bluuebunny/crossref_metadata_2025 huggingface dataset:
Latency and reactivation of JC virus in peripheral blood of human immunodeficiency virus type 1-infected patients
Authors: Dubois V , Dutronc H , Lafon M E , Poinsot V , Pellegrin J L , Ragnaud J M , Ferrer A M , Fleury H J
Published: January 2020

JC virus (JCV) acts as an opportunistic virus in immunocompromised human immunodeficiency virus type 1 (HIV-1)-infected patients. The role of peripheral blood cells in central nervous system invasion, before the onset of progressive multifocal leukoencephalopathy (PML), remains controversial. In order to clarify JCV latency or reactivation status in peripheral blood, 72 HIV-1-infected patients were studied, together with 7 HIV-1-positive PML patients and 50 blood donors. Blood leukocytes, plasma, and B lymphocytes were investigated by two complementary DNA amplification procedures within the early T and late VP1 JCV genes and two reverse transcription techniques for the detection of corresponding early transcripts and mRNAs. JCV DNA was detected in 40.3% of the HIV-1-infected patients but only 8% of the blood donors (P < 0.001). Leukocytes represented 82.7% of the positive samples, but plasma from 12 patients (41.4%) contained JCV DNA. B lymphocytes seemed to be involved in the natural history of JCV but did not represent the unique cell target. JCV DNA was intermittently found in blood, and JCV mRNAs for VP1 capsid protein were detected exclusively in one PML patient. Such observations demonstrate that JCV, when detected in blood, does not undergo active multiplication. They support the JCV hematogenous spread hypothesis, but do not indicate any direct link between peripheral virus and dissemination in the central nervous system at the time of immunodepression.
Molecular analysis of toxigenic Vibrio cholerae O139 Bengal strains isolated in Bangladesh between 1993 and 1996: evidence for emergence of a new clone of the Bengal vibrios
Authors: Faruque S M , Ahmed K M , Siddique A K , Zaman K , Alim A R , Albert M J
Published: January 2020

Vibrio cholerae O139 Bengal emerged in 1992 and rapidly spread in an epidemic form, in which it replaced existing strains of V. cholerae O1 in Bangladesh during 1992 and 1993. The subsequent emergence of a new clone of V. cholerae O1 of the El Tor biotype that transiently displaced the O139 vibrios during 1994 to 1995 and the recent reemergence of V. cholerae O139 and its coexistence with the El Tor vibrios demonstrated temporal changes in the epidemiology of cholera in Bangladesh. We studied clonal diversity among V. cholerae O139 strains isolated from cholera patients and environmental surface water since their first appearance until their transient disappearance in 1994 as well as the O139 strains that reemerged during 1995 to 1996 and were isolated in the capital Dhaka and four rural districts of Bangladesh to investigate the origin of the reemerged strains. Analysis of restriction fragment length polymorphisms in genes for conserved rRNA and cholera toxin (CT) (ctxA) or in DNA sequences flanking these genes revealed four different ribotypes and four different ctx genotypes among the 93 strains of V. cholerae O139 studied. Ribotypes I and II and ctx genotypes A through C were shared by strains isolated from the epidemic outbreak during 1992 and 1993 in Bangladesh and India, ribotype III was represented by a single CT-negative O139 strain from Argentina, and 16 of 27 (59.2%) of the reemerged strains isolated during 1995 and 1996 belonged to a new ribotype of O139 vibrios designated ribotype IV. All 16 strains belonging to ribotype IV also belonged to a new ctx genotype (genotype 4). These results provide evidence for the emergence of a new clone of toxigenic V. cholerae O139 in Bangladesh. Further analysis of the rfb gene cluster by PCR revealed the absence of a large region of the O1-specific rfb operon and the presence of an O139-specific genomic region in all O139 strains. The PCR amplicon corresponding to the rfaD gene of a CT-negative O139 strain from Argentina was smaller in length than those of the toxigenic O139 strains but was identical to those of seven non-O1 and non-O139 strains. All O139 strains except the CT-negative strain carried structural and regulatory genes for CT and toxin-coregulated pili (ctxA, tcpA, tcpI, and toxR). These results suggest that the O139 Bengal strains possibly emerged from an El Tor strain but that the CT-negative non-Bengal O139 strain might have emerged from a non-O1, non-O139 strain. Thus, strains belonging to the O139 serogroup may have emerged from similar serotype-specific genetic changes in more than one progenitor strain of V. cholerae.
Granulocytic ehrlichiosis in two dogs in Switzerland
Authors: Pusterla N , Huder J , Wolfensberger C , Litschi B , Parvis A , Lutz H
Published: January 2020

This case report describes two dogs with granulocytic ehrlichiosis. Dog 1 was a male Labrador retriever with clinical signs of lymphosarcoma. Dog 2 was a female Airedale terrier, whose clinical signs included apathy, pyrexia, diarrhea, and abdominal pain. Examination of blood smears revealed Ehrlichia organisms in the neutrophils of both dogs. There was thrombocytopenia in both dogs, and dog 2 also had leukopenia. In both dogs, bands of identical length were amplified from DNA of leukocytes via nested PCR. The bands had identical nucleotide sequences, which differed from the gene sequences of Ehrlichia equi and E. phagocytophila in three and two positions, respectively. Interestingly, the nucleotide sequence of the 16S rRNA was 100% homologous to that of a human granulocytic ehrlichia.
Identification of a Klebsiella pneumoniae strain associated with nosocomial urinary tract infection
Authors: Kil K S , Darouiche R O , Hull R A , Mansouri M D , Musher D M
Published: January 2020

