scholarly journals Infectivity titrations of myxoma virus in the rabbit and the developing chick embryo

1956 ◽  
Vol 54 (2) ◽  
pp. 246-257 ◽  
Author(s):  
Frank Fenner ◽  
G. A. McIntyre
Keyword(s):  
Chorioallantoic Membrane ◽  
Myxoma Virus ◽  
Close Approximation ◽  
Rabbit Skin ◽  
Maximum Value ◽  
Average Probability ◽  
Proportional Relationship ◽  
The Mean ◽  
Different Strains ◽  
Infectious Unit

Titrations of the same preparations of myxoma virus have been made on the chorioallantoic membranes of developing chick embryos and by the intradermal inoculation of rabbits. Six strains of widely differing virulence for the rabbit were used.No differences were found in the infectivity of different strains for either the rabbit or the egg, even though the severity of the symptoms produced in the rabbit varied greatly with different strains; and although some had never previously been inoculated in eggs and one had been subjected to seventy-five serial passages on the chorioallantoic membrane.The egg was less sensitive than the rabbit, the mean number of infections per dose for rabbits relative to eggs being 2.46, taken over all strains. This ratio did not differ significantly between strains of myxoma virus.There was evidence of some host variation in rabbit susceptibility and a great deal of variation in egg susceptibility. The maximum value for the average probability that an infectious unit would produce a lesion in the rabbit skin was about 0.6, and the maximum value for the average probability that an infectious unit would produce a pock on the chorioallantoic membrane was 0.25.Titration of several closely spaced dilutions of different strains of the virus on the chorioallantoic membrane showed a reasonably close approximation to a proportional relationship between the pock count and the virus dilution. The change with dilution in the proportion of failures to infect rabbits approximated to expectation. Both lines of evidence are consistent with the hypothesis that a pock or skin lesion is initiated by one infective unit of virus, and that the infective unit is stable with dilution.

scholarly journals IMMUNOLOGICAL AND CHEMICAL INVESTIGATIONS OF VACCINE VIRUS

1936 ◽  
Vol 64 (3) ◽  
pp. 439-452 ◽  
Author(s):  
Robert F. Parker ◽  
Thomas M. Rivers
Keyword(s):  
Coefficient Of Variation ◽  
Vaccine Virus ◽  
Agglutination Reaction ◽  
Test Antigen ◽  
End Point ◽  
Negative Results ◽  
The Mean ◽  
Different Strains ◽  
High Degree ◽  
Infectious Unit

Methods have been described by which the number of elementary bodies present in a suspension can be estimated. It has been shown that by means of replicate counts, in which the Petroff-Hausser chamber was used, a high degree of accuracy can be attained. By means of the Gates densitometer, the number of elementary bodies in a suspension can be determined with a coefficient of variation of about 3.0 per cent. A method has been described by which the accuracy of estimation of the infectious titer of a suspension can be increased without greatly enlarging the number of animals employed. This consists of selecting as the end-point that dilution of virus which on intradermal inoculation in a rabbit would lead theoretically to an equal number of positive and negative results. The statistical advantages of this method have been confirmed by the experiences of other laboratories. By the application of the methods described, there was shown to be a direct correlation between the number of elementary bodies and the number of infectious units of virus present in a given suspension. At the mean of the distribution this ratio is as the logarithms 9.62 to 8.0. To extrapolate this curve, in order to determine the number of elementary bodies present in a single infectious unit, while tempting, is probably not justifiable. It must likewise be remembered that the data given apply to a particular strain of vaccine virus, and that the number of infectious units has been determined by intradermal inoculation of rabbits. It appears also that this method may be of value in studies of the virulence of different strains of vaccine virus, since by its application one may determine not only the infectious liter of a suspension, but its content of elementary bodies. In the agglutination reaction it was found that optimum titers of serum were obtained when the test antigen contained from 2.0 x 109 to 1.05 x 1010 elementary bodies per cc. Approximately 1.95 x 108 particles per cc. of suspension were required for the production of visible agglutination.

