bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of 5-bromodeoxyuridine on vaccinia virus-induced polypeptide synthesis: selective inhibition of the synthesis of some post-replicative polypeptides
Authors: Pennington T H
Published: January 2020

The effect of 5-bromodeoxyuridine (BrdU) on vaccinia virus-induced polypeptide synthesis in BSC-1 cells has been investigated. Most virus-induced pre- and post-replicative polypeptides were synthesized in concentrations of 5-bromodeoxyuridine that inhibited virus growth. The synthesis of a few post-replicative polypeptides, however, was severely inhibited under these conditions; included in this group was the precursor of a major core component, polypeptide P4b. A delay in the switch-off of pre-replicative polypeptide synthesis and in the onset of post-replicative polypeptide synthesis was also observed. The significance of these observations is discussed.
Reovirus-specific polypeptides: analysis using discontinuous gel electrophoresis
Authors: Cross R K , Fields B N
Published: January 2020

The electrophoretic analysis of reovirus-specific polypeptides in infected cells using a discontinuous gel system has allowed the resolution of additional viral-specific polypeptides, including one large-sized gamma3 and two (or possibly three) medium-sized (mu3, mu4, mu5(?)) species. The proteins designated mu0, sigma1, and sigma2 based on electrophoretic mobility in gel systems containing phosphate-urea correspond to mu4, sigma2, and sigma1, respectively, when analyzed in systems containing Tris-glycine. It is likely that protein modifications (phosphorylation and glycosylation) are responsible for at least some of these differences.
Effect of trypsin on mouse mammary tumor virus
Authors: Sheffield J B , Zacharchuk C M , Taraschi N , Daly T M
Published: January 2020

Undisrupted mouse mammary tumor virus (MuMTV) derived from the milk of of RIII mice has been analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electron microscopy after treatment with insolubilized trypsin. No alterations were found in viral fine structure by either freeze-etch or negative-stain electron microscopy. No alterations were found in the ability of trypsinized virus to compete in a radioimmune assay for viral antigens. Infectivity experiments indicate no significant differences in the ability of treated virus to infect C57Bl mice. However, significant differences were observed in polypeptide composition. The intensely periodic acid-Schiff-positive band, gp140, was shown by galactose oxidase-borotritide labeling to be degraded into a fragment of 125,000 molecular weight. The major glycoprotein, gp55, was split into fragments of 36,000 and 23,000 molecular weight, both of which stained with periodic acid-Schiff stain. Gp68 was removed from the virus. Experiments with purified, iodinated gp55 showed that the trypsin-induced fragments of gp55 were immunologically active. We conclude that: (i) certain glycoproteins at the surface of MuMTV are accessible to an insoluble form of trypsin, (ii) the trypsin causes a nick in the polypeptide chain without affecting the configuration of the molecule; (iii) the nicked molecules remain bound to the virus; and (iv) the presence of these nicked molecules does not interfere with the biological or antigenic expression of virus function.
Hybridization of mRNA from adenovirus-transformed cells to segments of the adenovirus genome
Authors: Bachenheimer S , Darnell J E
Published: January 2020

Cytoplasmic viral-specific RNA from the 8617 line of adenovirus type 2 (Ad2) transformed rat cells was hybridized to DNA fragments derived either by Eco-RI or Sma-I restriction endonucleases. Three discrete classes of viral RNA (26S, 20S, and 15S) were detected by hybridization of total cytoplasmic RNA with the fragment, and all of these RNA molecules also hybridized to the much smaller Sma-E fragment of Ad2 DNA. Poly (A)-containing RNA (exposed to 90% formamide) contained only the 20S and 15S mRNA species, suggesting that the 26S RNA might be an aggregated species. Viral RNA of the same size derived from the same regions of the genome has not been detected in lytically infected cells, suggesting some change in the pattern of transcription or RNA processing of the Ad2 DNA in the integrated state.
Action of ethyl and methyl methane sulfonates on DNA injection and genetic recombination in T7 bacteriophage
Authors: Karska-Wysocki B , Mamet-Bratley M D , Verly W G
Published: January 2020

After treatment with methyl or ethyl methane sulfonate, T7 amber mutants display a reduced capacity for recombination. Moreover, alkylation reduces recombination frequency involving markers on the right-hand side of the genetic map more than it reduces recombination frequency involving markers on the left-hand side. We interpret this to mean that alkylation can stop DNA injection at any point along the DNA molecule, and that T7 phage injects its DNA in a unique fashion starting from the end carrying the genes for early proteins.
Type C viruses from Kirsten sarcoma-transformed mink cells co-cultivated with primate cells and expressing p30 antigens related to feline leukemia virus
Authors: Sherr C J , Benveniste R E , Lieber M M , Todaro G J
Published: January 2020

Two type C viruses with new antigenic and biological properties were isolated by co-cultivating secondary cell strains established from the kidneys of a baboon (Papio papio) and a patas monkey (Erythrocebus patas) with mink cells non-productively transformed by Kirsten sarcoma virus. Both new isolates (designated PP-1R and EP-1R) contain major structural proteins (p30) that are immunologically most closely related to the p30 proteins of feline leukemia viruses. The reverse transcriptases of both viruses, although antigenically related to polymerases of murine and rat type C viruses, are distinct from those of previously described type C viral groups. Both PP-1R and EP-1R can be transmitted to canine and feline cells and to sarcoma virus-transformed, but not normal, mink cells. Both viruses contain RNA genomes partially homologous to those of endogenous mouse and rat type C viruses and the Kirsten sarcoma virus. In addition, the RNA of PP-1R contains a portion of the nucleic acid sequences found in a type C virus isolated from the baboon species P. papio. We propose that both new isolates are genetic recombinants formed between endogenous primate type C viral genomes and sequences found in Kirsten sarcoma-transformed mink cells.
Membrane protein biosynthesis in bacteriophage BF23-infected Escherichia coli
Authors: Billmire E W , Duckworth D H
Published: January 2020