To differentiate between relapse of infection and reinfection of the urinary tract due to Klebsiella pneumoniae, 33 K. pneumoniae isolates collected from 20 patients with spinal cord injury (SCI) over 2 years were typed by genomic fingerprinting by repetitive-element PCR. Clinical isolates obtained from the same patients with recurrent episodes of urinary tract infection (UTI) revealed identical genomic fingerprints indicating relapse of UTI due to K. pneumoniae, despite appropriate antibiotic therapy. Seventeen isolates obtained from 8 of the 20 SCI patients shared a common genotype, termed RD6. Among non-SCI patients residing in other nursing units, the RD6 genotype was found in 5 of 10 patients with K. pneumoniae UTI but in only 1 of 20 patients with K. pneumoniae infection that did not involve the urinary tract, suggesting a strong association of this genotype with UTI. All RD6 isolates exhibited strong adherence (> or =50 adherent bacteria per cell) to HEp-2 cells, whereas other K. pneumoniae isolates generally did not adhere to or adhered very weakly to HEp-2 cells (< or =5 adherent bacteria per cell). Adherence was inhibited either by 4% D-mannose or by anti-type 1 fimbrial rabbit serum. These results suggest that the capacity of K. pneumoniae RD6 isolates to cause UTI may be mediated by its striking adherence to mammalian cells.
Evidence for recombination in the flagellin locus of Campylobacter jejuni: implications for the flagellin gene typing scheme
Authors: Harrington C S , Thomson-Carter F M , Carter P E
Published: January 2020

The flagellin subunit of the flagellar filament in Campylobacter jejuni is encoded by two highly homologous tandem genes, flaA and flaB. The flaA gene was sequenced in 18 strains of C. jejuni, including isolates from three outbreak groups. Sequences obtained were compared with flaA sequences available in the GenBank database, and all were analyzed for mosaic gene structure by using recently described statistical tests for detecting gene conversion among aligned sets of sequences. Strong evidence was found supporting recombination between flaA genes of different strains (i.e., intergenomic recombination). Intragenomic recombination between the flaA and flaB genes of C. jejuni TGH9011 was also demonstrated. Both mechanisms of recombination may act as a potential means by which pathogenic strains can generate increased antigenic diversity, so allowing them to escape the immunological responses of the host. Furthermore, demonstration of recombination within and between flagellin loci of natural strains suggests that flagellin gene typing (restriction fragment length polymorphism analysis of PCR-amplified flagellin genes) cannot be considered a stable method for long-term monitoring of pathogenic Campylobacter populations.
Comparison of use of enzyme-linked immunosorbent assay-based kits and PCR amplification of rRNA genes for simultaneous detection of Entamoeba histolytica and E. dispar
Authors: Mirelman D , Nuchamowitz Y , Stolarsky T
Published: January 2020

A comparison of the use of three commercially available enzyme-linked immunosorbent assay-based kits and PCR amplification of rRNA genes to detect and differentiate Entamoeba histolytica from E. dispar was carried out. Only the Techlab kit did not cross-react with E. dispar antigens, but it was 100 times less sensitive than PCR in detection of and differentiation between the two types of Entamoeba.
Wooden sticks as the source of a pseudoepidemic of infection with Rhizopus microsporus var. rhizopodiformis among immunocompromised patients
Authors: Verweij P E , Voss A , Donnelly J P , de Pauw B E , Meis J F
Published: January 2020

Wooden sticks used to suspend feces obtained for surveillance cultures were found to be the source of Rhizopus microsporus var. rhizopodiformis causing a pseudo-outbreak among 17 immunocompromised patients cared for in three different wards. Nonsterile wooden products should therefore not be used for collecting, handling, and processing specimens for microbiological examination.
A new experimental in vitro culture medium for cultivation of Leishmania species
Authors: Limoncu M E , Balcioğlu I C , Yereli K , Ozbel Y , Ozbilgin A
Published: January 2020

A new liquid culture medium prepared with chemicals that can be obtained economically and commercially was tested in in vitro cultivation of Leishmania promastigotes to obtain a large number of organisms to use in serological studies. The number of Leishmania infantum and Leishmania tropica promastigotes taken from Novy-MacNeal-Nicolle (NNN) medium reached 1 x 10(7)/ml at the end of the 8th day in our new medium, though in NNN medium the number of organisms reached only 5 x 10(6)/ml. After 10 subsequent passages, the culture medium prepared was evaluated as being quite inexpensive, simple, and successful compared with other commercially available liquid culture media.
Genetic Variability of Long Terminal Repeat Region between HIV-2 Groups Impacts Transcriptional Activity
Authors: Le Hingrat Quentin , Visseaux Benoit , Bertine Mélanie , Chauveau Lise , Schwartz Olivier , Collin Fidéline , Damond Florence , Matheron Sophie , Descamps Diane , Charpentier Charlotte
Published: January 2020

Over 1 million patients are infected with HIV-2, which is often described as an attenuated retroviral infection. Patients frequently have undetectable viremia and evolve at more slowly toward AIDS than HIV-1-infected patients. Several studies have reported a smaller viral reservoir in peripheral blood mononuclear cells in HIV-2-infected patients than in HIV-1-infected patients, while others have found similar sizes of reservoirs but a reduced amount of cell-associated RNA, suggesting a block in HIV-2 transcription. Recent studies have found associations between mutations within the HIV-1 LTR and reduced transcriptional activities. Until now, mutations within the HIV-2 LTR region have scarcely been studied. We conducted this research to discover if such mutations exist in the HIV-2 LTR and their potential association with the viral reservoir and transcriptional activity. Our study indicates that transcription of HIV-2 group B proviruses may be impaired, which might explain the small viral reservoir observed in patients.
Structure and Development of Rabies Virus in Tissue Culture
Authors: Hummeler Klaus , Koprowski Hilary , Wiktor Tadeusz J.
Published: January 2020

