bluuebunny/crossref_metadata_2025 huggingface dataset:
Culturing selects for specific genotypes of Borrelia burgdorferi in an enzootic cycle in Colorado
Authors: Norris D E , Johnson B J , Piesman J , Maupin G O , Clark J L , Black W C
Published: January 2020

In Colorado, Borrelia burgdorferi sensu stricto, the etiologic agent of Lyme disease, is maintained in an enzootic cycle between Ixodes spinipalpis ticks and Neotoma mexicana rats (27). The frequencies of flagellin (fla), 66-kDa protein (p66), and outer surface protein A (ospA) alleles were examined in 71 B. burgdorferi isolates from samples from Colorado. Approximately two-thirds of these samples were isolates from I. spinipalpis ticks that had been cultured in BSK-H medium prior to DNA extraction. The remaining samples were from total DNA extracted directly from infected I. spinipalpis ticks. A portion of each gene was amplified by PCR and screened for genetic variability by single-strand conformation polymorphism (SSCP) analysis. We identified three alleles in the fla gene, seven in the p66 gene, and seven in the ospA gene. Sequencing verified that the amplified products originated from B. burgdorferi template DNA and indicated 100% sensitivity and specificity of the SSCP analysis. The frequencies of the p66 and ospA alleles were significantly different between cultured and uncultured spirochetes. The number of three-locus genotypes and the genetic diversity of alleles at all loci were consistently lower in cultured spirochetes, suggesting that culturing of B. burgdorferi in BSK-H medium may select for specific genotypes.
Stabilities of free and complexed human immunodeficiency virus p24 antigens during short- and long-term storage
Authors: Arens M , Meyer W , Brambilla D , Bremer J , Fiscus S , Griffith B , Hammer S , Hodinka R , Kabat W , Yen-Lieberman B , Myers L , Reichelderfer P
Published: January 2020

By the standard p24 assay there was a 25 to 27% decrease in free p24 antigen in serum after storage at 4 degrees C over 14 days but no loss at -70 degrees C. There was no loss at either temperature by the immune complex dissociation (ICD) procedure. Furthermore, there was no significant loss of detectable p24 in serum by either the ICD or the standard p24 assay after 700 days of storage at -70 degrees C.
Subtyping of human immunodeficiency virus type 1 strains by using antibodies specific for the third variable domain (V3) of gp120: results may be affected by divergent V3 sequences
Authors: Sherefa K , Sällberg M , Johansson B , Salminen M , Sönnerborg A
Published: January 2020

Human immunodeficiency virus type 1 serotype C was found in 545 of 712 Ethiopian patients by peptide enzyme immunoassay. Serotyping failed in 146 samples due to the absence of V3 antibodies or multiple reactivities. In 6 of 34 samples, discordant results were obtained by serotyping and genotyping, possibly due to divergent V3 sequences.
Effect of the Inhibition of Protein Synthesis on the Establishment of Transformation by Polyoma Virus
Authors: Marin Guglielmo , Basilico Claudio
Published: January 2020

Puromycin was used to study the effect of the inhibition of protein synthesis on transformation of hamster cells (BHK21) by polyoma virus. The drug was used at a concentration (10
−4
m
) which caused in these cells a drastic but fully reversible inhibition of protein synthesis. A two- to threefold enhancement of transformation rate was obtained when the cells were exposed to puromycin for a period of 5 hr that started at the end of the virus adsorption period. No further enhancement was produced by prolonging puromycin treatment up to 13 hr after infection. The possibility that the observed effect on transformation rate could be mainly attributed to cell selection by puromycin was excluded. In addition, the relevance of a number of possible secondary effects of puromycin (inhibition of cell division, inhibition of deoxyribonucleic acid synthesis, etc.) was also ruled out. The effect of puromycin on transformation appeared to be dependent on the time (relative to infection) of addition of the drug. In fact, no transformation enhancement was observed when the cells were exposed to puromycin prior to infection or beyond the 10th hr after infection. Since another drug known to affect protein synthesis (
p
-fluorophenylalanine) was also shown to produce similar effects, it is suggested that transformation enhancement results from the inhibition of protein synthesis during a sensitive period closely following adsorption of the virus.
Morphogenesis of Type 2 Parainfluenza Virus Examined by Light and Electron Microscopy
Authors: Howe C. , Morgan C. , Cyr C. de Vaux St. , Hsu K. C. , Rose H. M.
Published: January 2020

The development of type 2 parainfluenza virus in HeLa and stable human amnion cells was examined by use of antisera labeled with fluorescein and ferritin. Serum containing antibody predominantly to soluble viral antigen gave specific fluorescence which was first detectable in small cytoplasmic foci 8 to 10 hr after initiation of infection. By 20 to 24 hr, when the production of infective virus and hemagglutinin was maximal, large perinuclear aggregates of fluorescence were observed which corresponded in distribution and time of appearance to the eosinophilic inclusions seen in similar preparations stained with azure eosin. The inclusions, examined by electron microscopy, were composed of fibrils, presumably viral ribonucleoprotein, which specifically bound the antibody labeled with ferritin. With antiserum to concentrated virus, on the other hand, specific fluorescence was most marked at the surface of infected cells. Foci of fluorescence at the surface represented segments of membrane which had become differentiated morphologically and antigenically to resemble the viral envelope. These were the sites where mature virions appeared. The latter exhibited marked pleomorphism; in some instances, particles were formed which lacked recognizable internal fibrils but which possessed an enclosing membrane bearing viral antigen. Filamentous forms showing an organized internal structure were also observed at the cell surface, but were never encountered in negatively stained preparations. No clear relationship between these filaments and the spherical or oval forms could be established. In negatively stained preparations, nucleocapsid released by rupture of viral particles was similar in appearance to that reported for other paramyxoviruses. It seems probable that this component has a helical configuration.
Reovirus-directed Ribonucleic Acid Synthesis in Infected L Cells
Authors: Shatkin A. J. , Rada B.
Published: January 2020

