bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Determinants of Altered Virulence of Type O Foot-and-Mouth Disease Virus
Authors: Yang Fan , Zhu Zixiang , Cao Weijun , Liu Huanan , Wei Ting , Zheng Min , Zhang Keshan , Jin Ye , He Jijun , Guo Jianhong , Liu Xiangtao , Zheng Haixue
Published: January 2020

FMD is probably the most important livestock disease in the world due to the severe economic consequences caused. The alteration of several viral genes may give the virus selective advantage to maintain its prevalence in nature. Here, we identified that a 70-nucleotide deletion in the S fragment combined with a single leucine insertion in the leader protein (L
pro
) is a novel determinant of restricted growth on bovine cells, which significantly contributes to the altered virulence of serotype O FMDV in cattle. A synergistic and additive effect of the 70-nucleotide deletion in the S fragment and the single leucine insertion in L
pro
on the virulence and host specificity of the virus was determined. These results will benefit efforts to understand the vial pathogenicity mechanism and molecular characteristics of FMDV.
Enzyme Induction in Green Monkey Kidney Cultures Infected with Simian Adenovirus
Authors: Kit Saul , Piekarski Lech J. , Dubbs Del R. , de Torres Ramon A. , Anken Milton
Published: January 2020

Thymidine kinase was induced after infection of an established strain of green monkey kidney cells (CV-1) with simian adenovirus SV15. Increased levels of thymidine kinase were first observed 8 to 10 hr postinoculation (PI), and the levels increased four- to eightfold by 16 to 24 hr PI. A transient increase (1.5- to 3-fold) of deoxyribonucleic acid (DNA) polymerase activity was also observed about 18 hr PI, but the level of deoxycytidylic deaminase was not enhanced. The inductions of thymidine kinase and DNA polymerase were not obtained when protein synthesis was inhibited with 10
−5
M cycloheximide. However, the enzyme increases did take place when infected cultures were treated with 1-β-D-arabinofuranosylcytosine (ara-C), an inhibitor of DNA synthesis and SV15 replication. The incorporation of tritium-labeled thymidine (
H
3
-dT) into DNA was also stimulated 8 to 24 hr after infection with SV15.
Relationship Between Protein Synthesis and Viral Deoxyribonucleic Acid Synthesis
Authors: Kates J. R. , McAuslan B. R.
Published: January 2020

Evidence is presented that poxvirus deoxyribonucleic acid (DNA) synthesis required concurrent protein synthesis. The protein requirement in question can be distinguished from viral-induced thymidine kinase and DNA polymerase by virture of the instability of its messenger ribonucleic acid and its stoichiometric rather than catalytic relation to DNA synthesis. The protein(s) required did accumulate in the presence of fluorodeoxyuridine, an inhibitor of DNA synthesis, and, thus, appeared to be an “early” poxvirus function. The protein(s) was stable since it did function several hours after its synthesis had been terminated by puromycin. Two possible roles for such a protein requirement are discussed.
Cellular Compartmentalization of Herpesvirus Antigens During Viral Replication
Authors: Roizman Bernard , Spring Susan B. , Roane Philip R.
Published: January 2020

HEp-2 cells infected with herpes simplex virus develop five distinct immunofluorescent elements. Three (small nuclear granules, large nuclear granules, and an amorphous mass filling the nucleus) contain antigens which react with a rabbit serum prepared against boiled infected cell debris. A labeled pool of human antibody revealed antigens making up cytoplasmic granules and those responsible for a diffuse cytoplasmic fluorescence. All five immunofluorescent elements are demonstrable with a rabbit serum prepared against unheated infected cell debris. Viral antigens are segregated in the nucleus or in the cytoplasm; within the limits of detection, each antigen accumulates in one compartment only. The antigens responsible for the diffuse cytoplasmic fluorescence and for the amorphous nuclear mass are synthesized early in infection; they are formed in arginine-deprived cells and exist in a form which does not sediment on centrifugation at 79,000 ×
g
for 2 hr. The antigens comprising the nuclear and cytoplasmic granules arise relatively late in infection; they are not formed in arginine-deprived cells, and they are readily sedimented on centrifugation at 79,000 ×
g
for 2 hr. Heating (60 C for 2 hr) confers on one or more cytoplasmic viral antigens a new specificity; the altered antigens are demonstrable with labeled rabbit anti-boiled infected cell serum which normally does not combine with cytoplasmic antigens.
Synthesis of an
S
-Adenosylmethionine-cleaving Enzyme in T3-infected
Escherichia coli
and Its Disturbance by Co-infection with Enzymatically Incompetent Bacteriophage
Authors: Hausmann Rudolf
Published: January 2020

Synthesis of an
S
-adenosylmethionine-cleaving enzyme evoked by infection of
Escherichia coli
with phage T3 was independent of the multiplicity of infection with the wild type, T3
sam
+
. It was depressed, however, by mixed infection with related phages genetically incapable of directing enzyme production, such as T3
sam
−
, or phage T7. The depressor effect of enzymatically incompetent genomes depended on their proportion among the input phage and not on their absolute multiplicity. The effect was more pronounced with homologous, enzymatically incompetent phage (T3
sam
−
) than with heterologous phage (T7). After ultraviolet irradiation, enzymatically incompetent genomes lost their depressing power; at a survival level of 10
−7
, no depression by either homologous or heterologous phage upon T3
sam
+
-directed enzyme synthesis was detected.
Properties of Infectious T1 Deoxyribonucleic Acid
Authors: Brody Edward N. , Mackal Roy P. , Evans E. A.
Published: January 2020

