Search PubMed⌕ Search

Biomedical subjects

D L Rosen

Publications and source records attributed to D L Rosen.

6 recordsLinked to original sources
PubMed1988

Interference between coinoculated viroids.

Experiments were carried out to seek evidence of an interaction between two viroid RNAs introduced to tomato plants in the same inoculum. At the level of symptom expression, the severe isolate of potato spindle tuber viroid (PSTV) dominated the mild isolate. Seventy-five percent of the plants inoculated with a 100-fold excess of the mild isolate developed unattenuated symptoms of severe disease. Other experiments revealed that infectious RNA molecules transcribed from cloned DNA templates containing PSTV sequences reduced the level of hop stunt viroid (HSV) RNA present in nucleic acid extracts of plants which had been inoculated with a mixture of dimeric plus-strand transcripts of these two viroids. Plants inoculated with dual transcripts--containing two copies of PSTV linked to two copies of HSV--developed characteristic symptoms of severe PSTV. Dot hybridization demonstrated that only PSTV replicated to detectable levels in these plants. A likely interpretation of these results is that the HSV portion of the dual transcripts failed to replicate because of interference from PSTV. These results raise questions about how the process of viroid replication is related to symptom expression, and lead to suggested models for the effect of viroid-like RNAs in cells under both normal and pathogenic circumstances.

Plant Diseases↗
PubMedDate not supplied

Differential behavior of liposome-introduced specific RNAs in living Drosophila cells.

We have developed a protocol for efficiently introducing macromolecules into Drosophila tissue culture cells using liposomes. By carefully adjusting the fusion parameters, conditions have been established to routinely encapsulate 15-30% of the starting material into liposomes and to introduce 20-30% of the liposome-encapsulated material into the cells during a 30-minute fusion period. Essentially, all of the cells receive material from the liposomes and 10(9) cells can be fused at once. The fusion does not have any measureable effect on cell viability as assayed by trypan blue exclusion, growth rate, and cell morphology. We have utilized this technique to introduce radioactive RNAs into nonradioactive cells, thus enabling the behavior of the introduced RNAs to be followed unambiguously. Liposome-introduced small nuclear RNAs (snRNAs) are stable in the cell for at least 25 hours (approximately two cell generations), with 80% of the radioactivity remaining trichloroacetic acid (TCA) precipitable and the gel electrophoresis pattern remaining essentially unchanged. This is in contrast to liposome-introduced cytoplasmic RNAs, which are only 20% TCA precipitable after the first hour. In the cell, the introduced snRNAs attain a 10-35-fold higher concentration in the nucleus than the cytoplasm. Nuclear accumulation is not seen with Drosophila tRNA or 5S RNA, both of which attain the same nuclear as cytoplasmic RNA concentration.

Animals↗
PubMedDate not supplied

Effects of age on pilocarpine-induced c-fos expression in rat hippocampus and cortex.

The effect of age on pilocarpine-induced expression of the immediate-early gene c-fos was examined in the hippocampus and cortex of Long-Evans rats. Rats were treated with either pilocarpine (25 mg/kg) or saline, and sacrificed 90 min. following injection. The level of c-fos mRNA and Fos-like protein expression was determined using in situ hybridization histochemistry, and immunocytochemistry, respectively. In saline-treated animals, comparable levels of c-fos mRNA and Fos-like protein were observed in the hippocampus and cortical regions of young (6 month) and aged (24-26 months) rats. The expression of Fos-like protein following pilocarpine treatment was increased, however, in frontal, retrosplenial, and cingulate cortex of aged compared to young rats. In frontal and retrosplenial cortex, the changes in Fos-like protein were accompanied by changes in c-fos mRNA expression. In contrast, no age difference was detected in the hippocampus or parietal cortex of pilocarpine-treated rats. These regionally-specific age differences in response to pilocarpine administration suggest that mechanisms localized to those areas play an important role in determining the response to cholinergic stimulation mediated through post-synaptic muscarinic receptors.

Aging↗