivity to the products of the virion-derived 35S RNA. On the other hand, translation of the intracellular 24S RNA fraction resulted in the synthesis of proteins, of which two (of about 70,000 daltons) could be immunoprecipitated with anti-gp47 serum, but not with anti-p27 serum. From these data we conclude that MuMTV core and envelope proteins are synthesized from two different mRNAs with approximate sizes of 35S and 24S, respectively. Our results also imply that the intracellular 24S mRNA is synthesized by a process more complex than simple cleavage of the 35S RNA.
Growth and morphology of colonies of Chinese hamster ovary cells growing on agar is affected by insulin
Authors: Aidells Bruce D. , Konrad Michael W. , Glaser Donald A.
Published: May 2006

As a model for the effect of hormones and growth factors on three-dimensional growth of mammalian cells, we have analyzed the effect of insulin on the three-dimensional growth and morphology of Chinese hamster ovary (CHO) colonies grown on the surface of agar. Sequential photographs in dark-field illumination of growing colonies have been analyzed with computer-assisted techniques. In this analysis the entire shape of each colony in a sizeable population (up to 10
5
colonies per experiment) can be measured and distributions of parameters derived from these measurements can be studied. In fetal calf serum (FCS), insulin has a dose-related stimulatory effect on cell growth that is most pronounced when growth has slowed down. In 10% FCS, insulin has a similar but diminished effect. When CHO cells are grown conventionally on plastic substrata or in suspension, insulin has little effect on cell growth at 4% serum concentration. Computer analysis of changes in the distribution of colony morphology proved to be a sensitive, dose-dependent, and reproducible assay of a hormonal effect. As little as 5 ng of insulin per ml added to 10% FCS causes a shift in the distribution of colony morphologies. In 4% FCS, 50 ng of insulin per ml is required to produce a detectable change in the colony morphology distribution. Computer analysis of cells grown three-dimensionally on agar provides a powerful approach to studying the effects of hormones and provides observations not available when cells are grown on plastic substrata.
Chemotactic factor for tumor cells derived from the C5a fragment of complement component C5.
Authors: Orr W , Phan S H , Varani J , Ward P A , Kreutzer D L , Webster R O , Henson P M
Published: May 2006

Previously, we have stablished that the fifth component of complement (C5) serves as an important source of mediators that have locomotory (chemotactic) activity for leukocytes and tumor cells. C5a, a fragment (Mr 11,200) derived from the NH2-terminal portion of the alpha chain of C5, is the major chemotactic peptide for leukocytes. The present studies demonstrate that cleavage of C5a with trypsin generates a derivative peptide that is chemotactic for tumor cells (Walker carcinosarcoma). This fragment has an estimated Mr of 6000 as assessed by gel filtration and does not require the COOH-terminal arginine of C5a, because equivalent amounts of chemotactic activity for tumor cells can be generated from des-Arg-C5a by digestion with trypsin. The C5a-derived chemotactic peptide for tumor cells demonstrates peak activity at approximately 1 pM. These studies emphasize the key role of the C5a region of the C5 molecule in the generation of peptides that affect locomotory responses of cells.
Protective effect of immunization with nonviral antigens against Friend leukemia virus in mice
Authors: Nahon-Merlin Evelyne , Lacour Fanny , Friend Charlotte , Revoltella Roberto
Published: May 2006

DBA/2 mice immunized with poly(A)·poly(U) complexed with methylated bovine serum albumin and emulsified in Freund's complete adjuvant were protected against challenge with Friend leukemia virus. There was no correlation between the level of antibody to the immunogen in the prechallenge serum and induced resistance to the virus. Although prechallenge sera of mice given the same amount of the duplex in a single inoculum bound 9.7% of poly(A)·poly([
3
H]U) input, as compared to 45.3% bound by the prechallenge sera of mice given the immunogen in divided doses, both groups of mice were equally resistant to infection. Immunization with two other nonviral agents, bovine serum albumin fraction V or dinitrophenylated keyhole limpet hemocyanin, induced the same level of protection. A sparing effect of approximately 10
1.5
in infectivity was afforded the immunized mice. Immunization with either poly(A)·poly(U) alone or with the carrier methylated bovine serum albumin was ineffective.