T1 deoxyribonucleic acid (DNA) infection of spheroplasts was characterized by the following. A small number of the DNA molecules initiated infectious centers, and a small number of the spheroplasts were infected by T1 DNA. Once a favorable encounter of T1 DNA with spheroplast occurred, a minimum of 20 to 30 min was required for T1 DNA to enter the spheroplast. The mature T1 particles produced in the infection of spheroplasts by T1 DNA were released in a burst, but the average burst size was quite small compared with a normal burst of the phage-infected bacteria. T1 DNA preparations, capable of causing viral growth in spheroplasts, did not require detectable amounts of protein for infectivity, were homogeneous in band and boundary sedimentation, and had a guanine plus cytosine content of 48% and a minimal molecular weight of 35 × 10
6
. Denatured T1 DNA, like denatured λDNA, did not infect spheroplasts. Renatured T1 DNA was not infectious; this was in marked contrast to renatured λDNA.
Deoxyribonucleic Acid Replication and Expression of Early and Late Bacteriophage Functions in
Bacillus subtilis
Authors: Pène Jacques J. , Marmur Julius
Published: January 2020

The role of deoxyribonucleic acid (DNA) replication in the control of the synthesis of deoxycytidylate (dCMP) deaminase and lysozyme in
Bacillus subtilis
infected with bacteriophage 2C has been studied. These phage-induced enzymes are synthesized at different times during the latent period. It was shown by actinomycin inhibition that the formation of the late enzyme (lysozyme) required messenger ribonucleic acid (mRNA) synthesized de novo after the initiation of translation of mRNA which specifies the early function (dCMP deaminase). The inhibition of phage DNA synthesis by mitomycin C prevented the synthesis of lysozyme only when added before the onset of phage DNA replication, but it did not affect the synthesis or action of dCMP deaminase when added at any time during the latent period. Treatment of infected cells with mitomycin C after phage DNA synthesis had reached 8 to 10% of its maximal rate resulted in the production of normal amounts of lysozyme. These observations suggest that mRNA specifying early enzymes can be transcribed from parental (and probably also from progeny) DNA, whereas late functional messengers can be transcribed only after the formation of progeny DNA.
Control of Bacteriophage-induced Enzyme Synthesis in Cells Infected with a Temperature-sensitive Mutant
Authors: Mathews Christopher K. , Kessin Richard H.
Published: January 2020

The timing of “early” and “late” protein synthesis in
Escherichia coli
infected with T-even bacteriophage was studied with a temperature-sensitive phage mutant, T4
ts
L13. This strain was completely unable to direct the synthesis of phage deoxyribonucleic acid (DNA) at 44 C because it makes a deoxycytidylate hydroxymethylase which cannot act at that temperature. However, the mutant did multiply normally at 30 C. No detectable formation of the late protein, lysozyme, occurred at 44 C, in agreement with the idea, proposed by several workers, that DNA replication is necessary for activation of late genetic functions. However, the formation of an early enzyme, thymidylate synthetase, was shut off at about 10 min, as in normal infection. This implied that separate mechanisms were responsible for cessation of early functions and activation of late ones. That the infected cell at 44 C retained the capacity for synthesis of early enzymes was shown by the fact that DNA synthesis occurred after a culture was transferred from 44 to 30 C as late as 30 min after infection. This synthesis was inhibited by chloramphenicol, indicating that de novo synthesis of an early enzyme can take place at a late period in development. It is suggested that cells infected under normal conditions maintained an appreciable rate of early enzyme synthesis throughout the course of infection.
Electron Microscopy of a Plant-Pathogenic Virus in the Nervous System of Its Insect Vector
Authors: Hirumi Hiroyuki , Granados Robert R. , Maramorosch Karl
Published: January 2020

The central nervous system of wound tumor virus (WTV)-infected
Agallia constricta
was studied by electron microscopy to obtain information concerning the virus distribution in the nervous system. Wound tumor virions were mostly found in the cytoplasm of the ganglion cells and less frequently in the glial cells. WTV was occasionally observed in the perineurium cells, nerve axons, tracheoblasts, and lateral nerves. In the ganglion cells, virions appeared as individual isolated particles (V
1
), in tubular formation (V
2
), and occasionally in aggregates (V
3
). In the glial cells, the virions were mostly seen in the V
3
formation, and very seldom in the V
1
and V
2
formations. In the perineurium cells and tracheoblasts, only small V
3
formations were observed. The isolated virions were usually surrounded with polyribosomes, and often appeared around the foci of the viroplasm. Sometimes degenerating ganglion cells infected with the WTV were encountered. These damaged cells strongly indicated that WTV exerted a cytopathogenic effect on the nerve cells.
Concentration of Enteroviruses on Membrane Filters
Authors: Wallis Craig , Melnick Joseph L.
Published: January 2020

Enteroviruses can be made to adsorb or to pass through membrane filters by manipulation of the suspending medium. Salts facilitate virus adsorption, but membrane-coating components (MCC) interfere. Because cells release MCC into the culture medium during viral growth, MCC must be removed before virus can be adsorbed to membranes. Adsorbed virus can be eluted with diluents containing MCC (cell extracts or serum) or agents that reduce surface tension (sodium lauryl sulfate). By membrane adsorption and elution, enteroviruses can be readily concentrated and quantitatively recovered from crude virus harvests.
Structure and Function of Bacteriophage R17 Replicative Intermediate Ribonucleic Acid II. Properties of the Parental Labeled Molecule
Authors: Erikson R. L. , Erikson E.
Published: January 2020

