Changes in non-protein nitrogen metabolism during tobacco mosaic virus biosynthesis

1. Discs cut from tobacco leaf tissue infected with tobacco mosaic virus and cultured in water contain less non-protein nitrogen than comparable uninfected discs during the time at which TMV is formed. This deficiency disappears when virus formation ceases. Discs cultured in nutrient solution form about twice as much TMV as discs cultured in water. The maximum non-protein nitrogen deficiency is comparable in magnitude to the amount of virus synthesized. 2. The largest difference between injected and uninfected tissue occurs in the ammonia content. Smaller, but significant differences in amide content are found. Infected discs cultured in water show no significant differences from control discs in free amino acid content; infected discs cultured in nutrient solution develop a small deficiency in amino acid nitrogen. 3. The general patterns of change in composition of the pool of soluble nitrogen are similar in both infected and uninfected discs. 4. The data indicate that the bulk of the nitrogen incorporated into virus protein is withdrawn from the leaf's pool of soluble nitrogen; virus is formed de novo from ammonia nitrogen and non-nitrogenous carbon sources. The effect of virus infection on host nitrogen metabolism appears to be due to the formation of virus rather than to its presence.

Measuring resistance to virus infection

Dilution series of viruses often do not fit the exponential curve which they should fit if the usual assumptions of the theory of dilution series were true. Suppose the density of the virus suspension is λ, the average number of virus particles per unit volume of the inoculum (we suppose that unit volume is the amount actually used in inoculating the egg or other test material). Let C be the proportion of infective virus so that Cλ is the effective density of virus particles, and X is a factor depending on the dilution used such that CλX is the expected number of infective particles in the inoculum.

Studies in the epidemiology of infectious myxomatosis of rabbits. IV. Observations of disease behaviour in two localities near the northern limit of rabbit infestation in Australia, May 1952 to April 1953

Field observations supplemented by laboratory tests were carried out on the occurrence of myxomatosis at two sites with contrasting environments near the northern limit of rabbit infestation in Australia, during the period May 1952 to April 1953.

In spite of the very low incidence of cases of myxomatosis observed in wild rabbits during that period great reductions in the rabbit population occurred.

Analysis of the results of serum surveys indicates that myxomatosis was present and caused minor unobserved epizootics during this period, The overlap in this area of rabbit breeding and active transmission of myxomatosis probably led to a high death rate in the sub-adult rabbit population.

In spite of continued reintroduction of fully virulent standard virus into the areas, all strains of virus recovered were somewhat attenuated. There was a suggestion that at Texas the degree of attenuation increased during the study period.

Sex ratios and data on reproduction are presented for the 1488 rabbits shot at the two areas. Recovery from myxomatosis appeared to have no adverse effect on the fecundity of the female rabbit.

The structure of fowl-pox inclusions (Bollinger bodies)

The cytoplasmic inclusion bodies produced by fowl-pox virus in the chorioallantoic membrane of the egg consist of a mass of virus particles, frequently surrounding an apparently normal component of the cytoplasm. Finely granular or filamentous material is seen in the centre of the inclusion and round the more central virus particles into whose structure it appeared to be incorporated. The inner virus bodies consisted of a granular core surrounded by a single membrane. The outer virus bodies consisted of a cortical layer 20 mμ thick, enclosing a space in which lay a core with a granular centre.

Epizootic diarrhea of infant mice: indentification of the etiologic agent

Electron micrographs of intestinal epithelium of infant mice infected with epizootic diarrhea virus have demonstrated intracellular spherical structures measuring 65 to 75 m(micro) in diameter which have a complex morphology resembling several virus particles. They have ben interpreted as being the etiologic agent of this disease. The particles were present in association with, in some cases within, vesicles of the endoplasmic reticulum of intestinal epithelial cells. They were never seen in the nucleus.