Models of superinfection and acquired immunity to multiple parasite strains

1996 ◽  
Vol 33 (04) ◽  
pp. 915-932 ◽  
Author(s):  
P. J. M. Milligan ◽  
D. Y. Downham
Keyword(s):  
Control Measures ◽  
Older Individuals ◽  
Close Approximation ◽  
Cross Sectional ◽  
Vector Borne Diseases ◽  
Duration Of Infection ◽  
Bivariate Poisson Distribution ◽  
Vector Borne ◽  
The Mean ◽  
Different Strains

Individuals in communities in which different strains of pathogen are circulating can acquire resistance by accumulating immunity to each strain. After considering susceptibility, models of infection and immunity are defined for vector-borne diseases such as malaria and trypanosomiasis. For these models the prevalence of infection, the number of infections per individual, and the mean duration of infection, increase rapidly in young individuals, but decrease in older individuals as immunity is acquired to the various strains of pathogen; the mean interval between successive infections lengthens with age. The bivariate Poisson distribution is shown to be a close approximation to some stochastic processes. The models explain observed cross-sectional patterns of age prevalence, and longitudinal patterns in which individuals typically continue to become infected as they age, albeit with decreasing frequency. In these models the time spent infected depends on parasite diversity, as well as the inoculation and recovery rates. It is shown that control measures can cause an increase in the number of infections and the prevalence of infection in older individuals, and in the average prevalence in the community, even when strain-specific immunity is life-long.

Models of superinfection and acquired immunity to multiple parasite strains

1996 ◽  
Vol 33 (4) ◽  
pp. 915-932 ◽  
Author(s):  
P. J. M. Milligan ◽  
D. Y. Downham
Keyword(s):  
Control Measures ◽  
Older Individuals ◽  
Close Approximation ◽  
Cross Sectional ◽  
Vector Borne Diseases ◽  
Duration Of Infection ◽  
Bivariate Poisson Distribution ◽  
Vector Borne ◽  
The Mean ◽  
Different Strains

Individuals in communities in which different strains of pathogen are circulating can acquire resistance by accumulating immunity to each strain. After considering susceptibility, models of infection and immunity are defined for vector-borne diseases such as malaria and trypanosomiasis. For these models the prevalence of infection, the number of infections per individual, and the mean duration of infection, increase rapidly in young individuals, but decrease in older individuals as immunity is acquired to the various strains of pathogen; the mean interval between successive infections lengthens with age. The bivariate Poisson distribution is shown to be a close approximation to some stochastic processes. The models explain observed cross-sectional patterns of age prevalence, and longitudinal patterns in which individuals typically continue to become infected as they age, albeit with decreasing frequency. In these models the time spent infected depends on parasite diversity, as well as the inoculation and recovery rates. It is shown that control measures can cause an increase in the number of infections and the prevalence of infection in older individuals, and in the average prevalence in the community, even when strain-specific immunity is life-long.

scholarly journals The differential transmissibility of myxoma virus strains of differing virulence grades by the rabbit flea Spilopsyllus cuniculi (Dale)

1975 ◽  
Vol 75 (2) ◽  
pp. 237-247 ◽  
Author(s):  
A. R. Mead-Briggs ◽  
J. A. Vaughan
Keyword(s):  
Host Resistance ◽  
Oryctolagus Cuniculus ◽  
Selective Advantage ◽  
Myxoma Virus ◽  
Laboratory Studies ◽  
Natural Conditions ◽  
Male And Female ◽  
The Mean ◽  
Virus Strains ◽  
Sampling Times

SUMMARYLaboratory studies showed that few rabbit fleas (Spilopsyllus cuniculi (Dale)) transmitted myxomatosis after removal from wild rabbits (Oryctolagus cuniculus (L)) that had been infected for fewer than 10–12 days, irrespective of the virulence of the myxoma virus strain involved. Rabbits infected with fully virulent (Grade I) strains died within 10–15 days and few fleas from these hosts became infective; averaging all the samples taken, 12% of the fleas were infective. Also, few fleas acquired infectivity on individual rabbits which recovered from infection with attenuated strains; the mean was 8% infective. Rabbits which died between 17 and 44 days after infection had higher proportions of infective fleas at all sampling times; the mean was 42% infective. Male and female fleas transmitted virus with equal efficiency.For rabbits infected with any of the attenuated virus strains the mean percentage of infective fleas was inversely related to the survival time of the host. Rabbits infected with moderately attenuated strains (Grades IIIA and IIIB) had, on average, the highest proportion of infective fleas; hence such strains have a selective advantage and have become predominant under natural conditions in Britain. The changes that might occur if there is an increase in host resistance to myxomatosis are discussed.

scholarly journals Statistical Characteristics of Unsteady Storms in Radar Observations for the Beijing–Tianjin Region

2015 ◽  
Vol 54 (1) ◽  
pp. 106-116 ◽  
Author(s):  
Yu Wang ◽  
Hong-Qing Wang ◽  
Lei Han ◽  
Yin-Jing Lin ◽  
Yan Zhang
Keyword(s):  
Warm Season ◽  
Environmental Parameters ◽  
Statistical Characteristics ◽  
Movement Speed ◽  
Movement Direction ◽  
Upper Troposphere ◽  
Maximum Value ◽  
Dynamic Factors ◽  
The Mean ◽  
Wind Profiles