Replicative intermediate ribonucleic acid (RNA), designated RI, which contained parental RNA labeled with
32
P was separated by filtration through agarose from the nucleic acids prepared from
32
P-labeled RNA phage-infected
Escherichia coli.
A larger amount of ribonuclease-sensitive parental label was found in the rapidly sedimenting forms of RI than in the slower sedimenting forms, indicating that parental RNA is displaced to form a single-stranded tail. This result indicates that some phage RNA is generated by asymmetric semiconservative replication of RI, but it does not mean that a portion of the RI duplexes cannot be conserved during generation of phage RNA. Parental RNA was also found in double-stranded RNA with no apparent tails which sedimented with an
S
value of 13. This RNA was soluble in 2
m
NaCl, and its sedimentation rate was unaffected by ribonuclease; nevertheless, single-strand scissions were produced by ribonuclease and were detected after the duplex was converted to its component single strands.
Characteristics of Tφ3, a Bacteriophage for
Bacillus stearothermophilus
Authors: Egbert Larre N. , Mitchell Herschel K.
Published: January 2020

A bacteriophage (Tφ3) which infects the thermophilic bacterium
Bacillus stearothermophilus
ATCC 8005 was isolated and characterized. Infection of the bacterium by the bacteriophage was carried out at 60 C, the optimal growth temperature of the host. At 60 C, the phage had a latent period of 18 min and a burst size of about 200. The phage was comparatively thermostable in broth. The halflife of Tφ3 was 400 min at 60 C, 120 min at 65 C, 40 min at 70 C, and 12 min at 75 C. The activation energy for the heat inactivation of Tφ3 was 56,000 cal. The buoyant density of Tφ3 in a cesium chloride density gradient was 1.526 g/ml. Electron micrographs of Tφ3 indicate that the phage has a head that is 57 mμ long. The dimensions and shape of the head are compatible with those of a regular icosahedron. Each edge of the head is 29 mμ long. The tail of Tφ3 is 125 mμ long and 10 mμ wide. There are about 30 cross-striations that are spaced at 3.9-mμ intervals along the tail. Under the conditions investigated, Tφ3 adsorbed slowly to the host. Only 2.8% of the phage adsorbed in 10 min at 60 C, the normal incubation temperature that was used. Tφ3 was not infective to four other thermophilic strains or to two mesophilic strains of bacteria.
Respiratory Syncytial Virus Isolation by Combined Continuous Flow-Isopycnic Banding Centrifugation
Authors: Cline G. B. , Coates Helen , Anderson N. G. , Chanock R. M. , Harris W. W.
Published: January 2020

A new zonal centrifuge rotor (B-IX) which combines continuous sample flow centrifugation with isopycnic banding has been used to isolate and concentrate respiratory syncytial virus from liter volumes of culture fluid. This isolation technique utilizes a sucrose density gradient to trap and isopycnically band the virus particles, and permits recovery of the particles from the rotor in an unaggregated condition.
Chronology of Viral Functions in Bacteriophage α
Authors: Gaeta F. S. , Donini P. , Veneziani-Brizi L. , Graziosi F.
Published: January 2020

Temperature-sensitive mutants of phage α were subjected to short pulses of permissive temperature at various times during the lytic cycle. All the mutants showed an optimal response to the permissive pulse at a specific time after infection. The optimal responses of the mutants belonging to the same complementation group fell close together in the same time interval; the optimal responses of mutants contained in 20 different complementation groups were more or less uniformly scattered throughout the lytic cycle. Temperature sensitivity, therefore, seems to afford, at least in the case of phage α, an independent way of grouping the genes in an ordered sequence with respect to the steps they control.
Amber Mutants of Bacteriophages T3 and T7 Defective in Phage-directed Deoxyribonucleic Acid Synthesis
Authors: Hausmann R. , Gomez Beatriz
Published: January 2020

Amber mutants of the related phages T3 and T7 were isolated and tested for their ability to restore—as the wild type does—thymidine incorporation in ultraviolet (UV)-irradiated, UV-sensitive, nonpermissive host bacteria (
Escherichia coli
B
s-1
). Most amber mutants had this ability. However, in both T3 and T7, mutants unable to promote thymidine incorporation under these conditions were found and classified into two well-defined complementation groups: T3DO-A and T3DO-B, T7DO-A and T7DO-B. Infection of B
s-1
cells with representatives of groups DO-A had the following characteristics: (i) phage-directed uridine uptake in UV-irradiated cells was reduced to less than 20% of normal; (ii) breakdown of host deoxyribonucleic acid (DNA) was delayed and incomplete; (iii) no serum-blocking antigens appeared; (iv) no cell lysis occurred; (v) the ability to exclude the heterologous wild type was impaired. Amber mutants of the DO-B groups, infecting B
s-1
, were able to: (i) promote an efficient phage-directed uridine uptake in UV-irradiated cells; (ii) bring about rapid breakdown of host DNA; (iii) synthesize serum-blocking antigens; (iv) lyse the host cells, generally after the normal latent period; (v) exclude efficiently the heterologous wild type. Although physiological similarities between the respective DO-A mutants or DO-B mutants of T3 and T7 were evident, no physiological cross-complementation occurred, and genetic crosses gave no evidence of genetic homologies between groups of T3 and T7.
Envelope Protein of Influenza Virus I. Hemagglutinating Activity of Reassociated Subunits
Authors: Eckert Edward A.
Published: January 2020