When Escherichia coli is infected with bacteriophage BF23, two new proteins with molecular weights greater than 10,000, as indicated by polyacrylamide gel electrophoresis, are found associated with the cells' membranes. One of these, found associated with both the inner and outer membrane, has a molecular weight of about 55,000 and is regulated by the A1 gene of this phage, a gene found on the spontaneously injected 8% piece of BF23 DNA, DNA that codes for the synthesis of proteins necessary for the injection of the whole phage genome. The other protein, often undetected in whole membrane preparations, is found exclusively associated with the inner membrane. Evidence indicates that this protein is also regulated by the initially injected 8% piece of the DNA.
Analysis of gene function of bacteriophage phi 29 of Bacillus subtilis: identification of cistrons essential for viral assembly
Authors: Hagen E W , Reilly B E , Tosi M E , Anderson D L
Published: January 2020

Restrictive infection of Bacillus subtilis by suppressor-sensitive (sus) mutants of phi 29 has been used to search for cistrons that function in viral assembly. The products of cistrons 7, 9, 10, and 16 are necessary for head morphogenesis. The neck upper collar protein P10 and the tail protein P9 must be present for DNA packaging to occur. The protein P7 must be present for phage-related particles to form. A prohead-like particle has been isolated during 16-restrictive infection. The particle is composed of the proteins Hd, P10, F, and P7. P16 must function for DNA-filled particles to accumulate. A DNA-containing particle produced in the absence of the cistron 11 product may be an intermediate in the phi 29 assembly pathway. The protein P13 interacts with P9 and P11 to form a stable DNA-filled particle. The products of cistrons 2 and 3 are essential for viral DNA synthesis, and in their absence virus-related particles are not detected.
Characterization of some pneumococcal bacteriophages
Authors: Porter R D , Guild W R
Published: January 2020

The growth of pneumococcal phages at high cell and phage densities is enhanced strongly by the substitution of potassium for sodium in the medium. Initial titers of 2 X 10(10) to 4 X 10(10) PFU/ml are readily obtained, and concentrated stocks are stable in a storage buffer described here. The mechanism of the cation effect is obscure. Phages omega3 and omega8 each have linear double-stranded DNA of 33 X 10(6) daltons per particle, with an apparent guanine plus cytosine content of 47 to 49 mol%, as determined by buoyancy and melting temperature, but with an unusual absorbance spectrum. Efficiency of plating is high if sufficient time is allowed for a relatively slow adsorption, which differs several-fold in rate between the two phages. Morphologically, these and other pneumococcal phages are similar to coliphage lambda but with a longer tail and tail fiber. Upon UV inactivation, omega3 and omega8 have D37 values of 33 and 55 J/m2, respectively, and each shows multiplicity reactivation. A total of 13 ts mutants have been isolated from the two phages, representing only two complementation groups; complementation and recombination occur between omega3 and omega8 mutants. Both phages provoke high-titer antisera with extensive cross-reactivity against a number of newly isolated pneumococcal phages.
Comparison of JC and BK human papovaviruses with simian virus 40: DNA homology studies
Authors: Osborn J E , Robertson S M , Padgett B L , Walker D L , Weisblum B
Published: January 2020

Studies were performed to ascertain the relationship of human papovavirus JC to BK virus and to simian virus 40 (SV40) by further restriction endonuclease analysis and by DNA-DNA competition hybridization on membrane filters. Form I DNA extracted from two new isolates from cases of progressive multifocal leukoencephalopathy of human papovaviruses that were JC-like in their antigenic properties were found to yield restriction endonuclease fragmentation patterns similar to those of prototypic JC virus DNA and different from those of BK or SV40. Form I DNA preparations of JC and BK viruses were found to be related to each other and to SV40 DNA to a similar extent, with JC and BK virus DNAs containing sequences homologous to both early and late regions of the SV40 genome. The relatedness in each comparison was less than 50%, and heterologous hybrids between either JC or BK and SV40 DNAs were found to be less stable than homologous SV40-SV40 hybrids in high concentrations of formamide, suggesting substantial mismatch within homologous regions, to the extent of 15 to 30%. The new JC-like isolates were also studied in competition hybridization reactions with SV40 DNA and yielded results similar to those obtained with JC virus.
Process of infection with bacteriophage phi X174 XLI. Synthesis of defective phi X particles at 15 degrees C
Authors: Espejo R T , Sinsheimer R L
Published: January 2020

At 15 degrees C, phi X174-infected cells make single-stranded viral DNA fragments, varying in size from 0.2 to 0.9 times that of phi X DNA. In non-deproteinized lysates, this single-stranded DNA is found associated with proteins in particles sedimenting heterogeneously with an S20, w average of 80 to 90S. These particles do not differ appreciably from mature virus in polypeptide composition. Chase experiments, at 37 degrees C, of the label incorporated into this DNA at 15 degrees C suggest that both the single-stranded DNA fragments and the 80 to 90S particles are not precursors of virions but are defective end products.
Genetic analysis of heterogeneous DNA circles formed after prophage Mu induction
Authors: Parker V , Bukhari A I
Published: January 2020

