[Pain therapy in addicted patients]. / Schmerztherapie bei suchtmittelabhängigen Patienten.

Each individual is entitled to an adequate and sufficient pain therapy. However, only a few studies have examined the peculiarities of pain management in drug-dependent or formerly addicted patients. Any addiction is disadvantageous for a successful pain therapy, since some of the prescribed drugs may themselves cause addiction. Drug-dependent patients are often tolerant to opioids. Additionally, there is a risk of iatrogenic pain becoming chronic due to disregard for already known risk factors and comorbidities. However, a history of addiction should not prevent sufficient pain therapy, especially since there is no risk of addiction when the pain therapy employed is adequate for the pathophysiology involved. There are adequate pain therapies for addicted patients. The best results are achieved by taking into account the physiological and psychological peculiarities of drug-dependent patients. Importantly, this should be combined with a variety of different, optimized, multimodal therapeutic regimes, as well as with an interdisciplinary approach.

Genetic analysis of Nicotiana pollen-part mutants is consistent with the presence of an S-ribonuclease inhibitor at the S locus.

Self-incompatibility (SI) is a genetic mechanism that restricts inbreeding in flowering plants. In the nightshade family (Solanaceae) SI is controlled by a single multiallelic S locus. Pollen rejection in this system requires the interaction of two S locus products: a stylar (S)-RNase and its pollen counterpart (pollen S). pollen S has not yet been cloned. Our understanding of how this gene functions comes from studies of plants with mutations that affect the pollen but not the stylar SI response (pollen-part mutations). These mutations are frequently associated with duplicated S alleles, but the absence of an obvious additional allele in some plants suggests pollen S can also be deleted. We studied Nicotiana alata plants with an additional S allele and show that duplication causes a pollen-part mutation in several different genetic backgrounds. Inheritance of the duplication was consistent with a competitive interaction model in which any two nonmatching S alleles cause a breakdown of SI when present in the same pollen grain. We also examined plants with presumed deletions of pollen S and found that they instead have duplications that included pollen S but not the S-RNase gene. This finding is consistent with a bipartite structure for the S locus. The absence of pollen S deletions in this study and perhaps other studies suggests that pollen S might be required for pollen viability, possibly because its product acts as an S-RNase inhibitor.

A molecular description of mutations affecting the pollen component of the Nicotiana alata S locus.

Mutations affecting the self-incompatibility response of Nicotiana alata were generated by irradiation. Mutants in the M1 generation were selected on the basis of pollen tube growth through an otherwise incompatible pistil. Twelve of the 18 M1 plants obtained from the mutagenesis screen were self-compatible. Eleven self-compatible plants had mutations affecting only the pollen function of the S locus (pollen-part mutants). The remaining self-compatible plant had a mutation affecting only the style function of the S locus (style-part mutant). Cytological examination of the pollen-part mutant plants revealed that 8 had an extra chromosome (2n + 1) and 3 did not. The pollen-part mutation in 7 M1 plants was followed in a series of crosses. DNA blot analysis using probes for S-RNase genes (encoding the style function of the S locus) indicated that the pollen-part mutation was associated with an extra S allele in 4 M1 plants. In 3 of these plants, the extra S allele was located on the additional chromosome. There was no evidence of an extra S allele in the 3 remaining M1 plants. The breakdown of self-incompatibility in plants with an extra S allele is discussed with reference to current models of the molecular basis of self-incompatibility.

Self-incompatibility in flowering plants.

Fertilization in flowering plants begins with a pollen grain bearing the male gametes landing on the female stigma. Several mechanisms enable the stigma to discriminate between the different types of pollen that it may receive, of which the best studied is self-incompatibility. The molecules that regulate self-incompatibility are well characterized in two plant families, the Solanaceae and Brassicaceae. This list has recently been extended to include candidates for self-incompatibility molecules from the Rosaceae, Papaveraceae and Poaceae. The information provided by the sequences of these molecules gives insight into the mechanisms and evolution of self-incompatibility in the different families of flowering plants.