Structure and development of two fixed rabies virus strains in baby hamster kidney cells (BHK/21) were investigated by electron microscopy. The morphological development was correlated with fluorescent-antibody staining and infectivity titration. The uptake of virus was enhanced by addition of diethylaminoethyl dextran, and structural changes became apparent in the cytoplasm 8 to 9 hr after infection, when fluorescent-antibody staining was first discernible. These changes consisted of matrices containing fibers replacing normal cytoplasmic structures. Virus particles appeared at the edges of these matrices and inside them at 24 to 48 hr. This corresponded to significant rises in intracellular infectious virus. Formation of virus particles by budding from cell membranes was seen at 72 hr. Further incubation of the infected cells resulted in synthesis of bizarre structural elements. The complete virus particle was bullet-shaped with an average size of 180 by 75 mμ. It consisted of an inner core of filamentous material surrounded by two membranes of different densities. The surface showed a honeycomb arrangement with surface protrusions 60 to 70 A long having a knoblike structure at their distal end. These surface protrusions were absent at the flat end of the virus particle.
Multiplicity Reactivation of Vaccinia Virus Particles Treated with Nitrogen Mustard
Authors: Kim K. S. , Sharp D. G.
Published: January 2020

The nitrogen mustard bis(β-chloroethyl)methylamine, a radiomimetic alkylating agent, is known for its ability to inactivate viruses in general and poxvirus in particular. These experiments show that vaccinia virus is rapidly inactivated by it. They show, in addition, that the treated virus exhibits multiplicity reactivation in L cells, closely resembling that experienced with the same virus after exposure to ultraviolet rays. These findings have come from observations of plaque titer, on the one hand, and virus particle aggregation (measured in the electron microscope), on the other. The titer of the treated virus is very sensitive to particle aggregation, increasing and decreasing in a reversible manner as the degree of clumping among the particles is changed. The magnitude of these changes is such that they must be considered in any situation involving plaque assay of the fraction of virus surviving treatment with nitrogen mustard.
Agrobacterium tumefaciens
Conn IV. Bacteriophage PB2
1
and Its Inhibitory Effect on Tumor Induction
Authors: Stonier Tom , McSharry James , Speitel Thomas
Published: January 2020

Strain B2 of
Agrobacterium tumefaciens
Conn produces plaques when seeded against strain B6-806 of the same organism. From such a plaque, a highly virulent bacteriophage was obtained by use of D'Herelle's technique of selecting for virulent phage. On nutrient agar, this phage, PB2
1
, produced large clear plaques which did not overgrow. Plaques produced on a glutamate medium and on White's plant tissue culture medium were even larger and in White's medium had a three-dimensional appearance. PB2
1
does not appear to be an oncogenic virus. To the contrary, the addition of phage under circumstances which insure mass lysis completely inhibited tumor initiation. Fewer than 10 phage particles present at the beginning of a 21-hr induction period were able, at times, to inhibit completely tumor induction by highly virulent bacteria (strain B6). The data lend further support to the concept that anything which interferes with the metabolic activity associated with the growth of the bacteria interferes with the tumor-inducing process. Attempts to use the phage to rid crown gall tissue of bacteria were unsuccessful.
Intrinsic Interference: a New Type of Viral Interference
Authors: Marcus Philip I. , Carver David H.
Published: January 2020

The hemadsorption-negative plaque test has revealed a new type of viral interference, termed intrinsic interference. Several unrelated types of noncytopathic viruses were shown to induce in infected host cells a state of interference unique in being directed solely against superinfection by Newcastle disease virus (NDV). The NDV-refractory state arises only in those individual cells of a population actually infected by the inducing virus, and presumably results from the action of a protein(s) coded for by the viral genome. Thus, intrinsic interference differs fundamentally from that mediated by an extrinsic protein detectable under conditions favoring resistance to a broad spectrum of viruses and characteristic of interference induced by interferon, the latter being coded for by the cell genome. Intrinsic interference is defined as a viral genome-induced cellular state of resistance to challenge by high multiplicities of NDV, coexistent with a state of susceptibility to a broad spectrum of other viruses, similarly tested at high multiplicities. The capacity to induce intrinsic interference was demonstrated with rubella virus, Sindbis virus (arbovirus, group A), West Nile virus (arbovirus, group B), poliovirus (MEF, type 2), the lactic dehydrogenase virus (Riley's agent), and an unidentified nonhemadsorbing, noncytopathic adventitious virus. A state of intrinsic interference was also observed in the V5 line of mouse cells carrying a murine leukemia virus, probably resulting from some heretofore unsuspected contaminating virus. The molecular basis for intrinsic interference is not known, but it appears to involve a step in the NDV growth cycle beyond that of viral attachment, entry, and eclipse.
Virus-specific Ribonucleic Acid Synthesis in KB Cells Infected with Herpes Simplex Virus
Authors: Flanagan John F.
Published: January 2020