Induction of a Mu prophage in Escherichia coli Hfr strains lyosgenic for Mu cts62 leads to the generation of F' episomes. Each episome thus formed carries at least one copy of the Mu genome. These results suggest that integration of Mu is mandatory for the formation of the heterogeneous circles during the lytic cycle. The circles may be precursors for phage maturation.
Cleavage of lambda DNA by a site-specific endonuclease from Serratia marcescens
Authors: McParland R H , Brown L R , Pearson G D
Published: January 2020

Three sites recognized by SmaI endonuclease, purified from Serratia marcescens SB, have been located on lambda DNA at 0.406, 0.656, and 0.825 fractional lengths from the left end of the DNA molecule.
Properties of condensed bacteriophage T4 DNA isolated from Escherichia coli infected with bacteriophage T4
Authors: Hamilton S , Pettijohn D E
Published: January 2020

Methods developed for isolating bacterial nucleoids were applied to bacteria infected with phage T4. The replicating pool of T4 DNA was isolated as a particle composed of condensed T4 DNA and certain RNA and protein components of the cell. The particles have a narrow sedimentation profile (weight-average s=2,500S) and have, on average, a T4 DNA content similar to that of the infected cell. Their dimensions observed via electron and fluorescence microscopy are similar to the dimensions of the intracellular DNA pool. The DNA packaging density is less than that of the isolated bacterial nucleoid but appears to be roughly similar to its state in vivo. Host-cell proteins and T4-specific proteins bound to the DNA were characterized by electrophoresis on polyacrylamide gels. The major host proteins are the RNA polymerase subunits and two envelope proteins (molecular weights, 36,000 and 31,000). Other major proteins of the host cell were absent or barely detectable. Single-strand breaks can be introduced into the DNA with gamma radiation or DNase without affecting its sedimentation rate. This and other studies of the effects of intercalated ethidium molecules have suggested that the average superhelical density of the condensed DNA is small. However, these studies also indicated that there may be a few domains in the DNA that become positively supercoiled in the presence of high concentrations of ethidium bromide. In contrast to the Escherichia coli nucleoid, the T4 DNA structure remains condensed after the RNA and protein components have been removed (although there may be slight relaxation in the state of condensation under these conditions).
Defective interfering passages of Sindbis virus: nature of the defective virion RNA
Authors: Kennedy S I , Bruton C J , Weiss B , Schlesinger S
Published: January 2020

Defective interfering particles of Sindbis virus contain 20S RNA identical to that found in BHK cells co-infected with standard and defective virions. We have characterized these RNAs by their oligonucleotide fingerprints. Most of the oligonucleotides were identical to those found in the mRNA (26S RNA) that codes for the virion structural proteins. Three oligonucleotides found in 20S RNA were absent from the 26S RNA pattern and may represent sequences from the 5' end of the virion RNA. Previous difficulties in describing the nature of the defective virion RNA were due to the aggregated state of the RNA. Nucleocapsids obtained from standard and defective virions were essentially the same size and had about the same density, suggesting that defective particles contain more than a single molecule of 20S RNA.
Biochemical and Biophysical Properties of
Hyphomicrobium
Bacteriophage Hyφ30
Authors: Kaplan Raymond L. , Yelton David B. , Gerencser Vincent F.
Published: January 2020

Hyphomicrobium
bacteriophage Hyφ30 and its nucleic acid were studied to determine some of their biochemical and biophysical properties. The molecular weight of the phage is 55.4 × 10
6
, and its buoyant density is 1.508 g/ml. The nucleic acid of Hyφ30 is linear, double-stranded DNA with a molecular weight of 29.7 × 10
6
. The guanine-plus-cytosine content of the DNA was 62% as determined from its melting temperature and buoyant density.
Single major polypeptide of a calicivirus: characterization by polyacrylamide gel electrophoresis and stabilization of virions by cross-linking with dimethyl suberimidate
Authors: Schaffer F L , Soergel M E
Published: January 2020

A calicivirus, San Miguel sea lion virus serotype 4, isolate 15FT, externally labelled with 125I, was shown by gel electrophoresis to possess a single major polypeptide. The polypeptide migrated anomalously upon electrophoresis in two sodium dodecyl sulfate (SDS) systems: more slowly than bovine serum albumin in a continuous phosphate-buffered system and more rapidly than bovine serum albumin in a discontinuous system. Estimated molecular weights in the two systems were approximately 71,000 and 64,000, respectively. There was no clear evidence for a minor virion polypeptide. Treatment of purified San Miguel sea lion virions with dimethyl suberimidate, a cross-linking reagent, preserved virion integrity during long-term storage at 4 degrees C. Oligomeric species of the polypeptide were observed upon electrophoresis of products from cross-linked virions. Based upon a preferred polypeptide molecular weight estimate of 71,000 and distribution of oligomeric species, a calicivirion model with 120 monomeric protein units is proposed as an alternative to a 180-unit model.
Cell-free translation of virion RNA from nondefective and transformation-defective Rous sarcoma viruses
Authors: Pawson T , Martin G S , Smith A E
Published: January 2020

