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Effects of Promastigote Growth Phase, Frequency of Subculture, and Host Age on Promastigote‐initiated Infections with Leishmania donovani in the Golden Hamster* †

1974; Wiley; Volume: 21; Issue: 4 Linguagem: Inglês

10.1111/j.1550-7408.1974.tb03692.x

2375-0804

Mariette Giannini,

Trypanosoma species research and implications

SYNOPSIS Promastigotes of Leishmania donovani , 3S strain, were cultured from homogenized infected hamster spleen incubated at 25 C in a particle‐free modification of Tanabe's (1923) medium, and were subcultured in this medium from 1 to 4 times. Promastigotes were inoculated intracardially to golden hamsters ( Mesocricetus auratus ). Promastigotes that were subcultured frequently by transfer from log phase of growth retained their infectivity for hamsters, as assayed by numbers of amastigotes in the liver at 16 days post infection. Promastigotes that were subcultured infrequently by transfer from stationary phase declined in infectivity. The extent of the decline was roughly proportional to the length of the incubation periods of the primary culture plus 1st subculture. Promastigotes harvested from log phase of growth were significantly less infective for hamsters than those harvested from stationary phase of growth, in that numbers of amastigotes found in the liver after 16 days were lower, and times to death longer, when log phase organisms were used to infect hamsters. The age of the hamster at the time of inoculation was found to affect the apparent infectivity of promastigotes from a 1st or 2nd subculture. When weanling (age 4 weeks), juvenile (age 8 weeks) and adult (age 24 to 32 weeks) hamsters received the same numbers of promastigotes, the weanlings had the highest numbers of liver amastigotes at 16 days, and shortest times to death, of the 3 groups; juveniles were intermediate between weanlings and adults; and adults had the lowest numbers of parasites and longest times to death of the host. Differences were statistically significant only between weanlings and adults. Responses of weanling and adult hamsters to infection with promastigotes could be rendered indistinguishable if the promastigotes were inoculated on the basis of 10 5 promastigotes per g of host body weight.