The production of virus-specific ribonucleic acid (RNA) was investigated in KB cells infected with herpes simplex virus. A fraction of RNA annealable to virus deoxyribonucleic acid (DNA) was found in these cells as early as 3 hr after virus inoculation. Production of this species of RNA increased up to 6 or 7 hr after infection, at which time elaboration of virus messenger RNA (mRNA) declined. At 24 hr after infection, the rate of incorporation of uridine into this RNA was approximately one-half of the rate present at 6 hr after inoculation. Nucleotide analysis of the RNA annealable to virus DNA was compatible with that expected for virus mRNA. Centrifugation showed considerable spread in the size of the virus-induced nucleic acid, the bulk of this RNA sedimenting between 12 and 32
S.
Incorporation of uridine into cell mRNA, ribosomal precursor RNA, and soluble RNA was suppressed rapidly after infection. As is the case with most other cytocidal viruses investigated to date, virus-induced suppression of cell RNA synthesis appears to be a primary mechanism of cell injury.
How Bacteriophage χ Attacks Motile Bacteria
Authors: Schade Sylvia Z. , Adler Julius , Ris Hans
Published: January 2020

Bacteriophage χ attaches to the filament of a bacterial flagellum by means of a tail fiber, but the ultimate receptor site for the phage is located at the base of the bacterial flagellum. Here, the phage injects its deoxyribonucleic acid into the bacterium, leaving the empty phage attached at the base. It is suggested that χ slides along the filament of the flagellum to the base, owing to the movement of the flagellum. The role of motility would thus be to provide for rapid adsorption of the phage by guiding the phage to the adsorption sites at the bases of the flagella. Bacteria whose motility has been strongly inhibited by cold or anaerobic conditions still adsorb χ at the filaments and bases of flagella if a high multiplicity is used. This indicates that direct collisions with the bases may also be possible. Bacteria must be flagellated in order for χ to attach, but only a short flagellum, perhaps only the flagellar base, is necessary.
Characterization of the Strain of Adenovirus Type 7 Carrying the Defective Monkey Cell-adapting Component
Authors: Butel Janet S.
Published: January 2020

The strain of adenovirus type 7 carrying the defective monkey cell-adapting component (MAC) has been further characterized. MAC is more sensitive to inactivation by ultraviolet light than the associated adenovirus, which, in turn, is more rapidly inactivated than complete simian virus 40 (SV40). The 37% dose was 16 sec for MAC, 60 sec for adenovirus, and 84 sec for SV40. Filtration through membranes revealed that both MAC and adenovirus were retained by 100-mμ filters. MAC equilibrated in cesium chloride at the same buoyant density as the complete adenovirions (1.34 g/ml). Deoxyribonucleic acid extracted from green monkey kidney cells infected with MAC-adenovirus 7 did not hybridize in vitro with SV40 complementary ribonucleic acid. The two components (MAC and adenovirus) of the virus population possess such similar biophysical properties that their separation has not yet been achieved. Evidence to date indicates that MAC is probably not derived from SV40.
Effect of Polycations on Growth and Dissemination of the Encephalomyocarditis Virus in Mice
Authors: Craighead John E.
Published: January 2020

Pathogenicity of the encephalomyocarditis (EMC) virus for adult mice was increased when polycations of diverse type were mixed with virus and inoculated by the subcutaneous or intraperitoneal routes. Diethylaminoethyl (DEAE) dextran, hexadimethrine (polybrene), polymyxin B, polylysine, and calf thymus histone in various concentrations stimulated multiplication of virus in tissues at the injection site and enhanced entry of virus into the blood. The nonpathogenic r
+
variant of EMC which grows locally in tissues but fails to disseminate after subcutaneous and intraperitoneal inoculation was used in most experiments. This virus caused viremia and fatal central nervous system disease only when the polycations were included in the inoculum. DEAE dextran and polybrene stimulated the release of interferon in infected tissues but had no effect in the absence of virus multiplication. Histological studies of tissues from the injection site showed that polycations provoke a mononuclear cell reaction and alter the integrity of connective tissue. However, the mechanism by which the substances enhance virus growth and dissemination was not defined.
Immune Electron Microscopy of Rhinoviruses
Authors: Kapikian Albert Z. , Almeida June D. , Stott E. J.
Published: January 2020

Aggregates of three rhinovirus serotypes have been readily observed by utilizing the technique of immune electron microscopy. The aggregates generally fell into three categories: those with complete virions, those with “empty” capsids, and those in which the two types of particles were mixed.
Transcription After Bacteriophage SPP1 Infection in
Bacillus subtilis
Authors: Milanesi G. , Cassani G.
Published: January 2020

The role of the host polymerase in
Bacillus subtilis
infected with phage SPP1 was studied in vivo with regard to production of phage-specific and host-specific ribonucleic acid (RNA) and to phage yield. Evidence is presented that the subunit(s) of
B. subtilis
RNA polymerase which is sensitive to rifampin and streptolydigin is necessary at all times during infection for phage production. The synthesis of phage RNA and the phage yield in strains resistant to either antibiotic were unaffected by the drug. Host RNA synthesis continued throughout infection; phage-specific RNA never accounted for more than 20% of pulse-labeled RNA at any time during infection.
Growth Characteristics of Kilham Rat Virus and Its Effect on Cellular Macromolecular Synthesis
Authors: Salzman Lois Ann , White Wesley L. , McKerlie Louese
Published: January 2020

