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At least 1,153 records · Page 64Linked to original sources

PubMed1995

Induction of leukemia in mice using a radiation leukemia virus-induced cell line: a model system for studying oncogenic progression.

Leukemogenesis induced by slowly transforming retroviruses is a multistep process which is difficult to dissect because of its long latency and the problem of distinguishing oncogenic from differentiative events. A method for leukemia induction in mice has been developed using a cell line isolated following in vitro infection with the slowly transforming murine radiation leukemia virus (RadLV). The CI-V13D cell line represents a lymphoid precursor cell type at an early stage in cell transformation and can develop subcutaneous tumors in irradiated syngeneic hosts but not in allogeneic mice even after sublethal irradiation. Selective growth in allogeneic (CBA/H) mouse thymus has been demonstrated, but this requires preirradiation of the recipient. Upon reisolation from CBA/H thymus, C1-V13D progeny clones displayed increased tumorigenic potential in comparison to the 'parental' CI-V13D cell line. Tumorigenicity was shown to increase with serial passage through thymus and electron micrographs of clones also revealed increased production of C-type retroviruses. This new model for oncogenic progression should be more amenable to analysis of early genetic changes occurring during replication of leukemia in the thymus.

Animals↗

PubMed1988

Tn916-dependent conjugal transfer of PC194 and PUB110 from Bacillus subtilis into Bacillus thuringiensis subsp. israelensis.

The Staphylococcus aureus plasmids pC194 and pUB110 were introduced into Bacillus thuringiensis subsp. israelensis by using the Streptococcus faecalis transposon Tn916 as a mobilizing agent. Plasmid transfer occurred only when B. thuringiensis subsp. israelensis was mated with a B. subtilis donor that contained both pC194 and pUB110 and Tn916; plasmid transfer was not observed in the absence of the transposon. B. thuringiensis transconjugants resistant to chloramphenicol (Cmr) and tetracycline (Tetr) were detected at a frequency of 1.96 x 10(-6) per recipient cell, whereas the Tetr phenotype, but not the Cmr, was observed at a frequency of 1.09 x 10(-4). The converse, Cmr but not Tetr, was observed at a frequency of 2.94 X 10(-5). The transfer of pUB110 from B. subtilis to B. thuringiensis subsp. israelensis was observed at a frequency of 3.0 x 10(-6) per recipient cell but concomitant transfer of pUB110 and Tn916 was not observed. Mobilization of plasmid pE194 was not observed under these conditions. Transconjugants were detected in filter matings only, not in broth. The Tn916 phenotype was maintained during serial passage of B. thuringiensis without selection, whereas the pC194 phenotype was not. Unlike pC194, however, pUB110 remained stable in B. thuringiensis during several passages through nonselective medium. Southern hybridization analysis demonstrated that Tn916 had inserted into several different sites on the B. thuringiensis chromosome and that pC194 and pUB110 were maintained as an autonomous plasmid.

Bacillus subtilis↗

PubMed1982

Scanning and freeze-fracture electron microscopy of rabies virus infection in murine neuroblastoma cells.

A persistent infection of CVS strain of rabies virus was established in murine neuroblastoma cells, C-1300, by a serial passage of the cells infected with a low input multiplicity. Little cytopathic effects were seen in the infected cultures and the cell growth was not interfered, although 90-100% of the cells were bearing intracytoplasmic inclusions and the infectious virus was constantly recovered from the supernatant. Scanning electron microscopy disclosed preferential budding of the virus from fine cellular processes with a relative sparing of the cell body. Freeze-fracture of the infected cells revealed that the intracytoplasmic inclusion (matrix) was composed of an aggregate of fine particles with a diameter of approximately 200 A. Intramembrane particles were distributed sparsely and randomly in the viral envelope.

Animals↗

PubMed1990

Recent data on the epidemiology and prophylaxis of human rabies in France.