The hemagglutinating properties of influenza virus envelope protein, prepared by reassociation of polypeptide subunits, have been defined and compared with those of virus and ether-split hemagglutinin. In general, the characteristics of the intact and ether-split virus were found to be similar, whereas those of the envelope protein were distinctly different. The use of chicken, pigeon, and guinea pig erythrocytes both at 23 and 4 C disclosed that the hemagglutinating titers of envelope protein preparations were particularly dependent on the system employed. Under optimal conditions, with guinea pig cells at 4 C, the titers of envelope protein preparations were equivalent to those of the original virus concentrates. The hemagglutinating activity of envelope protein was particularly sensitive to elevated temperature, concentrated urea, sulfhydryl-reducing reagents, and tryptic digestion at high salt concentrations. In all these respects, the intact virus was more resistant than the envelope protein. Interpretation of the data indicates that the hemagglutinin is stabilized when associated with the lipid micelle at the surface of the virus.
Specific Role of Each Human Leukocyte Type in Viral Infections I. Monocyte as Host Cell for Vesicular Stomatitis Virus Replication In Vitro
Authors: Edelman Robert , Wheelock E. Frederick
Published: January 2020

Each major leukocyte type of the peripheral blood of healthy donors was studied in vitro for its ability to support vesicular stomatitis virus (VSV) replication. Purified cultures of each white blood cell type were prepared by the selective adsorption and elution of cells from silicone-treated glass beads. It was found that monocytes and macrophages (derived from the rapid transformation of monocytes in vitro) were the principal host cells for VSV replication. Interferon added to mixed leukocyte cultures, prior to virus inoculation, reduced virus yields and prevented destruction of macrophages. Cultures of small lymphocytes, containing no detectable monocytes or macrophages, produced amounts of virus equivalent to 1% of that produced in leukocyte cultures which contained 7% monocytes. Small lymphocytes did not undergo demonstrable cytopathic alterations in virus-infected cultures. VSV neither replicated nor produced cytopathic effects in polymorphonuclear leukocytes.
In Vivo and In Vitro Synthesis of Human Rhinovirus Type 2 Ribonucleic Acid
Authors: Yin F. H. , Knight E.
Published: January 2020

HeLa cells infected with human rhinovirus type 2 synthesize a mixture of single-and double-stranded ribonucleic acid (RNA). The RNA synthesized by the membrane-bound RNA polymerase complex in vitro is also a mixture of single- and double-stranded RNA, whereas the deoxycholate-treated RNA polymerase complex synthesized only double-stranded RNA. Although twice as much cell-associated viral RNA is synthesized in vivo at 34 C than at 37 C, there is no difference in the rate of RNA synthesized in vitro at 34 C and 37 C by the polymerase complex. The RNA polymerase complex, after treatment with deoxycholate, sediments as a broad peak with an average sedimentation value of 120
S
.
Direction of Translation and Size of Bacteriophage φX174 Cistrons
Authors: Benbow Robert M. , Mayol Robert F. , Picchi Joanna C. , Sinsheimer Robert L.
Published: January 2020

Translation of the bacteriophage φX174 genome follows cistron order D-E-F-G-H-A-B-C. To establish this, the position of a nonsense mutation on the genetic map was compared with the physical size (molecular weight) of the appropriate protein fragment generated in nonpermissive cells. Distances on the φX174 genetic map and distances on a physical map constructed from the molecular weights of φX174 proteins and protein fragments are proportional over most of the genome with the exception of the high recombination region within cistron A.
Dissociation of Vesicular Stomatitis Virus and Relation of the Virion Proteins to the Viral Transcriptase
Authors: Bishop D. H. L. , Roy Polly
Published: January 2020

A procedure has been developed for the sequential removal and purification of the glycoprotein and membrane protein of vesicular stomatitis virus (VSV). Neither of these proteins exhibited transcriptase activity. All of the activity was recovered in the ribonucleic acid (RNA)-ribonucleoprotein complex of VSV, which also has four other minor proteins associated with it. During transcription of 41% of the RNA of a virus preparation, no dissociation of the ribonucleoprotein from the viral RNA was observed.
Antigenic Relationship Between the Herpesviruses of Infectious Bovine Rhinotracheitis, Marek's Disease, and Burkitt's Lymphoma
Authors: Evans D. L. , Barnett J. W. , Bowen J. M. , Dmochowski L.
Published: January 2020

Common herpesvirus (HV) antigens in infectious bovine rhinotracheitis (IBR), Marek's disease (MDV), and Burkitt's lymphoma (EBV) were found. Immunodiffusion tests in 0.7% agarose demonstrated a line of identity with the HV preparations by using specific antisera prepared against, IBR, MDV, and EBV. These common antigens were found to consist of multiple components: i.e., at least two MDV antigens were identical to IBR and EBV components when subjected to immunoelectrophoresis in 0.7% agarose. Indirect immunofluorescence testing of EBV strain P
3
HR-1 and IBR-infected embryonic bovine kidney cells, with antisera prepared against partially purified IBR, MDV, and EBV antigens, revealed identical activity of the three antisera as demonstrated by brilliant nuclear fluorescence (perinuclear clumping) in P
3
HR-1 cells and evenly distributed cytoplasmic activity in 18-hr IBR-infected bovine kidney cell cultures. Initial physical-chemical studies of the partially purified antigens were carried out by differential centrifugation cycles (6,000, 25,000 and 100,000 ×
g
), rate zonal centrifugation in 5 to 20% sucrose density gradients, and analysis by disc electrophoresis in 5 and 7% polyacrylamide gels. These studies revealed similar molecular weight (>1,000,000) and size characteristics and similar electrophoretic mobilities among the three partially purified HV antigens.
Immunological Studies on Viral Polypeptide Synthesis in Cells Replicating Murine Sarcoma-Leukemia Virus
Authors: Shanmugam G. , Vecchio Giancarlo , Attardi Domenica , Green Maurice
Published: January 2020