Kilham rat virus (KRV) is adsorbed into the rat nephroma cell within 1 hr after infection. There follows a latent period of about 12 hr during which less than 1% of the input infectious virus can be accounted for. New infectious virions can be detected at about 12 hr and the maximal yield of virus is attained by 23 hr after infection. The increase in final virus yield is about 200-fold over that found in the latent period. During this 23-hr period of virus growth, the rate of protein synthesis remains 75 to 100% of that in the uninfected cell. Ribonucleic acid (RNA) synthesis during this period is maintained at 100 to 150% of that found in the control cells. The addition of the inhibitor of deoxyribonucleic acid (DNA) synthesis, 5-fluoro-deoxyuridine (FUDR), up to 8 hr after infection completely suppresses virus production. After 8 hr, viral DNA production has started and FUDR inhibition progressively decreases until by 23 hr the addition of the inhibitor no longer causes a reduced virus yield. Viral DNA synthesis once initiated is required for the remainder of the 23-hr virus cycle. Viral DNA synthesis probably begins about 4 hr before the production of infectious virions. In the KRV-infected cells, DNA synthesis decreased sharply for 6 to 7 hr after infection in comparison to the uninfected cell. At 7 to 8 hr after infection, DNA synthesis in the infected cell increased and was maintained at a higher level than in the control cells for the rest of the virus growth period.
Nonviral Microbodies with Viral Antigenicity Produced in Cytomegalovirus-Infected Cells
Authors: Craighead John E. , Kanich Robert E. , Almeida June D.
Published: January 2020

Masses of homogeneous electron-dense material accumulate in the cytoplasmic inclusions of cultured fibroblasts which have been infected with “wild” and “adapted” strains of human cytomegalovirus. The substance appears to be produced by microtubular membranes and the Golgi apparatus; ultrastructural histochemistry suggests that it is not lysosomal in nature nor is it comprised of lipids or polysaccharides. The dense material “buds” into cytoplasmic tubules forming circumscribed bodies having an investing membrane similar to the viral envelope. After transport to the extracellular milieu in cytoplasmic tubules and vesicles, virions and dense bodies can be demonstrated by immune electron microscopy. The homogeneous dense body appears to be a unique product of the cytomegalovirus-infected cell which possesses a limiting membrane having antigenic determinants common with the viral envelope.
Structural Roles of Polyoma Virus Proteins
Authors: Friedmann Theodore , David Denise
Published: January 2020

The superhelical, closed circular form of polyoma deoxyribonucleic acid (DNA) (Co 1) is bound in a 25
S
DNA-protein complex to the viral histone-like proteins after alkaline disruption of the virion. Nicked viral DNA or linear DNA are largely free of protein. Most of the viral protein disruption is in the form of capsomeres, sedimenting principally at 10
S
and 7
S
. Despite the relatively constant ratio of 10
S
to 7
S
material in many preparations, (1:5.5 to 1:6.0, respectively), the two classes of capsomeres are indistinguishable by electron microscopy and contain only P
2
, P
3
, and P
4
in molar ratios of approximately 5:1:1 or 6:1:1, respectively. Material with sedimentation rates of approximately 1 to 3
S
is enriched for P
5
and contains small amounts of P
2
, P
3
, and P
4
. During the in vitro reassembly of DNA-free, shell-like particles from disrupted virus, proteins P
1
, P
2
, P
3
, P
4
, and P
7
are reincorporated efficiently, whereas P
5
and P
6
are not. The presence in empty reassembled particles of histone-like protein, expecially P
7
, implies that at least this one of the minor protein components of the virion may participate in protein-protein interactions with other components of the capsid.
Structure of the Bluetongue Virus Capsid
Authors: Verwoerd D. W. , Els H. J. , De Villiers Ethel-Michéle , Huismans H.
Published: January 2020

Seven polypeptides were found to be present in the capsid of the bluetongue virus (BTV), four of which are major and three are minor components. This number and size distribution is the same as that found in reovirus, which has a similar segmented, double-stranded ribonucleic acid genome. In both viruses an excellent correlation is found between the molecular weights of certain genome segments and those of the polypeptides, suggesting a direct coding relationship between them. Careful comparison, however, indicates that the correlation patterns of the two viruses are different, suggesting that different genome segments may be utilized to code for certain capsid proteins. This phenomenon may be related to the fact that these viruses can be distinguished morphologically, reovirus having a larger diameter and possessing a double-layered capsid against the smaller single capsid of the BTV. Utilizing the degrading effect of CsCl gradients, it was demonstrated, however, that two of the BTV polypeptides are present as a diffuse protein layer surrounding the capsid. This outer layer probably has some of the functions of the reovirus outer capsid, one being the “masking” of a viral transcriptase which could be demonstrated after its removal.
Role of F Pili in the Penetration of Bacteriophage fl
Authors: Jacobson Ann
Published: January 2020

Early stages of infection of
Escherichia coli
with the filamentous bacteriophage f1 were examined in the electron microscope. Purified phage-bacteria complexes were prepared at various time intervals after the initiation of synchronous infection. Cells were scored for the total number of F pili, the number of F pili with f1 attached, the number of intact phage particles which occurred at the surface of the cell, and F pilus length. Electron microscope autoradiographs were also prepared at each time interval. The results showed that the average number of F pili with f1 attached decreased with time as phage deoxyribonucleic acid (DNA) entered the cell. Concomitant with this loss, the remaining F pili became shorter. The rate of entry of phage DNA into the cell followed, with a short lag, the rate of loss of F pili with f1 attached. During the lag period, intact phage particles accumulated at the surface of the cell. The results from radioautographs showed that no phage DNA could be located within the F pilus. These results suggest that F pili are resorbed by the cell during infection with the bacteriophage f1. Parallel experiments with noninfected cultures further suggest that pilus resorption may be a normal cellular phenomenon.
Effect of Zn
2+
on the Adsorption of Male-Specific Filamentous Deoxyribonucleic Acid and Isometric Ribonucleic Acid Bacteriophages
Authors: Ou Jonathan T. , Anderson Thomas F.
Published: January 2020