Rabies is an animal disease which is transmitted to man only by accident, most often through the bite (more rarely after scratches or licks of mucosa) of a rabid animal, domestic or wild. A good knowledge of the epizootiology of animal rabies is therefore necessary to establish, on solid grounds, the prophylaxis of human rabies. Inter-human transmission of rabies being an exceptional event which will be considered separately, the epidemiology of human rabies mainly studies the sources and circumstances of human exposure to rabid animals, which differ according to the epizootiology of animal rabies in a given country: either enzootic (or hyperenzootic) canine rabies, or enzootic selvatic rabies. It appears that the risk of human rabies is higher in the first situation for two reasons: (i) rabies viruses show an increased virulence due to numerous serial passages in dogs (viruses with short incubation period) and (ii) high frequency of dog-man contacts due to the high density of both populations.

Animals↗

PubMed1981

Growth regulator from spinal cord: produced in cultures of glial cells.

Spinal cord cultures produced a regulatory factor which inhibited myogenesis. After serial passage (x 3) production of this factor continued as neuronal cells disappeared and large, pale polygonal cells rich in cytoplasmic microfilaments with morphology of astrocyte precursors became predominant. These glial cells responded to dibutyryl cyclic AMP by assuming a star-shaped appearance with multiple, radiating cytoplasmic processes. Cultures active in production of the growth regulator also produced nonneuronal-type enolase and glutamine synthetase. It is suggested that the growth regulator is produced by astrocytic glia in culture.

Animals↗

PubMed1984

Neurite-promoting factors from embryonic neurons.

Dissociated chick embryo peripheral and central nervous system cultures enriched for neurons by differential adherence, defined medium and cytosine arabinoside release to the culture environment molecular species which enhance the performance of neurons in limiting conditions. Culture medium conditioned by the neurons can be depleted of substrate-attached material by serial passage on poly-D-lysine substrate, leaving in the medium factors which promote neurite outgrowth on poly-D-lysine. The substrate-attached material which enhances neuron survival and neurite extension is heat- and trypsin-labile but is not affected by prior treatment with antisera to mouse NGF, human plasma fibronectin or laminin. The autostimulation phenotype displayed by neurons may play a role in neuronal survival or axonal growth during neuronal development.

Animals↗

PubMed1988

Schwann cell-conditioned medium promotes neurite outgrowth from explants of fetal rat retina and tectum in vitro.

We have examined the ability of Schwann cell-conditioned medium (SCCM) to promote neurite growth from embryonic retina and tectum in explant culture. Both retinal and tectal explants adhered to polylysine substrates, but neurite outgrowth from the explants was minimal when grown in the presence of non-conditioned serum-free defined medium. The addition of SCCM resulted in a significant extension of neurites from both types of explants. The neurite outgrowth from the retinal explants was mainly radial and appeared to be in fascicles of small diameter. Neurite outgrowth from the tectal explants stimulated by the SCCM tended to be in larger fascicles and in a more convoluted pattern than that seen from the retinal explants. After serial passaging of the SCCM to remove any substrate-adsorbable factors all neurite-promoting activity was lost. Neurite growth from 100% of the explants was seen on the tissue culture plates that had been preincubated with the SCCM. SCCM was analyzed by immunoblot to determine whether it contained laminin, a potent promoter of neurite outgrowth. Samples of media were electrophoresed on a sodium dodecyl sulphate (SDS)-polyacrylamide gel alongside purified laminin, transferred to nitrocellulose and stained with an antibody to laminin. Purified laminin ran in two bands at 400 kDa and 200 kDa. The conditioned media had a laminin positive band at 200 kDa. Antibody to laminin, when added to the conditioned media, resulted in a loss of the neurite promoting activity of the SCCM. These results suggest that the conditioned media contained laminin or a laminin-like molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Flow cytometric and karyotypic analysis of a primary small cell carcinoma of the prostate: a xenografted cell line.

A human small cell undifferentiated carcinoma of the prostate, xenografted in nude mice, was analyzed both cytogenetically and by DNA flow cytometry. The DNA content of the line indicated its stability on serial passage, and was consistent with the cytogenetic findings. The banded karyotype was hypodiploid with nonrandom losses of chromosomes #6, #7, #10, and #13. Structural rearrangements involved chromosomes #1 and #2, and there were three unidentified markers. The findings were compared with those described in other types of prostatic carcinoma.