In addition to antibodies to the respective immunogens, the prechallenge sera of the immunized mice also contained antibody to Friend leukemia virus gp71. The presence of such viral antibodies was not always related to resistance to infection by Friend virus. Some immunized mice that survived infection did not have gp71 antibody in their serum before challenge, and mice immunized with poly(A)·poly(U) alone were susceptible to infection, although their prechallenge sera contained antibody to gp71. The mechanism involved in the induction of resistance to infection is not known. The effect may be mediated through a modification of the expression of both endogenous and exogenous type C viruses and affect immunological mechanisms controlling cellular responses.
Detection of a nuclear antigen in Herpesvirus ateles-carrying marmoset lines by the acid-fixed nuclear binding technique.
Authors: Ohno S , Luka J , Klein G , Daniel M D
Published: May 2006

In vitro binding of a Herpesvirus ateles (HVA)-associated soluble antigen to amphibian erythrocyte nuclei was demonstrated by the acid-fixed nuclear binding technique in combination with anticomplement immunofluorescence. Incubation of concentrated salt-extracted soluble antigens derived from HVA-carrying marmoset lines with methanol/acetic acid-fixed erythrocytes of frogs and salamanders resulted in a brilliant nuclear fluorescence after exposure to a live virus-boostered, anti-HVS-positive squirrel monkey serum. Anti-HVS-negative sera did not stain. The activity of the positive serum could be abosrbed completely with extracts of HVA-carrying cells but not with Epstein-Barr virus-carrying or Herpesvirus papio-carrying cells. The HVA-associated antigen was also present in lytically HVA-infected marmoset kidney cells.
Structural studies on oncornavirus-related sequences in chicken genomic DNA: two-step analyses of EcoRI and Bgl I restriction digests and tentative mapping of a ubiquitous endogenous provirus digests and tentative mapping of a ubiquitous endogenous provirus.
Authors: McClements W , Hanafusa H , Tilghman S , Skalka A
Published: May 2006

DNA from a variety of uninfected chicken cell types has been analyzed by using restriction endonuclease digestion and RPC-5 ion-exchange chromatography followed by agarose gel electrophoresis. Endogenous retrovirus sequences were detected by using a 32P-labeled avian leukosis viral RNA probe. One simple pattern was identified in an individual containing unexpressed endogenous proviral genes (gs-chf-phenotype for group-specific antigens and chicken helper factor) that was common to all individuals studied. A tentative restriction has been derived for this and one other gs-chf-endogenous provirus. Other gs-chf-individuals and individuals with other phenotypes (e.g., gs+ chf+ and gsl chlfhE) showed more complicated patterns that often included additional bands and thus probably additional proviruses. RNA from an avian sarcoma virus was used to detect cellular sequences (sarc) homologous to the viral transforming gene (src). Results have revealed that a single restriction endonuclease EcoRI fragment of 13 x 10(6) daltons contains the majority of these sequences and confirm that they are not adjacent to the endogenous provirus.
Activation of phenotypic expression of human globin genes from nonerythroid cells by chromosome-dependent transfer to tetraploid mouse erythroleukemia cells
Authors: Deisseroth Albert , Hendrick Don
Published: May 2006

Chromosome-dependent gene transfer mediated by cell fusion was used to show that it is possible to activate phenotypic expression of human α globin genes derived from nonerythroid cells. Hybrid cells containing the human α globin structural genes were derived by fusion of populations of adult human peripheral blood mononuclear cells (devoid of identifiable erythroid cells) with adenine phosphoribosyl-transferase-deficient mouse erythroleukemia cells that contained close to a tetraploid complement of mouse chromosomes. The hybrid cells retained a near tetraploid complement of mouse chromosomes but had lost 80% of the chromosomes of the human parent cell. All of these hybrid cells and their subclones, which contained human chromosome 16, exhibited synthesis of human α globin chains. Human α globin mRNA was also demonstrated to be present in one of these hybrid cells by RNA·cDNA molecular hybridization analysis. We conclude that the mechanism responsible for restricting expression of the human globin genes in nonerthroid cells is not irreversible, at least for those globin structural genes that are actively transcribed in erythroid cells during adult life. Moreover, some genetic factor or process in the tetraploid mouse erythroleukemia cell is, under the conditions of our experiments, capable of reactivating phenotypic expression (production of globin chains) of human globin genes derived from nonerythroid hematopoietic cells after chromosome-dependent gene transfer.
Diamagnetic anisotropy of the peptide group.
Authors: Pauling L
Published: May 2006

