Ribosomal satellite

Indeed, a bDNA assay for diagnosis of African trypanosomiasis was developed and compared with buffy coat microscopy for detection of T brucei in human blood samples (Harris etal., 1996). Two repetitive DNA sequences found only in the T. brucei complex, a 177-bp satellite repeat and the ribosomal mobile element, were selected as targets in the bDNA assay. The assay used the standard bDNA components capture probes, target probes, amplifier molecules, and alkaline phosphatase-labeled probes. Various blood fractions and sample preparation methods were examined. Ultimately, buffy coat samples resulted in the highest sensitivity. Although typanosomes do not infect leukocytes, they cosediment with them. 

Preparative gradients have been widely used for preparing satellite DNAs such as the highly repetitous mouse satellite, the DNA sequences coding for ribosomal RNA and mitochondrial DNA (e.g. Flamm et al. 1969). They can be used for separating RNA-DNA hybrids from native and denatured DNA for preparative and analytical purposes (e.g. Birnstiel et al. 1968). DNA can be density-labelled with deuterium, N and bromo-deoxyuridine and normal and heavy DNA separated (e.g. Meselson, Stahl and Vinograd 1957 Braun and Will 1969). 

To sum up, four retroviruses, three of C-type (BLV, RSV, HTLV-1) and one of D-type (MMTV), were localized in four mammalian species. The data show that integrated retroviral sequences are not spread at random in the host genomes, but are found in some host genome compartments approximately matching the viral sequences in composition. This conclusion is stressed by a presentation of the results in terms of proviral density in host DNA (Fig. 6.5). Expectedly, in none of the cases investigated were the proviral sequences found in satellite or ribosomal DNA. 

Fig. 3. Nerve cell from the trigeminal gcmglion of a mouse injected iv with cadmium in a dose of 5 mg/kg bw and killed after 24 h. The cisternae of the rough endoplasmic reticulum are dilated (arrows) and mitochondria display increased matrical density. Ribosomes are lying freely in the cytoplasm. Lipid vacuoles (1) are present in a satellite cell. Reproduced with permission of Acta Neuropathologica.

Browning, K. S., Leung, D. W., and Clark, J. M., Jr., 1980, Protection of satellite tobacco necrosis virus ribonucleic acid by wheat germ 40 S and 80 S ribosomes. Biochemistry 19 2276. 

Kaempfer, R., Van Emmelo, J., and Piers, W., 1981, Specific binding of eukaryotic initiation factor 2 to satellite tobacco necrosis virus RNA at a 5 -terminal sequence comprising the ribosome binding site, Proc, Natl, Acad. Sci. USA 78 1542. 

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