ALBERT

Notes: Summary Phagocytosis by polymorphonuclear leukocytes triggers a burst of oxidative metabolism resulting in hydrogen peroxide and superoxide production, and these active oxygen species function in the killing of microorganisms. A new cytochemical technique, based on a manganese dependent diaminobenzidine oxidation, has been developed to detect superoxide in these cells. It has been shown that superoxide generation is associated with the plasma membrane in cells activated by particulate (zymosan) and nonparticulate (phorbol myristate acetate) stimuli. This membraned activity is maintained during invagination such that reduced oxygen is generated within the endocytic vacuoles. Reaction product is absent from unstimulated cells; additionally, formation of precipitate is blocked by omission of Mn++, low temperature, glutaraldehyde prefixation, and the presence of superoxide dismutase in the incubation medium.

Notes: Summary Normal skeletal and cardiac striated muscle from adult rats was incubated for the cytochemical detection of acid phosphatase activity with cerium as the capture metal. Results from these experiments show that normal striated muscle has a greater number of acid phosphatase-positive structures, which are presumed to be lysosomes, than has been indicated by several previous cytochemical studies.

Notes: Abstract The fundamental theory for discontinuous fibre reinforcement of plastics is reviewed and compared to experimental data obtained from a range of single-fibre composite tests. Given that the theory provides an adequate description of fibre reinforcement, predictions for the critical fibre length in model composites based on glass fibres embedded in a range of matrices with different volume fractions have been made. The model has been used to predict the modulus for unidirectional discontinuous glass fibre-reinforced composites with a high volume fraction of glass fibres with different mean fibre lengths, diameters and matrices. From this study the concept of a critical aspect ratio, required for effective composite performance, has been defined generally for this type of material. The critical aspect ratio has been found to depend upon fibre diameter, matrix modulus and fibre volume fraction. A brief review of this class of material in the scientific literature has been made in the areas of deformation and failure. To aid the developments in the theory behind discontinuous fibre composites, a series of deformation experiments have been performed on model discontinuous glass fibre/nylon 6,6 compounds produced by extrusion and pultrusion compound technology. The materials were processed using multilive feed technology, to produce effective representations of unidirectional discontinuous glass-fibre composites. Given that the model compounds contained variations in fibre lengths and diameters, the deformation experiments performed were a fundamental test of the theory presented for the critical fibre aspect ratio and the results of theory and experiment have been compared. Based on the predictions of the model and the experimental work, conclusions are offered on the type of fibre that should be used for discontinuous fibre-reinforced composites.

Notes: Summary A simple technique is described for ultrastructural enzyme cytochemistry using small volumes and numbers of single cells. Small aliquots (1–5 μl) of single cells suspended in a glutaraldehyde fixative are incubated on poly-L-lysine-coated glass coverslips. Cells in contact with the coated coverslip become immobilized to that support. All changes of solutions are accomplished without repeated centrifugation.

Notes: Abstract With the establishment of plantation eucalypts around the world there is an increasing need for reference data which can be used to diagnose the nutrient status of eucalypt seedlings. Therefore, deletion glasshouse nutrient trials were set up in sand and solution culture to obtain deficiencies of N, P, K, Mg, Ca, S, Fe, Zn, Cu and Mn in the spotted iron gum (Eucalyptus maculata). Nutrient concentration ranges were obtained for leaves at defined growth stages for (a) healthy plants, (b) plants where yield was just depressed or where symptoms first appeared, and (c) plants with severe symptoms. The defined symptoms and nutrient concentration ranges should be useful in identifying single nutrient deficiencies in nursury grown seedlings or young plants with juvenile foliage in the field.

Notes: Summary The PMN is exquisitely designed to combat invading micro-organisms. The relationship between structure and function is nowhere more evident than in this cell type. The elaborate biochemical machinery which the PMNs possess for killing ingested micro-organisms works as a highly integrated system, with each step occurring in sequence and at a particular site. In the past decade or so it has become apparent that the Klebanoff system (myeloperoxidase-halide-H2O2) and possibly other active O2 species as well, play an important role in the bactericidal activity of PMNs. Application of cytochemical techniques for oxidative enzymes and for end-products of oxidative reactions has localized the sites within the phagocytosing or stimulated PMN at which these various components of the cidal systems are active and generated. In this fashion, biochemical data have been not only confirmed, but in several instances, the cytochemical approach has led the way in extending our knowledge and thinking regarding PMN metabolism and cidal functions. In our laboratory we have studied the bactericidal machinery of PMNs by cytochemical means. We have established, at the ultrastructural level, that the myeloperoxidase-containing azurophil granules fuse with the phagosome membrane and empty their contents into the phagosome (Baehneret al., 1969). We have shown that H2O2 is generated within the phagosome (Briggset al., 1975b). This established that the myeloperoxidase-H2O2 system could work within the phagosome, since both of these components are present following phagocytosis. We determined that H2O2 could be detected on the cell surface and within the phagosome following phagocytic stimulation of NADH oxidase activity (Briggset al., 1975a). The cell surface localization of H2O2 was an important finding since the phagosome membrane is derived from the plasmalemma. Thus internalization of the plasmalemma, with components capable of generating H2O2, can explain the presence of H2O2 within the phagosome. We have also shown that when PMNs are treated with non-particulate stimuli of the respiratory burst, similar results are found, that is, H2O2 is present on the cell surface and within vesicles, which are presumed to be of surface origin (Badweyet al., 1980). We have shown that D-amino acid oxidase, another enzyme capable of generating H2O2 is cytochemically demonstrable and that it can utilize cell wall components of ingested bacteria as substrates for enzyme activity (Robinsonet al., 1978). The PMNs from CGD patients do not kill certain bacteria. This inability to kill bacteria is related to the low levels of H2O2 produced during phagocytosis. Using the cerium reactioon we determined that PMN from CGD patients produce little cytochemically detectable H2O2 and that what little is present is restricted to the phagosome (Briggset al., 1977). Some PMNs contain other oxidases which are capable of generating H2O2 and O 2 − from O2 consumed during phagocytosis. The guinea-pig PMN (but not human) has an unusual aldehyde oxidase. Cytochemically the aldehyde oxidase activity is restricted to the phagosome (Robinsonet al., 1979). We have also developed a method for localization of sites of O 2 − production following stimulation. In phorbol myristate acetate-stimulated PMNs, reaction product for O 2 − is present within surface-derived vesicles, and in some cases, on the cell surface. Cytochemical detection of enzymes and products of enzymatic activity (H2O2 and O 2 − ) associated with stimulation of the respiratory burst in PMN has thus provided further evidence for the importance of active oxygen species in phagocytosis. Furthermore, the site-specific information obtained from cytochemistry has provided an important link in understanding the structure-function interplay associated with phagocytosis in PMNs. It should be realized, however, that the cytochemical methods we have utilized detect in most instances the end product of an enzymatic reaction (for example, H2O2) and not the site of the enzyme itself. This is important, for instance in the case of H2O2, because this entity appears to begenerated on the surface of the plasmalemma or on the luminal surface of the phagosomal membrane. However, the enzyme responsible may well be situated on the cytoplasmic side of these membranes, and the generation of the H2O2 may involve an electron shuttle across the membrane. Such a mechanism may involve cytochrome and quinone compounds as carriers (Segal & Jones, 1979; Millardet al., 1979). Experiments are now being designed to localize the sites of the enzymesper se by immunocytochemistry. This approach should help resolve these important questions.