Nondefective and transformation-defective virion subunit RNAs from two strains of Rous sarcoma virus (RSV) were translated in cell-free systems derived from Krebs IIA ascites cells, wheat germ, and L-cells. In each case the predominant viral-specific product was a polypeptide of molecular weight 76,000 that is related to the internal viral group-specific antigens, as judged by immunoprecipitation with monospecific antisera and tryptic peptide fingerprinting. No difference could be detected between the translation products of 35S RNA from nondefective and transformation-defective RSV virions, nor of 35S RNA from different strains of RSV. The 76,000-molecular-weight polypeptide synthesized in response to 35S RNA in vitro was labeled with formyl-methionine from initiator tRNA. Models for viral protein synthesis are discussed in the light of these results, and arguments positioning the group-specific antigen gene at the 5' end of the 35S RNA are presented.
Relationship of Plaque Size and Virulence for Chickens of 14 Representative Newcastle Disease Virus Strains
Authors: Schloer G. M. , Hanson R. P.
Published: January 2020

Ability of 14 Newcastle disease virus strains to produce large plaques was related to virulence for chickens. Plaque-size comparisons were made under standard conditions in chick embryo cell monolayers. All plaque-producing strains showed a range of plaque sizes modified to a degree by the overlay medium used. An increase in size was found for most strains under methyl-cellulose overlay medium. Markedly larger plaques were found under this medium for both Calif-RO and Calif-CG strains. Heterogeneity in plaque size was most pronounced in velogenic (high virulence) strains. Only populations of small plaques were found in mesogenic (intermediate virulence) strains, and plaques were rarely found in lentogenic (low virulence) strains. Statistical analysis showed that the plaque size of velogenic strains differed significantly from mesogenic strains. None of the 11 plaque-producing strains had a normal distribution of plaque sizes, owing primarily to the presence of different genotypes within the plaquing population of a strain. This was demonstrated by derivation of clones from two of the strains. The populations of the large (Herts L) and small (Herts S) clear plaque clones derived from Eng-Herts were homogenous and distinct from one another on the basis of plaque size. Herts L was more virulent than Herts S. Although Herts L became more heterogenous in respect to plaque size upon repeated passage in embryonated eggs, no decrease in virulence of the strain was observed.
Transformation by Murine Sarcoma Virus: Fixation (Deoxyribonucleic Acid Synthesis) and Development
Authors: Nakata Yozo , Bader John P.
Published: January 2020

Transformation of rat embryo cells by murine sarcoma virus (MSV) was contingent upon synthesis of deoxyribonucleic acid (DNA) during the first 12 hr of infection. Inhibition of DNA synthesis by thymidine (20 m
m
) or cytosine arabinoside (0.1 m
m
) resulted in the protection of cells from transformation by MSV. Transient suppression of DNA synthesis prior to infection or after a 12-hr delay had little effect on subsequent transformation, emphasizing the critical time period in in which DNA synthesis was necessary for intracellular fixation of the viral genome. These results are similar to those previously described for Rous sarcoma virus. Development of transformed cells after viral fixation was shown to be influenced by cellular density. Under conditions which allowed fixation of virus in confluent cellular monolayers, less than 20% of these cells developed into transformed foci.
Inhibition of Host Protein Synthesis During Infection of
Escherichia coli
by Bacteriophage T4 I. Continued Synthesis of Host Ribonucleic Acid
Authors: Kennell David
Published: January 2020

The ribonucleic acid (RNA) synthesized at specified intervals during infection of
Escherichia coli
K-12 by bacteriophage T4 was hybridized to denatured
E. coli
or T4 deoxyribonucleic acids (DNA). The reactions were performed under conditions that maximized the yield and at RNA/DNA inputs such that excess DNA sites were available for all RNA species. Most of the RNA synthesized at any time during the first 3 min of infection was host-specific. The fraction declined rapidly as infection progressed; host RNA represented about half that made between 3 and 4 min. It is unlikely that this represented RNA synthesized by bacteria that had escaped infection, as judged by the kinetics of adsorption and killing as well as by the rapid inhibition of β-galactosidase induction after infection. The nature of the host RNA was also examined. Part of the RNA synthesized during infection of cells rendered sensitive to actinomycin was stable in the presence of this inhibitor. This RNA was essentially all host-specific and it sedimented as ribosomal and transfer RNA; most of the ribosomal RNA was incorporated into 30
S
and 50
S
ribosomes. Hybridization analyses suggested that unstable
E. coli
messenger RNA was also synthesized for several minutes after infection; the proportion of unstable to stable host RNA synthesized appeared to be similar in infected and uninfected cells. Thus, it is concluded that significant amounts of
E. coli
RNA are synthesized during the first minutes of T4 infection. Host messenger RNA initiated after infection may not be translated into enzymes; alternatively, it is conceivable that continued bacterial messenger RNA synthesis only reflects the completion of transcription of operons whose reading was initiated prior to infection.
Interference Among Group A Arboviruses
Authors: Zebovitz Eugene , Brown Arthur
Published: January 2020

Interference among group A arboviruses is described which does not involve the mediation of interferon. Interference was observed only if the interfering virus had an advantage over the challenge virus, either in time or in multiplicity of infection. Adsorption, penetration, and uncoating of challenge virus did not appear to be inhibited, but the synthesis of infectious viral ribonucleic acid of the challenge virus was significantly retarded. It was shown with temperature-sensitive viruses or mutants that the replication of viral ribonucleic acid by the interfering virus was required to establish interference. A mechanism of interference based on a competition for replication sites or substrates is compared with other possible explanations.
Induction of Poxvirus Ribonucleic Acid Polymerases
Authors: Pitkanen A. , McAuslan B. , Hedgpeth J. , Woodson B.
Published: January 2020