By means of both electron microscopy and plaque assay techniques, 10
−3
m
Zn
2+
has been shown to reduce the adsorption rate of male-specific filamentous deoxyribonucleic acid bacteriophages to the tips of F pili. In contrast, 10
−3
m
Zn
2+
did not affect the adsorption of male-specific ribonucleic acid phages to the sides of F pili.
Detection of Avian Tumor Virus RNA in Uninfected Chicken Embryo Cells
Authors: Hayward William S. , Hanafusa Hidesaburo
Published: January 2020

Uninfected chicken embryo cells were analyzed for the presence of viral ribonucleic acid (RNA) by molecular hybridization with the single-stranded deoxyribonucleic acid (DNA) product of the RNA-dependent DNA polymerase contained in avian sarcoma-leukosis virions. Viral RNA was detected in all cells which contained the avian tumor virus group-specific antigen and the virus-related helper factor. The amounts of viral RNA in these cells ranged from approximately 3 to 40 copies of viral-specific sequences per cell. In general, the viral RNA content correlated with the level of helper activity in the cells. Cells infected with Rous-associated virus 2 contained 3,000 to 4,000 copies of viral RNA per cell. RNA from these infected cells hybridized with nearly 100% of the viral
3
H-DNA. By contrast, a maximum of less than 50% hybridization was obtained with RNA from the uninfected helper-positive cells, suggesting that not all of the viral RNA sequences were present in these cells. No viral RNA was detected in cells which lacked group-specific antigen and helper activity. Under the conditions used in these studies, less than 0.3 viral genome equivalents of RNA per cell would have been detected.
Protein Synthesis Directed by an RNA
−
Temperature-Sensitive Mutant of Sindbis Virus
Authors: Waite Marilynn R. F.
Published: January 2020

The structural proteins of wild-type Sindbis virus were shown to arise by posttranslational cleavage of larger precursors. The proteins synthesized in wildtype infection were compared with those specified by
ts
-11, a temperature-sensitive mutant unable to synthesize viral RNA at the restrictive temperature. Abnormally large, virus-specific proteins were found in the mutant-infected cells after the shift from 28 C to 41.5 C. These large polypeptides were presumably precursors which were cleaved too rapidly to be detected in the wild-type infection. The largest had a molecular weight of 133,000 and was the same size as the apparent precursor detected during infection with a group of Sindbis mutants which could not form nucleocapsids at the nonpermissive temperature. The stability of
ts
-11-specific RNA synthesis, after shift from permissive to restrictive conditions, differed from that in cells infected by wild-type virus, indicating that the virus had a genetic lesion in an enzyme involved in RNA synthesis. This mutation might have caused the precursor to fold incorrectly so that it could not be cleaved. The possibility cannot be excluded, however, that a second lesion in an uncharacterized viral function, such as a protease, was the cause of the accumulation of the precursors.
Turnip Yellow Mosaic Virus RNA as a Substrate of the Transfer RNA Nucleotidyltransferase II. Incorporation of Cytidine 5′-Monophosphate and Determination of a Short Nucleotide Sequence at the 3′ End of the RNA
Authors: Litvak S. , Tarrago-Litvak L. , Chapeville F.
Published: January 2020

Turnip yellow mosaic virus (TYMV) RNA treated with snake venom phosphodiesterase accepts cytidine 5′-monophosphate and adenosine 5′-monophosphate (AMP) when it is incubated in the presence of cytidine 5′-triphosphate (CTP), adenosine 5′-triphosphate, and
Escherichia coli
transfer RNA nucleotidyltransferase; untreated TYMV RNA accepts only AMP. When α
32
PCTP was used for terminal labeling, the nearest neighbor analyses and the anallyses after action of various nucleases showed that the sequence of five nucleotides at the 3′ end of TYMV RNA is: pGpCpApCpC. A nuclease present in commerical preparations of snake venom phosphodiesterase leads to the fragmentation of TYMV RNA, the 3′ end of which is found in a fragment having a sedimentation constant close to 5
s
.
Picornaviral Gene Order: Comparison of a Rhinovirus with a Cardiovirus
Authors: McLean Charles , Rueckert Roland R.
Published: January 2020

We describe conditions for unmasking virus-specific protein synthesis in cells infected with rhinoviruses 1A and 2. The gene order and cleavage pattern of rhinovirus 1A show many similarities to those of encephalomyocarditis virus and of poliovirus.
On the Question of Crown-Gall Tumor Initiation by DNA of Bacteriophage PS8
Authors: Beiderbeck Rolf , Heberlein Gary T. , Lippincott James A.
Published: January 2020

DNA of
Agrobacterium tumefaciens
bacteriophage PS8 was isolated by using several procedures. Whole phage and phage DNA were tested for tumor-inducing ability on 10 species of plants with various additions to assist such activity. The reported tumorigenicity of phage PS8 DNA could not be confirmed, and no evidence to implicate phage PS8 involvement in tumor initiation was obtained.
Identification of the Block in the Intracellular Replication of Single-Stranded DNA of Photodynamically Inactivated Bacteriophage φX174
Authors: Chaudhuri Utpal C. , Poddar Ramendra K.
Published: January 2020

