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Biomedical subjects

N Hahon

Publications and source records attributed to N Hahon.

54 records · Page 3Linked to original sources
PubMed1970

Assay of Chikungunya virus in cell monolayers by immunofluorescence.

Chikungunya virus was quantitatively assayed by counting immunofluorescent foci after infection of BHK21/C13 cell monolayers. The speed and efficiency of virus attachment to cells were markedly enhanced when augmented by centrifugal force. By this procedure, a proportionality was obtained between the number of immunofluorescent foci and the volume of inoculum. Virus penetration into cells was linear and complete within 15 min at 35 C. From observations on the sequential development of viral antigen within cells and immunofluorescent focus counts, foci of infected cells may be enumerated as early as 16 hr after inoculation of cell monolayers. A linear function was demonstrated between immunofluorescent focus counts and relative virus concentration. The immunofluorescent assay was comparable in sensitivity but more precise and rapid than virus assays based on the intracerebral inoculation of suckling mice or on plaque counting. By the immunofluorescent procedure, the 50% neutralizing end point of antiviral serum was rapidly and quantitatively determined.

Animals↗
PubMed1970

Assessment of aerosol mixtures of different viruses.

Aerosol mixtures of the psittacosis agent, yellow fever virus, and variola virus were assayed by selective immunofluorescence in conjunction with fluorescent cell counting. The aerosol behavior of each agent could be readily delineated at test conditions of 80 F (26.67 C) and three relative humidities (30, 50, or 80%). Of the three agents, variola virus exhibited the lowest biological decay. The biological decay rates of the airborne agents were not significantly affected by humidity changes.

Aerosols↗
PubMed1970

Multiple assessment and serum neutralization of arbovirus mixtures.

Mixtures of Venezuelan equine encephalomyelitis, Rift Valley fever, and chikungunya viruses may be assayed by selective immunofluorescence staining of infected cell monolayers. A multiple serum neutralization test is described for quantifying reactions of these viruses with mixtures of serum antibodies.

Antibodies↗
PubMed1970

Serum Neutralization Anti-IgG Test for Psittacosis.

Levels of antibodies in sera from patients with diagnoses of subclinical or established psittacosis infections were determined by the serum neutralization anti-IgG test and by conventional tests. Relatively high levels of serum neutralizing anti-bodies were detected in tests in which anti-IgG was used, whereas conventional tests disclosed only marginal levels of antibody. Use of the serum neutralization anti-IgG test in conjunction with the fluorescent cell-counting technique permitted serum antibody determinations within 24 hr.

Journal Article↗
PubMed1970

Interferon induction by the psittacosis agent in Guinea pig leukocyte cultures.

High titers of interferon were induced by the psittacosis agent in guinea pig leukocyte cultures. Optimal yields of interferon were produced from freshly prepared guinea pig leukocyte cultures containing 4 x 10(6) cells per ml inoculated with a psittacosis/cell multiplicity of 1.0 and incubated at 35 C for 24 hr. Leukocytes obtained from 2- to 4-month-old guinea pigs produced 20 times more interferon than leukocytes from 3- to 4-week-old animals. The biological activity of interferon and the kinetics of its production from psittacosis-infected guinea pig leukocyte cultures were similar to those reported for virus-induced leukocyte interferons.

Journal Article↗
PubMed1968

Assessment of aerosol stability of yellow fever virus by fluorescent-cell counting.

The effects of three temperatures [30, 50, and 80 F (-1.11, 10, and 26.67 C)] and three relative humidities (30, 50, and 80%) on biological and physical decay rates of aerosols of yellow fever virus were investigated. Neither temperature nor relative humidity, independently or jointly, significantly affected biological or physical decay rates. The advantages of assaying yellow fever virus by the fluorescent-cell counting technique are discussed.

Aerosols↗
PubMed1967

Primary virus-cell interactions in the immunofluorescence assay of Venezuelan equine encephalomyelitis virus.

The conditions under which Venezuelan equine encephalomyelitis (VEE) virus attached to host cells markedly influenced the assay of virus by the fluorescent cell-counting technique. When virus inoculum was centrifuged onto McCoy cell monolayers, approximately 97% of virus was attached to cells within 10 min, in contrast to 34% after stationary incubation at 35 C for 2 hr. Maximal binding of virus occurred only in the presence of 0.1 to 0.15 m NaCl. This salt requirement, added to evidence of (p)H dependence and temperature independence of VEE virus attachment to cells, indicated that the initial union involved electrostatic forces. Virus penetration, measured by the insensitivity of virus-cell complexes to viral antiserum, was complete in 30 min at 35 C. The process was temperature-dependent and un-affected by the ionic content of medium. For assay of VEE virus by the fluorescent cell-counting technique, infected cells may be enumerated as early as 12 hr after infection of cell monolayers. The relationship between virus concentration and cell-infecting units was linear; the distribution of fluorescent cells was random. The virus assay was equivalent in sensitivity but more precise and rapid than that of intracerebral inoculation of mice.

Animals↗
PubMed1965

Assay of variola virus by the fluorescent cell-counting technique.

A quantitative assay for infective variola virus particles was developed which is based on the enumeration of cells containing fluorescent viral antigen after infection of McCoy cell monolayers. The direct fluorescent-antibody technique was employed to stain cells. The efficiency of virus adsorption was markedly enhanced by centrifugation of virus inoculum onto McCoy cell monolayers at 500 x g for 15 min. By this procedure, a proportionality was obtained between the number of fluorescent cells and volume of inoculum. Observations on the sequential development of viral antigen within cells and counts of fluorescent cells showed that the optimal time for enumerating fluorescent cells was after an incubation period of 16 to 20 hr. A linear function existed between virus concentration and cell-infecting units. Fluorescent cells were distributed randomly in infected cover slip cell monolayers. The assay was demonstrated to be highly sensitive, precise, and reproducible.

Animals↗