bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural changes in BHK cell plasma membrane caused by the binding of vesicular stomatitis virus
Authors: Altstiel L D , Landsberger F R
Published: January 2020

Spin label electron spin resonance techniques using a nitroxide derivative of stearic acid were used to detect changes in plasma membrane structure caused by the binding of vesicular stomatitis virus (VSV) to cell plasma membranes of intact BHK-21 cells. The results indicate that binding of VSV to cell surface receptors causes an increase in the observed rigidity of the plasma membrane lipid bilayer. This change in membrane structure, which appears to be caused by the cross-linking of receptors in the plane of the plasma membrane, could be prevented by treating the cells with colchicine before addition of virus and could be reversed by treating the cells with colchicine after addition of virus. Cells treated with a monovalent, water-soluble derivative of VSV G-protein (Gs) did not show an increase in plasma membrane bilayer rigidity. However, addition of anti-VSV G-protein immunoglobulin G to cells pretreated with G8 caused an increase in plasma membrane bilayer rigidity. This increased rigidity could also be reversed by the addition of colchicine. Fluorescence microscopy was used to determine the distribution of fluorescein-labeled VSV particles on the cell surface after addition of virus. Approximately 30 min after addition of virus, discrete areas on the cell surface showed fluorescent staining, which coalesced to apical regions of the cell after approximately 40 min.
Synthesis of subgenomic mRNA's of mouse hepatitis virus is initiated independently: evidence from UV transcription mapping
Authors: Jacobs L , Spaan W J , Horzinek M C , van der Zeijst B A
Published: January 2020

The target sizes of the templates for the synthesis of the genome-sized RNA and the six subgenomic RNAs found in cells infected with mouse hepatitis virus strain A59 were determined by UV transcription mapping. Infected Sac(-) cells were irradiated at 6 h postinfection, the time when virus-specific RNA synthesis starts to increase exponentially. The effect of increasing UV doses on the synthesis of the individual RNAs was determined by quantitation of these RNAs after separation by agarose gel electrophoresis. The UV target sizes calculated for the templates were almost identical to the physical sizes of the RNAs. The results of these experiments seem to exclude the possibility that the subgenomic RNAs are processed or spliced from a common precursor. The data are consistent with independent initiation of transcription on a genome-sized, negative-stranded template or on smaller templates.
Identification of a protein kinase activity in purified foot- and-mouth disease virus
Authors: Grubman M J , Baxt B , La Torre J L , Bachrach H L
Published: January 2020

Purified preparations of foot-and-mouth disease virus types A, O, and C contain a protein kinase activity which can transfer the gamma phosphate of [32P]ATP to virion structural proteins VP2 and VP3 and exogenous acceptor proteins. Utilizing protamine sulfate as an acceptor, the kinase activity can be demonstrated in disrupted virus but not in intact virus. The enzyme is heat labile with optimal activity at pH 7 or greater. Serine residues of protamine sulfate were identified as the amino acid phosphorylated by the protein kinase. Treatment of purified virus with trypsin, which cleaves VP3, did not affect the protein kinase activity. The results indicate that the protein kinase activity found in FMDV is present in an internally located protein of viral or host origin.
Glycopeptides of Murine Leukemia Viruses III. Glycosylation of
env
Precursor Glycoproteins
Authors: Kemp Maurice C. , Famulari Nancy G. , Compans Richard W.
Published: January 2020

We have compared the glycopeptides obtained after extensive pronase digestion of the
env
precursors (PrENV proteins) of ecotropic, xenotropic, and dual-tropic murine leukemia viruses. Two glycopeptide size classes, having molecular weights of approximately 2,200 and 1,500, were shown to be associated with the PrENV proteins of all murine leukemia viruses studied. Glycopeptides associated with the
env
precursors were totally susceptible to endo-β-
N
-acetyglucosaminidase H. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of partial endo-β-
N
-acetylglucosaminidase H digestion products of the
env
precursor of dual-tropic mink cell focus-forming virus (MCF 247) revealed the presence of seven bands, suggesting that six glycosylation sites were present on the precursor molecule. The MCF 247 PrENV protein had been previously shown to be accessible to lactoperoxidase-catalyzed radioiodination on the surface of infected cells. The cell surface PrENV molecules had the same electrophoretic mobility as pulse-labeled PrENV protein, and after endo-β-
N
-acetylglucosaminidase H treatment a similar shift in electrophoretic mobility was observed for the cell surface PrENV protein and the pulse-labeled precursors, a finding which indicated that the PrENV protein located on the cell surface also possessed only mannose-rich oligosaccharides. These results indicated that the
env
precursor glycoproteins of dual-tropic viruses had the unusual property of migrating to the cell surface without undergoing the normal oligosaccharide processing and proteolytic cleavage events that had been observed for ecotropic and xenotropic murine leukemia virus glycoproteins.
Application of Arrhenius kinetic theory to viral eclipse: selection of bacteriophage phi X174 mutants
Authors: Incardona N L
Published: January 2020