Reovirus replication in L-929 mouse fibroblasts was unaffected by 0.5 μg of actinomycin per ml, a concentration which inhibited cell ribonucleic acid (RNA) synthesis by more than 90%. Under these conditions of selective inhibition, the formation of both single-stranded and double-stranded virus-specific RNA was detected beginning at 6 hr after infection. The purified double-stranded RNA was similar in size and base composition to virus RNA and presumably was incorporated into mature virus. The single-stranded RNA formed ribonuclease-resistant duplexes when annealed with denatured virus RNA but did not self-anneal, thus indicating that it includes copies of only one strand of the duplex. The single-stranded RNA was polyribosome-associated and may function as the virus messenger RNA. Production of both types of virus-induced RNA required protein synthesis 6 to 9 hr after infection. At later times in the infectious cycle, only double-stranded RNA synthesis was dependent on continued protein formation.
Infective Virus Substructure from Vesicular Stomatitis Virus
Authors: Brown F. , Cartwright B. , Crick Joan , Smale C. J.
Published: January 2020

Treatment of suspensions of vesicular stomatitis virus with Tween-ether results in a rapid and considerable loss of infectivity (ca. 4 logs in 2 min), but the residual infectivity is comparatively stable to further treatment with ether. The infectivity remaining after the short exposure to Tween-ether is not due to virus for the following reasons. (i) It is much less infective for tissue cultures than for mice, whereas the intact virion is equally infective for both hosts. (ii) The residual infectivity is much less stable than virus infectivity in both sucrose and tartrate gradients. (iii) Virus immune serum does not neutralize its activity. (iv) The infectivity is associated with material which sediments further in sucrose gradients and has a greater buoyant density in tartrate gradients than the virion. Experiments with
32
P-labeled virion showed that the infective substructure contains ribonucleic acid with the same sedimentation characteristics as that extracted from the virion. Electron microscopy shows that the infective component has the same overall bullet-like structure as the virion but lacks the outer envelope and fringe structure.
Properties of Venezuelan Equine Encephalomyelitis Virus Grown In Vivo
Authors: Soper William T. , Hearn Henry J.
Published: January 2020

One intracerebral passage of either the parent egg seed (PES) or an attenuated variant (10t) of the Trinidad strain of Venezuelan equine encephalomyelitis (VEE) virus in young adult mice produced progeny that were no longer differentiated unequivocally on the basis of plaque size. Plaques averaging about 2 mm in diameter, which was somewhat smaller than those formed by the PES virus and larger than those of the 10t strain, were formed by both strains. Seven serial passages of the PES virus in mouse brain failed to alter its virulence appreciably. In contrast, passage in mouse brain progressively changed the properties of the attenuated 10t strain. A substrain was isolated that possessed virulence similar to that of the PES virus and formed small plaques similar to those of the 10t strain. These findings showed a unique dissociation between the plaque size and virulence of the 10t strain. The new substrain differed from the PES virus and the 10t strain in its capacity for growth in mouse tissues after intraperitoneal inoculation. The substrain multiplied poorly in splenic tissue, which supports growth of the PES and 10t strains, but grew to high titers in the brain, which does not support appreciable growth of the 10t strain.
Effect of Magnesium on Replication of Rhinovirus HGP
Authors: Fiala Milan , Kenny George E.
Published: January 2020

It is known that plaque formation by some rhinoviruses is greatly enhanced by increasing the concentration of MgCl
2
. The mechanism of this action was studied by investigating the effects of MgCl
2
on rhinovirus HGP adsorption, growth, clumping, thermal stability, and cell susceptibility to viral cytopathic effect. The latent period was at most 7 hr, whether virus was propagated in cells maintained in 0.8 or 30 m
m
MgCl
2
, but virus release was 8- to 310-fold greater in the presence of 30m
m
MgCl
2
, depending on initial multiplicity. Intracellular virus content appeared unaffected by Mg
++
and reached maximal yield (plateau phase) at about 10 hr. Viral adsorption was increased when cells were maintained in 30m
m
Mg
++
. It is likely that the two effects of magnesium, enhanced adsorption and increased virus release, both contribute to enhancement of plaque formation.
Nonidentity of Some Simian Virus 40-induced Enzymes with Tumor Antigen
Authors: Kit Saul , Melnick Joseph L. , Anken Milton , Dubbs Del Rose , de Torres R. A. , Kitahara Tsunehiro
Published: January 2020