Animals↗

PubMed1989

Cytogenetic and quantitative DNA analysis of primary and xenografted human osteosarcomas.

We have analyzed, cytogenetically and by flow DNA cytometry, three human osteosarcomas. From one case, both the primary tumor (T9) and three of its serial passages in nude mice were analyzed. From the two other tumors (T1, T4), nude mouse xenografts were examined. Complex karyotypic rearrangements were invariably found in the short-term culture preparations. The major clones were hypodiploid in T1 but near-triploid in all other tumor samples. No rearrangement common to all tumors could be identified. The DNA indexes were 1.0/2.0 (T1), 1.4 (T4), 0.9/1.8 (T9 primary), and 1.7 (all T9 xenografts). Thus, there was good correlation between the DNA indexes and the chromosome numbers. Chromosomal evolution could be studied in one case, in which both the primary tumor (T9) and its xenograft passages (1, 4, and 7), obtained 1, 7, and 11 months after the first transplantation of T9 cells to nude mice, were analyzed. All but one of the clonal marker chromosomes found in the primary tumor were retained in all passages. On the other hand, several new clonal markers developed.

Animals↗

PubMed1985

A comparison of the susceptibility of three human gut tumour-derived differentiated epithelial cell lines, primary monkey kidney cells and human rhabdomyosarcoma cell line to 66-prototype strains of human enteroviruses.

The growth of prototype strains of 31 serotypes of ECHO, 3 polio, 6 Coxsackie B, 24 Coxsackie A and enterovirus serotypes 70 and 71 were tested in parallel in primary monkey kidney cells (PMK), RD cells and three gut tumour-derived differentiated epithelial cell lines (HRT-18 HT-29 in SKCO-1). All 31 serotypes of ECHO viruses grew in HT-29, 27 and SKCO-1, 5 in HRT-18, 29 in PMK and 29 in RD. There was good growth of poliovirus serotypes in all five cell types. Coxsackie B viruses grew well in all the cell lines except RD. Fifteen of the Coxsackie A viruses grew in SKCO-1, 4 in HT-29, 3 in HRT-18 and 7 in RD. Enterovirus serotypes 70 and 71 grew only in RD cells after 3 serial passages. These results showed that 2 of the gut tumour-derived cell lines, HT-29 and SKCO-1 had a markedly wider susceptibility, with comparable or wider sensitivity, for enteroviruses, than PMK and RD. While their use for field isolation from clinical samples is not yet fully established HT-29 and SKCO-1 would appear to be ideal for a variety of laboratory manipulations of the majority of enteroviruses.

Animals↗

PubMed1986

The persistent infection of a canine thymus cell line by equine infectious anaemia virus and preliminary data on the production of viral antigens.

Equine infectious anaemia virus (EIAV) was adapted to the Cf2Th cell line, a heterologous malignant line from canine thymus. A persistent infection was monitored for 100 serial passages by demonstrating the presence of virus and viral antigens at each 10th passage by electron-microscopy, immunodiffusion and immunofluorescence. Chromosome analysis of EIAV-infected cells indicated they had a karyotype resembling the control cells of similar passage history. Virus-infected cells, grown in roller cultures for 65 days without subculturing, continuously produced viral antigens into supernatant fluids which were harvested every 3-4 days. Antigen peaks were observed at approximately 12-day intervals. Immunoprecipitin lines of identity were demonstrated between ether-extracted antigens from virus-infected canine cell line and known positive EIAV antigen extracted from infected equine spleen and a commercial source. Replication of a non-oncogenic retrovirus (EIAV) resulted in the continuous release of viral antigens from a persistently infected and infinite cell line.

Animals↗

PubMed1996

A baculovirus vector derived from immediately early gene promoter of Autographa californica nuclear polyhedrosis virus.