Analysis of the bacteriophage phi X174 eclipse period in terms of Arrhenius kinetic theory suggests the following hypothesis: mutants should exist with two concomitant physiological characteristics as their phenotype. These are an eclipse rate lower than that of the wild type at permissive temperatures for plaque formation and an eclipse rate too low at lower temperatures to permit plaque development. Thus, enrichment of a mutagenized virus population for mutants that fail to eclipse during a short period at permissive temperatures should yield eclipse mutants with the cold-sensitive (cs; nonpermissive temperature, 25 degrees C), and not the temperature-sensitive (ts; nonpermissive temperature, 42 degrees C), plaque phenotype. In several trials, the frequency of the cs phenotype in the population increased from less than 0.2% to between 2 and 4% after the enrichment step, whereas the frequency of the ts phenotype remained unchanged (less than 0.2%). Moreover, 80% of these cs mutants have eclipse rates that are 3- to 40-fold lower than that of the wild type at both 37 degrees C and 25 degrees C. The successful application of the Arrhenius theory to phi X eclipse may provide insights into the molecular mechanism whereby the phi X174 genome is delivered into the host cell. Since the eclipse kinetics of other nonenveloped viruses are similar to those of phi X174, kinetic theory may be broadly applicable in the selection and characterization of viral eclipse mutants.
Synthesis of deoxythymidylate and the unusual deoxynucleotide in mature DNA of Bacillus subtilis bacteriophage SP10 occurs by postreplicational modification of 5-hydroxymethyldeoxyuridylate
Authors: Witmer H
Published: January 2020

Mature DNA of Bacillus subtilis W23 phage SP10 contains a hypermodified nucleotide (YdTMP) that replaces ca. 20% of the DTMP. SP10 DNA was pulse-labeled for 1 min at 20 degrees C with 32Pi. Among the oxopyrimidine nucleotides, virtually all of the radioactivity was recovered as 5-hydroxymethyldeoxyuridylate (HMdUMP). During the subsequent chase, radioactivity was lost from HMdUMP and recovered as YdTMP. At 37 degrees C, exogenous [6-3H]5-hydroxymethyldeoxyuridine (HMdUrd) was incorporated into SP10 DNA. Label administered as HMdUrd was phosphorylated to HMdUTP in the infected cells, but all radioactivity was recovered from SP10 DNA as YdTMP and dTMP. Two heat-sensitive mutants defective in hypermodification of SP10 DNA are described. In one mutant, HMdUMP replaces YdTMP in DNA. The other mutant generates a DNA containing a novel deoxynucleotide in place of YdTMP. The novel deoxynucleotide seems to consist of PPi esterified to the 5-hydroxymethyl function of HMdUMP (PP-HMdUMP). Both mutants make normal amounts of dTMP. The data are discussed in terms of the following conclusions. (i) Both oxopyrimidine nucleotides in mature SP10 DNA are derived by postreplicative modification of HMdUMP in nascent DNA. (ii) PP-HMdUMP is an intermediate that facilitate formation of a putative exocyclic methylene intermediate which receives the hypermodification. It is also argued that PP-HMdUMP and the same exocyclic methylene intermediate could serve as intermediates in reductive modification to dTMP. (iii) YdTMP is not an intermediate in the formation of dTMP, and reductive modification proceeds independently of hypermodification.
Partial purification and properties of an exonuclease inhibitor induced by bacteriophage Mu-1
Authors: Williams J G , Radding C M
Published: January 2020

From an induced lysogen of bacteriophage Mu-1, we partially purified a substance of high molecular weight that blocks the action of several exonucleases on double-stranded DNA. The presence of the inhibitor in cell-free extracts is dependent on induction of a Mu prophage. The Mu-related inhibitor acts by binding to double-stranded DNA rather than by interacting with the DNase. The inhibitor protects linear duplex DNA of Mu, P22, and phi X174am3 from exonucleolytic degradation by recBC DNase and lambda exonuclease. Single-stranded DNA, however, is not protected by the inhibitor from degradation by either recBC DNase or exonuclease I. The inhibitor preparation contains a protein that binds to linear duplex DNA, but not to circular duplex DNA; ends are required for binding to occur. Single-stranded DNA is not a substrate for the binding protein. These and other results suggest that the binding protein and the inhibitor are the same activity.
Translational elongation rate changes in encephalomyocarditis virus-infected and interferon-treated cells
Authors: Ramabhadran T V , Thach R E
Published: January 2020

Infection of mouse L cells with encephalomyocarditis virus results in a rapid inhibition of host protein synthesis before the synthesis of viral proteins. Although no alterations in initiation factor activities have been demonstrated in encephalomyocarditis virus-infected mouse cells, a defect in polypeptide chain elongation has been shown to occur in infected cell extracts. We investigated the significance of this elongation defect in the host shutoff phenomenon in vivo. Average polypeptide chain elongation rates were measured at various times after infection. Interferon was used as a reagent to separate temporarily the virus-induced alterations. Encephalomyocarditis virus infection of L cells was shown to lead to a progressive reduction in the elongation rate. Whereas interferon pretreatment delayed the decrease in elongation rate in a dose-dependent manner, it failed to alter the kinetics of host shutoff, suggesting that slowing of elongation steps played no significant role in this phenomenon. In addition, interferon pretreatment of either mock-infected or virus-infected cells led to no elongation defect that could be attributed to interferon action.
Simian virus 40 maturation: chromatin modifications increase the accessibility of viral DNA to nuclease and RNA polymerase
Authors: Brady J , Radonovich M , Lavialle C , Salzman N P
Published: January 2020