The complement-fixing tumor (T) antigen induced by simian virus 40 (SV40) has been prepared from SV40-infected cell cultures, from infected cell cultures treated at the time of infection with 1-β-
d
-arabinofuranosylcytosine (ara-C), and from SV40-transformed cells. Upon partial purification, the T antigen exhibited the following properties: it was tightly adsorbed by calcium phosphate gel, it was precipitated by acetic acid at
p
H 5 or by ammonium sulfate at about 20 to 32% saturation, and it had a molecular weight greater than 250,000, as estimated by Sephadex G-200 gel chromatography. In contrast, deoxycytidylate (dCMP) deaminase, thymidylate (dTMP) kinase, and thymidine (dT) kinase were less strongly bound to calcium phosphate and were not precipitated at
p
H 5; these enzymes also had much lower molecular weights than the T antigen, as did dihydrofolic (FH
2
) reductase. Furthermore, higher ammonium sulfate concentrations were required to precipitate dCMP deaminase, dTMP kinase, and FH
2
reductase activities than to precipitate the T antigen. Another difference was that the T antigen was not stabilized, but dCMP deaminase, dTMP kinase, and dT kinase, were stabilized, respectively, by dCTP, dTMP, and dT or dTTP. Deoxyribonucleic acid (DNA) polymerase activity resembled the T antigen in adsorption to calcium phosphate, in precipitation by ammonium sulfate or at
p
H 5, and in the rate of inactivation when incubated at 38 C. However, the polymerase activity could be partly separated from the T antigen by Sephadex G-200 gel chromatography. The cell fraction containing partially purified T antigen also contained a soluble complement-fixing antigen (presumably a subunit of the viral capsid) which reacted with hyperimmune monkey sera. The latter antigen was present in very low titers or absent from cell extracts prepared from SV40-infected monkey kidney cell cultures which had been treated with ara-C at the time of infection, or from SV40-transformed mouse kidney (mKS) or hamster tumor (H-50) cells. The T antigen, however, was present in usual amounts in SV40-transformed cells or ara-C treated, infected cells.
Comparative Studies of the Regeneration of HeLa Cell Receptors for Poliovirus T1 and Coxsackievirus B3
Authors: Levitt Neil H. , Crowell Richard L.
Published: January 2020

Enterovirus receptors of live HeLa cells have been shown to reappear after inactivation by proteolytic enzymes, provided the cells are incubated at 37 C in a nutritionally adequate medium. Regeneration of receptor activity for poliovirus T1 occurred at a significantly faster rate than for coxsackievirus B3. The regenerative process for both types of receptors studied evidently required an active process of protein synthesis, since it was found that reappearance of receptor activity was inhibited by streptovitacin A, puromycin, and actinomycin D. Substitution of
p
-fluorophenylalanine for the naturally occurring amino acid, at concentrations which inhibited virus synthesis, was without effect on regeneration of receptor activity. It is anticipated that these findings will aid in the study of the biosynthesis and subsequent chemical characterization of viral receptors of living host cells.
Denaturation and Renaturation of Viral Ribonucleic Acid II. Characterization of the Products Resulting from Annealing R17 Ribonucleic Acid with Denatured Replicative Form or with Denatured Replicative Intermediate
Authors: Iglewski Wallace J. , Franklin Richard M.
Published: January 2020

The ribonucleic acid (RNA) product resulting from annealing R17 RNA with denatured replicative form or replicative intermediate could be divided into two distinct types of RNA by precipitation in 1.5
m
NaCl. The RNA found in the salt supernatant fluid was resistant to digestion by ribonuclease, had a sedimentation coefficient of 15
S
, and displayed a sharp thermal transition. The RNA in the salt supernatant fluid appeared to be identical to replicative form. The RNA found in the salt precipitate was resistant to digestion by ribonuclease, but possessed both single- and double-stranded characteristics. The RNA sedimented as a broad band in a sucrose gradient, with a sedimentation coefficient of 15
S
, and displayed a melting transition characteristic of a mixture of single- and double-stranded RNA. Mild ribonuclease digestion of the salt-precipitable RNA produced a ribonuclease-resistant material with sedimentation properties identical to the RNA found in the salt supernatant fluid.
Electron Microscopy of Adenovirus 12 Replication 1. Fine Structural Changes in the Nucleus of Infected KB Cells
Authors: Martinez-Palomo A. , Le Buis J. , Bernhard W.
Published: January 2020

The ultrastructure of KB cells infected with oncogenic adenovirus 12 was studied at various intervals from 4 to 72 hr after viral inoculation. At 12 hr after infection, the nucleus and the nucleolus became hypertrophic. At 16 hr, bundles of fibers digestable by proteolytic enzymes were seen in the nucleus; they are considered as the early viral antigens identified immunologically by others. Between 24 and 26 hr, four types of nuclear inclusions appeared. Their sequence of appearance and fine structure are described. On the basis of their sensitivity to proteolytic digestion in thin sections, and the results of immunoferritin studies made by others, some of these inclusions are believed to represent viral structural antigens. Throughout the cycle of viral replication, the nucleolus displayed prominent and constant changes in the form of focal condensations and loosening of the nucleolonema, followed by atrophy and fragmentation. It is suggested that the early nucleolar changes reflect an active participation of the nucleolus in the synthesis of adenovirus 12. A hitherto unknown striated structure with definite periodicity, which is easily digested by proteolytic enzymes, was found in the nuclei during the late stages of adenovirus 12 replication.
Comparative Study of Cultured Burkitt Tumor Cells by Immunofluorescence, Autoradiography, and Electron Microscopy
Authors: Zur Hausen Harald , Henle Werner , Hummeler Klaus , Diehl Volker , Henle Gertrude
Published: January 2020

