Immunological Comparison of Transferrins of Some European Cypirinid Fish

Double immunodiffusion in agar gel with antiserum to carp transferrin was used to prove immunological relatedness between the transferrins of some European cyprinid fish. Quantitative differences between transferrins of nine species of cyprinid fish were studied by micro-complement fixation with the use of entisera to transferrins of four species. Immunological distances were conspicuously great and amounted on average to about 125 immunological distance units (IDU). A high rate of evolution of transferrins wes obtained. namely 4.2 IDU/million years, which represents about 0.84% sequence differences per million years.     

The Sinorhizobium meliloti Insertion Sequence (IS) Element ISRm14 Is Related to a Previously Unrecognized IS Element Located Adjacent to the Escherichia coli Locus of Enterocyte Effacement (LEE) Pathogenicity Island

ISRm14 is 2695 basepairs (bp) in size and bordered by 22 bp imperfect inverted repeats (IRs). A 9-bp target sequence is duplicated upon ISRm14 transposition. The DNA strand that putatively encodes the transposase enzyme carries three open reading frames (ORFs) designated ORFs1 to 3, which specify putative proteins of 15.9 kDa, 13.1 kDa, and 61.1 kDa, respectively. According to its structural characteristics, ISRm14 belongs to the recently proposed IS66 family of IS elements. The ORFs1 to 3 encoded putative proteins displayed significant similarities to ORFs of the previously unrecognized IS element ISEc8, which is inserted adjacent to the locus of enterocyte effacement (LEE) pathogenicity island of Escherichia coli EDL933. Analyses of the distribution of ISRm14 in a natural S. meliloti population showed its widespread occurrence in 66% of the strains tested with a copy number ranging from 1 to 6. Received: 13 May 1999 / Accepted: 14 June 1999     

Cultivation of avian malaria parasites in mammalian liver cells

The exoerythrocytic stages of Plasmodium lophurae and P. fallax were grown in cell cultures derived from embryonic mouse livers. Liver cell monolayers were maintained in continuous culture with frequent subculturing for extended periods of time. Morphologically, the main cell type was a large, flat cell which closely resembled in shape the mouse parenchymal cell, although small colonies of spindle-shaped cells could also be found. Mammalian cells were labelled with thymidine-³H prior to infection with avian merozoites so they could be positively distinguished from any avian cells which might be present in the merozoite inoculum as contaminants. Merozoites were observed inside the labelled mammalian cells within three hours and large forms were seen at 48 hr. The mammalian cells supported parasite growth comparable to that observed in avian cell cultures.