Antibodies to disrupted murine sarcoma-leukemia virus (MSV[MLV]) were used to study the synthesis of viral polypeptides in the transformed, virus-producing rat cell line 78A1. When cultures were labeled for 10 min with radioactive amino acids, about 9% of the total labeled proteins were precipitated with antiserum against purified MSV(MLV), and 3 to 4% were precipitated with the same antiserum after it had been absorbed with an extract from uninfected rat cells. The difference is due to the presence in the unabsorbed antiserum of antibodies to cellular proteins that are present in purified virus preparations. Intracellular viral proteins labeled with radioactive amino acids were isolated by immunoprecipitation and analyzed by electrophoresis in sodium dodecyl sulfate-polyacrylamide gels. The mobilities of intracellular viral polypeptides were identical to those of the purified virion. However, labeled polypeptides having electrophoretic mobilities lower than that of the major virion polypeptide, the group-specific antigen of molecular weight 31,000, were present in higher proportion in the total cell extract and in the membrane fraction than in the virion. These polypeptides appear to be of cellular origin for they were present only in minute amounts in the immunoprecipitates obtained with the absorbed serum. After a 10-min labeling period, radioactive proteins were assembled into extracellular virions rapidly for the first 4 hr followed by a slower rate. More than 2% of the total proteins of the cell labeled in a 10-min pulse were assembled into virions at the completion of a 24-hr chase. The high-molecular-weight polypeptides with the same mobilities as those detected in the immunoprecipitate of intracellular proteins were found in virions released from cells after a 10-min pulse. A larger proportion of these high-molecular-weight proteins was detected in virions released after short chase periods (30-120 min) than after longer chase periods (6-24 hr). Two possible interpretations of these data are that the high-molecular-weight cell-derived polypeptides (i) have a turnover rate higher than that of the major virion polypeptides or (ii) are cleaved proteolytically from the virions during long incubation in the culture media.
Virus Deoxyribonucleic Acid Sequences in Subdiploid and Subtetraploid Revertants of Polyoma- Transformed Cells
Authors: Shani Moshe , Rabinowitz Zelig , Sachs Leo
Published: January 2020

Polyoma-transformed cells can revert in the properties characteristic of transformation, although they maintain the polyoma-specific T antigen. Transformed cells contain the same number of copies of polyoma virus deoxyribonucleic acid (DNA) per cell (eight) as revertants with a subdiploid or a subtetraploid chromosome number. The results indicate that the duplication of chromosomes in the subtetraploid revertants did not include the chromosomes that carry the viral genome. The virus DNA in both transformed and revertant cells was associated with high-molecular-weight cell DNA. Reversion of the properties of transformed cells was, therefore, not associated either with a decrease in number of virus DNA copies per cell or with a lack of association of the virus DNA with cell DNA.
Membrane-Associated Replication Complex in Arbovirus Infection
Authors: Friedman Robert M. , Levin Judith G. , Grimley Philip M. , Berezesky Irene K.
Published: January 2020

Cytoplasmic extracts of chicken embryo fibroblast cells infected with Semliki Forest virus were subjected to isopycnic centrifugation in discontinuous sucrose gradients. Seven distinct bands were usually formed. The four upper bands contained predominantly smooth membranes and the lowest band was enriched in rough endoplasmic reticulum. One fraction (fraction 5), banding at a density of 1.16 g/cm
3
, was found to be heavily enriched in pulse-labeled ribonucleic acid (RNA), viral RNA polymerase, and viral RNA forms associated with RNA replication. Thus, fraction 5 evidently contained a membrane-associated viral replication complex of a type previously defined in picornavirus infections. Fraction 5 was also consistently enriched with unique membranous structures previously observed in intact cells as type 1 cytopathic vacuoles (CPV-1). When the CPV-1 in fraction 5 were isolated from cells briefly incubated with
3
H-uridine and
3
H-adenosine prior to cell disruption, a large proportion was found to be labeled by high-resolution autoradiography. Thus, ultrastructural, biochemical, and biological evidence were all consistent with the interpretation that the CPV-1 membranes represent a significant element of the viral replication complex.
Change in Methylation of
Salmonella
Bacteriophage P3 Deoxyribonucleic Acid with Host-Controlled Modification by
Escherichia coli
Authors: Nutter Robert L. , Bullas Leonard R. , Siapco Benjamin S. , Pearson Clark A.
Published: January 2020

Modification of bacteriophage P3 by passage through
Escherichia coli
K was correlated with a 54% decrease in the content of 6-methylaminopurine in the phage deoxyribonucleic acid.
Isolation and Preliminary Characterization of Temperature-Sensitive Mutants of Influenza Virus
Authors: Sugiura A. , Tobita K. , Kilbourne Edwin D.
Published: January 2020

Isolation of temperature-sensitive (ts) mutants was attempted from the WSN strain of influenza A virus which was grown and assayed in MDBK cells. After growth of wild-type virus in the presence of 5-fluorouracil, 15 ts mutants were selected for which the ratio of plaquing efficiency at 39.5 C to that at 33 C was 10
−3
or less. In pairwise crosses of ts mutants, recombination and complementation were either very efficient or undetectable. It is suggested, therefore, that the viral genome consists of physically discrete units and recombination occurs as an exchange of these units. All 15 mutants have been assigned with certainty into five recombination groups. Three mutants are suspected to be double mutants. Any two complementing mutants always recombined with each other, and noncomplementing mutants did not recombine. In physiological tests, mutants showed diverse patterns of functional defects at the nonpermissive temperature. However, it was not always possible to correlate these physiological defects with the results of genetic characterization.
Isolation of Temperature-Sensitive Mutants of Murine Sarcoma Virus
Authors: Scolnick Edward M. , Stephenson John R. , Aaronson Stuart A.
Published: January 2020