Two distinct ribonucleic acid polymerase activities were induced in HeLa cells by poxvirus infection. These activities differ both in their properties and the time of their appearance after infection. One catalyzes the dAT (copolymer of deoxyadenylate and deoxythymidylate)-primed conversion of adenosine triphosphate and uridine triphosphate into an acid-insoluble product. This enzyme is detectable only if deoxyribonucleic acid synthesis has been blocked. In contrast, the accumulation of progeny genomes is a necessary condition for induction of the second enzyme. The latter activity, which is unmasked by detergent treatment, is found exclusively in maturing virus particles. The possibility that both enzymes are involved in transcribing the viral genome is discussed.
Loss of Host-controlled Restriction of λ Bacteriophage in
Escherichia coli
Following Methionine Deprivation
Authors: Grasso Robert J. , Paigen Kenneth
Published: January 2020

λ Bacteriophages produced in
Escherichia coli
C (designated as λ · C) are restricted in their ability to grow in
E. coli
K-12. The rare successful infections that arise in the K-12 population occur in “special” cells which have lost their capacity to restrict λ · C. These infections yield modified progeny phage (designated as λ · K) which, unlike λ · C, plate equally well on
E. coli
C and
E. coli
K-12. When methionine, but no other amino acid, was removed from the growth medium of a mutant strain of
E. coli
K-12, the number of special cells rapidly increased 500- to 3,000-fold. These new special cells retain their capacity to produce modified λ · K progeny. This conversion of restricting cells into special cells does not require the synthesis of new protein. The special cells formed when methionine was removed from the culture did not revert into restricting cells when methionine was restored. Such cells have also lost the ability to divide for at least 4 hr after methionine supplementation. When methionine was restored, the remaining restricting cells, but not the special cells, immediately resumed growth. Removing methionine from cultures of
E. coli
B caused a similar increase in the number of special cells able to support the growth of λ · C and λ · K. However, when
E. coli
K-12 (P1) cultures were deprived of methionine, the number of special cells increased for λ · C but not for λ · K. Thus, retention of the P1-restriction system, unlike the B- and the K-12-systems, does not require the presence of methionine.
Studies of Base-Sequence Homology Among Some Cytoplasmic Deoxyriboviruses of Vertebrate and Invertebrate Animals
Authors: Bellett Alan J. D. , Fenner Frank
Published: January 2020

Relationships among some cytoplasmic deoxyriboviruses were investigated by deoxyribonucleic acid/ribonucleic acid hybridization experiments. Evidence of base-sequence homology between nucleic acids of different viruses was found within, but not between, the poxvirus and iridescent virus groups. Viruses of the vaccinia subgroup of poxviruses were 30 to 100% related, and the degree of relatedness was correlated with serological relatedness. Relationships within the iridescent virus group depended on the laboratory of origin and passage history of the virus strains used. None of these viruses was related to a superficially similar virus of frogs.
Morphological and Cytochemical Studies on Lymphocytic Choriomeningitis Virus
Authors: Dalton A. J. , Rowe W. P. , Smith G. H. , Wilsnack R. E. , Pugh W. E.
Published: January 2020

Lymphocytic choriomeningitis (LCM) virus was observed by electron microscopy in thin sections of infected tissue cultures. The particles were pleomorphic and varied greatly in size. The smaller particles (50 to 200 nm) appeared to be spherical, whereas the largest (over 200 nm) were often cup-shaped. All particles contained one to eight or more electron-dense granules which were removed by ribonuclease. The particles were formed by budding from the plasma membrane and appeared to have spikes. The morphological evidence suggests that LCM should be considered as belonging to the presently unclassified group of lipoprotein-enveloped ribonucleic acid viruses.
Biophysical Studies on Rhinovirus and Poliovirus
Authors: McGregor Sandy , Mayor Heather D.
Published: January 2020

An explanation has been sought for the high buoyant density of rhinoviruses, which are classified as acid-sensitive picornaviruses. Heat degradation of purified preparations of rhinovirus type 1B and poliovirus type LSc leads to the extrusion of ribonucleoprotein strands. Contour lengths of these strands were measured by electron microscopy, and the molecular weights of rhinovirus and poliovirus ribonucleic acid (RNA) were determined. Values of 2 × 10
6
and 4 × 10
6
daltons were obtained for the molecular weight of poliovirus and rhinovirus RNA, respectively. This additional nucleic acid in the rhinovirion probably accounts for the increased density and may be related to the acid sensitivity of the rhinovirus.
Characteristics of and Relationship Between C Particles and Intracisternal A Particles in Cloned Cell Strains
Authors: Hall William T. , Hartley Janet W. , Sanford Katherine K.
Published: January 2020

