Ultrastructural Study of Pneumocystis carinii in Explant Cultures of Rabbit Lung and in Cultures with and without Feeder Cells

Pneumocystis carinii-parasitizcd lung explains were obtained from corticoid-lreated rabbits and maintained in vilro. Twenty-one days after the beginning of explant cultures, the ullrastructura! morphology of trophozoite, precyst and cyst forms was normal as compared to the in vivo ui-trastrucuirc of P. carinii from infected rabbit. However, after the 36th day, only altered forms of P. carinii were observed. Lung tissue showed only minor alterations. fntracytoplasmic lamellar inclusions were observed in type 2 alveolar cells from which they were released. While the total number of parasites increased approximately 4-fold from day 0 to day 41, trophozoite counts increased approximately 6 times. Pneumocystis cells from inocula and supcmaics of cultures with and without Vera cells showed important ullrastructural alterations.     

Systematics of the black rat in Madagascar: consequences for the transmission and distribution of plague

The plague has been present for a century in Madagascar; the only known reservoir is the black rat, which is also the main victim of this disease. Whereas the two plague foci are restricted to an altitude above 800 m, the black rat is distributed over the whole island, the only morphological variation being a within-site variability in belly colour. To resolve these apparent contradictions, an analysis of the different belly colour morphs and of populations living in different habitats and altitudes was undertaken. An allozymic study demonstrated that sympatric white- and grey-bellied rats ( N  = 26) living within the plague foci, all belonged to the same species: Rattus rattus . This specific assignment was confirmed by a chromosomal analysis which showed that all 90 individuals studied presented the same diploid number, 2 n  = 38, whatever the habitat and altitude. This study indicates that all specimens investigated in Madagascar could be referred to the same black rat species. Survival of rat populations, despite a century of coexistence with the plague, is most likely related to their high reproductive and recolonization potential, as well as selection of plague resistant genotypes. As the altitudinal limit of the plague foci does not seem to be related to characteristics of the rodent reservoir, investigations concerning the vectors are now essential.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78 , 335–341.