The accessibility of extracellular and nuclear simian virus 40 (SV40-M and SV40-I, respectively) virion chromatin DNAs to micrococcal nuclease, DNase I, BglI, EcoRI, and RNA polymerase was examined. Our results support the following conclusions: (i) the intranucleosomal DNA of SV40-I chromatin, similar to the precursor 75S chromatin complex, is resistant to enzymatic activity; and (ii) SV40-M virion chromatin is modified in a manner which increases the accessibility of viral DNA to enzymes, and the distinction between nucleosomal DNA and linker DNA is absent. Micrococcal nuclease digestion of SV40-I virion chromatin gave a typical nucleosomal DNA ladder pattern with a repeat unit of 205 base pairs of DNA. SV40-I chromatin was sensitive to cleavage with endonuclease BglI, but not with EcoRI. When SV40-I virion chromatin was used as a template, the rate of incorporation of ribonucleoside triphosphates into RNA was 5% of that obtained with naked form SV40 form I DNA. Micrococcal nuclease digestion of SV40-M virion chromatin resulted in submonomeric DNA fragments of approximately 55 base pairs, but no larger repeating unit of DNA was observed. SV40-M virion chromatin was sensitive to cleavage with either BglI or EcoRI and was approximately 20% more susceptible to digestion with DNase I than was SV40-I virion chromatin. The transcriptional efficiency of the extracellular virion chromatin was almost equivalent to that of naked SV40 form I DNA and was 16-fold higher than the rate observed with nuclear virion chromatin. The increased transcriptional activity was dependent upon the presence of nonhistone viral protein VP1 or VP2 or both.
Purified low-molecular-weight protein kinase from murine sarcoma virus particles catalyzes tyrosine phosphorylation endogenously but phosphorylates cellular proteins at serine
Authors: Sen A
Published: January 2020

The low-molecular-weight (LMW) protein kinase associated with high-titer murine sarcoma virions have been extensively purified by ammonium sulfate fractionation. Bio-Gel P-100 gel filtration, DEAE-cellulose and carboxymethyl cellulose chromatography. The purified enzyme migrates as a 16K polypeptide in polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The enzyme catalyzes phosphotransfer with ATP as a phosphate donor to various exogenously added proteins as acceptors; it requires Mg2+ and is independent of cyclic AMP. The enzyme preparation catalyzes a low level of phosphorylation in the absence of any exogenously added substrate and forms phosphotyrosine. However, in the presence of acceptor protein molecules including total soluble cytoplasmic proteins of murine sarcoma virus-transformed mouse cells, the phosphorylated end products contain predominantly phosphoserine. The virion-associated enzyme also shows a preference for phosphorylating certain polypeptides in the soluble cytoplasmic extracts of murine sarcoma virus-transformed cells.
Conservation and variation in the hemagglutinins of Hong Kong subtype influenza viruses during antigenic drift
Authors: Both G W , Sleigh M J
Published: January 2020

The nucleotide sequence was determined for the hemagglutinin gene of the Hong Kong subtype influenza strain A/Bangkok/1/79. The amino acid sequence predicted from these data shows a total of 36 amino acid changes as compared with hemagglutinin for a 1968 Hong Kong strain, 11 more than had occurred in a 1975 strain. The distribution of these changes confirmed that there are conserved and highly variable regions in hemagglutinin as the viral gene evolves during antigenic drift in the Hong Kong subtype. Of the four variable regions found in this study, only two have been seen previously. Correlation of highly variable areas in the hemagglutinins of Hong Kong subtype field strains with sites of amino acid changes in antigenically distinct influenza variants enabled us to predict likely antigenic regions of the protein. The results support and extend similar predictions made recently, based on the three-dimensional arrangement of hemagglutinin from a 1968 influenza strain.
Expression of Viral DNA in Adenovirus Type 12-Transformed Cells, in Tumor Cells, and in Revertants
Authors: Schirm Sabine , Doerfler Walter
Published: January 2020

The expression as cytoplasmic RNA of integrated human adenovirus type 12 (Ad12) DNA in transformed and tumor cell lines and in revertants was investigated. The transformed and tumor cells contained multiple copies of the viral genome, 3 to 22 copies per cell in different cell lines. The integrated Ad12 DNA molecules persisted intact or nearly intact and in most cases colinear with the virion DNA. In the revertant cell lines, which were derived from cell line T637 (22 copies of Ad12 DNA per cell), all of the Ad12 DNA molecules were lost (line F10) or only one copy and a fraction of a second copy persisted (line TR12). The size classes and map locations of Ad12-specific cytoplasmic RNAs in three Ad12-transformed hamster cell lines (T637, HA12/7, and A2497-3), in two revertant lines (F10 and TR12), in one Ad12-induced hamster (CLAC3), and in one rat brain tumor line (RBT12/3) were determined. Cytoplasmic RNA from uninfected B3 hamster cells and from human KB cells productively infected with Ad12 served as controls. In the latter control experiments, the RNA was isolated early or late postinfection. With respect to the amounts of Ad12-specific RNAs detected in cytoplasmic RNA from various Ad12-transformed or Ad12-induced tumor cell lines, we could not establish any correlations to the number of Ad12 genome copies integrated into the cellular DNAs. Thus, the expression of the integrated viral genomes in these lines was regulated by mechanisms more complicated than simple gene dosage effects. Using cloned fragments of Ad12 DNA as hybridization probes, we analyzed the cytoplasmic RNAs from the cell lines mentioned by electrophoresis on agarose gels, blotting, and DNA-RNA hybridization. For each transformed and tumor cell line, except for the revertants, several size classes of Ad12-specific cytoplasmic RNA were detected for the early E1, E2, and E4 regions of Ad12 DNA. Some of these size classes were similar but not identical to those observed in cytoplasmic RNA isolated early from human KB cells productively infected with Ad12. Only cell lines A2497-3, T637, and RBT12/3 contained several size classes of cytoplasmic RNA homologous to the E3 region of Ad12 DNA. Weak homologies to the E1 region of Ad12 DNA were also detected in the revertant lines F10 and TR12. Late regions of Ad12 DNA were expressed as cytoplasmic RNA in cell lines CLAC3 and RBT12/3. Weak homologies were detected between certain segments of the Ad12 genome (the
Eco
RI-B, -C, and -D fragments) and the cytoplasmic RNA from uninfected hamster cells. These homologies had no apparent counterpart at the level of DNA, perhaps because these homologies could be detected only due to an overrepresentation of RNA sequences. In preliminary experiments, we failed to detect the expression as cytoplasmic RNA of the so-called virus-associated RNA in transformed and tumor cell lines. Virus-associated RNA represents a population of low-molecular-weight RNAs that map at around 30 fractional length units on the viral genome.
Transcriptional and translational mapping of a 6.6-kilobase-pair DNA fragment containing the junction of the terminal repetition and unique sequence at the left end of the vaccinia virus genome
Authors: Wittek R , Cooper J A , Moss B
Published: January 2020

