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J L MELNICK

Publications and source records attributed to J L MELNICK.

At least 109 records · Page 6Linked to original sources
PubMed1959

Double infections of single cells with ECHO 7 and Coxsackie A9 viruses.

Virus particles derived from single cells infected with two enteroviruses have been studied. Evidence was obtained to indicate that phenotypic, but not genotypic, mixing occurs between Coxsackie A9 (CAP) and ECHO 7 (E7) viruses. Monkey kidney cultures in monolayer were doubly infected with high multiplicities of CA9 and E7 viruses. During the latent period, the infected cells were suspended, diluted, and distributed under oil into droplets each containing a single cell, as checked by microscopic observation. The virus particles released by individual cells into the microdrop were characterized in differential plaque neutralization tests. Fifteen per cent of the microdrops contained doubly neutralizable particles, 53 per cent yielded either CA9 or E7 particles, and 34 yielded particles of an intermediate character (deficits between 37 and 75 per cent). On passage, the doubly neutralizable particles yielded progeny of both parental types. All passage strains behaved like the corresponding parent strain as regards pathogenicity for newborn mice, which is to say that this property was limited to virus particles with CA9 antigenicity. Coxsackie A9 has a more rapid growth cycle than ECHO 7 in rhesus monkey kidney cell cultures, and a slower one in patas cultures. In rhesus, when E7 virus was added first, CA9 could be added up to 2 hours later, and still a significant number of cells yielded either CA9 or doubly neutralizable virus. The converse was observed in patas cells.

Animals↗
PubMed1959

In vitro differentiation of virulent and attenuated polioviruses by their growth characteristics on MS cells.

The MS character of polio-virus particles is described. Strains that produced relatively large plaques, up to 6 mm. in diameter, on a monkey stable (MS) cell line, were classified as MS(+). Such strains were found to include the highly virulent poliovirus strains. Attenuated strains appeared deficient in this gene, for they produced tiny plaques less than 1 mm. in size, or no visible plaques at all; they were considered as MS mutants. Strains of maximum neurovirulence for the monkey possessed the MS(+) and d(+) characters, while those of greatest attenuation were MS d. Strains possessing the MS d(+) character showed high or intermediate attenuation. Virulent strains grew equally well in MS or primary monkey kidney (MK) cells. Attenuated strains gave lower titers in MS cultures than in MK cultures. While MS cells after infection with a virulent virus yielded about 100 to 200 PFU per cell, only one PFU per MS cell was detected after infection with an attenuated virus. A study of newly isolated Type 3 strains showed them to consist of the MS(+)d(+) or MS d(+) type. The MS(+)d(+) virus proved to be highly paralytogenic for monkeys even by the intramuscular route, while the MS d(+) virus was of the partially attenuated type. The study of in vitro characters of viruses from children fed attenuated poliovirus offers a possibility for following genetic changes of the viruses after multiplication in the human enteric tract.

Animals↗
PubMed1959

Measles virus.

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Humans↗
PubMed1959

Enteroviruses.

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Enterovirus↗
PubMed1959

Neutralizing-antibody-combining (NAC) test for measuring antigenic potency of poliomyelitis vaccine.

An in vitro test for the quantitative determination of the antigenic potency of poliomyelitis vaccine is described. This test-termed the neutralizing-antibody-combining (NAC) test-is based on the measurement of the capacity of an inactivated virus in tissue culture to bind neutralizing antibody. Details of the experimental design and technique are given, the authors stressing the importance of using small and precisely known dosages of virus and antiserum and of incubating the test mixtures for a sufficiently long period. In preparing the test mixtures, it is essential to incubate first the vaccine + antiserum, and then add the virus. No vaccine activity will be demonstrable if the test is set in the reverse order.EXPERIMENTS CARRIED OUT WITH THE NAC TEST HAVE SHOWN THAT: (a) the test is type-specific; (b) the antigen-antibody union in the system is irreversible; (c) vaccines containing preservative yield the same potency titres as untreated vaccines; (d) the test gives reproducible results; (e) the results of the NAC test did not always agree with those obtained in animal potency tests, probably because of vagaries in the latter; (f) dried vaccines retain their complement-fixing activity, but lose their power to combine with neutralizing antibody in vitro and to produce neutralizing antibodies in vivo-a finding which suggests that the NAC test measures in vitro the same antigen responsible for neutralizing-antibody production in vivo.

Animals↗
PubMed1958

Cytological aberrations in cultures of normal monkey kidney epithelial cells.

A cytological study was made of short term primary cultures of monkey kidney epithelial cells grown in serum-containing (M-H) and synthetic (SM-2) media. The mitotic activity of the cultures reached a peak 3 to 5 days after seeding, and rapidly declined if the medium was not changed. With replenishment at 48 hour intervals a high mitotic rate was maintained through the 8th day. Cultures subjected to a glycine- and glucose-deficient medium showed a sharp decline in mitotic activity within 24 hours. When such cultures were replenished a burst of mitotic activity occurred 20 to 30 hours later. Mitotic aberrations such as multipolar spindles, anomalous spindles with scattered chromosomes, lagging or precocious movement of chromosomes, chromosome fragments, and chromosome bridges were found in all cultures ranging from 16 to 40 per cent of the dividing cells. Non-mitotic aberrations such as giant nuclei, multinucleate cells, nuclear fragmentation, micronuclei, nuclear inclusions, and phagocytosis were found in approximately 3 to 7 per cent of the non-dividing cell population. The frequency and types of mitotic abnormalities were generally independent of the medium used and the mitotic index of the cultures.

Animals↗