32
P-labeled single-stranded DNA phage φX174 was photodynamically inactivated by irradiation in air with visible light in the presence of the acridine dye, proflavine sulfate. The inactivated phages could adsorb to the host cells but failed to lyse them. Formation of intracellular mature phages was almost completely inhibited. Photodynamic lesions in φX174 DNA caused intracellular formation of defective double-stranded replicative form molecules which ultimately reverted to the single-stranded configuration.
Bacteriophage T4 Inhibits Colicin E2-Induced Degradation of
Escherichia coli
Deoxyribonucleic Acid II. Inhibition by T4 Ghosts and by T4 in the Absence of Protein Synthesis
Authors: Swift Robert L. , Wiberg John S.
Published: January 2020

The deoxyribonucleic acid (DNA) of
Escherichia coli
B is converted by colicin E2 to products soluble in cold trichloroacetic acid; we showed previously that this DNA degradation (hereafter termed solubilization) is subject to inhibition by infection with phage T4 and that at least two modes of inhibition can be differentiated on the basis of their sensitivity to chloramphenicol (CM). This report deals exclusively with the inhibition of E2 produced by T4, or T4 ghosts, in the absence of protein synthesis. The following observations are described. (i) The stage of T4 infection that inhibits E2 occurs after reversible adsorption of the phage to the bacterial surface, but probably prior to injection of T4 DNA into the cell's interior. (ii) The extent of inhibition increases as the T4 multiplicity is increased; however, the fraction of bacterial DNA that eventually is solubilized is virtually independent of the phage multiplicity. (iii) Phage ghosts (DNA-less phage particles) possess an approximately 15-fold greater inhibitory capacity toward E2 than do intact phage; however, because highly purified T4 (completely freed of ghost contamination) still inhibit E2, we discount the possibility that preparations of “intact phage” inhibit exclusively by virtue of contaminating ghosts. (iv) T4 infection does not liberate an extracellular inactivator of E2. In fact, infection with sufficiently high multiplicities of T4 produces a supernatant factor that protects E2 from nonspecific inactivation at 37 C. This protective factor does not interfere with the colicin's ability to induce DNA solubilization. (v) Inhibition of E2 occurs even when phage are added well after initiation of DNA solubilization by E2, suggesting that a late stage of E2 action is the target of inhibition by T4 infection. (vi) Increasing the CM concentration from 50 μg/ml to 200 μg/ml appears to reduce the inhibition appreciably; however, this can be attributed to an enhancement by CM of the rate of E2-induced DNA solubilization. (vii) The same degree of inhibition of E2 by T4 seen in CM is observed when CM is replaced by puromycin or rifampin. (viii) Others have shown that raising the multiplicity of E2 increases the rate of DNA solubilization. We find that the fractional inhibition (i), [i = (1 − y
i
/y
o
), where y
i
and y
o
represent the inhibited and uninhibited rates of solubilization of DNA, respectively], produced by a given T4 multiplicity is independent of the multiplicity of E2 and hence is independent of the rate of DNA solubilization induced by E2.
Molecular Weight Determination of Sendai RNA by Dimethyl Sulfoxide Gradient Sedimentation
Authors: Kolakofsky Daniel , Bruschi Andrée
Published: January 2020

The molecular weight of the large RNA of Sendai virus has been determined by sedimentation analysis in sucrose gradients containing 99% dimethyl sulfoxide (DMSO) to be 2.3 × 10
6
. Sendai RNA recovered from 99% DMSO was found to cosediment with nondenatured Sendai RNA at 46 to 48
s
in ordinary sucrose gradients. The molecular weight value of 2.3 × 10
6
is considerably smaller than the estimates of 6 × 10
6
to 7 × 10
6
determined under nondenaturing conditions, suggesting a unique structure for Sendai RNA.
Bacteriophage Tail Components V. Complementation of T4D Gene 28
−
-Infected Bacterial Extracts with Pteroyl Hexaglutamate
Authors: Kozloff L. M. , Lute M. , Baugh C. M.
Published: January 2020

Synthetic pteroyl hexaglutamate (9 × 10
−6
M) stimulated the formation of new T4D particles in vitro in extracts of
Escherichia coli
B infected with T4D gene 28
−
. The stimulation was specific for this form of folic acid since neither pteroyl pentaglutamate nor pteroyl heptaglutamate stimulated phage formation. T4D formation in vitro in
E. coli
B extracts prepared after infection with 11 other phage mutants known to be involved in phage tail plate formation (5
−
, 6
−
, 7
−
, 8
−
, 10
−
, 25
−
, 26
−
, 27
−
, 29
−
, 51
−
, 53
−
) was not stimulated by the addition of pteroyl hexaglutamate. It can be concluded that the T4D gene 28 product is involved in the formation of the phage tail plate pteroyl hexaglutamate.
Fusion of Erythrocytes by Sendai Virus Studied by Immuno-Freeze-Etching
Authors: Bächi Thomas , Aguet Michel , Howe Calderon
Published: January 2020

Extensive fusion of human erythrocytes agglutinated by Sendai virus was observed after 30 s of incubation at 37 C. Electron microscopy of thin sections failed to reveal the presence of virions, viral fragments, or discrete viral antigens reactive with ferritin-labeled antibody at the sites of fusion. Immuno-freezeetching of membrane surfaces demonstrated the dispersal of viral envelope antigens from what appeared to be original sites of viral attachment. Virus-induced clustering of membrane glycoproteins was interpreted as resulting from interaction of viral antigens with membrane receptor proteins and forming the structural basis for fusion of membranes with one another.
Formation of Influenza Virus Proteins
Authors: Klenk Hans-Dieter , Rott Rudolf
Published: January 2020

