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Direct gene transfer into plant protoplasts has been recently developed, and conditions for high frequency transformation of SR1 tobacco protoplasts established. In this paper we analyse numerous transformation parameters in a comparative study on SR1Nicotiana tabacum and N. plumbaginifolia, and report on a simple chemical technique for very efficient protoplast transformation. It is based on the synergistic interaction of MgCl2 and PEG. The technique yielded up to 1400 transformants per 3×105 treated N. tabacum protoplasts (up to 4.8% of the survivors, late selected clones). Using N. plumbaginifolia, the frequencies were 10-fold lower, indicating that the ‘competence’ for transformation has a species-specific component.

The nitrate-reductase (NR) defective cell lines of Nicotiana plumbaginifolia isolated in our laboratory could not be regenerated into plants on the standard medium (Márton et al. 1982 a). The normal regeneration potential, however, was restored in somatic hybrids obtained by fusing the NR- (green) lines with a pigment deficient (P-), but NR+ line, A28. Somatic hybrid plants were fertile in two combinations (A28 + NA9 and A28 + NX9). As expected, segregation for NR- and P- was found after selfing the somatic F1 (SF1) obtained by protoplast fusion, and in the F2. The variable segregation ratios are explained by chromosome abnormalities. Co-segregation of the NR- phenotype and the altered response to shoot induction on standard medium suggest the involvement of the nitrate-assimilatory pathway in determining shoot regeneration ability.

Summary One hundred and forty-five children aged 3 months to 11.5 years, with rectal temperatures greater than 38.9°C, were randomly treated with aspirin 5, 10 or 15 mg/kg p.o. Temperatures were recorded just before medication, every 30 min thereafter for 4 h and subsequently hourly up to 6 h. In all dosage regimens the average temperature was significantly reduced in the time interval 1–6 h after drug administration; the antipyretic effect, however, was significantly greater with the 10 and 15 mg/kg doses. Both had significantly better and comparable clinical efficacy, defined as reduction in fever below 38.9°C. The duration of the clinical effect was not dose-related. A dose of 10 mg/kg appears rational for the treatment of children with fever.