Cultured Burkitt cells were examined by immunofluorescence, autoradiography, and electron microscopy in an effort to identify the stainable cells with those harboring herpes-type virus particles. Immediately after a 2-hr pulse of
3
H-thymidine, from 30 to 60% of the cells revealed heavy nuclear labeling. In most cases the grains were evenly dispersed, but in about 3 to 5% the grains showed a focal distribution and occasionally they extended into the cytoplasm. Such nuclear foci were rarely seen at 8 hr after the pulse. When the analysis was restricted to preselected immunofluorescent cells, up to 80% showed label at 8 hr and cytoplasmic grains were prominent. To reduce cellular deoxyribonucleic acid (DNA) synthesis, cells were X-irradiated with 3,000 to 6,000 R, and the isotope pulse was applied 1, 4, or 7 days later. Whereas the total number of labeled cells decreased in roughly twofold steps at the respective intervals (from 40 to 10%), the incorporation of
3
H-thymidine into fluorescent cells was not affected by X irradiation. In each series, about 70% of the fluorescent cells contained label when they were examined at 24 and 48 hr after the pulse, whereas at 8 and 72 hr fewer were positive. At the earlier intervals, unlabeled fluorescent cells most likely represented cells which had completed viral DNA synthesis prior to the pulse; at the later intervals, unlabeled fluorescent cells were probably cells which commenced viral replication after the pulse. These data support the conclusion that the immunofluorescent cells are the ones which harbor virus, and also confirm the expectation that the virus is a DNA virus from a member of the herpes group. This conclusion was firmly established by sectioning and electron microscopic examination of individual fluorescent cells, all of which contained numerous virus particles, whereas the nonstained cells prepared in a similar manner were free of them.
Virus Particles in Apparently Healthy
Peregrinus maidis
Authors: Herold F. , Munz K.
Published: January 2020

Virus-like particles were found in apparently healthy
Peregrinus maidis
(Ashm.) in Venezuela. The particles were observed in the salivary gland, intestine, mycetome, adipose tissue, ovary, and hemolymph. In the cells, the particles occurred in the cytoplasm singly, in groups, free or within vesicles, and in hexagonally arranged crystals. In
P. maidis
from Hawaii such particles were not found. However, in these insects, single particles or crystals were observed after injecting suspensions of intestines from
P. maidis
from Venezuela. The particles were not observed in insects feeding on plants soiled with excretions from particle-containing
P. maidis
. Particles in organs of insects or in pellets of intestines were polygonal and showed a weakly contrasted envelope and a highly contrasted core. The particles had a diameter of 54 ± 9 mμ. They are believed to represent a
Peregrinus
virus causing latent infection.
Characterization of Virus- and Endotoxin-induced Interferons Obtained from the Serum and Urine of Rabbits
Authors: Ke Yang H. , Ho Monto
Published: January 2020

Interferons induced in the rabbit by Newcastle disease virus or by endotoxin have been further characterized as to their physicochemical stability and molecular size by Sephadex G-100 gel filtration. Endotoxin-induced interferon obtained from serum was more labile than virus-induced interferon. Both endotoxin and virus induced interferons obtained from serum contained two peaks: a minor high molecular weight (>100,000) peak and a major lower molecular weight peak. The molecular weight of the major peak induced by endotoxin was 54,000, and that induced by Newcastle disease virus was 46,000. The gel filtration pattern of interferon recovered from the urine of animals inoculated with virus reflected faithfully the pattern found in serum except that there was proportionately less of the high molecular weight peak. However, the urine interferon from endotoxin-inoculated animals contained only one broad peak with a molecular weight of 35,000. This was not the peak fraction present in the serum of such animals. It is postulated that this may represent the basic unit of endotoxin-induced interferon, and that the serum components are either polymers or conjugates of this basic unit.
Replication of the Reticuloendotheliosis Virus (Strain T) in Chicken Embryo Cell Culture
Authors: Bose Henry R. , Levine Alvin S.
Published: January 2020

Investigations were conducted on the in vitro replication of the reticuloendotheliosis (RE) virus (strain T) in specific-pathogen-free chicken embryo fibroblast (CEF) cultures. Active virus production was detected in the tissue culture fluid 24 hr after infection. When injected into chickens, samples taken 42 hr after infection of the cell cultures killed approximately 50% of the birds at a 1:100 dilution. The RE virus titer remained at this level for 5 days before declining. Cell-free virus preparations from tissue cultures rarely resulted in 100% mortality of the assay birds. The level of cell-associated virus was very low. Evidence that the reticuloendotheliosis was not induced by a mycoplasma was indicated by failure to isolate an organism on PPLO Agar (Difco) and failure of kanamycin or amphotericin B to inhibit multiplication of RE virus in vitro. RE virus appeared to be unrelated to members of the avian leukosis and sarcoma complex. It did not induce resistance in CEF cultures to sarcoma viruses of the A or B subgroup of this complex. Similarly, preinfection of cell cultures with leukosis viruses of the A or B subgroup did not inhibit or reduce the replication of RE virus.
Studies on Circular Deoxyribonucleic Acid I. Isolation of Bovine Papilloma Virus and Characterization of Its Deoxyribonucleic Acid
Authors: Bujard H.
Published: January 2020

A simple method is described for the isolation of bovine papilloma virus and its deoxyribonucleic acid (DNA). As found with other representatives of this virus group, this DNA preparation contains two components, I and II, as shown by sedimentation and electron microscopic studies. Component I is a fast-sedimenting, twisted, circular DNA molecule and represents usually 70 to 90% of the DNA in the mixture. The direction of the twist in the superstructure is right-handed. Component II originates from I by one or more single-strand breaks and is the “relaxed” circular from of the viral DNA.
Analysis of Additional Interference Occurring After the Removal of Interferon
Authors: Lockart Royce Z.
Published: January 2020

Cultures of chick cells exposed to interferon continued to decrease in virus-producing ability during incubation after the interferon was removed. The rate of development of the additional interference and the degree of viral interference finally manifested were dependent on the concentration of interferon to which the cultures were exposed and the time of exposure. Additional interference occurred also in infected cells. Additional interference was inhibited by actinomycin D and puromycin. The best explanation of additional interference is that it results from interferon that is fixed to the cells during their initial period of contact.
Molecular Recombination in T4 Bacteriophage Deoxyribonucleic Acid II. Single-Strand Breaks and Exposure of Uncomplemented Areas as a Prerequisite for Recombination
Authors: Kozinski Andrzej W. , Felgenhauer Zoya Z.
Published: January 2020