Four murine tissue culture cell strains, which originated by cloning from one common cell of subcutaneous connective tissue origin, were examined for the presence of virus by electron microscopy and complement fixation techniques. The relative distribution of C particles and intracisternal A particles was determined. Thereafter, the characteristics of and relationship between A- and C-type particles were investigated. Cell extracts were passaged onto virus-free Swiss and C3Hf mouse embryo tissue cultures; CF and EM tests were again made to investigate the infective capacities of the various particle types. Although C particles were found in passage cultures exposed to extracts from the C particle-bearing strains, no A particles were found in any passage culture. These results indicate that the intracisternal A particle was neither infective nor developmentally associated with the C particle. A positive CF test was correlated with the presence of morphologically detectable C particles and was independent of the concentration of A particles.
Isolation and Properties of Newcastle Disease Virus Nucleocapsid
Authors: Kingsbury D. W. , Darlington R. W.
Published: January 2020

Deoxycholate (DOC) disrupted virions of Newcastle disease virus (NDV), releasing viral nucleocapsids. The nucleocapsids sedimented at about 200
S
in sucrose gradients and measured from 1.3 to 1.4 μ long by electron microscopy. NDV nucleo-capsids were resistant to pancreatic ribonuclease. These nucleocapsids contained all the 50
S
ribonucleic acid (RNA) in NDV virions, while virus-associated RNA sedimenting at less than 50
S
was external to the virions.
Number of Polypeptide Components in Bacteriophage T2L Contractile Sheaths
Authors: Farid S. A. A. , Kozloff L. M.
Published: January 2020

Isolated purified contractile tail sheaths of bacteriophage T2L were analyzed for their carboxyl terminal amino acids by carboxypeptidase treatment and hydrazinolysis. Glycine and serine were identified as the only two carboxyl end groups. Using corrections for the yields of these two amino acids upon hydrazinolysis, we calculated that there are 154 (±30) moles of C-terminal glycine and 130 (±45) moles of C-terminal serine per mole of sheath. It appears likely that sheaths contain
two
types of polypeptide chains in equal numbers, probably 144 of each. The relation of these two components to the mechanism of sheath contraction is discussed.
Density Gradient Centrifugation of Rubella Virus
Authors: McCombs Robert M. , Rawls William E.
Published: January 2020

Rubella virus was centrifuged in sucrose density gradients. One of two densities could be ascribed to the virus, depending upon the suspending medium used. The virus was found at a density of 1.16 g/cm
3
after centrifugation for 18 hr in sucrose gradients prepared in distilled water. By contrast, when the sucrose gradients were prepared in tris(hydroxymethyl)aminomethane (Tris)buffer containing ethylenediaminetetraacetic acid (EDTA), the virus was found at a density of 1.18 g/cm
3
after 18 hr of centrifugation. The virus banded at this higher density after only 2 hr of centrifugation when pretreated by overnight incubation in the Tris-EDTA buffer. A kinetic study showed that, in sucrose gradients containing this buffer, the virus gradually migrated as a single peak of infectivity from a density of 1.16 g/cm
3
after 2 hr of centrifugation to the higher 1.18 g/cm
3
density after 18 hr. The density change was shown to be reversible; after the removal of the Tris-EDTA buffer, rebanding of virus harvested at the heavy density resulted in its banding at the lower 1.16 g/cm
3
density. The data indicate that density change could not be explained on the basis of the loss of some component from the virus or on the basis of the failure of the virus to reach equilibrium. However, it is possible that the two densities observed were a reflection of the existence of rubella virus in different hydration states in the presence and absence of Tris buffer containing EDTA.
Soluble Antigens of Vaccinia-infected Mammalian Cells
Authors: Cohen Gary H. , Wilcox Wesley C.
Published: January 2020

The structural proteins of vaccinia virus can be divided into two classes on the basis of their times of synthesis in the infected cell. The production of one of these classes of proteins begins prior to the onset of viral deoxyribonucleic acid (DNA) replication. These are referred to as “early” proteins. Synthesis of the second class of structural proteins follows the onset of viral DNA replication; hence, the term “late” proteins for this class. We are able, by immunological procedures, to identify three “early” virus-structural proteins. These materials, when incorporated into virions, appear to be associated with the “core” of the virion and do not elicit production of virus-neutralizing antibody. It would seem, therefore, that those virus-structural proteins synthesized early in the course of infection act as internal components of the virion. The “late” proteins may be subdivided into two groups on the basis of certain physical properties and molecular weight differences. The first of these groups, comprised of at least two proteins, corresponds to the classical LS antigens and elicits production of neutralizing antibodies. These proteins, when incorporated into virions, are found only in the outer (“coat”) fraction of the virion. The second group of “late” antigens, also comprised of two proteins, termed the G antigens, do not elicit synthesis of neutralizing antibody. One of these proteins is associated with the virus “core”; the other is found in the “coat” fraction of the virion and appears to occupy an intermediary, subsurface position. Procedures suitable for the isolation of the G antigens are described, in addition to the partial characterization of these antigens.
Replication and Complementation of Human Adenoviruses and Simian Papovavirus at an Elevated Temperature
Authors: Jerkofsky Maryann , Rapp Fred
Published: January 2020

