PubMed · 7251898
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G Zaman, J Chayen. 1981. An aqueous mounting medium.. https://doi.org/10.1136/jcp.34.5.567
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Recent progress in the search for the physiological role of plant lectins supports the idea that some of these proteins are involved in the defence mechanisms of the plant. To place the evidence in favour of such a defensive role in a broad perspective, a short overview is given of the most important plant pathogens and predators. In addition, the solutions that plants have developed to resist the continuous threat of a hostile environment are briefly discussed in relation to the protective role of proteins in general. The presumed involvement of plant lectins in defence mechanisms is first inferred from an analysis of the biochemical, physiological, cellular biological and molecular biological properties of plant lectins. Subsequently, the available experimental evidence for the involvement of lectins in the plant's defence against viruses, bacteria, fungi and herbivorous invertebrates and vertebrates is discussed in some detail. Since the defensive role of plant lectins is determined largely by their ability to recognize and bind foreign glycans, a brief discussion is given of how the basically protective properties of these proteins can be exploited for histochemical applications in biological and biomedical research.
This retrospective reviews the methodology we have developed over several decades for detecting reactive oxygen species (ROS), using the activated polymorphonuclear leukocyte (PMN) as the paradigm of a cell which vigorously generates ROS through activation of NADPH oxidase. In the seventies, the sites of ROS generation by PMN were not clear from biochemical data, and we sought to develop new methods for the cytochemical localization of O2.-, H2O2, and the H2O2-myeloperoxidase (MPO)-halide system. The H2O2-MPO-halide system in phagocytosing cells was localized at the fine structural level by our development of 3,3'-diaminobenzidine (DAB) as a cytochemical probe for detecting peroxidase activities. Using DAB and exogenous H2O2, we confirmed that azurophil granules discharged MPO into the phagosome, and using particles coated with DAB and relying on endogenous H2O2 to yield oxidized DAB, H2O2 was localized to phagolysosomes. The subcellular sites of H2O2 generation were shown using cerium ions which react with H2O2 and precipitate electron opaque cerium perhydroxides (Ce(OH)2OOH and Ce(OH)3OOH). The results suggested that NADPH oxidase is associated with the plasma lemma, and that the enzyme enters the phagosome along with the invaginating plasmalemma, accounting for the presence of H2O2 in the phagosome. As O2.- is the major product of NADPH oxidase, its detection was of some importance. Based on the concept that O2.- oxidizes Mn2+ to Mn3+, and Mn3+ oxidizes DAB, a medium containing DAB-Mn2+ was used to localize sites of O2.- production in stimulated PMN. The localizations were, as expected, similar to those for H2O2. These techniques have been of considerable usefulness and in general provide the foundation for cytochemistry of ROS in other systems.
Despite the complex role of melanocytes in skin physiology, the function of oral mucosal melanocytes has attracted little research interest and remains largely unclear. This article reviews what is known about oral mucosal melanocytes and identifies areas of research that may shed further light on their role in oral biology.