The pentatricopeptide repeat proteins PPR4 and EMB2654 have been shown to be required for the transsplicing of plastid rps12 transcripts in Zea mays (maize) and Arabidopsis, respectively, but their roles in this process are not well understood. We investigated the functions of the Arabidopsis and Oryza sativa (rice) orthologs of PPR4, designated AtPPR4 (At5g04810) and OsPPR4 (Os4g58780). Arabidopsis atppr4 and rice osppr4 mutants are embryo-lethal and seedling-lethal 3 weeks after germination, respectively, showing that PPR4 is essential in the development of both dicot and monocot plants. Artificial microRNA-mediated mutants of AtPPR4 displayed a specific defect in rps12 trans-splicing, with pale-green, yellowish or albino phenotypes, according to the degree of knock-down of AtPPR4 expression. Comparison of RNA footprints in atppr4 and emb2654 mutants showed a similar concordant loss of extensive footprints at the 3 0 end of intron 1a and at the 5 0 end of intron 1b in both cases. EMB2654 is known to bind within the footprint region in intron 1a and we show that AtPPR4 binds to the footprint region in intron 1b, via its PPR motifs. Binding of both PPR4 and EMB2654 is essential to juxtapose the two intron halves and to maintain the RNAs in a splicing-competent structure for the efficient trans-splicing of rps12 intron 1, which is crucial for chloroplast biogenesis and plant development. The similarity of EMB2654 and PPR4 orthologs and their respective binding sites across land plant phylogeny indicates that their coordinate function in rps12 trans-splicing has probably been conserved for 500 million years.

In the village of Beşköprü, about five kilometres to the south-west of the town of Adapazari in western Turkey, and just to the north of the main Istanbul–Ankara highway, there stands a large well-constructed bridge; its fabric is generally in good condition apart from the destruction of a short section of the causeway near its eastern end to permit the passage of the branch railway line to Adapazan. Although the bridge now only spans two minor side channels of the small stream called the Çark Deresi, which drains Lake Sophon (modern Sapanca), there is no doubt that the bridge was originally designed on the orders of the emperor Justinian to span the mighty Sangarius (modern Sakarya) which at present flows in a south–north direction about three kilometres to the east of the bridge. The only detailed first-hand account of the bridge is still that by Texier, whose description has to be corrected on some important points.

The out of hours workload of a training practice in a suburban and semirural area on the south coast of England was studied for one year. An overall rate of contact of 273/1000 patients was found, which indicated a workload greater than that reported in most other studies. The duty doctor received over 35 telephone calls from patients during some Saturdays (1200 Saturday to 0800 Sunday) and Sundays (0800 to 0800 Monday), up to five being between 2300 and 0700. Of the patients who contacted a general practitioner, 44% were given advice by telephone and 4 9% were admitted to hospital. The admission rate was lower than that given in other studies. A considerable proportion of the workload arose from doctors covering the casualty department of a cottage hospital. Patients having a high expectation of 24 hour care by general practitioners in an area of comparative affluence (Jarman indices -13-8 to 1.7) may account for this aspect of the workload.

No abstract