The simian papovavirus SV40 replicated as well in simian cells incubated at 41 C as in cells incubated at 37 C, although the latent period was shortened at the elevated temperature. Human adenoviruses differed in their responses to the elevated temperature. Some serotypes, such as 3, 4, 5, 7, 8, 16, and 21, replicated as well, or almost as efficiently, in human cells incubated at 41 C as in cells incubated at 37 C, whereas with other serotypes, such as 1, 2, 6, 12, and 14, maximal yields in cultures incubated at 41 C were much lower than the yields from companion cultures incubated at 37 C. This difference was also detected in simian cells co-infected with SV40 and a human adenovirus; maximal complementation occurred with some serotypes at the elevated temperature but not with other serotypes. The degree of complementation observed in the simian cells at 41 C was directly correlated with the ability of the adenovirus to replicate at 41 C in human cells. Therefore, the capacity of SV40 to serve as a helper virus is not affected by the elevated temperature, showing that the complementation event supplied by the simian virus is heat-stable between 37 and 41 C. Maximal complementation appeared to depend upon a characteristic present in the adenovirus genome.
Incorporation of Iododeoxyuridine into Cellular Deoxyribonucleic Acid Synthesized After Infection with Simian Virus 40
Authors: Maass G. , Werchau H. , Brandner G. , Haas R.
Published: January 2020

Primary monkey kidney cells (
Cerocpithecus aethiops
) in the stationary phase of growth were labeled with
14
C-thymidine for 24 hr prior to infection with simian virus 40 (strain 777).
3
H-deoxyadenosine and 5-iodo-2′-deoxyuridine (IUdR) were added to some of the cultures 24, 48, or 72 hr after infection; 24 hr later the deoxyribonucleic acid (DNA) was extracted from these cultures and centrifuged in a CsCl density gradient. The portion of DNA which had become heavier because of incorporation of IUdR could be seen as a second peak in the sedimentation profile. This peak contained
14
C as well as
3
H activity. The possibility that the
14
C-labeled cellular DNA might be degraded and used for the synthesis of viral DNA could be excluded. On the basis of these results, it must be assumed that the infection of monkey kidney cells with simian virus 40 induces the synthesis of cellular DNA.
Vaccinia Virus Replication and Cytopathic Effect in Cultures of Phytohemagglutinin-treated Human Peripheral Blood Leukocytes
Authors: Miller George , Enders John F.
Published: January 2020

Titers of vaccinia virus consistently increased in cultures of washed phytohemagglutinin-treated, peripheral blood leukocytes of a vaccinated adult. Concomitantly, a gradual rise occurred in the numbers of infected leukocytes, as determined by the infective center assay. Increase in viral titer was accompanied by cell injury, decline in cell numbers, and decreased acid production. Leukocytes not pretreated with phytohemagglutinin appeared to form infective centers after exposure to the vaccinia agent, but they did not replicate infectious virus. For viral replication, the continuous presence of phytohemagglutinin was required.
In Vitro Morphology and Maturation of Lymphocystis Virus
Authors: Midlige F. H. , Malsberger R. G.
Published: January 2020

The temporal sequence of development of lymphocystis disease virus (LDV) was studied by electron microscopy of thin sections of infected tissue-culture monolayers. Neither the typical cytoplasmic inclusion nor virus was detected at 4 days postinfection (PI). Inclusions, but no viruses, were detected at 8 days PI. Inclusions and associated virions were detected at 15 days PI, and by 28 days PI the undisrupted cells were filled with the typical virions. No release mechanism was detected, and severe clumping of particles was noted. Negatively stained preparations revealed particles 200 nm in diameter with no capsomere structure and apparent spikes associated with the particle. The relationship of LDV to the well-defined deoxyribonucleic acid virus groups is discussed.
Enhancement of Infectivity of Murine Cytomegalovirus
in Vitro
by Centrifugal Inoculation
Authors: Osborn J. E. , Walker D. L.
Published: January 2020

Centrifugation of murine cytomegalovirus inocula from a variety of sources onto secondary mouse embryo cell monolayers at 1,900 ×
g
for 30 min regularly revealed 10- to 100-fold more infectious virus than could be found in the same materials using standard inoculation methods. Virus demonstrable only by centrifugation was present throughout the entire growth cycle in a constant proportion to virus measured without centrifugation. Extracellular growth curves of both populations revealed an 18- to 21-hr latent period, followed by a long-linear increase over the next 12 hr; final yield was 30 plaque-forming units (PFU) per cell. Centrifugation of cells prior to inoculation or after standard adsorption and removal of inoculum failed to result in any significant change in measured virus titer. However, even after 4-hr adsorption, the supernatant inoculum could be transferred and centrifuged onto a fresh monolayer resulting in the same increment of measurable virus. Neutralizing antibody and interferon were equally efficacious against 100 PFU of virus as defined by either method. Thus, this newly identified population of cytomegalo-virus represents the vast majority of potentially infectious units and appears to differ solely in ease of adsorption onto cell monolayers.
Replication of Mengovirus in HeLa Cells Preinfected with Nonreplicating Poliovirus
Authors: McCormick William , Penman Sheldon
Published: January 2020

The replication of mengovirus in HeLa cells preinfected with poliovirus in the presence of 10
−3
M guanidine was investigated. Although host cell protein synthesis is inhibited by the presence of nonreplicating poliovirus, it is found that mengovirus ribonucleic acid (RNA) and protein synthesis proceed normally under the same conditions. Furthermore, no effects on mengovirus growth by poliovirus can be detected either when Mengo protein synthesis is interrupted by Acti-Dione or when its RNA synthesis is reduced by incubation at 28 C. It is suggested that the poliovirus inhibitory factor may be able to distinguish between an RNA element required in the protein-synthesizing apparatus of the host cell and a comparable element in that of the heterologous virus.
T4 Bacteriophage Mutants Suppressible by a Missense Suppressor Which Inserts Glycine in Place of Arginine for the Codon AGA
Authors: Reid Parlane , Berg Paul
Published: January 2020