Three separate murine sarcoma virus nonproducer cell lines have been isolated which are temperature sensitive for the maintenance of transformation. In each case, a viral rather than a cellular genetic mutation is the reason for the temperature-sensitive effect. Superinfection of one of the mutants with murine leukemia virus overcomes the temperature-sensitive change in the transformed state.
Denaturation Pattern of the Deoxyribonucleic Acid from Chicken Embryo Lethal Orphan Virus
Authors: Younghusband H. Banfield , Bellett A. J. D.
Published: January 2020

The denaturation pattern of chicken embryo lethal orphan virus deoxyribonucleic acid confirms that the sequences are unique. The molecular weight of the deoxyribonucleic acid was determined by length measurements to be 29 × 10
6
.
Defective Concatemer Formation in Cells Infected with Deoxyribonucleic Acid-Delay Mutants of Bacteriophage T4
Authors: Naot Y. , Shalitin C.
Published: January 2020

Nonpermissive host cells infected with phage T4 mutants in genes 52, 39, and 58 through 61 are shown to form short intracellular single-stranded deoxyribonucleic acid in contrast to wild-type infected cells, which form dimers and trimers of T4 genome size.
Deoxyribonucleic Acid-Dependent Nucleotide Phosphohydrolase Activity in Purified Vaccinia Virus
Authors: Paoletti Enzo , Moss Bernard
Published: January 2020

A nucleotide phosphohydrolase (adenosine triphosphatase), which is associated with vaccinia virus cores, has been solubilized and shown to be deoxyribonucleic acid dependent.
Exclusion of Bacteriophages by T2 Ghosts
Authors: Fabricant Robert , Kennell David
Published: January 2020

T2 ghosts do not exclude T4, T7, or lambda-induction in
Escherichia coli
which survive ghost infection. Latent periods are extended, probably by the temporary inhibition of protein synthesis.
Distribution of Deoxyribonucleic Acid Complementary to the Ribonucleic Acid of Avian Myeloblastosis Virus in Tissues of Normal and Tumor-Bearing Chickens
Authors: Baluda M. A. , Drohan W. N.
Published: January 2020

3
H-labeled 70
S
ribonucleic acid (RNA) from purified avian myeloblastosis virus (AMV) was used as a probe in deoxyribonucleic acid (DNA)-RNA hybridization experiments to detect the presence of DNA complementary to the AMV genome in various tissues from noninfected normal chickens and from chickens infected with AMV. There was a remarkable constancy in the average cellular concentration of virus-specific DNA found in every tissue from the same uninfected chicken, and even in different chickens from the same strain. In contrast, different tissues from chickens bearing AMV-induced kidney tumors (embryonal nephromas) revealed an unequal distribution in the average virus-specific DNA content per cell. The increase was limited to tumor cells and to tissues that contain target cells for AMV, i.e., red blood cells, kidney cells, and possibly leukocytes. The red blood cells from AMV-infected chickens suffering from acute myeloblastic leukemia, although producing no virus, contained as many viral genome equivalents per cell as did leukemic myeloblasts known to produce large quantities of AMV. An increased viral DNA content was observed in the target cells of chickens that did not show any sign of tumor formation 6 months after infection with AMV. This study demonstrates that vertically transmitted viral DNA is uniformly and stably distributed among all tissues of the offspring, but that horizontal infection after hatching results in an increase in viral DNA content only in some dividing, target tissues that may or may not give rise to neoplasias.
Proteins Specified by Herpes Simplex Virus VIII. Characterization and Composition of Multiple Capsid Forms of Subtypes 1 and 2
Authors: Gibson Wade , Roizman Bernard
Published: January 2020

Two classes of herpesvirus capsids, designated A and B, were isolated from the nuclei of human cells infected with herpes simplex virus (HSV). A and B capsids share in common four structural proteins, i.e., no. 5, 19, 23, and 24. B capsids contain 7.7 to 9.7 times more deoxyribonucleic acid than A capsids; moreover, they contain proteins no. 21 and 22a in addition. All of the proteins contained in the capsid except no. 22a are present in the enveloped nucleocapsids (virions) in approximately the same molar ratios. The capsid proteins of HSV-1 cannot be differentiated from their HSV-2 counterparts with respect to electrophoretic mobility. A third class of capsids, designated C capsids, was isolated from virions contained in the cytoplasm of infected cells by the same procedure used to obtain A and B capsids. The C capsids contain all of the proteins present in A capsids plus proteins 1 to 3 and 21.
Visualization by Immune Electron Microscopy of a 27-nm Particle Associated with Acute Infectious Nonbacterial Gastroenteritis
Authors: Kapikian Albert Z. , Wyatt Richard G. , Dolin Raphael , Thornhill Thomas S. , Kalica Anthony R. , Chanock Robert M.
Published: January 2020

A 27-nm particle was observed by immune electron microscopy in an infectious stool filtrate derived from an outbreak in Norwalk, Ohio, of acute infectious nonbacterial gastroenteritis. Both experimentally and naturally infected individuals developed serological evidence of infection; this along with other evidence suggested that the particle was the etiological agent of Norwalk gastroenteritis.
Physical Properties of Lactic Dehydrogenase-Elevating Virus and Its Ribonucleic Acid
Authors: Darnell Margo B. , Plagemann Peter G. W.
Published: January 2020