AbstractThis study was designed to provide basic information for the improvement of storm nowcasting. According to the mean direction deviation of storm movement, storms were classified into three types: 1) steady storms (S storms, extrapolated efficiently), 2) unsteady storms (U storms, extrapolated poorly), and 3) transitional storms (T storms). The U storms do not fit the linear extrapolation processes because of their unsteady movements. A 6-yr warm-season radar observation dataset was used to highlight and analyze the differences between U storms and S storms. The analysis included geometric features, dynamic factors, and environmental parameters. The results showed that storms with the following characteristics changed movement direction most easily in the Beijing–Tianjin region: 1) smaller storm area, 2) lower thickness (echo-top height minus base height), 3) lower movement speed, 4) weaker updrafts and the maximum value located in the mid- and upper troposphere, 5) storm-relative vertical wind profiles dominated by directional shear instead of speed shear, 6) lower relative humidity in the mid- and upper troposphere, and 7) higher surface evaporation and ground roughness.

scholarly journals On some continuous observations of the rate of dissipation of electric charges in the open air

1905 ◽  
Vol 76 (508) ◽  
pp. 152-159 ◽  
Keyword(s):  
New Zealand ◽  
Individual Values ◽  
Similar Work ◽  
Maximum Value ◽  
Variable Quantity ◽  
The Mean ◽  
Atmospheric Conductivity ◽  
Rate Of Dissipation ◽  
The Individual ◽  
Sea Coast

During the latter part of 1902 and the early months of 1903 I resolved to take as many observations of the rates of dissipation of positive and negative electric charges as possible, and to continue them over the whole 24 hours of the day, and, when opportunity offered, over longer periods. There appeared to be little information regarding the rate of dispersion during the night hours. At about the same time that these observations were being made, Nilsson was doing similar work at Upsala, and found a noticeable maximum value for atmospheric conductivity at about midnight. The observations were made on the Canterbury Plains of New Zealand, at a station about 20 feet above sea-level and about five miles due west from the sea coast. The apparatus used was Elster and Geitel’s Zerstreuungs- apparat , and the formula of reduction used was that given by them, viz:- E = 1/ t log V 0 /V- n / t ' log V' 0 /V' . In this formula E is proportional to the conductivity of the gas surrounding the instrument—for positive or negative charges, as the case may be. The constant “ n ” = ratio of capacity without cylinder ____________________________________ capacity with cylinder was determined by me to be 0·47, as the instrument was always used, with the protecting cover. The cover was always at one height above the base of the instrument, and was set so as to be as nearly co-axial with the discharging cylinder as could be judged by eye. No attempt was made to determine the actual capacity of the condenser cylinder and protecting cover, which would be a somewhat variable quantity owing- (1) to the differences on different days in attempting to cause the two to be co-axial; (2) to a certain amount of looseness in the fit of the shank of the cylinder on to its hole. The value above given for “ n "is the mean of several deter­minations made with different settings of the cover and cylinder. The individual values of “ n ” varied over about 0.03.

scholarly journals Morphological characterization and genetic diversity in lentil (Lens culinaris medikus ssp. Culinaris) germplasm

2014 ◽  
Vol 4 (1) ◽  
pp. 70-76
Author(s):  
KU Ahamed ◽  
B Akhter ◽  
MR Islam ◽  
MR Humaun ◽  
MJ Alam
Keyword(s):  
Seed Weight ◽  
Female Flower ◽  
Morphological Characterization ◽  
Flower Initiation ◽  
Mean Values ◽  
Maximum Value ◽  
Cluster Distance ◽  
The Mean ◽  
100 Seed Weight ◽  
Number Of Seeds

Genetic divergence of 110 lentil germplasm with checks was assessed based on morphological traits using multivariate analysis. Mahalanobis generalized distance (D2) analysis was used to group the lentil genotypes. Significant variations among lentil genotypes were observed in respect of days to 1st flowering, days to 50% flowering, days to maturity, plant height, and number of pods per peduncle, number of pods per plant, number of seeds per plant, 100 seed weight and yield per plant. Considering the mean values, the germplasm were grouped into ten clusters. The highest number of genotypes (17) was in cluster X and lowest (5) both in cluster II and IV. Cluster IV had the highest cluster mean for number of pods per plant (297.08), number of seeds per plant (594.16), 100 seed weight (1.44 g) and yield per plant (8.53 g). Among them, the highest inter-cluster distance was obtained between the cluster IV and I (24.61) followed by IV and III (22.33), while the lowest was between IX and II (1.63). The maximum value of inter-cluster distance indicated that genotypes belonging to cluster IV were far diverged from those of cluster I. The first female flower initiation was earlier in BD-3812 (49 days) in cluster I and cluster IV had highest grain yield per plant (8.53). BD-3807 produced significant maximum number of pods per plant (298.40) in cluster IV. DOI: http://dx.doi.org/10.3329/ijarit.v4i1.21095 Int. J. Agril. Res. Innov. & Tech. 4 (1): 70-76, June, 2014

scholarly journals The growth in vitro of vaccinia virus in chick embryo chorio-allantoic memberane, minced embryo and cell suspensions

