Biomedical subjects
A Farquharson
Publications and source records attributed to A Farquharson.
Nucleotide sequence and gene organization of sea urchin mitochondrial DNA.
The 15,650 base-pair mitochondrial genome of the sea urchin Strongylocentrotus purpuratus has been cloned and sequenced. It exhibits a novel organization that suggests the primacy of post-transcriptional gene regulation. The same 13 polypeptides, two rRNAs and 22 tRNAs are encoded as in other animal mitochondrial DNAs, but are organized with extreme economy; non-coding information between genes is almost completely absent, some stop codons are generated post-transcriptionally and tRNA sequences are interspersed between only a minority of other structural genes. The genome uses a variant genetic code, in which AAA specifies asparagine, ATA isoleucine, TGA tryptophan and AGN serine, and has an unusual pattern of codon bias. The order of genes shows several differences from that of vertebrates. The genes for the large (16 S) ribosomal RNA and for NADH dehydrogenase subunit 4L (ND4L) are in different positions, located respectively between those encoding ND2 and cytochrome oxidase subunit I (COI) and between COI and COII. This organization is conserved amongst at least four regular echinoids diverging by some 225 million years. Most tRNA genes are also in different positions. The only long unassigned sequence in the genome (121 base-pairs) is located within a cluster of 15 tRNA genes. It contains elements resembling some of those found in the displacement (D) loop of vertebrate mtDNAs, notably polypurine/polypyrimidine tracts that may play a role in regulating transcription and the initiation of replication. The separation of the ribosomal RNA genes from each other and from the putative control region imposes special demands on the transcription of the genome.
[Function and role of self-help groups: from the First Self-Help Group Seminar].
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Single-layer anastomosis in the large bowel: ten years' experience.
Satisfactory experience with single-layer colorectal anastomosis during 1969-74 led to an analysis of the results of single-layer large bowel anastomosis during the subsequent years 1975-79. This technique has continued to be associated with a low incidence of anastomotic failure, but anastomotic integrity also depends on rigorous attitudes to bowel preparation, to bacterial contamination and to the avoidance of anastomosis when the risk of anastomotic failure is high.