Infectious lactic dehydrogenase-elevating virus propagated in primary cultures of mouse peritoneal macrophages in the presence of
3
H-uridine and isolated by isopycnic centrifugation was found to have a density of 1.12 g/cm
3
. Ribonucleic acid extracted from the virus by treatment with sodium dodecyl sulfate was single stranded with a sedimentation coefficient of approximately 48
S
.
Activation of Guinea Pig Herpesvirus Antigen in Leukemic Lymphoblasts of Guinea Pig
Authors: Nayak D. P.
Published: January 2020

Herpesvirus (GPHV) antigen is either present in very small amounts, or absent in leukemic lymphoblasts taken directly from strain 2 guinea pigs. However, after maintenance in tissue culture for 72 hr, almost 100% of these lymphoblasts contained GPHV antigen. The expression of GPHV antigen could be demonstrated by indirect immunofluorescent technique as well as by the direct
125
I labeled antibody technique. However, infectious virus or virus capsids could not be detected in these cells either by infectivity tests or electron microscopy.
Degradation of
Escherichia coli
Chromosome After Infection by Bacteriophage T4: Role of Bacteriophage Gene D2a
Authors: Souther Arthur , Bruner Robert , Elliott Joel
Published: January 2020

Mutations in the D2a gene of bacteriophage T4 have recently been shown to result in the stabilization of cytosine-containing phage deoxyribonucleic acid (DNA) made after infection by phage gene 56 (deoxycytidine triphosphatase) mutants. In the experiments reported here, we investigate the role of the D2a gene in the degradation of the host chromosome. We find that if T4 endonuclease II, a product of the phage gene
denA
, is active, host chromosome degradation appears normal, regardless of the presence of the D2a gene product. However, if T4 endonuclease II is absent, a small amount of host chromosome degradation occurs, but only if the D2a product is present. These results are interpreted in terms of the hypothesis that D2a controls a nuclease which degrades cytosine-containing DNA. Neither D2a nor
denA
mutations affect the shut-off of host DNA synthesis.
Host- and Phage-Mediated Repair of Radiation Damage in Bacteriophage T4
Authors: Wallace Susan S. , Melamede Robert J.
Published: January 2020

T4+ exhibits increased ultraviolet sensitivity on derivatives of
Escherichia coli
K12 or B lacking deoxyribonucleic acid (DNA) polymerase I. However, the sensitivity of T4
v
is not affected by the absence of host DNA polymerase. T4
x
and T4
y
also show increased sensitivity on DNA polymerase-deficient strains, but to a lesser extent than observed with wild-type T4. When T4
x
or T4
y
, but not T4+, are plated on a double mutant lacking both DNA polymerase and the
uvrA
gene product, a partial suppression of the polymerase effect is observed. Host ligase appears to be able to suppress to some extent the T4
y
phenotype but has no effect on wild-type T4 or other T4 mutants. T4
xv
incubated in
E. coli
B or B
s-1
in the presence of chloramphenicol (50 μg/ml) shows increased resistance over directly plated irradiated phage. Increased survival under the same conditions was not observed with T4+ or other T4 mutants. The repair of X-ray-damaged T4 was investigated by examining survival curves of T4+, T4
x
, T4
y
, T4ts43, and T4ts30. The repair processes were further defined by observing the effects of plating irradiated phage on various hosts including strains lacking DNA polymerase I or polynucleotide ligase. Two classes of effects were observed. Firstly, the
x
and
y
gene products seem to be involved in a repair system utilizing host ligase. Secondly, in the absence of host DNA polymerase, phage sensitivity is increased in an unknown manner which is enhanced by the presence of host
uvrA
gene product.
Superinfection Exclusion by Incomplete Genomes of Bacteriophage T4
Authors: Childs J. D.
Published: January 2020

The genetic basis of superinfection exclusion by bacteriophage T4 was investigated by using incomplete genomes derived from the gene 66 mutant
E920g
. Incomplete genomes, which included a region of T4 between genes 42 and 44, were able to exclude superinfecting phage with an efficiency similar to that of complete genomes. Those genomes which did not include this region were unable to exclude superinfecting phage. A mutant with reduced ability to exclude super-infecting phage was isolated after mutagenesis with hydroxylamine. The mutation maps midway between
amN122
in gene 42 and
amB22
in gene 43. The efficiency of exclusion of superinfecting phage (as measured by the percentage of superinfected cells which failed to release any phage carrying selected markers of the superinfecting phage) by this mutant was 50 to 60%, whereas for wild type it was 85 to 95%. Uptake of
3
H-leucine by cells infected with the mutant was inhibited by superinfection with ghosts and it has therefore been designated
imm1
, for lack of immunity to superinfecting phage and ghosts. The formation of infective centers by cells infected with
imm1
or another
imm
−
mutant (
imm2
) was not inhibited by superinfection with ghosts.
Aspects of the Encapsidation of Simian Virus 40 Deoxyribonucleic Acid
Authors: Girard Marc , Stehelin Dominique , Manteuil Simone , Pages Jacqueline
Published: January 2020

Growing subcloned CV
1
-cells were infected with simian virus 40, and the time course of virus formation was determined. When infected cells were fractionated into cytoplasmic and nuclear fractions, most of the progeny virus particles were recovered in the cytoplasmic extract and not in the nuclei. This result was independent of the technique used for the preparation of nuclei and of the time after infection at which the extracts were prepared. Leakage of the virions from the nucleus occurred during the course of cell fractionation, suggesting that the nuclear membrane of the infected cells is damaged. Virions were found to accumulate in a nonlinear fashion, at the time when the number of viral deoxyribonucleic acid (DNA) molecules increases linearly with time after infection. This suggests that the size of the intracellular pool of capsid proteins increases constantly during the late phase of virus replication. Progeny viral DNA to become encapsidated is withdrawn at random from the pool of replicated DNA molecules.
Mixed Infections of
Bacillus subtilis
Involving Bacteriophage SPO2c
1
Authors: Kolenbrander P. E. , Hemphill H. Ernest , Whiteley H. R.
Published: January 2020

