Effect of temperature on growth of guanidine-resistant mutants of poliovirus

1985 ◽  
Vol 31 (12) ◽  
pp. 1166-1168 ◽  
Author(s):  
Daniel R. Tershak
Keyword(s):  
Culture Medium ◽  
Effect Of Temperature ◽  
Virus Protein ◽  
Resistant Mutants ◽  
Peptide Maps

Guanidine-resistant (gr) mutants of poliovirus were previously categorized into four groups by electrophoretic properties and peptide maps of nonstructural virus protein 2C. Growth of mutants in the presence of guanidine depends upon temperature of incubation. The four groups of gr variants respond differently to temperature when guanidine is included in the culture medium. The data suggest clustering of gr mutations at several sites in the guanidine locus.

scholarly journals Receptiveness of the stigma and in vitro germination of orange pollen, submitted to different temperatures

2004 ◽  
Vol 28 (5) ◽  
pp. 1087-1091 ◽  
Author(s):  
Leila Aparecida Salles Pio ◽  
José Darlan Ramos ◽  
Moacir Pasqual ◽  
Flavia Carvalho Santos ◽  
Keize Pereira Junqueira
Keyword(s):  
Culture Medium ◽  
Calcium Nitrate ◽  
Pollen Grain ◽  
Effect Of Temperature ◽  
In Vitro Germination ◽  
Stigma Receptivity ◽  
Open Flower ◽  
Different Temperatures ◽  
The Ideal

The study was carried out in order to evaluate the effect of temperature and in vitor stigma receptivity on regeneration of orange cultivar (Valência, Pêra and Natal) pollen. Two experiments were carried out, in the first the ideal temperature of germination was assessed. Pollen was obtained from flowers at the balloon stage and inoculated in culture medium with 10 g L-1 agar, 200 mg L-1 boric acid, 100 g L-1 sucrose, 800 mg L-1 calcium nitrate, pH adjusted to 6,5 and incubated in a BOD chamber at temperatures of 23, 24, 25, 26 and 27ºC during a 24-hour photoperiod. After 12 hours of incubation, the best temperature for pollen grain germination was 25ºC for all varieties. In a second experiment, in order to test the receptivity of the stigma, flowers were collected at different flowering stages: small bud, balloon and open flower. The stigmas were by immersion exposed to hydrogen peroxide (perioxidase reaction), 3% for 3 minutes. Through the technique of Zeisler (1938), better results were detected at the balloon stage with 80 to 100% receptivity, while for the open flower the receptivity presented maximum indexes.

scholarly journals STUDIES ON THE ORIGIN OF BACTERIAL VIRUSES

1958 ◽  
Vol 42 (1) ◽  
pp. 109-136 ◽  
Author(s):  
John H. Northrop ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Growth Rate ◽  
Ultraviolet Light ◽  
Mutation Rate ◽  
Culture Medium ◽  
Phage Type ◽  
Small Samples ◽  
Resistant Mutants ◽  
High Concentrations ◽  
Resistant Cells

I. The Incidence of Phage-Producing Cells in Various B. megatherium Cultures Analyses of small samples containing a few cells each show that lysogenic B. megatherium produces phage particles in groups of from 10 to 1000 depending on the megatherium strain and the culture medium. These groups probably correspond to the number of particles produced by a single cell. The proportion of such phage-producing cells varies from <1 x 10-10 to about 1 x 10-2 depending on the megatherium strain and the culture medium. If a culture produces two types of phage, the different types usually appear in separate samples. If mixed samples occur, the number of such samples is about what would be expected for the probability that two separate groups would appear in one sample. This result indicates that the appearance of a distinct phage type is the result of a change in the bacterial cell rather than a change in a phage particle, since in the latter case a mixture of the two types would result. II. The Effect of Ultraviolet Light on the Incidence of Phage-Producing and of Terramycin-Resistant Cells in Various B. megatherium Cultures Low intensity of ultraviolet light increases the proportion of both phage-producing cells and of terramycin-resistant mutants. The increase in phage-producing cells is greater than the increase in terramycin-resistant cells. High intensities of ultraviolet light cause practically all the cells of some B. megatherium strains to produce phage. The number of terramycin-resistant mutants cannot be determined under these conditions. The effect of ultraviolet light varies, depending on the megatherium strain and the culture medium. III. The Effect of Hydrogen Peroxide on the Incidence of Phage-Producing and of Terramycin-Resistant Cells in Various B. megatherium Cultures Low concentrations of hydrogen peroxide increase the number of phage-producing cells and of terramycin-resistant cells, concomitantly, from two to five times. High concentrations of hydrogen peroxide cause almost all the cells of some strains of megatherium to produce phage. IV. Calculation of the Incidence of Phage-Producing Cells The time rate of the appearance of phage particles in normal cultures, or in cultures treated with ultraviolet light or hydrogen peroxide, may be calculated by the same equations which predict the occurrence of terramycin-resistant mutants in B. megatherium cultures. These equations predict that the number of mutants will increase more or less in proportion to the concentration of mutagenic agent, so long as the mutation rate remains very small compared to the growth rate. As the mutation rate approaches the growth rate, there will be a very rapid increase in the proportion of mutants. This explains the striking effect of higher concentrations of mutagenic agents. In order to calculate the results after exposure to strong ultraviolet light or hydrogen peroxide, it is necessary to assume that the change from normal to phage-producing cell occurs without cell division.

