Search results for "Viral Plaque Assay"
showing 10 items of 13 documents
The biological activity of bacteriophage DNA, prepared by the cationic detergent dilution technique
1975
Abstract The preparation of phage lambda DNA infecting E. coli K 12 with cationic detergent is described. This DNA infects E. coli spheroblasts with the same efficiency as DNA prepared by phenol methods.
Epistasis and the Adaptability of an RNA Virus
2005
Abstract We have explored the patterns of fitness recovery in the vesicular stomatitis RNA virus. We show that, in our experimental setting, reversions to the wild-type genotype were rare and fitness recovery was at least partially driven by compensatory mutations. We compared compensatory adaptation for genotypes carrying (1) mutations with varying deleterious fitness effects, (2) one or two deleterious mutations, and (3) pairs of mutations showing differences in the strength and sign of epistasis. In all cases, we found that the rate of fitness recovery and the proportion of reversions were positively affected by population size. Additionally, we observed that mutations with large fitness…
Repeated transfer of small RNA virus populations leading to balanced fitness with infrequent stochastic drift
1996
The population dynamics of RNA viruses have an important influence on fitness variation and, in consequence, on the adaptative potential and virulence of this ubiquitous group of pathogens. Earlier work with vesicular stomatitis virus showed that large population transfers were reproducibly associated with fitness increases, whereas repeated transfers from plaque to plaque (genetic bottlenecks) lead to losses in fitness. We demonstrate here that repeated five-plaque to five-plaque passage series yield long-term fitness stability, except for occasional stochastic fitness jumps. Repeated five-plaque passages regularly alternating with two consecutive large population transmissions did not cau…
Latency versus persistence or intermittent recurrences: Evidence for a latent state of murine cytomegalovirus in the lungs
1997
The state of cytomegalovirus (CMV) after the resolution of acute infection is an unsolved problem in CMV research. While the term "latency" is in general use to indicate the maintenance of the viral genome, a formal exclusion of low-level persistent productive infection depends on the sensitivity of the assay for detecting infectious virus. We have improved the method for detecting infectivity by combining centrifugal infection of permissive indicator cells in culture, expansion to an infectious focus, and sensitive detection of immediate-early RNA in the infected cells by reverse transcriptase PCR. A limiting-dilution approach defined the sensitivity of this assay. Infectivity was thereby …
Comparison of the immunosuppressive efficacy of 6-mercaptopurine, azathioprine, cyclophosphamide and 036.5122 (Asta) on the primary and secondary imm…
1976
Two alkylating (cyclophosphamide and 036.5122 Asta) and two antiproliferative agents (6-mercaptopurine and azathioprine) have been compared for their immuno-suppressive potency on the primary and secondary humoral immune response of mice. If equitoxic dosages of the respective drugs are compared, the alkylating agents proved to be of much higher immunosuppressive potency than the antiproliferative agents. In non toxic dosages alkylating agents were able to completely inhibit a primary or secondary immune response, whilst a similar effect with antiproliferative drugs could not be obtained even within toxic dose ranges. Induction of immunological tolerance was possible only by use of the alky…
Virtual Combinatorial Syntheses and Computational Screening of New Potential Anti-Herpes Compounds
1999
The activity of new anti-HSV-1 chemical structures, designed by virtual combinatorial chemical synthesis and selected by a computational screening, is determined by an in vitro assay. A virtual library of phenol esters and anilides was formed from two databases of building blocks: one with carbonyl fragments and the other containing both substituted phenoxy and phenylamino fragments. The library of virtually assembled compounds was computationally screened, and those compounds which were selected by our mathematical model as active ones were finally synthesized and tested. Our antiviral activity model is a "tandem" of four linear functions of topological graph-theoretical descriptors. A giv…
Genetic lesions associated with Muller's ratchet in an RNA virus
1996
The molecular basis of Muller's ratchet has been investigated using the important animal pathogen foot-and-mouth disease virus (FMDV). Clones from two FMDV populations were subjected to serial plaque transfers (repeated bottleneck events) on host BHK-21 cells. Relative fitness losses were documented in 11 out of 19 clones tested. Small fitness gains were observed in three clones. One viral clone attained an extremely low plating efficiency, suggesting that accumulation of deleterious mutations had driven the virus near extinction. Nucleotide sequence analysis revealed unique genetic lesions in multiply transferred clones that had never been seen in FMDVs isolated in nature or subjected to m…
Amino acids requirements of measles virus in HeLa cells.
1973
A low plating efficiency for measles virus was obtained when arginine, threonine and isoleucine were omitted from Eagle's basal medium and a stimulatory effect on the plaque production was produced by increasing the concentration up to 0.5 mm of arginine and glutamine. However, of all amino acids in Eagle's basal medium, only methionine was found to be essential for the synthesis of infectious progeny virus. Omission of any one of the other amino acids from the culture medium permitted limited virus production, but none whatever could be detected in the absence of mediummethionine. Moreover, when methionine was restored to infected cultures after 24 hours of deprivation, release of virus be…
Synthesis and antiviral activity of scopadulane-rearranged diterpenes.
2009
A new bioactive diterpene skeleton resulting from a backbone rearrangement is described. Activity of the rearranged product and several derivatives against Herpes Virus Simplex type 2 is reported.
Optimization of the detection of bacteriophages induced from Listeria sp.
1997
It is necessary to isolate new phages in order to improve the rate of typeability of Listeria monocytogenes strains. We propose a method which increases the detection of induced phages in the presence of inhibitory substances synthesized or liberated by the cells during phage production. Of the 29 phages isolated, 11 (38%) were detected by the spot-on-the-lawn technique and 18 (62%) were revealed by the soft-agar technique. To increase the rate of phage detection, both techniques appear useful. Listeria cultures were subjected to phage typing procedures utilizing these newly isolated phages and the French International set of phages. It appears that the newly isolated phages are good tools …