Deoxyribonucleic acid (DNA) from several “DNA-deficient” amber mutants was observed to be either nicked (amber 22, 82, 122, and wild type) or cut (amber 453) after injection into a nonpermissive host. This effect was inhibited by chloramphenicol (CM), indicating that it is due to phage-induced enzymes. Although most of the mutants tested for replication in a density-label system were in fact DNA-deficient (amber 22, 82, 122), one (amber 81) was found to replicate almost identically to the wild type, and another (amber 453) was found to assume a hybrid density only. The hybrid moiety was less than, or equal to, one phage equivalent length, and was more efficiently extracted from infected bacteria than was similarly replicated DNA from wild-type phage. Interparental recombination between heavy and light parental DNA was observed for amber 82, 122, and wild type, but was not observed for amber 453; it was inhibited by CM. In contrast to amber 82 and wild type, the amber 453 intracellular DNA does not have single-strand regions, Because amber 453, unlike amber 82 and wild type T4, does not recombine, nicking and exposure of single-strand regions is postulated to be a prerequisite for recombination.
Reproducible Plaquing System for Rabies, Lymphocytic Choriomeningitis, and Other Ribonucleic Acid Viruses in BHK-21 / 13S Agarose Suspensions
Authors: Sedwick W. D. , Wiktor T. J.
Published: January 2020

BHK21/13S-agarose suspension cultures provide an excellent plaquing system for rabies and lymphocytic choriomeningitis viruses. The system has facilitated accurate and reproducible assay of serum neutralization and cloning of these viruses. Rubella, reo, and Kern Canyon viruses may also be assayed by this technique.
New Assay Procedure for Separation of Mycoplasmas from Virus Pools and Tissue Culture Systems
Authors: Zgorniak-Nowosielska Izabella , Sedwick W. David , Hummeler Klaus , Koprowski Hilary
Published: January 2020

Presence of mycoplasma organisms in tissue culture systems and virus pools was detected by titration of the contaminated material on agarose-suspended BHK21/13S cells. The use of this method permitted isolation of mycoplasmas which could not be detected by standard assay methods. Mycoplasma colonies at concentrations ranging from 10
4
to 10
6
colony-forming units/ml in agarose-BHK21/13S media could be distinguished from virus plaques, and the two populations of microorganisms could be easily disassociated either by electron microscopy or by biological methods. All isolated mycoplasmas were identified in growth inhibition tests as belonging to the GDL group. The growth inhibition test on agarose-BHK21/13S cell suspension plates could also be applied directly to those strains which could not be isolated by standard assay procedures.
Immunofluorescence and Cytochemical Studies of Visna Virus in Cell Culture
Authors: Harter D. H. , Hsu K. C. , Rose H. M.
Published: January 2020

Sequential morphological changes occurring in sheep choroid plexus cells infected with visna virus were studied by direct immunofluorescence, acridine orange, and hematoxylin and eosin staining methods. Specific immunofluorescence was first detected in the perinuclear cytoplasm of solitary cells 24 hr after infection. As the infection progressed, viral antigen appeared in an increasing number of cells, and rounded globular cells with long slender processes harboring intense fluorescence were seen. Nuclear fluorescence was not observed in infected monolayers. Polykaryocytes formed within 6 hr after inoculation due to the direct cell-fusing effect of the virus inoculum did not show specific fluorescence. Viral antigen was found, however, in the cytoplasm of multinucleated giant cells in cover slips harvested after new infective virus had been released, and later in the course of infection circular fluorescent inclusions were seen in the cytoplasm of polykaryocytes. Comparable eosinophilic inclusions were observed in hematoxylin and eosin preparations, and acridine orange staining of infected monolayers demonstrated similar inclusions which fluoresced with the color characteristic of single-stranded nucleic acid and were susceptible to digestion with ribonuclease. Visna virus appears to be a ribonucleic acid virus which replicates in the cytoplasm.
Rescue of Rous Sarcoma Virus from Rous Sarcoma Virus-Transformed Mammalian Cells
Authors: Coffin John M.
Published: January 2020

Rat cells transformed by the B77 strain of avian sarcoma virus produce no virus-like particles, yet B77 virus was rescued from these cells by Sendai virus-mediated fusion with chicken cells. This virus rescue was not affected by treatment of the chicken cells with agents that rendered the cells incapable of dividing, although such treatment greatly reduced the ability of the chicken cells to plate as infectious centers after infection with B77 virus. Fusion of R(B77) cells with chicken erythrocytes also led to virus rescue, although with less efficiency than fusion with chicken fibroblasts. Therefore, virus rescue was probably due to a factor or factors contributed by chicken cells which aid in virus production.
Conformational Studies of Australia Antigen by Optical Rotatory Dispersion and Circular Dichroism
Authors: Sukeno Noriyoshi , Shirachi Ryoichi , Shiraishi Hiroyuki , Ishida Nakao
Published: January 2020

The optical rotatory dispersion and circular dichroism of intact, 8
m
urea- or sodium dodecyl sulfate-treated, and carbamidomethylated Australia antigen indicated that the antigen possesses a high α-helical content similar to human high-density lipoproteins.
Specific Fragments of φX174 Deoxyribonucleic Acid Produced by a Restriction Enzyme from
Haemophilus aegyptius
, Endonuclease Z
Authors: Middleton June H. , Edgell Marshall H. , Hutchison Clyde A.
Published: January 2020