The synthesis of ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) was studied in
Bacillus subtilis
cells mixedly infected with phages SPO2c
1
and either SP82 or β22. It was found that cells preinfected 5 min with either β22 or SP82 could not support significant amounts of RNA or DNA synthesis from the genome of superinfecting SPO2c
1
. Conversely, cells preinfected with SPO2c
1
remained susceptible to superinfection even at the midpoint of the latent period. When SP82 was added to cells preinfected 5 min with SPO2c
1
, the former greatly inhibited the replication and transcription of the SPO2c
1
, DNA, but if superinfection with SP82 was delayed until the 15th min of the SPO2c
1
latent period, RNA and DNA specific for both phages were synthesized. Both viral genomes were transcribed throughout the remainder of the lytic cycle when β22 was added to cells preinfected either 5 or 15 min with SPO2c
1
. In both the SPO2c
1
-SP82 and the SPO2c
1
-β22 mixed infections, the types of phage-specific RNAs synthesized at a given time in the latent period were similar to those synthesized in single infections with each phage. The association of SPO2c
1
DNA with the host cell membrane in certain of the doubly infected cells was different from that observed in singly infected cells. In the SPO2c
1
-SP82 infection, SPO2c
1
DNA was not released from the membrane; in the SPO2c
1
-β22 mixed infections, significantly less SPO2c
1
DNA was membrane-bound when β22 was added before SPO2c
1
. However, binding and release of SPO2c
1
DNA was normal in cells infected first with SPO2c
1
and then with β22. The synthesis of phage-specific nucleic acids and the binding of phage DNA to the membrane are discussed with respect to dominance relationships among these phages.
Gene Expression During the Development of
Bacillus subtilis
Bacteriophage φ29 I. Analysis of Viral-Specific Transcription by Deoxyribonucleic Acid-Ribonucleic Acid Competition Hybridization
Authors: Loskutoff D. J. , Pène J. J. , Andrews D. P.
Published: January 2020

The ribonucleic acid (RNA) specified by bacteriophage φ29 was analyzed to determine its composition at various times in the viral lytic cycle. Although viral-specific RNA was detected immediately after infection, a large increase in the rate was observed at 10 min when DNA synthesis began. φ29 was found to resemble other viruses in that gene expression occurred in two stages which could be defined temporally as “early” and “late.” Early RNA appeared before the onset of viral deoxyribonucleic acid (DNA) replication and accounted for approximately 40% of the viral genetic potential. This RNA was also present late in the infectious cycle because of the slow turnover rate of φ29-specific RNA (approximately 10 min half-life) and the continued synthesis of much early viral RNA throughout infection. Late RNA was first detected at approximately the same time as viral DNA replication, although late transcription was not dependent upon DNA synthesis. This RNA was only partially displaced by early RNA in the appropriate competition experiments, suggesting that it contained sequences not present in the early class. Expression of viral genes was sensitive to rifamycin throughout the lytic cycle, the sensitivity resulting from a dependence upon the rifamycin phenotype of the host RNA polymerase.
Nonlinkage of Neurovirulence Exclusively to Viral Hemagglutinin or Neuraminidase in Genetic Recombinants of A/NWS (H0N1) Influenza Virus
Authors: Mayer V. , Schulman J. L. , Kilbourne E. D.
Published: January 2020

Genetic recombination of the neurovirulent A/NWS/cc-p (H0N1) and the non-neurovirulent A/Jap.305/57 (H2N2) influenza viruses in which hemagglutinin and neuraminidase were segregated (H0N2, H2N1) were studied for neurovirulence in mice immunosuppressed with cyclophosphamide (CPA) which permitted full expression of virulence. Both H0N2 and H2N1 recombinants replicated in the brain (in contrast to the H2N2 parent) and both produced lethal effects in CPA-treated animals. Therefore we conclude that A/NWS (H0N1) neurovirulence is not exclusively linked with either the hemagglutinin or the neuraminidase of the virus. The H0N2 and H2N1 recombinants have revealed the existence of two separate attributes of neurovirulence: (i) the capacity of virus to initiate intracerebral infection and (ii) the capacity of infection, once initiated, to produce lethal disease. These studies provide further evidence for the polygenic nature of A/NWS neurovirulence.
Mapping of New
Escherichia coli
K and 15 Restriction Sites on Specific Fragments of Bacteriophage φX174 DNA
Authors: Sclair Morton , Edgell Marshall Hall , Hutchison Clyde A.
Published: January 2020

We have isolated several new φX174 mutants which contain sites sensitive to restriction by
Escherichia coli.
One contains an
E. coli
15 restriction site and three are double mutants containing an
E. coli
K site as well as the
E. coli
15 site. The replicative form (RF) DNA of one of the mutants containing a K site has been shown to be restricted in spheroplasts of a K-12 strain. The infectivity of this RF, but not wild-type RF, has also been shown to be inactivated by an
E. coli
K extract and by purified K restriction enzyme in vitro. The product of the RF treated with purified K restriction enzyme in vitro is a full length linear molecule. The mutant sites have also been localized to specific regions of the φX174 genome by a fragment mapping technique, making use of specific fragments of φX174 RF DNA obtained by digestion with a specific endonuclease.