The penultimate EcoRI fragments from the left and right ends of the vaccinia virus genomes were cloned in phage lambda. Heteroduplex analysis and comparison of restriction fragments indicated that the inverted terminal repetition extended 780 base pairs (bp) beyond the EcoRI site or about 9,800 bp from each end of the genome. Detailed physical, transcriptional, and translational maps of the 6,600-bp left penultimate EcoRI fragment were prepared so as to extend previous maps of the 9,000-bp terminal EcoRI fragment. Polypeptides with molecular weights of 6,000 (6K polypeptide), 13,000, 19,000, 21,000, and 60,000 were synthesized in a reticulocyte cell-free system programmed with immediate early RNA (made in the presence of cycloheximide) or early RNA (made in the presence of cytosine arabinoside) and selected by hybridization to immobilized recombinant DNA. A 22K polypeptide was detected as a translation product of late RNA that hybridized to this DNA fragment. A variety of biochemical procedures were used to size and map the mRNA's. Of the five messages that hybridized to this 6,600-bp EcoRI fragment, only the one for the 21K polypeptide was encoded within the inverted terminal repetition and hybridized to the rightward-reading DNA strand. (Three additional early polypeptides were encoded within the first 9,000 bp of the inverted terminal repetition.) The remaining early polypeptides were encoded within the unique portion of the penultimate EcoRI fragment and were transcribed from the leftward-reading strand. Additional high-molecular-weight early RNAs of unknown function were also detected; however, there was no evidence indicating that mature mRNA's were spliced.
Infectious process of the parvovirus H-1: correlation of protein content, particle density, and viral infectivity
Authors: Paradiso P R
Published: January 2020

The infectious particles of the parvovirus H-1 were characterized with respect to protein content, density in CsCl, and specific infectivity. Heavy-full and light-full particles were purified from infected simian virus 40-transformed newborn human kidney (NB) cells and from simian virus 40-transformed hamster kidney (THK) cells. Analysis of the protein content of these particles demonstrated that the ratio of viral protein VP2' to VP2 was the same in heavy-full and light-full particles derived from the same cell line, but differed significantly between the two hosts. However, the infectivity of the particles from each cell line was the same for all four viral species.. Also, in vitro conversion of VP2' to VP2 did not enhance the particle infectivity of either heavy-full or light-full virus. When the fate of input virus was studied with 125I-labeled H-1, the conversion of VP2' to VP2 occurred in a time-dependent manner up to 24 h postinfection. Simultaneous with the proteolytic cleavage, there was a shift in the density of the heavy-full virus to the light-full density. However, protein analysis of the 125I-labeled light-full virus at various times postinfection indicated that they were not enriched in VP2 when compared with heavy-full virus or the total virus population. Thus, the cleavage of VP2' to VP2 is not responsible for the shift in density from heavy-full to light-full virus, and although these events might be required for infection they appear not to be interdependent.
DNA gyrase inhibitors block development of Bacillus subtilis bacteriophage SP01
Authors: Alonso J C , Sarachu A N , Grau O
Published: January 2020

SP01 development was inhibited by nalidixic acid and novobiocin in the sensitive host Bacillus subtilis 168M. Inhibition by novobiocin was prevented by a Novr mutation in the cellular DNA gyrase gene. Nalidixic acid inhibition persisted in hosts carrying a Nalr gyrase, but could be overcome by phage mutation. We conclude that SP01 requires for its development subunit B of the host DNA gyrase, but replaces or modifies subunit A.
Unintegrated viral DNA sequences in a hamster tumor induced by bovine papilloma virus
Authors: Moar M H , Campo M S , Laird H M , Jarrett W F
Published: January 2020

A fibrosarcoma was induced in a hamster by bovine papilloma virus type 2 (BPV2). The content of BPV2 DNA sequences was measured by DNA-DNA and cRNA-DNA hybridizations. The tumor contained approximately 300 BPV2 genome equivalents per cell. Southern blot hybridization indicated that the viral DNA was in free form, the entire genome most likely being present. In situ hybridization with BPV2 cRNA showed that multiple genome copies were present in each cell. Neither virus particles nor virus coat antigens could be detected in the tumor. A cell line was established from the fibrosarcoma, and the cells contained multiple copies of the BPV2 genome. The latter was in free form, and all of the DNA sequences appeared to be present in multiple copies and in all cells. An extensive search failed to reveal the presence of virus or viral antigens.
In Vitro Synthesis and Modification of mRNA by Exvectorial Isolates of Wound Tumor Virus
Authors: Nuss Donald L. , Peterson Andrew J.
Published: January 2020