A simple theory of the diamagnetic anisotropy of noncyclic planar groups of atoms with resonance structures (mobile electrons)leads to the value --5.36 x 10(-6) cm-g-sec electromagnetic units for the molar diamagnetic anisotropy of the peptide group.
Upper surfaces of epithelial sheets and of fluid lipid films are nonadhesive for platelets.
Authors: Margolis L B , Vasilieva E J , Vasiliev J M , Gelfand I M
Published: May 2006

Platelet-rich rabbit plasma was incubated with surfaces of two different types--sheets of cultured mouse kidney epithelium and films of different lipids. The upper surface of epithelial sheets was found to be nonadhesive for platelets; in the same cultures, the platelets attached easily to the glass surface not covered by epithelial cells. Platelets did not attach to the surface of lipids (egg lecthin and dioleoyllecithin) that were in the liquid-crystalline state at 23 degrees C. In contrast, the surface of the films made of lipids (dipalmitoyl- and distearoyllecithin) that were in the crystalline state at 23 degrees C was adhesive for platelets. It had been found previously that the surfaces of epithelial sheets and of liquid lipid films are nonadhesive for fibroblasts. Possible mechanisms responsible for the nonadhesiveness of these surfaces are discussed. It is stressed that the factors responsible for nonadhesiveness of epithelial surfaces may be similar to those responsible for nonadhesiveness of the luminal surface of endothelium in blood vessels.
Integration of different sarcoma virus genomes into host DNA: evidence against tandem arrangement and for shared integration sites.
Authors: Akiyama Y , Vogt P K
Published: May 2006

Cellular DNA of 50--54 S was extracted from chicken embryo cells doubly infected with two different avian sarcoma viruses and was analyzed by the infectious DNA assay. Approximately 80--90% of the transformed foci that were induced by this DNA were found to give rise to one kind of avian sarcoma virus only, indicating that most proviral genomes are not integrated in tandem. When the two infecting viruses were varied with respect to multiplicity or time of infection, the initial infecting virus or the virus of higher multiplicity of infection was recovered at higher frequency in foci produced by the extracted DNA. This observation suggests that existence of common integration sites for different avian sarcoma viruses. Cells uniformly infected with avian leukosis virus could be transformed by superinfection with an avian sarcoma virus from a different envelope subgroup. Infectious DNA recovered from such cells contained 3--10 50% infectious dose (ID50) units of leukosis virus per microgram but only 0.3--0.4 ID50 of sarcoma virus. DNA from cells infected with sarcoma virus alone contained 3 sarcoma virus ID50 per microgram. These results suggest that, even though a second virus integrates with lower efficiency into preinfected cells, there is not a complete block of integration sites by the first virus.
Thermodynamic properties of solid C
2
H
4
Authors: Ma Shao-mu , Eyring Henry
Published: May 2006

The significant structures procedure of liquids has been used to calculate the thermodynamic properties of solid C
2
H
4
. Two degeneracy terms were used to describe the behavior in the vicinities of the two phase transitions. The calculated entropy and specific heat agree well with experimental results from a few kelvins to the melting point. Less satisfactory agreement is obtained for compressibility and thermal expansion coefficients. This simple model represents surprisingly well the phase transitions in the solid state.
Oceanic warming of western Europe
Authors: Stommel Henry
Published: May 2006

In the northern North Atlantic off Europe, deep convection flushes buoyancy and heat out of the upper ocean each winter. It is replaced by horizontal advection during the remainder of the year. Absolute geostrophic currents can be computed from an application of the heat conservation equation. A remarkable spiral with depth emerges as a key feature in the process. The computed field of flow appears to be consistent with several buoyancy and heat flux requirements, with the independent physical information of locally vanishing curl of the wind-stress, and with its implications through the Sverdrup relation.
Kinetics and mechanism of tobacco mosaic virus assembly: direct measurement of relative rates of incorporation of 4S and 20S protein.
Authors: Shire S J , Steckert J J , Adams M L , Schuster T M
Published: May 2006

