Pathogen-induced proteins with inhibitory activity toward Phytophthora infestans.

A bioassay using Phytophthora infestans was developed to determine whether inhibitory proteins are induced in pathogen-inoculated plants. Using this bioassay, AP24, a 24-kilodalton protein causing lysis of sporangia and growth inhibition of P. infestans, was purified from tobacco plants inoculated with tobacco mosaic virus. Analysis of the N-terminal amino acid sequence identified AP24 as the thaumatin-like protein osmotin II. The sequence was also similar to NP24, the salt-induced protein from tomato. Subsequently, we purified a protein from tomato plants inoculated with P. infestans that had inhibitory activities identical to those of the tobacco AP24. The N-terminal amino acid sequence of this protein was also similar to those of osmotin and NP24. In general, both the tobacco and tomato AP24 caused lysis of sporangia at concentrations greater than 40 nanomolar and severely inhibited hyphal growth at concentrations greater than 400 nanomolar. Because both proteins were induced by pathogen inoculation, we discussed the possible involvement of these proteins as a plant defense mechanism.

Adverse effects of drugs on the blood.

Amongst adverse drug reactions blood dyscrasias are not frequent, but they may have serious consequences. Compared with Sweden, data from The Netherlands are scarce. It is to be expected that regular reports about the incidence of drug-induced blood dyscrasias may play an important role in general prevention. Blood dyscrasias may be caused by a variety of drugs, from many pharmacotherapeutic groups with diverse chemical structures and with all application forms. Metabolism and distribution may influence the activity of drugs. Drug-induced anaemias, including aplastic anaemia, are briefly discussed. Toxic and immune mechanisms may occur. The same holds with regard to the leucopenias. Drug-induced thrombocytopenia is mainly immune-mediated (cytostatics being excluded as causative agents). In immune-mediated drug-induced blood dyscrasias often haptens must be formed. They can be formed in vivo in the liver or in the lymphocytes. In some cases they appear to be formed even in vitro. Tracing the causative agent of a dyscrasia, be it a drug or some other substance, requires a series of investigations, comprising usage of the drug, serology and cell culture. Provocation tests are seldom justified. Distinct preventive measures can be taken to minimize the risk of blood dyscrasias: avoidance of risky drugs, awareness of the patient about early clinical signs and haematological control.