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J S MURPHY

Publications and source records attributed to J S MURPHY.

13 recordsLinked to original sources
PubMed1960

Studies of two kinds of virus particles which comprise influenza A2 virus strains. III. Morphological characteristics: independence to morphological and functional traits.

Seven strains of influenza A2 virus were serially passed in the chick embryo, and morphological characteristics of the passages were examined in the electron microscope. With serial passage there was a change from a prominently filamentous appearance in early passages to an almost entirely spherical appearance in later passages. The number of passages required for the conversion to spherical morphology varied with different strains. The filament-sphere variation was found to be independent of the properties which differentiate "+" and "-" influenza A2 virus particles, and both highly filamentous and spherical populations of "+" and of "-" virus particles were obtained. The usefulness of these pairs of independent markers for genetic studies is discussed.

Animals↗
PubMed1960

Genetic studies of influenza viruses. I. Viral morphology and growth capacity as exchangeable genetic traits. Rapid in ovo adaptation of early passage Asian strain isolates by combination with PR8.

The passage of newly isolated, filamentous Asian (A2) influenza viruses in the presence of non-infective PR8 (A) virus results in the rapid emergence of virus of Asian (A2) antigenicity but PRS-like growth capacity and spherical morphology. Evidence is presented that this effect results from genetic interaction of the infective Asian and non-infective PR8 viruses rather than from spontaneous change of the Asian strain. It is concluded that influenza viral morphology, growth rate and growth capacity are associated genetic traits which distinguish unadapted from adapted strains, and which are transferable by recombination. A pragmatic consequence of these experiments is the fact that conditions have been defined for the rapid adaptation of early passage influenza virus isolates to the chick embryo allantoic sac. Such adaptation is attended by an increase in viral yield which has obvious implications for vaccine production during future epidemics with new antigenic types.

Animals↗
PubMed1956

Appearance of new phage types and new lysogenic strains after adaptation of lysogenic B. megatherium to ammonium sulfate culture medium.

1. Lysogenic B. megatherium 899a was adapted to growth in a minimal ammonium sulfate medium (ASCM). 2. Adaptation took place slowly and the following changes in the culture occurred: (a) The growth rate increased from 0.5 to 1.5-2.0/hr. (b) The culture changed from diffuse to mucoid. (c) The total phage titer, and the gelatinase concentration decreased to 1/100 or less. (d) The types of phage produced changed from >99 per cent T (wild type) to 30 to 60 per cent miscellaneous clear types. The original T phage was replaced by a different smaller t, never observed in the original 899a culture. (e) Several new colony types also appeared, but the colony morphology was not correlated with the phage types produced. None of the colony types was stable on repeated transfer either in peptone or ASCM, but continued to disassociate into different colony types (cf. Ivánovics, 1955). 3. Control experiments showed that these changes in phage production and colony types could not be brought about by growing sensitive B. megatherium in the presence of the various new phages, in ASCM. It is therefore unlikely that the changes observed in adapted culture were due to infection of a sensitive cell with phage. 4. Continued growth of the ASCM-adapted strain in peptone resulted in increasing the total phage titer, and also the gelatinase concentration. The growth rate returned to its original value and the ability to grow rapidly in ASCM was soon lost. The phage types, however, remained the same as in the ASCM. 5. An improved cell for steady state growth is described.

Ammonium Sulfate↗
PubMed1954

Some mutant phages produced directly by Bacillus megatherium 899a with their rate of occurrence.

The rate at which cultures of B. megatherium 899a produce certain mutants of its phage T (wild type) has been investigated in two media; one (peptone) in which reinfection of sensitive cells, if present, is virtually certain, and one (asparagine) in which reinfection is extremely unlikely. Little difference either in the number or types of mutants produced has been detected. It is concluded that phage mutants are produced directly by B. megatherium 899a and that no intermediate passage through a sensitive cell is necessary for the mutation. 396 individual mutant plaques have been isolated and classified into at least 18 types of plaque-forming mutants of B. megatherium 899a. The over-all mutant ratio found was in the order of 1:2000 while individual mutants appeared with rates between 1:7000 and less than 1:100,000.

Bacillus↗
PubMed1953

Recombinations of mutant phages of Bacillus megatherium 899a.

A group of mutant phages stemming from the virus of B. megatherium 899a (lysogenic), growing on a sensitive B. megatherium strain (KM), have been studied with respect to their recombination reactions. All these mutants and many of their recombinations can be recognized by a characteristic plaque morphology. A similar group of phages have been isolated directly from a culture of B. megatherium 899a in this laboratory. Previous work has shown that when two different plaque mutant phages both infect essentially all the bacteria in a culture, a characteristic per cent of recombinants is produced. This percentage depends on the two recombinants used, each pair having its own value. Hershey and coworkers (2-5) have demonstrated with coli-phage T2, that the percentages of recombination found can be handled mathematically and that they demonstrate the existence of a relationship between the mutations entirely comparable to crossover percentages as used in gene locus maps in genetics. This has been found to hold true for the phages studied in the present work. Only one "linkage group" has been detected and all the mutants studied showed low percentages of recombination (0.8 to 7.6). B. megatherium 899a phage and some of its mutants have been examined with an electron microscope and no differences have been detected between the different mutant strains.

Bacillus↗
PubMed1952

Observations with the electron microscope on cells of the chick chorio-allantoic membrane infected with influenza virus.

Preparations of influenza-infected chick chorio-allantoic membrane made by two types of tissue culture and by sectioning, have been studied in the electron microscope. Comparisons have been made of influenza A' (FM1), influenza A (PR8), and swine influenza (V15), three strains which produce different relative numbers of filaments. Normal surface projections which may be confused with influenza filaments are described. Extruded products of degenerating cells, usually bleb-shaped, may also be found both in uninfected allantoic fluid and tissue cultures. It appears that the filaments and spheres of influenza virus, concurrently projecting from the free cell surface, represent the only visible change in the cells until late in the infection,-how late the present work does not tell. No definite evidence of a generalized infection throughout the cytoplasm or of inclusions was found. Additional evidence is presented for the assumption that the filaments have a significant role in the final development of the free virus.

Allantois↗
PubMed1952

Mutants of a bacteriophage of Bacillus megatherium.

Repeated transfers in 5 per cent peptone or asparagine media of sensitive B. megatherium cultures containing C phage have made possible the isolation of lysogenic bacteria which produce different strains of phage. This is probably due to the failure of C virus to make the lysogenic adjustment while those of its variants which can succeed are selected. Four distinct plaque types have been isolated by this method and some of their reactions in mixedly infected bacteria are described. It has been shown that it is possible to isolate either C or T analogues of each of the strains, bringing the reported plaque types of B. megatherium phage to eight. No success was obtained in an attempt to isolate a wild type and a phage carrying two mutations when crosses were made of two phages each differing by one mutational step.

Bacillus↗