A restriction-like enzyme has been purified from
Haemophilus aegyptius.
This nuclease, endonuclease Z, produces a rapid decrease in the viscosity of native calf thymus and
H. influenzae
deoxyribonucleic acids (DNA), but does not degrade homologous DNA. The specificity of endonuclease Z is different from that of the similar endonuclease isolated from
H. influenzae
(endonuclease R). The purified enzyme cleaves the double-stranded replicative form DNA of bacteriophage φX174 (φX174 RF DNA) into at least 11 specific limit fragments whose molecular sizes have been estimated by gel electrophoresis. The position of these fragments with respect to the genetic map of φX174 can be determined by using the genetic assay for small fragments of φX174 DNA.
Cell Cycle-Dependent Activation of Rous Sarcoma Virus-Infected Stationary Chicken Cells: Avian Leukosis Virus Group-Specific Antigens and Ribonucleic Acid
Authors: Humphries Eric H. , Temin Howard M.
Published: January 2020

Stationary chicken embryo fibroblasts exposed to Rous sarcoma virus (RSV) remained stably infected for at least 5 days, but they did not release infectious virus or become transformed until after cell division. These infected stationary cells did not contain avian leukosis virus group-specific antigens or ribonucleic acid (RNA) hybridizable to deoxyribonucleic acid (DNA) made by the RSV endogenous RNA-directed DNA polymerase activity.
Stability of Cytosine-Containing Deoxyribonucleic Acid After Infection by Certain T4
r
II-D Deletion Mutants
Authors: Bruner Robert , Souther Arthur , Suggs Sidney
Published: January 2020

When T-even phage infect
Escherichia coli
, synthesis of host deoxyribonucleic acid (DNA) rapidly ceases. If the phage carry a mutation in a gene essential for phage DNA synthesis, then the infected bacteria should make no DNA, either host DNA or phage DNA. However, we have found that infection with certain T4 gene 56 (deoxycytidine triphosphatase)-
r
II double mutants leads to substantial DNA synthesis. Only
r
II deletion mutations which extend into the middle third of the adjacent, nonessential D region lead to the anomalous DNA synthesis, when combined with a gene 56 mutation; the requirement probably is that the deletion extend into the D2a transcriptional unit identified by Sederoff et al. Genetic evidence indicates that the observed anomalous DNA synthesis is synthesis of phage DNA. We suggest that the D2a region controls, directly or indirectly, a nuclease involved in the breakdown of cytosine-containing DNA. In the absence of the D2a product, the cytosine-containing phage DNA made by the gene 56 mutant is stabilized.
Adenylate-Rich Sequences in Sendai Virus Transcripts from Infected Cells
Authors: Pridgen C. , Kingsbury D. W.
Published: January 2020

Virus-specific complementary ribonucleic acid (RNA) from cells infected with Sendai virus was isolated by a procedure involving hybridization with virion RNA and isopycnic centrifugation of the RNA hybrids. The complementary RNA contained adenylate-rich sequences which sedimented at about 4
S
.
Deoxyribonucleic Acid Polymerase Activities in Normal and Leukovirus-Infected Chicken Embryo Cells
Authors: Weissbach A. , Bolden A. , Muller R. , Hanafusa H. , Hanafusa T.
Published: January 2020

Chicken embryo cells normally contain, in addition to deoxyribonucleic acid (DNA)-dependent DNA (D-DNA) polymerases, a novel “R-DNA-polymerase” which specifically copies polyriboadenylic acid strands. This R-DNA polymerase cannot copy natural ribonucleic acid or polyribocytidylic acid strands to a significant extent. Infection of cells with the leukovirus RAV-2 leads to the intracellular formation of large amounts of the viral RNA-dependent DNA polymerase whose properties differ from the cell R-DNA polymerase. Chicken cells transformed by a Rous sarcoma virus mutant which produce noninfectious alpha-type Rous sarcoma virus (f), a leukovirus known to be deficient in the viral RNA-dependent DNA polymerase, do not contain detectable viral RNA-dependent DNA polymerase, whereas the cellular R-DNA polymerase is found in normal amounts. There seems to be no relationship between the cellular R-DNA polymerase and the RNA-dependent DNA polymerase of the avian leukoviruses.
Reverse Transcriptase-Containing Particles Induced in Rous Sarcoma Virus-Transformed Rat Cells by Arginine Deprivation
Authors: Kotler Moshe , Weinberg Eynat , Haspel Osnat , Becker Yechiel
Published: January 2020

Incubation of rat cells transformed by Rous sarcoma virus (RSV) in an arginine-deficient medium resulted in accumulation of particles in the culture medium. Such particles did not appear when the transformed rat cells were incubated in a complete medium nor in the medium of primary rat cells which were incubated either in arginine-deficient or complete media. The particles which were released from the arginine-deprived transformed rat cells resemble C-type particles in their properties. These particles band in sucrose gradients at a density of 1.16 g/ml and contain 35
S
ribonucleic acid (RNA) molecules and a reverse transcriptase activity. Analysis of the cytoplasm of transformed and primary rat cells, deprived and undeprived of arginine, revealed the presence of reverse transcriptase-containing particles which banded in sucrose gradients at a density of 1.14 g/ml. These particles differed from the particles released into the medium by the arginine-deprived RSV-transformed rat cells. The deoxyribonucleic acid (DNA) molecules synthesized in vitro by the reverse transcriptase present in the particles isolated from the medium of arginine-deprived cells hybridized to RSV RNA, whereas the DNA synthesized by the cell-bound enzyme had no homology to RSV RNA.
Transfer Ribonucleic Acid Nucleotidyltransferase and Transfer Ribonucleic Acid in Sendai Virions
Authors: Kolakofsky Daniel
Published: January 2020