scholarly journals Sendai Virus and Simian Virus 5 Block Activation of Interferon-Responsive Genes: Importance for Virus Pathogenesis

1999 ◽  
Vol 73 (4) ◽  
pp. 3125-3133 ◽  
Author(s):  
L. Didcock ◽  
D. F. Young ◽  
S. Goodbourn ◽  
R. E. Randall
Keyword(s):  
Protein Synthesis ◽  
Culture Medium ◽  
Sendai Virus ◽  
Simian Virus ◽  
Human Cells ◽  
Virus Protein ◽  
Marked Contrast ◽  
Rnase Protection ◽  
Highly Pathogenic ◽  
Simian Virus 5

ABSTRACT Sendai virus (SeV) is highly pathogenic for mice. In contrast, mice (including SCID mice) infected with simian virus 5 (SV5) showed no overt signs of disease. Evidence is presented that a major factor which prevented SV5 from productively infecting mice was its inability to circumvent the interferon (IFN) response in mice. Thus, in murine cells that produce and respond to IFN, SV5 protein synthesis was rapidly switched off. In marked contrast, once SeV protein synthesis began, it continued, even if the culture medium was supplemented with alpha/beta IFN (IFN-α/β). However, in human cells, IFN-α/β did not inhibit the replication of either SV5 or SeV once virus protein synthesis was established. To begin to address the molecular basis for these observations, the effects of SeV and SV5 infections on the activation of an IFN-α/β-responsive promoter and on that of the IFN-β promoter were examined in transient transfection experiments. The results demonstrated that (i) SeV, but not SV5, inhibited an IFN-α/β-responsive promoter in murine cells; (ii) both SV5 and SeV inhibited the activation of an IFN-α/β-responsive promoter in human cells; and (iii) in both human and murine cells, SeV was a strong inducer of the IFN-β promoter, whereas SV5 was a poor inducer. The ability of SeV and SV5 to inhibit the activation of IFN-responsive genes in human cells was confirmed by RNase protection experiments. The importance of these results in terms of paramyxovirus pathogenesis is discussed.

scholarly journals Bacteriophages with Potential to Inactivate Aeromonas hydrophila in Cockles: In Vitro and In Vivo Preliminary Studies

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 710
Author(s):  
João Duarte ◽  
Carla Pereira ◽  
Pedro Costa ◽  
Adelaide Almeida
Keyword(s):  
Aeromonas Hydrophila ◽  
Pathogenic Bacteria ◽  
Culture Medium ◽  
Phage Therapy ◽  
Maximum Reduction ◽  
Liquid Culture Medium ◽  
Resistant Mutants ◽  
Bivalve Shellfish

The recurrent emergence of infection outbreaks associated with shellfish consumption is of extreme importance for public health. The present study investigated the potential application of phages AH-1, AH-4, and AH-5 to inactivate Aeromonas hydrophila, a causative agent of infections in humans associated with bivalve shellfish consumption. The inactivation of A. hydrophila was assessed in vitro, using a liquid culture medium, and in vivo, using artificially contaminated cockles with A. hydrophila ATCC 7966. In the in vitro experiments, all phages were effective against A. hydrophila, but phage AH-1 (with a maximum reduction of 7.7 log colonies forming units CFU/mL) was more effective than phages AH-4 and AH-5 (with reductions of 4.9 and 4.5 log CFU/mL, respectively). The cocktails AH-1/AH-4, AH-1/AH-5, AH-4/AH-5, and AH-1/AH-4/AH-5 were slightly more effective than the single phage suspensions. The phages presented a low emergence rate of phage-resistant mutants. When artificially contaminated cockles were treated in static seawater with phage AH-1, around 44% of the added A. hydrophila (1.0 log CFU/g) was inactivated. The results of this study suggest that phage therapy can be an effective alternative to control human pathogenic bacteria during depuration.

Nucleation of Disorder in Fe3Al Alloys

1967 ◽  
Vol 25 ◽  
pp. 312-313
Author(s):  
P. R. Swann ◽  
W. R. Duff ◽  
R. M. Fisher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Temperature ◽  
Antiphase Domain ◽  
Effect Of Temperature ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Higher Temperature ◽  
The One

Recently we have investigated the phase equilibria and antiphase domain structures of Fe-Al alloys containing from 18 to 50 at.% Al by transmission electron microscopy and Mössbauer techniques. This study has revealed that none of the published phase diagrams are correct, although the one proposed by Rimlinger agrees most closely with our results to be published separately. In this paper observations by transmission electron microscopy relating to the nucleation of disorder in Fe-24% Al will be described. Figure 1 shows the structure after heating this alloy to 776.6°C and quenching. The white areas are B2 micro-domains corresponding to regions of disorder which form at the annealing temperature and re-order during the quench. By examining specimens heated in a temperature gradient of 2°C/cm it is possible to determine the effect of temperature on the disordering reaction very precisely. It was found that disorder begins at existing antiphase domain boundaries but that at a slightly higher temperature (1°C) it also occurs by homogeneous nucleation within the domains. A small (∼ .01°C) further increase in temperature caused these micro-domains to completely fill the specimen.

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