A transfer vector was constructed in which the neomycin resistance (neo) gene was under the control of a copy of Autographa californica nuclear polyhedrosis virus (AcMNPV) IE1 gene promoter at the p10 locus. After cotransfection of Spodoptera frugiperda (Sf9) cells with the transfer vector and infectious AcMNPV DNA, the recombinant virus-containing neo gene was selected by serial passage of the mixed progenies from cotransfection. This was done at low MOI in the presence of G418 in growth medium and was followed by limited dilution. RNA dot hybridization showed that the neo gene was transcribed from immediately early phase to very late phase, in infected Sf9 cells. These results demonstrate that a new baculovirus vector system had been constructed in infected cells. Furthermore, a new method for selection of positive recombinant baculovirus had been developed.

Animals↗

PubMed1984

Antiviral action of 5-amino-2-(2-dimethyl-aminoethyl)benzo-[de]-isoquinolin-1,3-dion e.

A newly synthesized imide derivative of 3-nitro-1,8-naphthalic acid, 5-amino-2-(2-dimethylaminoethyl)benzo-[de]-isoquinolin-1,3-dione (designated M-FA-142), was tested on chick embryo cells against herpes simplex virus type 1 (HSV-1) and vaccinia virus (VV), and on Vero cells against African swine fever virus (ASFV). At a concentration of 4 micrograms/ml the drug inhibited VV replication by about one order of magnitude, and that of HSV-1 by about three orders of magnitude. A minor effect was shown against ASFV. Virus inhibition was found to depend on the amount of drug and multiplicity of infection. No virucidal effect was observed on the viruses tested, except for a slight effect on HSV-1. Inhibition of virus growth could be reversed when the drug was removed from the cell culture medium. Serial passages of HSV-1 and VV in the presence of the drug caused the appearance of drug-resistant viruses.

Adenine↗

PubMed1987

The inhibition of bovine herpesvirus-1 by methyl 2-pyridyl ketone thiosemicarbazone and its effects on bovine cells.

Methyl 2-pyridyl ketone thiosemicarbazone (MPKT) was found to inhibit bovine herpesvirus-1 (BHV-1) at an ED50 concentration of approximately 5-10 microM. Several virus strains were shown to have similar sensitivity to the drug and serial passage of virus in the presence of MPKT failed to yield resistant progeny. There was evidence for toxic effects on cells at drug concentrations similar to those required to inhibit virus and passage of cells in low concentrations of MPKT gave results suggesting cumulative toxicity. Pre-incubation of cells in the presence of MPKT produced a residual antiviral effect. Taken together, these observations cast doubt on the selectivity of the drug for BHV-1, at least in the bovine system under test.

Animals↗

PubMed1990

Anti-influenza virus activity of the compound LY253963.

The compound LY253963 (1,3,4-thiadiazol-2-ylcyanamide) inhibited the in vitro replication of representative influenza A and B viruses in Madin-Darby canine kidney (MDCK) cells at concentrations of 1-3.2 micrograms/ml. The yield of an influenza A (H3N2) virus in primary rhesus monkey kidney (RMK) cells was inhibited at 0.1-0.3 micrograms/ml. However, similar concentrations were inhibitory for the growth of uninfected MCDK or RMK cells. Combination drug studies generally found indifferent interactions between LY253963 and ribavirin or rimantadine. In timing of additional studies, hemagglutinin expression was inhibited to the greatest extent when LY253963 exposure was begun at least 8 h before viral infection, which suggested either slow uptake or intracellular metabolism of LY253963 to an active form. Virus-specific protein synthesis was inhibited to a greater extent by ribavirin 10 micrograms/ml or rimantadine 1 microgram/ml than by LY253963 10 micrograms/ml. No drug-resistant mutants were detected during serial passage of an influenza A (H3N2) virus in the presence of LY253963 1-16 micrograms/ml. In summary, we found that LY253963 inhibited influenza A and B virus replication in several cell types, but that it was associated with cytostatic effects at low concentrations. These studies failed to identify a selective anti-influenza action.