1957 ◽  
Vol 55 (3) ◽  
pp. 347-360 ◽  
Author(s):  
H. B. Maitland ◽  
D. I. Magrath
Keyword(s):  
Chick Embryo ◽  
Vaccinia Virus ◽  
Growth Curve ◽  
Chorioallantoic Membrane ◽  
Growth Cycle ◽  
Cell Suspensions ◽  
Rabbit Skin ◽  
Chick Chorioallantoic Membrane ◽  
Considerable Doubt

The growth curve of rabbit skin-adapted vaccinia virus in the chick chorioallantoic membrane incubated in Hanks' solution showed a drop in titre of virus for about 10 hr. followed by growth. At least 25% of virus, sometimes more, remained infective. A similar fall in titre was observed in heated membranes in which the virus did not grow and this occurred also when membranes, either normal or heated, were infected and disintegrated before incubation.The growth curve of virus in minced chick-embryo was similar to that in chorioallantoic membrane.Virus in cell suspensions prepared from chick embryo and incubated in a nutrient medium showed only a small loss of infectivity before growth in some experiments and rarely dropped below 65–70 % of the original titre in others.These results throw considerable doubt on the view that loss of infectivity preceding growth of vaccinia virus should be interpreted as an essential part of a growth cycle.

RADIATION DOSE TO PATIENTS IN CORONARY INTERVENTIONAL PROCEDURES: A SURVEY

2018 ◽  
Vol 184 (1) ◽  
pp. 1-4 ◽  
Author(s):  
A Brindhaban
Keyword(s):  
Interventional Procedures ◽  
Coronary Intervention ◽  
Skin Dose ◽  
Radiation Doses ◽  
Dose Area Product ◽  
Maximum Value ◽  
Percutaneous Coronary ◽  
The Mean ◽  
Area Product ◽  
Peak Skin Dose

Abstract The objective of this study was to evaluate dose–area product (DAP) and peak skin dose (PSD) for coronary angiography (CA) and percutaneous coronary intervention (PCI). The DAP and PSD of 300 randomly selected patients who were referred to CA and/or PCI, over a period of 3 months were recorded and analyzed. The mean DAP of 32 Gy cm2 and mean PSD of 412 mGy for CA were lower than 118 Gy cm2 and 857 mGy, respectively, for PCI. The DAP range of 2–84 Gy cm2 for CA and 12–378 mGy for PCI were also established. The maximum value of PSD for PCI procedures reached above the 2 Gy threshold for erythema. However, these values are similar to those available in literature. Periodic surveys may be required to monitor and/or reduce radiation doses in coronary interventional procedures.

scholarly journals RATIOS OF VACCINIA VIRUS PARTICLES TO VIRUS INFECTIOUS UNITS

1959 ◽  
Vol 110 (3) ◽  
pp. 461-480 ◽  
Author(s):  
John R. Overman ◽  
D. Gordon Sharp
Keyword(s):  
Vaccinia Virus ◽  
Chorioallantoic Membrane ◽  
Growth Curves ◽  
Infective Virus ◽  
Ratio Increase ◽  
Marked Rise ◽  
Rabbit Skin ◽  
Virus Particles ◽  
Tissue Extracts ◽  
Particle Counts

Total virus particle counts, infectivity titrations and the ratios between particles and infective units have been determined for vaccinia virus infected tissues. Growth curves of vaccinia in the chorioallantoic membrane are characterized by relatively low ratios from 1 to 4 days after inoculation and a marked rise in the ratio at more prolonged intervals. Ratio determinations of vaccinia virus passages in the egg, rabbit skin, and guinea pig skin have been made to study the phenomenon of adaptation in different hosts. The embryonated egg chorioallantoic membrane shows no variation in the ratio of particles to infectious units during passage and it is concluded that this host is completely susceptible to vaccinia. During adaptive passages on the skin of rabbits and guinea pigs relatively large amounts of non-infective virus appear as indicated by a rise in the particle-infectivity ratios. The extent of ratio increase appears related to the general resistance of the host to the virus. Finally, treatment of crude tissue extracts with sonic vibration is described as an aid in dispersing the virus particles for quantitative particle counts.

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