Nontransmissible (exvectorial) isolates of wound tumor virus retain the ability to catalyze in vitro synthesis of RNA. Furthermore, exvectorial virus particles exhibit mRNA-2′-
O
-methyltransferase activity even after long-term (30-year) passage in a host that lacks this enzyme activity.
Effect of Host Cell Wall Material on the Adsorbability of Cofactor-requiring T4
Authors: Brown Dennis T. , Anderson Thomas F.
Published: January 2020

The adsorbability of T4 on host cells was determined as a function of time after their liberation from infected cells. Freshly liberated (nascent) particles are readily adsorbed but lose their adsorbability with a half-time of about 2 days at 5 C, but only about 20 min at 37 C. They can be made adsorbable again with an α-amino acid cofactor like
l
-tryptophan, and this state of adsorbability can be stabilized by cell wall material from
Escherichia coli
. Such stabilized particles lose their adsorbability at a rate similar to that at which nascent particles lose theirs. Most freshly liberated particles are observed by means of electron microscopy to have “debris” attached to their baseplates and to have most of their six, long tail fibers free, whereas “old” particles that have lost their adsorbability appear relatively “clean” with most of their tail fibers wrapped around their sheaths. Nascent particles have densities that are lower than those of old particles. The material responsible for nascent adsorbability seems to be a fragment of the host's cell wall, for nascent adsorbability is destroyed by lysozyme. Furthermore, nascent T4 particles liberated from host cells with radioactively labeled walls carry the label in density gradients but lose it as they lose adsorbability. In addition, only a small proportion of particles liberated from infected spheroplasts are nascently adsorbable, whereas most particles liberated from intact cells are adsorbable.
Kinetics of Nucleic Acid Synthesis in Human Embryonic Kidney Cultures Infected with Adenovirus 2 or 12: Inhibition of Cellular Deoxyribonucleic Acid Synthesis
Authors: Ledinko Nada , Fong Caroline K. Y.
Published: January 2020

Infection of human embryonic kidney (HEK) cell cultures with adenovirus types 2 or 12 resulted in an initial drop in the rate of incorporation of
3
H-thymidine into deoxyribonucleic acid (DNA) during the early latent period of virus growth, followed by a marked rise in label uptake. It was shown by cesium chloride isopycnic centrifugation that, after adenovirus 2 infection, there was a decrease in the rate of incorporation of thymidine into cellular DNA. Moreover, DNA-DNA hybridization experiments revealed that, by 28 to 32 hr after infection with either adenovirus 2 or 12, the amount of isolated pulse-labeled DNA capable of hybridizing with HEK cell DNA was reduced by approximately 60 to 70%. Autoradiographic measurements showed that the inhibition of cellular DNA synthesis was due to a decrease in the ability of an infected cell to synthesize DNA. The adenovirus-induced inhibition of host cell DNA synthesis was not due to degradation of cellular DNA.
3
H-thymidine incorporated into cellular DNA at the time of infection remained acid-precipitable, and labeled material was not incorporated into viral DNA. Furthermore, when zone sedimentation through neutral or alkaline sucrose density gradients was employed, no detectable change was observed in the sedimentation rate of this cellular DNA at various times after infection with adenovirus 2 or 12. In addition, there was no increase in deoxyribonuclease activity in cells infected with either virus. Cultures infected for 38 hr with adenovirus 2 or 12 incorporated three to four times as much
3
H-uridine into ribonucleic acid (RNA) as did non-infected cultures. Furthermore, the net RNA synthesized by infected cultures substantially exceeded that of control cultures. The activity of thymidine kinase was induced, but there was no stimulation of uridine kinase.
Effect of Puromycin and Actinomycin D on a Persistent Mumps Virus Infection In Vitro
Authors: Northrop R. L.
Published: January 2020

Puromycin and actinomycin D were used to treat a line of human conjunctiva cells persistently infected with mumps virus (C-M cells) in order to determine where virus synthesis is inhibited. Although 90% of the cells in C-M cultures are infected, little or no infectious virus is produced by most cells in a growing culture. Adding puromycin to inhibit protein synthesis resulted in the production of infectious virus. Thus, all the viral proteins needed for virus completion were made in the growing cells. When actinomycin D was added to growing cells, infectious virus was again produced. Since mumps virus synthesis is actinomycin D-insensitive, this suggested a host control of the virus. Interferon was not detected. The possible mechanisms of host control are discussed.
Ultrastructure of Measles Virus in Cultures of Hamster Cerebellum
Authors: Raine C. S. , Feldman L. A. , Sheppard R. D. , Bornstein M. B.
Published: January 2020

Replication of Edmonston strain of measles virus in cultures of hamster central nervous system tissue was studied by electron microscopy of ultrathin sections. Infected cultures were fixed from 3 hr to 39 days postinoculation (PI). Measles nucleocapsid was first seen within the cytoplasm of giant cells, the latter appearing 5 to 6 days PI. Measles virus particles were most abundant at 10 days PI and appeared to bud off from areas of the cell membrane along which nucleocapsid was aligned. Intranuclear nucleocapsid was more abundant at later stages, and by 39 days PI entire nuclei were seen to be occupied. By this time, the cytoplasmic formations, which had been sequestered by membranes, appeared to lose their regular structure. Budding viral particles at 39 days PI were of a much simplified structure and did not involve the alignment of nucleocapsid about their periphery.
Disruption of Myxoviruses with Tween 20 and Isolation of Biologically Active Hemagglutinin and Neuraminidase Subunits
Authors: Webster R. G. , Darlington R. W.
Published: January 2020

