Tomato: a crop species amenable to improvement by cellular and molecular methods

Tomato is a crop plant with a relatively small DNA content per haploid genome and a well developed genetics. Plant regeneration from explants and protoplasts is feasable which led to the development of efficient transformation procedures. In view of the current data, the isolation of useful mutants at the cellular level probably will be of limited value in the genetic improvement of tomato. Protoplast fusion may lead to novel combinations of organelle and nuclear DNA (cybrids), whereas this technique also provides a means of introducing genetic information from alien species into tomato. Important developments have come from molecular approaches. Following the construction of an RFLP map, these RFLP markers can be used in tomato to tag quantitative traits bred in from related species. Both RFLP's and transposons are in the process of being used to clone desired genes for which no gene products are known. Cloned genes can be introduced and potentially improve specific properties of tomato especially those controlled by single genes. Recent results suggest that, in principle, phenotypic mutants can be created for cloned and characterized genes and will prove their value in further improving the cultivated tomato.

Effect of treatment on established osteoporosis in young women with amenorrhoea

Background and Objective - Amenorrhoea in women of reproductive age causes loss of bone mineral. This study assessed the effect of treatment of amenorrhoea on bone mineral density. Design - Serial measurements of bone mineral density were obtained in women receiving treatment for amenorrhoea. Patients - Eighty-five women aged 17-40 with a past or current history of amenorrhoea, from various causes, with median duration of 46.5 months (range 8 months-21 years). Measurements - Bone mineral density in the lumbar spine was measured by dual-energy X-ray absorptiometry. Results - Initial vertebral bone mineral density was low, mean 0.85 (SD 0.10) g/cm2. After an interval of 19.6 (SD 7.5) months on treatment there was a highly significant increase to 0.89 (SD 0.10) g/cm2 (P < 0.0005). This was equivalent to a gain in bone mass of 2.1% per year (95% confidence interval 1.5-2.8%). Improvement was seen in all diagnostic groups (except polycystic ovary syndrome) and with all types of therapy. We observed no difference in the response of previously untreated patients compared with those already on treatment, nor any change in response with increasing duration of treatment. No new fractures were reported during the study. Conclusions - Bone mineral density in young women with amenorrhoea is improved by appropriate treatment, but recovery is not substantial. Hence early diagnosis and therapy is essential to prevent bone loss