The mechanism of assembly of tobacco mosaic virus has been investigated under conditions in which the rates of incorporation of the 4S and 20S proteins can each be directly measured by analytical centfrifugation. Under these conditions, pH 6.5, 6.5 degrees C, 0.10 M ionic strength potassium orthophosphate, the protein can be made to exist as a metastable 20S aggregate that is necessary for efficient reconstitution. The overall assembly process consists of an initiation (nucleation) reaction that requires two to three 20S disk aggregates per RNA molecule and is followed by an elongation (growth) reaction. In the elongation phase of assembly the 4S protein is incorporated 50 to 70 times faster than the 20S disk, calculated on the basis of a steady-state kinetic analysis. Therefore, under these conditions, in which the rate of assembly is about 0.06 of that at pH 7, 20 degrees C, 0.10 M ionic strength orthophosphate, the 4S protein preferentially participates in the elongation phase. At this slow reconstitution rate intermediate assembly states (about 70-168 S) can be observed. The kinetics of both protein incorporation and nucleoprotein formation suggest that the elongation process is composed of at least two different, possibly sequential, rate-limiting reactions.
Physical modifications of rhodopsin boundary lipids in lecithin-rhodopsin complexes: a spin-label study.
Authors: Davoust J , Schoot B M , Devaux P F
Published: May 2006

The microviscosity of rhodopsin boundary lipids was studied with a spin-labeled fatty acid covalently attached to rhodopsin, in rhodopsin-egg lecithin vesicles. When the lipid-to-protein ratio was high (500:1, mole to mole), only narrow peaks were visible in electron paramagnetic resonance spectrum at 37 degrees C. This enabled us to show that, under these conditions, not more than 10% of the probes have their motion strongly restricted by the proximity of the protein. When the temperature was reduced, a second component characteristic of strong immobilization appeared. It corresponds to 50% of the signal at -5 degrees C. At all temperatures reduction of the lipid-to-protein ratio also resulted in an increase of the amount of immobilized lipid. These results show that the rhodopsin boundary layer under physiological conditions is associated with low microviscosity. However, low temperatures, low lipid-to-protein ratios, or combinations of the two can induce dramatic modifications of the physical state of the boundary lipids, which under these conditions may no longer be representative of the functional biological system. These results are relevant to the general theory of lipid-protein interaction.
Immunosuppression by a mouse tumor resembles antigenic competition.
Authors: Cocito C G , Michot B , Radovich J , Talmage D W
Published: May 2006

The intraperitoneal injection of gamma-radiated, UV-radiated, or unradiated P-815 tumor cells into syngeneic or allogeneic mice suppressed the immune response to a subsequent intraperitoneal injection of sheep erythrocytes in a manner similar to the suppression caused by the injection of manner similar to the suppression caused by the injection of horse erythrocytes and termed antigenic competition. In both cases, the greatest suppression occurred when the sheep erythrocytes were injected at the same site (intraperitoneal) as the tumor or antigen several days after the tumor or antigen and in a dose of 10(8) erythrocytes or less.
An
L
2
form of Bernstein's inequality
Authors: Backus George E.
Published: May 2006

Suppose
P
is a
p
th degree real polynomial function in
n
variables and
f
=
P
ǀ
S

n
-1

is the restriction of
P
to the unit sphere
S

n
-1

in

R
n

. Bernstein's inequality asserts that ([unk]
0

k
f

)
2
+
p
2
([unk]
0

k
-1

f
)
2
≤
p

2
k

∥
f
∥∞
2
, where
k
≥ 1 and differentiation is with respect to arc length θ along any geodesic in
S

n
-1

. We find the constant corresponding to
p

2
k

when ∥
f
∥∞ is replaced by ∥
f
∥
2
. One application is a condition on the coefficients of the expansion in surface spherical harmonics of any
g: S

n
-1

→
R
, which condition suffices to assure that
g
is
k
times differentiable.
Pollen—stigma interactions: Identification and characterization of surface components with recognition potential
Authors: Clarke Adrienne , Gleeson Paul , Harrison Susan , Knox R. Bruce
Published: May 2006