Myxoviruses were disrupted with Tween 20 at high
p
H, and the major surface antigens were separated in biologically active form. The neuraminidase had a sedimentation coefficient of 10.8
S
, and the hemagglutinin had a sedimentation coefficient of 8.1
S
. Electron microscopic examination of negatively stained preparations revealed structures identical in size and morphology to the neuraminidase and hemagglutinin subunits described by others. Inhibition of neuraminidase activity by antibody to the hemagglutinin which occurred with intact viruses (probably for “steric” reasons) did not occur after the viruses were disrupted with Tween 20. Serological assays for neuraminidase were possible in the presence of the mild surfactant, whereas serological assays for hemagglutinin were possible after removal of the reagent. Disruption of myxoviruses with Tween 20 therefore provides a method for the independent study of these antigens during antigenic drift.
Properties of Adenovirus Messenger Ribonucleic Acid Synthesized In Vitro
Authors: Warren Richard J.
Published: January 2020

Adenovirus deoxyribonucleic acid (DNA) was used as template for the in vitro synthesis of viral-specific ribonucleic acid (RNA). When the kinetics of the reaction were compared by using native and heat-denatured DNA templates, the latter synthesized RNA at a slower rate. The fate of the DNA after acting as template and physical characteritstics of the RNA product were studied. The DNA template, according to its sedimentation rate, was not significantly degraded by the
Micrococcus lysodeicticus
RNA polymerase. The products of the RNA polymerase reaction had the following properties. (i) Hybridization experiments revealed a high degree of complementarity (50 to 70%) for its homologous DNA. (ii) A very low complementarity (6 to 7%) was found for its heterologous DNA. (iii) The sedimentation rate of the synthetic RNA in a sucrose gradient was 5 to 10
S
when native DNA was used as the template. When heat-denatured DNA was used, the resulting RNA product, free of the template, sedimented at a rate of 3 to 16
S.
A rapidly sedimenting (>30
S
) DNA-RNA complex resulted when denatured DNA was the template. The DNA moiety of the complex was sensitive to 125 μg of deoxyribonuclease per ml. The RNA of the complex, however, was fully refractory to 50 μg of ribonuclease per ml. When the adenovirus DNA was sonically treated and then used as template, the RNA product sedimented at 3 to 9
S.
The heat-denatured sonically treated DNA template yielded a DNA-RNA complex that also sedimented at an unusually fast rate (>18
S
).
Characterization of Temperate
Bacillus
Bacteriophage φ105
Authors: Birdsell Dale C. , Hathaway Gary M. , Rutberg Lars
Published: January 2020

Temperate
Bacillus
phage φ105 is serologically unrelated to previously described virulent
Bacillus
phages. Phage φ105 is incapable of generalized transduction. Prophage φ105 is inducible with mitomycin C. Phage φ105 contains double-stranded deoxyribonucleic acid (DNA) with a molecular weight of about 25 × 10
7
as determined by band sedimentation and electron microscopy. The per cent guanine plus cytosine of φ105 DNA is 43.5 as determined by buoyant density in CsCl and by thermal denaturation. Phage φ105 DNA may contain complementary single-stranded ends.
Morphogenesis of Aura Virus
Authors: Lascano Eduardo F. , Berría María I. , Oro Julio G. Barrera
Published: January 2020

Aura virus, a member of the Western equine-encephalitis-Whataroa subgroup of group A arboviruses, was studied by electron microscopy in suckling mouse brain and chick embryo cultured cells. Virus precursors, budding particles, and complete virus particles were first detected 10 hr after infection in chick embryo cells and 24 hr after inoculation in mouse brain. Virus precursors were generally seen aligned along cytomembranes, and were less frequently seen closely associated with viroplasm-like foci, tubular aggregates, or scattered in the cytoplasmic matrix without an apparent connection to any other structure. The assembly of mature virus was observed to take place by a budding process of the virus precursor from the plasma membrane into the extracellular space, and from the cytoplasmic membranes into the lumina of vacuoles and cisternae. It was demonstrated that the endoplasmic reticulum participates in the assembly of intracellular virions. Indirect evidence was found to indicate that the Golgi complex may also form mature virus. Aura virions had a size, shape, and structure similar to those of the previously described group A arboviruses.
Inhibition of Arbovirus Assembly by Cycloheximide
Authors: Friedman Robert M. , Grimley Philip M.
Published: January 2020

Addition of cycloheximide (100 μg/ml) to cultures of chick cells infected with Semliki Forest virus (SFV) halted subsequent increase in virus titers. When added after 4 hr of infection, the drug had no effect on the rate of viral ribonucleic acid (RNA) synthesis, although marked inhibition of protein synthesis was seen. All of the previously identified forms of SFV RNA were seen in the drug-treated cells at higher concentrations than were present in untreated controls. The latter observation appeared to result from a failure to form viral “cores” or nucleocapsids in the cycloheximide-treated cells, resulting in sequestration of viral RNA intracellularly. The failure to form new virus cores was correlated with the failure of type II cytopathic vacuoles to appear in thin sections. Virus budding from the cell surface and the formation of type I cytopathic vacuoles persisted in cycloheximide-treated cells. The cellular pool of the major protein present in the virus core appeared to be small. None of this protein was found in a free pool in cytoplasm. The results indicated that, in the presence of cycloheximide, virus assembly was impaired because of the small size of the cellular pool of the major protein required for virus core formation.
Inactivation of Bacteriophage Lambda Containing Semiconserved Alkylated Deoxyribonucleic Acid
Authors: Ronen A.
Published: January 2020