Sendai virions contain both transfer ribonucleic acid (tRNA) nucleotidyltransferase and its substrate, tRNA missing its CCA-OH end.
Effect of Vesicular Stomatitis Virus Infection on the Histocompatibility Antigen of L Cells
Authors: Hecht Toby T. , Summers Donald F.
Published: January 2020

When mouse L cells are infected for 22 hr with vesicular stomatitis virus (VSV), a ribonucleic acid-containing enveloped virus, greater than 70% of the major histocompatibility antigen (H-2), is no longer detectable by the method of inhibition of immune cytolysis. Infected cells prelabeled with
14
C-glucosamine also show a correspondingly greater loss of trichloroacetic acid-insoluble radioactivity than uninfected cells. The loss of H-2 antigenic activity is not due to the viral inhibition of host cell protein synthesis since cells cultured for 18 hr in the presence of cycloheximide have the same amount of H-2 activity as untreated controls. Also, cells infected with encephalomyocarditis virus, a picornavirus, show no loss of H-2 activity at a time when host cell protein synthesis is completely inhibited. VSV structural proteins associated in vitro with uninfected L-cell plasma membranes do not render H-2 sites inaccessible to the assay. Although antibodies may not combine with all the H-2 antigenic sites on the plasma membrane, anti-H-2 serum reacted with L cells before infection does not prevent a normal infection with VSV. H-2 activity can be detected in virus samples purified from the medium of infected L cells; this virus purified after being mixed with L-cell homogenates shows greater H-2 activity than virus purified after being mixed with HeLa cell homogenates. However, VSV made in HeLa cells shows no H-2 activity when mixed with L-cell homogenates.
Mutant of Vesicular Stomatitis Virus Which Allows Deoxyribonucleic Acid Synthesis and Division in Cells Synthesizing Viral Ribonucleic Acid
Authors: Farmilo A. J. , Stanners C. P.
Published: January 2020

Some temperature-sensitive mutants of vesicular stomatitis virus were tested for their ability to block the initiation of deoxyribonucleic acid (DNA) synthesis and division in serum-stimulated hamster embryo fibroblasts at the nonpermissive temperature. Although the parental strain blocked these processes, one particular mutant allowed essentially normal DNA synthesis and division. By autoradiography, it was shown that individual cells infected with this mutant could synthesize viral ribonucleic acid and at the same time initiate DNA synthesis and divide. Cells infected with such conditional defective mutants appear to be suitable for studies on the effects of persistent viral infections on molecular and cellular functions in proliferating cell populations.
Deoxyribonucleic Acid Polymerase Activity in a Deoxyribonucleic Acid Polymerase I-Deficient Mutant of
Bacillus subtilis
Infected with Temperate Bacteriophage SPO2
Authors: Rutberg Lars , Armentrout Richard W.
Published: January 2020

Increased deoxyribonucleic acid (DNA) polymerase activity is found in soluble extracts from a polymerase I-negative mutant of
Bacillus subtilis
after infection with temperate phage SPO2, or after induction of SPO2 prophage in lysogenic derivatives of this mutant. No increased enzyme activity is found after SPO2 infection in the presence of chloramphenicol. Infection of the polymerase-negative mutant with the DNA-negative sus mutant SPO2 L244 gives no increased enzyme activity, whereas infection with DNA-negative sus mutant SPO2 J385 gives enzyme activities comparable to those found in wild-type infected cells. These findings suggest that SPO2 determines a DNA polymerase activity essential for synthesis of phage DNA.
Arrangement of Herpesvirus Deoxyribonucleic Acid in the Core
Authors: Furlong D. , Swift H. , Roizman B.
Published: January 2020

The core of the herpes simplex virion consists of an electron-dense toroidal structure 50 nm high, with an inside diameter of 18 nm and an outside diameter of 70 nm, penetrated by a less dense cylindrical mass. The toroid contains deoxyribonucleic acid (DNA), as evident from the observation that uranyl ion staining is removed by ethylenediaminetetraacetic acid under conditions which result in the extraction of uranyl ions bound to nuclear DNA. Studies on negatively stained preparations of purified capsids suggest that the toroid consists of DNA arranged as if it were spooled around the cylindrical mass.
Inhibition by α-Amanitin of Simian Virus 40-Specific Ribonucleic Acid Synthesis in Nuclei of Infected Monkey Cells
Authors: Jackson Arlene Hildebrandt , Sugden Bill
Published: January 2020

Conditions affecting the synthesis of simian virus 40-specific ribonucleic acid (RNA) in nuclei isolated from lytically infected cells were investigated. Deoxyribonucleic acid-RNA hybridization results show that an α-amanitin-sensitive RNA polymerase activity is responsible for transcription of simian virus 40 deoxyribonucleic acid.
Ribonucleotides Covalently Linked to Deoxyribonucleic Acid in T4 Bacteriophage
Authors: Speyer J. F. , Chao J. , Chao L.
Published: January 2020

Bacteriophage T4 was grown in the presence of labeled uridine. The deoxyribonucleic acid (DNA) of the phage was shown to contain covalently attached ribonucleotides. The label appears not to be internal in the DNA strands. Presumably, it is at the ends of the DNA strands and this may be related to DNA initiation.
Isolation and Characterization of Adenovirus Messenger Ribonucleic Acid in Productive Infection
Authors: Lindberg Uno , Persson Torgny , Philipson Lennart
Published: January 2020