Male—female recognition in flowering plants is initiated by mutual contact of pollen and stigma surface components. Analysis of the surface macromolecules of both stigma and pollen of
Gladiolus gandavensis
revealed a complex mixture of proteins, glycoproteins, and glycolipids. The carbohydrate-containing components amounted to 6% in pollen and 23% in stigma and contained the monosaccharides galactose, arabinose, glucose, mannose, and rhamnose. All the mannose of both preparations was associated with a fraction that bound to concanavalin A. The stigma surface contained an arabinogalactan or arabinogalactan protein as a major component. This component has been isolated by affinity chromatography on tridacnin-Sepharose and shown to be similar in composition to a style canal component isolated in the same way. The capacity of the stigma surface preparations to bind nonspecifically to macromolecules from pollen and other sources has been demonstrated
in vivo
and
in vitro
. Specific binding of concanavalin A to the stigma surface decreases the adhesive capacity for pollen protein. The arabinogalactan of the stigma surface may act as an adhesive base. The pollen and stigma surfaces apparently complement one another to provide all the components of an ideal adhesive.
A pseudoduplication in
Lycopersicon pimpinellifolium
Authors: Rick Charles M. , Tanksley Steven D. , Fobes Jon F.
Published: May 2006

A double-banded variant of
Prx-2
encountered in a single wild plant in a previous survey of the peroxidases of
Lycopersicon pimpinellifolium
was subjected to genetic analysis. Segregations obtained from crosses of this true-breeding type with various alleles of
Prx-2
yielded anomalous segregations that are not compatible with a single locus model and suggest activity of alleles of a gene at another, independent locus. A critical test was afforded by studying simultaneous segregation for the apparent duplication and for two alleles at the neighboring
Prx-3
, a gene which proves to be very tightly linked with
Prx-2
. The results of the new test revealed independence between the double-banded type and
Prx-3
, hence also between the former and
Prx-2
. The most tenable hypothesis stipulates that an independent gene
mPx2
1
modifies post-translationally the product coded by
Prx-2
+
to yield two electrophoretically separable isozymes. These results reveal the risk of assuming, without appropriate genetic tests, that gene duplication is necessarily the cause of multiple banding.
A DNA primase specified by I-like plasmids.
Authors: Lanka E , Scherzinger E , Günther E , Schuster H
Published: May 2006

An enzyme has been isolated from Escherichia coli strains harboring the I-like plasmid R64drd11, which is capable of initiating DNA synthesis on the circular, single-stranded DNA of phages phi X174, fd, and G4. In the conversion of these templates to duplex forms in vitro, the enzyme can substitute for the functions of E. coli dna B-dnaB-dnaC-dnaG proteins, E. coli RNA polymerase, and E. coli dnaG protein, respectively. The enzyme requires all four ribonucleoside triphosphates for optimal activity, although a combination of ATP, CTP, and GTP can almost completely satisfy the rNTP requirement. The enzyme appears to cooperate specifically with DNA polymerases III because single-stranded DNA-dependent synthesis takes place in extracts deficient in DNA polymerases I and II but not in extracts from a dnaZ mutant. Highly purified enzyme preparations consist mostly of two major polypeptides, Mr 140,000 and 180,000, when analyzed by sodium dodecyl sulfate gel electrophoresis. These polypeptides cosediment with the enzyme activity through a glycerol gradient with a sedimentation coefficient of 3.6 S. DNA priming activity in extracts of E. coli strains harboring the mutant plasmids R64drd11 or ColIdrd1, which are derepressed in functions of conjugational DNA transfer, severalfold higher than the activity from strains carrying the corresponding wild-type plasmid. This correlation suggests that the enzyme may play a role in conjugational DNA synthesis.
An adenovirus type 5 early gene function regulates expression of other early viral genes.
Authors: Jones N , Shenk T
Published: May 2006

We have identified an adenovirus type 5(Ad5) early gene function located in early region 1 which is required for the production of early cytoplasmic mRNAs corresponding to early regions 2, 3, and 4. Mutant dl312 (lacks the segment between 1.5 and 4.5 map units) grows as well as wild-type virus in 293 cells (Ad5-transformed human embryonic kidney cells), but its growth is severely restricted in HeLa cells. We detect no viral RNAs in the cytoplasm of dl312-infected HeLa cells. Viral RNA sequences are present, however, in dl312-infected HeLa cell nuclei.
Use of the UGA terminator as a tryptophan codon in yeast mitochondria.
Authors: Macino G , Coruzzi G , Nobrega F G , Li M , Tzagoloff A
Published: May 2006

We propose that the UGA terminator regularly occurs as a tryptophan codon in yeast mitochondrial DNA. This conclusion is based on the sequence analysis of mitochondrial DNA regions coding for structural genes of cytochrome b, cytochrome oxidase, and the ATPase.