Immediate and delayed inactivation of ethylmethane sulfonate (EMS)-treated λ phage were studied. Phage particles with one alkylated and one intact deoxyribonucleic acid (DNA) strand were obtained by allowing host-modified, EMS-treated phage to undergo one growth cycle in a nonmodifying host and selecting the progeny with semiconserved parental DNA on a restricting host. The results indicate that particles with one alkylated DNA strand are more sensitive to a second treatment with the alkylating agent. When incubated at 37 C, they are subject to inactivation at a rate which is smaller than that of phages containing two alkylated DNA strands. It appears that depurination events in one of the DNA strands of a phage particle are sufficient to cause death.
Site of Host Restriction of Simian Virus 40 Mutants in an Established African Green Monkey Kidney Cell Line
Authors: Ozer Harvey L. , Takemoto Kenneth K.
Published: January 2020

A previously described large-plaque morphology mutant of SV40 (SV-L) in primary African green monkey kidney (AGMK) cells has been shown to be restricted in the established AGMK line CV-1. The site of restriction is an early step in infection, involving the virus particle. A block in penetration or uncoating has been tentatively proposed. Restriction is observed in a number of other established lines, including monkey, human, and mouse. Independent large-plaque mutants were isolated in AGMK and their properties were compared with SV-L (temperature restriction, host restriction, and virion antigen). They can be separated into two classes. Both are restricted on CV-1, though to a lesser degree than SV-L. Further-more, both are coat mutants as determined by immunological analysis of their virions, suggesting a relationship between coat mutants associated with large-plaque morphology in AGMK and host restriction in established cell lines. Temperature restriction is seen with one but not the other of the mutants.
Synthesis of Vaccinia Viral Proteins in Cytoplasmic Extracts
Authors: Katz Ehud , Moss Bernard
Published: January 2020

Polypeptide synthesis has been studied in cell-free systems prepared from vaccinia virus-infected and uninfected HeLa cells. Cytoplasmic extracts containing endogenous messenger ribonucleic acid were used. Amino acid incorporation into hot trichloroacetic acid-precipitable material was linear for 15 to 20 min at 37 C. The initial rate of protein synthesis was approximately 15% of the rate in intact cells. Optimal conditions for polypeptide synthesis were similar in cell-free systems prepared from infected or uninfected cells. Requirements for an energy source and Mg
++
were demonstrated. The optimal Mg
++
concentration was 4 to 5 m
m
. Ribonuclease, puromycin, and cycloheximide were inhibitory. The molecular weights of the polypeptides labeled in the cell-free systems, as determined by gel filtration in 5
m
guanidine hydrochloride, ranged from 16,000 to above 68,000. Polyacrylamide gel electrophoresis indicated that the polypeptides labeled in cell-free extracts of uninfected and infected cells were different. The latter closely corresponded in electrophoretic mobility with the viral polypeptides made in intact, infected cells.
Analysis of the Ribonucleic Acid of Murine Leukemia Virus
Authors: Bader John P. , Steck Theodore L.
Published: January 2020

Cells producing the Rauscher strain of murine leukemia virus (MLV) were exposed to
3
H-uridine, and labeled virus was collected at hourly intervals. Ribonucleic acid (RNA) extracted from virions (vRNA) had a characteristic single peak when analyzed by electrophoresis in polyacrylamide-agarose composite gels. Exposure of vRNA to dimethyl sulfoxide, urea, formaldehyde, or heat altered the mobility to a faster moving form (vRNA′). This vRNA′ sedimented more slowly than native vRNA in sucrose gradients. Incubation of labeled virions at 37 C resulted in fragmentation of viral RNA which was detectable only after denaturation. Also, large differences in the temperature required for the change from vRNA to vRNA′ were seen with alterations in NaCl concentration. These experiments demonstrate that the vRNA of MLV is held in a specific conformation by hydrogen bonds distributed over a large part of the molecule. The possibility that an undefined factor is associated with viral RNA is discussed.
Morphological Comparison of Machupo with Lymphocytic Choriomeningitis Virus: Basis for a New Taxonomic Group
Authors: Murphy Frederick A. , Webb Patricia A. , Johnson Karl M. , Whitfield Sylvia G.
Published: January 2020

Striking morphologic similarities between Machupo, Tacaribe, and lymphocytic choriomeningitis viruses were found by thin-section electron microscopy. It is proposed that these viruses be brought together into a single taxonomic group.
Cellular Deoxyribonucleic Acid Synthesis and Loss of Contact Inhibition in Irradiated and Contact-Inhibited Cell Cultures Infected with Fibroma Virus
Authors: Tompkins W. A. F. , Walker Duard L. , Hinze Harry C.
Published: January 2020

Cultural changes that follow infection of rabbit kidney cells with fibroma virus were studied. Characteristic alterations of cell morphology and development of multilayered piles and cords of cells were found to occur in infected cultures in which cell division was blocked by gamma radiation or by cell crowding and serum deprivation, thus indicating no dependence upon cell division. Fibroma virus infection did not remove blocks to cell division, but it did exert distinct effects upon nuclear deoxyribonucleic acid synthesis in cells blocked by radiation or cell crowding. Use of tritium-labeled thymidine and autoradiography demonstrated that after infection initial inhibition of nuclear incorporation was followed by sharply increased nuclear labeling at a time that coincided with beginning alterations of cell morphology and development of cell piling.
Host Influence on the Antigenic Composition of the Kilham Rat Virus
Authors: Nicholson Bruce L. , Hetrick Frank M.
Published: January 2020

