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Biomedical subjects

B Appel

Publications and source records attributed to B Appel.

106 records · Page 6Linked to original sources
PubMed1982

Post-transcriptional nucleotide addition is responsible for the formation of the 5' terminus of histidine tRNA.

All sequenced histidine tRNAs have one additional nucleotide at the 5' end when compared to other tRNA species. Sequence analysis of histidine tRNA genes from Drosophila melanogaster and Schizosaccharomyces pombe showed that the terminal guanylate residue of the mature tRNAs is not encoded by the genes. Analysis of the products from in vitro transcription of these genes in extracts from Drosophila Kc cells demonstrated that the 5'-terminal nucleotide present in the mature tRNA is added post-transcriptionally. The addition reaction requires ATP. A portion of the mature tRNAs are then modified at the 5'-terminal pG. Analysis of the RNA species formed during the in vitro maturation of the Drosophila histidine tRNA primary transcript uncovered the following maturation scheme: (i) the primary transcript is processed by RNase P at the 5' end to form an intermediate precursor; (ii) the 3'-flanking sequence is endonucleolytically removed, and a guanylate moiety is added to the 5' end to form mature-sized histidine tRNA; and (iii) a fraction of the 5'-terminal guanylate residues then undergoes modification. In contrast to the capping of eukaryotic mRNA, the guanylate addition to histidine tRNA results in the formation of a (3'-5')-phosphodiester bond. There are no precedents for the post-transcriptional addition of nucleotides (in phosphodiester linkage) to the 5' end of RNA precursors.

Animals↗
PubMed1981

Determination of base pairing in yeast 5S and 5.8S RNA infrared spectroscopy.

Infrared Spectroscopy was used to determine the numbers of base pairs for yeast 5S RNA and 5.8S RNA. The spectra were recorded at 20 degrees C and 50 degrees C, where tertiary interactions are assumed to be of less importance. It may be concluded that the structure of both RNAs is highly ordered and that there are large contributions of tertiary interactions. The results are compared with data derived from structural models that were proposed in the literature as well as with data previously published for prokaryotic 5S RNAs.

Base Composition↗
PubMed1979

Determination of base pairing in Escherichia coli and Bacillus stearothermophilus 5S RNAs by infrared spectroscopy.

The extent of base pairing in Escherichia coli and Bacillus stearothermophilus 5S RNAs was determined by infrared spectroscopy. From the infrared spectra taken at 20 degrees and 52 degrees C it is concluded that E. coli and B. stearothermophlius 5S RNAs possess a large number of base pairs (Table I). Comparison of our results with those previously published using other methods leads to the conclusion that the structures of prokaryotic 5S RNAs involve a large number of tertiary interactions, in which the base pairing is not necessarily solely of the Watson-Crick type.

Base Composition↗
PubMedDate not supplied

Epidural abscess causing tetraparesis: case report.

A case is presented of a 26-year-old male with a 8-day history of fever and back pain, and limb weakness beginning 24 hours before admission. An abscess caused by a staphylococcus aureus was localised in the thoracic paravertebral region with penetration in the subarachnoidal space at T1. Myelography appeared to be superior to CAT-scan and NMRI of the cervico-thoracal region in supporting the diagnosis. Treatment by laminectomy of C7-T3 48 hours after admission did not lead to neurological improvement and an incomplete tetraplegia persisted. The importance and difficulty of early diagnosis is stressed.

Abscess↗
PubMedDate not supplied

[The relationship of plasmids from environmental Yersinia isolates and the virulence plasmid of enteropathogenic Yersinia strains].

The human pathogenic strains of Yersinia harbour a conserved plasmid carrying the Yop virulon. The virulence plasmid of Yersinia enterocolitica strains belonging to the serogroups O:3 and O:9 were used as probes to detect homologous sequences in plasmids of "avirulent" Yersinia strains. "Avirulent" Yersinia strains (Y. enterocolitica biogroup 1A, Y. intermedia, Y. kristensenii and Y. frederiksenii) lack the virulence plasmid. They are widely distributed in the environment and can frequently be isolated from clinical samples. Hybridisation experiments revealed a number of common genetic elements of the virulence plasmid and the plasmids of "avirulent" Yersinia strains. These elements were identified as genes involved in plasmid replication, as an endonuclease gene and as mobile genetic elements. However, none of the plasmid encoded virulence genes was present in the plasmids of "avirulent" Yersinia strains. The frequent occurrence and the possible etiological relevance of "avirulent" isolates will be discussed.

Animals↗
PubMedDate not supplied

Methanol intoxication. Parkinsonism and decreased Met-enkephalin levels due to putaminal necrosis.

Due to methanol intoxication, a 38-year-old male developed permanent parkinsonism with visual impairment. Brain computerized tomography (CT) and magnetic resonance imaging (MRI) revealed cystic resorption of the putamen. An alteration of the central noradrenergic activity and the opioid system can be assumed because of increased dopamine beta-hydroxylase (D beta H) activity and decreased methionine-enkephalin (Met-Enk) levels in the cerebrospinal fluid (CSF).

Adult↗
PubMedDate not supplied

Brain ischaemia.

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Brain Ischemia↗
PubMedDate not supplied

Repeat thallium-201 SPECT in cerebral lymphoma.

The authors report on the contribution of Thallium-201 brain SPECT in the diagnosis and follow-up of a non-immunosuppressed patient, presenting with primary cerebral lymphoma. The tumoral process was at first not diagnosed on CT-scan, but Thallium-201 SPECT suggested a tumoral invasion. During corticosteroid treatment the tumor volume on CT-scan decreased, while on Thallium-201 SPECT there was an enhancement of the accumulation and an increasing tumor to non-tumor ratio. These scintigraphical findings more closely reflected the clinical course and the postmortem results.

Aged↗