Messenger ribonucleic acid (mRNA) from cells productively infected with adenovirus type 2 was isolated by affinity chromatography on polyuridylic acid [poly (U)] bound to Sepharose. At least 90% of the polyadenylic acid [poly (A)]-containing polysomal mRNA was retained by the poly (U) Sepharose and thus separated from more than 95% of the ribosomal RNA and transfer RNA. In these experiments, 65% of the early (3 to 5 hr postinfection) and 85% of the late (14 to 16 hr postinfection) virus-specific RNA was retained by the poly (U) Sepharose. Early in the infection 18%, and late in the infection more than 95%, of the poly (A)-containing fraction, eluted from the poly (U) Sepharose with 90% formamide, was adenovirus-specific, as shown by exhaustive hybridization. Different patterns, containing several distinct species of viral mRNA, were detected early and late in the infectious cycle. No distinct viral mRNA lacking poly (A) was discovered.
Association of Replicative T4 Deoxyribonucleic Acid and Bacterial Membranes
Authors: Miller Robert C.
Published: January 2020

Experiments utilizing CsCl density gradient analysis and radioactive labels specific for bacteriophage T4 deoxyribonucleic acid (DNA) and membranes have shown that replicative T4 DNA is associated with host membranes. The association is inhibited by chloramphenicol and takes place just prior to semi-conservative replication of the phage DNA.
Formation of Sindbis Virus Proteins: Identification of a Precursor for One of the Envelope Proteins
Authors: Schlesinger Sondra , Schlesinger Milton J.
Published: January 2020

Exposure of Sindbis virus-infected chicken embryo cells to a short pulse of radioactive amino acids revealed the formation of primarily three proteins: the nucleocapsid (C) of the virus, one of the viral envelope proteins (E1), and a glycoprotein that did not appear in the virion. This third protein (PE2) has now been identified as a precursor of the other viral envelope protein (E2) on the basis of two observations: (i) the simultaneous disappearance of radioactive PE2 and appearance of labeled E2 in pulse-chase experiments, and (ii) the identity of
14
C-arginine tryptic peptides in fingerprints of the two proteins. The nucleocapsid was the most heavily labeled protein in the cell and appeared in the virus during the short pulse. The two
14
C-labeled envelope proteins, although having different kinetics of labeling in the cell, appeared simultaneously in the virus only after the chase. Addition of pactamycin, a drug inhibiting initiation of protein synthesis, preferentially inhibited the formation of capsid protein Assuming that Sindbis virus proteins are formed initially as a single polypeptide, our studies locate the nucleocapsid at the amino-terminal end of the polypeptide chain.
Comparison of the 3′ Termini of Discrete Segments of the Double-Stranded Ribonucleic Acid Genomes of Cytoplasmic Polyhedrosis Virus, Wound Tumor Virus, and Reovirus
Authors: Lewandowski Leon J. , Leppla S. H.
Published: January 2020

The 3′ terminal nucleosides of the isolated components of double-stranded ribonucleic acids of reovirus, wound tumor virus, and cytoplasmic polyhedrosis virus were determined by labeling with tritiated sodium borohydride. All wound tumor virus and cytoplasmic polyhedrosis virus components appear to contain approximately equal amounts of U
OH
and C
OH
termini. Reovirus segments have essentially only C
OH
termini.
Ribonuclease H: a Ubiquitous Activity in Virions of Ribonucleic Acid Tumor Viruses
Authors: Grandgenett Duane P. , Gerard Gary F. , Green Maurice
Published: January 2020

Ten ribonucleic acid (RNA) tumor viruses grown in five different host cell species and three non-oncogenic viruses from three different virus groups have been examined for ribonuclease H content. Three different substrates were used to assay ribonuclease H: calf thymus [
3
H]RNA-deoxyribonucleic acid (DNA) hybrid prepared with denatured calf thymus DNA and
Escherichia coli
DNA-directed RNA polymerase,
3
H-polydenylic acid [
3
H-poly(A)] complexed to polydeoxythymidylic acid [poly(dT)], and
3
H-polyuridylic acid [
3
H-poly(U)] complexed to polydeoxyadenylic acid [poly(dA)]. All ten RNA tumor viruses contained ribonuclease H activity which degraded the RNA of both the calf thymus hybrid and poly(A)-poly(dT), whereas only the ribonuclease H in the Moloney strain of murine sarcoma-leukemia virus and in RD-feline leukemia virus hydrolyzed the RNA strand of poly(U)-poly(dA). No appreciable ribonuclease H activity was detected in influenza, Sendai, or vesicular stomatitis virus. The ribonuclease H and RNA-directed DNA polymerase activities in Moloney murine sarcoma-leukemia virus were inseparable by phosphocellulose chromatography or glycerol gradient centrifugation, but appeared to be partially separated by diethylaminoethyl-cellulose chromatography.
Thermosensitive Block of the Sabin Strain of Poliovirus Type I
Authors: Fiszman Marc , Reynier Max , Bucchini Danielle , Girard Marc
Published: January 2020

The thermosensitive defect of the Sabin LSc2ab strain of poliovirus type I was studied. Transfer of infected KB cells from 36 to 38.5 C resulted in 30% inhibition of viral RNA replication but in 90% inhibition of formation of virions. Neither 74
S
procapsids nor 14
S
particles were detected in the cells transferred to the non-permissive temperature. However, procapsids, once accumulated at 36 C, were normally stable at 38.5 C and could transform into virions at that temperature. Viral proteins synthesized at the nonpermissive temperature were not different from those synthesized at permissive temperature, as judged from their pattern in polyacrylamide gel electrophoresis and from the fact that they normally matured into virions when the infected cells were brought back to permissive temperature, even under conditions of inhibition of protein synthesis. This leads to the conclusion that the defect in the Sabin strain studied lies in the assembly of its viral capsid proteins into capsomeres.