The Kilham rat virus (RV) was found to vary in infectivity and antigenic characteristics when propagated in two different host systems. Both cross hemagglutination-inhibition (HI) and cross virus-neutralization tests revealed that a nonreciprocal or one way cross exists between RV propagated in rat embryo cell cultures (RE-RV) and RV propagated in suckling hamsters (H-RV). Specifically, immune serum to RE-RV inhibited hemagglutination and infectivity by both viruses to the same extent. Immune serum to H-RV, however, exhibited higher HI and neutralization titers to H-RV than to RE-RV. Infectivity studies demonstrated that, although both viruses were able to infect either host, the virus showed a higher infectivity titer for the last host in which it had been propagated. Serological studies indicated that H-RV possesses an antigen(s) not found on the RE-RV. This host-controlled variation did not result after a single passage in the new host, but rather required at least three passages for a complete conversion to occur, and did not appear to result from the incorporation of unaltered host antigens into the virus particle. Solubilization of purified RV propagated in each host with sodium dodecyl sulfate, 2-mercaptoethanol, and urea followed by electrophoresis in polyacrylamide gels indicated that the number of components in the protein of each virus was not the same.
Absence of Adenine-Rich Ribonucleic Acid from Purified Infectious Reovirus 3
Authors: Krug Robert M. , Gomatos Peter J.
Published: January 2020

The basic properties of released and cell-associated reovirus are the same. Both contained as their total nucleic acid complement only double-stranded ribonucleic acid (RNA) with an adenine content of 28%. Preparations of purified cell-associated virus, but not released virus, contained adenine-rich RNA which could be separated from the virus with little or no loss of infectivity. These adenine-rich ribonucleic acids were present in the virus preparations either as free RNA or associated with some structures of molecular weight less than 25 × 10
6
daltons. In contrast to our previous report, double-stranded reovirus RNA possessed little or no template activity for the
Escherichia coli
deoxyribonucleic acid and RNA polymerases.
Immunological and Other Biological Characteristics of Pentons of Human Adenoviruses
Authors: Wadell Göran , Norrby Erling
Published: January 2020

Comparative hemagglutination-enhancement (HE) tests demonstrated diversified patterns of antigenic specificities both in the fiber and vertex capsomer part of pentons of human adenovirus types 3, 11 (subgroup I), 9, 15 (II), 1, 2, 4, 5, 6 (III), and 12. All fibers contained a type-specific antigen. Subgroup II and III fibers, in addition, contained specificities both unique for each subgroup and also common to the two subgroups. Fibers of serotypes 4 and 12 displayed a somewhat deviating behavior. All vertex capsomers tested shared a group-specific part. This was the only antigenic specificity demonstrable for serotype 12. Maximal penton HE titers of all sera were reached in tests with incomplete hemagglutinin of type 11. In addition, maximal HE activity of sera against individual serotypes also was recorded against pentons of other members of the same subgroup. Antigen characteristics of vertex capsomers of type 4 indicated a closer relationship to subgroup I than to subgroup III. The toxin activity of pentons was more sensitive to trypsin treatment than their capacity to function as incomplete hemagglutinin. Homotypic antipenton sera, unabsorbed or absorbed with homotypic fibers to remove antibodies against this component, and, to a varying extent, also heterotypic antipenton sera could neutralize toxin activity. Antifiber sera could neutralize toxin activity of pentons carrying short fibers (10 nm, type 3) but not of those carrying long fibers (28 to 31 nm, type 2). It is concluded that toxin activity is carried by a specific part of vertex capsomers and that cell detachment can be brought about via a direct contact between this component and cell membranes. Fiber-mediated attachment does not seem to be necessary for this biological activity to become expressed.
Isolation of Two Plaque Mutants of Western Equine Encephalitis Virus Differing in Virulence for Mice
Authors: Simizu Bunsiti , Takayama Naohide
Published: January 2020

Two plaque mutants were isolated from tissue cultures infected persistently with Western equine encephalitis virus. A large plaque mutant proved to be markedly avirulent for mice.
Comparison of the Ribonucleic Acid Subunits of Reovirus, Cytoplasmic Polyhedrosis Virus, and Wound Tumor Virus
Authors: Kalmakoff J. , Lewandowski L. J. , Black D. R.
Published: January 2020

Double-stranded ribonucleic acid (RNA) from intact cytoplasmic polynedrosis virus (CPV) and wound tumor virus (WTV) was analyzed by polyacrylamide gel electrophoresis. Using RNA from type 3 reovirus as a standard, it was calculated that CPV-RNA consisted of 9 subunits corresponding to a molecular weight of 12.7 × 10
6
and WTV-RNA consisted of 12 subunits corresponding to a molecular weight of 15.5 × 10
6
.
Pasteurella
Bacteriophage Sex Specific in
Escherichia coli
Authors: Molnar Dorothy M. , Lawton William D.
Published: January 2020

Phage H, thought to be specific for
Pasteurella pestis
, was shown to plate efficiently on F
−
strains of
Escherichia coli
but not on F
+
, F′, or Hfr strains. The phage was adsorbed rapidly to F
−
strains but was not adsorbed to strains carrying F. Comparison with seven other reported female-specific phages showed that, although phage H was similar to the other phages in some characteristics, the exceptionally low efficiency of plating (<10
−9
) on F-containing cells makes phage H a particularly useful female-specific phage.