Antiviral Agents↗

PubMed1993

Ribavirin efficacy in an in vivo model of Crimean-Congo hemorrhagic fever virus (CCHF) infection.

After intraperitoneal (i.p.) infection of infant mice with CCHF virus, virus titers in liver remained significantly higher than in other organs except blood (serum). Within the liver, virus antigen was first found by immunofluorescence (IFA) in Kupffer cells followed by more extensive hepatic spread. Later, virus was found in other organs including brain and heart. Ribavirin treatment significantly reduced infant mouse mortality and extended the geometric mean time to death. Ribavirin treatment reduced CCHF virus growth in liver and significantly decreased, but did not prevent, viremia. Despite a substantial viremia, infection of other organs including brain and heart was not detected in ribavirin-treated mice. A hepatotropic virus subpopulation with less neurovirulence than the parent was isolated from liver of ribavirin-treated mice (single dose, 100 mg/kg). After serial passage in placebo-treated mice, the exclusive hepatotropism was lost.

Animals↗

PubMed1987

DNA contents and molecular karyotypes of hybrid Trypanosoma brucei.

We have used restriction fragment length polymorphism markers to characterise parental and hybrid trypanosome stocks. Unexpected differences in the intensities of Southern hybridisation banding patterns led us to suspect that the hybrid organisms contained more DNA than the parental stocks. This has been confirmed using flow cytofluorimetry (FCF). Hybrids contained significantly more DNA than the parents, both as procyclic organisms (1.5 fold) and as bloodstream forms (1.5-1.6 fold). The DNA contents of both forms were stable through prolonged culture (procyclics), or serial passage (bloodstream forms), although limited data indicated that falls in DNA content could occur in bloodstream forms. FCF analysis of purified nuclei revealed that the increased DNA content of hybrids could be wholly ascribed to nuclear DNA. Our methods are able to detect hybrid organisms with elevated DNA contents in uncloned isolates following cyclical mixed transmission. We have used alternating field electrophoresis techniques to investigate whether the inheritance by the hybrids of the smaller chromosomes could account for their elevated DNA contents. Hybrids lacked the single 500 kb chromosome from one of the parents but appeared to have virtually double the amount of minichromosomes. However, this increase could only account for about 20% of the additional DNA. We are unable at present to distinguish between models for hybrid formation based on the fusion of predominantly diploid cells, and models in which the diploid chromosomes participate in conventional meiosis.

Animals↗

PubMed1990

Recurrent de novo appearance of small linear DNAs in Leishmania major and relationship to extra-chromosomal DNAs in other species.

We have detected several new chromosome-sized DNAs in lines derived from the LT252 isolate of Leishmania major. These DNAs appeared de novo in two clonal lines undergoing methotrexate (MTX) selection (clone 7-R50, clone 15-R50), in a stably MTX-resistant population reverting from MTX pressure (R1000-11-P55rev), and spontaneously during routine serial passage of the wild-type LT252 line in vitro (LT252+). No association of these new DNAs with drug resistance was detected. The new chromosomes were present in multiple copies, stably maintained, linear, and hybridized to a telomere-specific probe, and ranged in size from 180 to 220 kb. Southern blot hybridization revealed that all four new DNAs were related, and the family was designated the 715 class of small linear DNAs (SLDs). A 715-class SLD hybridization probe also identified small chromosomes described previously in Leishmania donovani (LD-1, HU-3 minichromosome) and Leishmania braziliensis (LD-1); LD-1 is known to be related to a smaller circular DNA, CD-1. A cloned probe derived from CD-1 (from K. Stuart and C. Tripp) identified two of the four L. major 715 class of SLDs in addition to the LD-1 DNAs of L. donovani and L. braziliensis, however the 715-class SLD probe did not identify CD-1 itself. L. major and L. donovani possess a homologous 1.5 Mb chromosome containing both the CD-1 and 715 sequences within a 40-kb region, whose size remained unaltered following appearance of the SLDs. These data suggest that SLDs and CD-1 may arise from an evolutionarily conserved chromosomal reservoir.

Animals↗