Eight virus-specific proteins have been found in chicken embryo fibroblasts infected with fowl plague virus. Among them are two glycoproteins which are the constituents of the hemagglutinin on the virus particle. They are derived from a large precursor glycoprotein by cleavage of a covalent linkage. The reaction can be blocked by the protease inhibitor diisopropylfluorophosphate and the amino acid analogue fluorophenylalanine. This indicates that a peptide bond is cleaved. If infected cells are kept at 25 C, a temperature at which virus maturation is inhibited, the precursor glycoprotein is cleaved at a significantly slower rate than at 37 C. It appears, however, that a reduced synthesis of the carbohydrate-free envelope protein is responsible for the block of virus maturation at 25 C rather than the lower cleavage rate of the precursor.
Electron Microscope Study of Length and Partial Denaturation of
Rhizobium
Bacteriophage DNA
Authors: Mayer Frank , Lotz Wolfgang , Lang Dimitrij
Published: January 2020

By electron microscopy and melting of the DNA of some bacteriophages from the soil bacterium
Rhizobium lupini
, it was found that molecular weights range between 27 and 50 Mdaltons and GC contents between 53 and 62%. All DNAs studied are linear; one has exposed single-stranded terminals. Partial heat denaturation of two phage DNA permitted mapping of AT-rich sites within unique nucleotide sequences. The maps are asymmetric with respect to the midpoints of the DNA.
Mutagenic Effect of Temperature-Sensitive Mutants of Gene 42 (dCMP Hydroxymethylase) of Bacteriophage T4
Authors: Chiu Che-Shen , Greenberg G. Robert
Published: January 2020

Certain temperature-sensitive mutants of gene 42 of bacteriophage T4 increase the reversion rates of some
rII
mutants in the same genome by about 4 to 10 times. This effect was usually found at 34 C, an intermediate permissive temperature, but not at 28 C.
Membrane Proteins of Uninfected and Rous Sarcoma Virus-Transformed Avian Cells
Authors: Bussell Robert H. , Robinson William S.
Published: January 2020

A method for preparing large membrane fragments and cell ghosts was developed for uninfected and Rous sarcoma virus-transformed chicken embryo fibroblasts in culture. Membrane proteins were analyzed by electrophoresis in acrylamide gels containing sodium dodecyl sulfate. A major amino-acid-containing component of uninfected cell membranes was greatly diminished in amount or absent in membranes of virus-transformed cells. This component, called MP-1, had an electrophoretic mobility in sodium dodecyl sulfate-containing gels similar to that of a protein of a mol wt of 1.42 × 10
5
. MP-1 was not altered by changes in cell growth rate or in cells infected with the nontransforming virus RAV-1.
Intragenic Complementation Between Temperature-Sensitive Mutants of Gene 42 (dCMP Hydroxymethylase) of Bacteriophage T4
Authors: Chiu Che-Shen , Greenberg G. Robert
Published: January 2020

Interallelic complementation between certain temperature-sensitive mutants of gene 42 of bacteriophage T4 was demonstrated by measuring the incorporation of labeled thymine into DNA.
Early Inhibition of Cellular DNA Synthesis by High Multiplicities of Infectious and UV-Inactivated Reovirus
Authors: Shaw James E. , Çox Donald C.
Published: January 2020

Inhibition of cellular DNA synthesis began 6 to 8 h after reovirus infection at a multiplicity of infection of 10 PFU per cell. However, as the multiplicity of infection was increased to a maximum of 10
3
PFU/cell, inhibition of DNA synthesis began earlier after infection (2-4 h postinfection), and the initial rate of inhibition increased. The enhanced inhibition of DNA replication at high virus multiplicities appeared to be selective since RNA synthesis was not detectably altered as late as 9 h postinfection and inhibition of protein synthesis did not begin until 7 to 9 h after infection. Early inhibition of DNA synthesis did not appear to be related to changes in thymidine pool characteristics, thymidine kinase activity, or detectable degradation of cellular DNA. Even though the particle-to-PFU ratio was increased by ultraviolet light inactivation of virus, the ability to induce early inhibition of DNA synthesis was not diminished.
Transfection of
Escherichia coli
Spheroplasts III. Facilitation of Transfection and Stabilization of Spheroplasts by Different Basic Polymers
Authors: Henner William D. , Kleber Ingrid , Benzinger Rolf
Published: January 2020

The only compound which fully replaced protamine sulfate in facilitating transfection of
Escherichia coli
spheroplasts by phage DNAs was spermine; poly-
l
-lysine, poly-
l
-arginine, DEAE-dextran, histones, and many other polyamines were only slightly effective. Higher-molecular-weight compounds were effective at lower concentrations, and each compound had a sharp concentration optimum. The specificity of the facilitation of transfection is discussed in light of Leonard and Cole's (1972) isolation of a polyamine- or protamine-like, natural competence factor from
Streptococci
. By standardizing growth conditions for spheroplast cultures, storing spheroplasts in minimal medium, and adding both protamine sulfate and polyamines to spheroplasts, reproducible competence levels were obtained. Thus, 95% of all spheroplast preparations gave efficiencies of transfection between 10
−3
and 3 × 10
−4
for lambda DNA; between 10
−6
and 3 × 10
−8
for T7 DNA; and between 3 × 10
−6
and 10
−7
for T5 phage DNA. The stability of the spheroplasts was extended from 10 h to between 2 and 5 days, depending on the DNA used for transfection.