Phage mutants of T4 have been isolated which can multiply only on
Escherichia coli
strains which contain a missense suppressor which is known to cause the substitution of glycine for arginine in response to the AGA codon. Mutations producing the suppressible phenotype were mapped and shown to occur in six different phage cistrons. Two of the cistrons were concerned with deoxyribonucleic acid synthesis, two were concerned with phage structural components, and two were concerned with functions required for growth in
E. coli
K-12 but not in
E. coli
B. The burst size of the different phage mutants grown on strains carrying the same suppressor was dependent upon the efficiency of suppression, which in turn is known to be dependent upon the glycyl-transfer ribonucleic acid synthetase activity.
Methylation of high-molecular-weight subunit RNA of feline leukemia virus
Authors: Thomason A R , Brian D A , Velicer L F , Rottman F M
Published: January 2020

The high-molecular-weight subunit RNA of feline leukemia virus (Rickard strain) (FeLV-R) was analyzed for the presence of methyl groups. After purification of native 50-60S FeLV-R RNA on nondenaturing aqueous sucrose density gradients. FeLV-R 28S subunit RNA, doubly labeled with [14C]uridine and [methyl-3H]methionine, was isolated by centrifugation through denaturing sucrose density gradients in dimethyl sulfoxide. As calculated from their respective 3H/14C ratios. FeLV-R 28S RNA was methylated to the same degree as host cell poly(A)+ mRNA. When the 28S FeLV-R RNA was hydrolyzed to completion with RNase T2 or alkali, all of the methyl-3H chromatographed with mononucleotides on Pellionex-WAX, a weak anion exchanger. The methyl-labeled material co-chromatographed with 6-methyladenosine if the mononucleotide fraction obtained by Pellionex-WAX chromatography was hydrolyzed to nucleosides by bacterial alkaline phosphatase or with 6-methyladenine if purine bases were released from the mononucleotides by acid hydrolysis. In another experiment in which FeLV-R 28S RNA uniformly labeled with 32P was hydrolyzed and then analyzed by Pellionex-WAX chromatography, all of the 32P label again co-chromatographed with mononucleotides. Thus FeLV-R 28S RNA does not appear to contain a 5' structure, either methylated or nonmethylated similar to those recently reported for cellular and some animal virus mRNA's.
Bacteriophage-specific DNA-binding proteins in P22-lysogenic and in P22-infected Salmonella typhimurium
Authors: Schumann W , Lindenblatt E , Bade E G
Published: January 2020

Crude extracts of Salmonella typhimurium lysogenic for phages P22 or L contain proteins that specifically retain phage DNA on nitrocellulose filters. Three DNA-binding activities were found after infection with P22. One is P22 specific, accounts for the largest proportion of DNA-binding proteins, and corresponds most likely to the c2 repressor. An early transient binding activity measured with both P22 and L DNA was found to be directly related to the expression of genes c1 and c3. A third, late binding activity for P22 and L DNA is related to phage production.
Infection of resistant avian cells by subgroup B Rous sarcoma virus
Authors: Linial M
Published: January 2020

Chicken fibroblasts derived from the H & N flock, which have been characterized as resistant to subgroup B avian oncornaviruses in focus assays, can be infected in suspension shortly after trypsinization by subgroup B sarcoma and leukosis viruses. Once cells are plated, resistance to infection reappears rapidly. C/BE cell suspensions obtained by treatment with EDTA instead of trypsin are not as sensitive to infection. Late interference established by preinfection with subgroup B leukosis viruses is not overcome by trypsinization. In addition to C/BE H & N chicken cells, C/ABE RPRL line 7 cells can also be infected by subgroup B viruses shortly after trypsinization; however, none of the cell types can be made sensitive to subgroup E infection. These results are discussed in relation to current information on the genetic control of resistance to avian oncornaviruses.
Presence of murine leukemia virus envelope proteins gp70 and p15(E) in a common polyprotein of infected cells
Authors: Famulari N G , Buchhagen D L , Klenk H D , Fleissner E
Published: January 2020

The murine leukemia virus envelope proteins, p15(E) and gp70, exhibit a mode of processing distinct from that of virion core proteins according to three criteria. First, the incorporation of both p15(E) and gp70 into virions is more sensitive to the metabolic analogue 2-deoxy-D-glucose than the incorporation of core proteins. Second, the kinetics with which the newly synthesized envelope proteins appear in the released virions is delayed relative to the appearance of core proteins. Third, immunoprecipitation of large polypeptides from infected cells reveals the presence of gp70 and p15(E) in a common precursor distinct from the core polyprotein.
Streptomycin-resistant Escherichia coli mutant temperature sensitive for the production of Qbeta-infective particles
Authors: Engelberg-Kulka H , Dekel L , Israeli-Reches M
Published: January 2020

A streptomycin-resistant Escherichia coli mutant has been isolated that is temperature sensitive for Qbeta phage, but not for the group I RNA phages f2, MS2, and R17. The growth of Qbeta in the mutant at the nonpermissive temperature (42 degrees C) results in the release of a near-normal burst of noninfectious particles that cosediment with Qbeta in a sucrose gradient. It is assumed that the mutant is defective at elevated temperatures in the suppression of nonsense codons, thereby producing Qbeta-like particles which are noninfectious because of the lack of the read-through protein A1.