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The ultrastructure of the septal pore cap (SPC) of Asterodon, Asterostroma and Coltricia were examined to establish the taxonomic position of these genera. Asterostroma has dolipores with perforate SPCs and is classified in the Lachnocladiaceae. In contrast, Asterodon and Coltricia have dolipores with imperforate SPCs and belong to the Hymenochaetaceae. Other selected species of genera belonging to the Hymenochaetaceae like Hydnochaete, Coltriciella, Inonotus, Onnia, and Cyclomyces also contained imperforate SPCs. Coltriciella, Inonotus and Cyclomyces moreover presented a lamella of endoplasmic reticulum above the imperforate SPC after chemical fixation. Such a lamella could rarely be observed in Coltricia only after high-pressure freezing and freeze substitution. Cryofixed fungal cells of Cyclomyces and Coltricia showed differences in the architecture of the matrix of the SPC. Coltricia showed a more layered matrix structure than the SPC of Cyclomyces. In addition, transmission- and scanning electron microscopy revealed an indent in the centre of the imperforate SPC of Cyclomyces, indicating a reduced thickness, and resulting into a tented profile in cross-sections.

Dolipore septa and septal pore caps (SPCs) in filamentous basidiomycetes may play an important role in maintaining the integrity of hypal cells. We have investigated the ultrastructure of the dolipore septum and the SPC in Rhizoctonia solani hyphal cells after high-pressure freezing, freeze substitution, and Spurr embedding. We visualized the SPC with associated cell ultrastructures in three dimensions by automated electron tomography of thick-sectioned cells, followed by 3D tomographic reconstructions. Using these methods we were able to document the passage of mitochondria through the SPC, small tubular membranous structures at the entrance of the septal pore channel, filamentous structures connecting the inner side of the SPC with pore-plugging material, thin filaments anchoring the pore-plugging material with the plasma membrane, small vesicles attached to the plugging material, and tubular endoplasmic reticulum continuous with the base of the SPC. We hypothesize that the SPC, the filamentous structures, the plugging material, and the endoplasmic reticulum act in a coordinated fashion to maintain cellular integrity, intercellular communication, and the transport of solutes and cell organelles in the filamentous fungus R. solani. (C) 2000 Academic Press.

A procedure to enrich microbodies from Penicillium chrysogenum and a method to evaluate the purity and integrity of the microbodies are described. As a P. chrysogenum microbody marker acyltransferase (AT) was used. The P. chrysogenum hyphae were converted into protoplasts with Novozym 234. In Percoll-sucrose buffer the protoplasts were separated from mycelial debris after 10,000 x g centrifugation. Purified protoplasts were lysed, and the cell homogenate was centrifuged to form a 14,000 x g pellet. After 2 h, 45,000 x g isopycnic centrifugation of the 14,000 x g pellet on a continuous 20-60% nycodenz gradient, ten fractions were collected. The fractions were analyzed for AT containing microbodies by immuno-blotting and immuno-electron microscopy. The results showed that AT-microbodies are enriched in the 38% nycodenz fraction. The microbodies had a diameter of 400 to 500 nm, revealed an intact single membrane and confined AT. The estimated equilibrium density of the P. chyrsogenum microbodies was 1.20 g ml-1 as deduced from the 38% (w/v) nycodenz concentration.

Portland Press, 1998. £39.50/$65.50 (326 pages)ISBN 1 85578 060 7Glauert and Lewis take the reader from fixation to embedding of biological specimens in ten chapters. In the first three chapters, the reader is introduced to the criteria of ultrastructural preservation, artifacts and hazards. The popular chemical fixatives are described in detail, together with how they interact with biological components. The user will find practical tips about fixation methods, such as immersion, injection, perfusion and surface application, improvement of fixing a biological sample, fixation of cells pellets, and fixatives used in cytochemical and immunological techniques.Chapter 4 describes organic solvents required for dehydrating fixed specimens. Besides the removal of water and lipids, swelling and shrinkage occur. Swelling of the specimen is partially prevented by adding Ca2+, subjecting the specimen to 70% ethanol or by performing freeze-substitution. Chapters 5 and 6 elaborate the advantages and disadvantages of epoxy and acrylic resins. Many details are given concerning embedding in different epoxy resins, and about monomers, hardeners, accelerators, flexibilizers, plasticizers and their hazards. In addition, there are also water-miscible epoxy resins that do not require dehydration. The next section introduces the acrylic resins and proceeds to give their advantages and disadvantages. It is important to know that LR White has a shelf life of 12 months, and the reader is advised to purchase uncatalysed LR White. Chapter 8 describes extensively the Lowicryl resins K4M, K11M, HM20 and HM23. This is followed by an introduction to the polyester resins, water-miscible melamine resins and reversible waxy media. Chapter 10 summarizes the preparation methods and shows processing schedules for ultrastructural study, general cytochemistry, enzyme cytochemistry and immunocytochemistry. The book ends with an appendix of suppliers, their addresses and a subject index.The chapters are clearly written, well illustrated with many molecular structures, electron micrographs, drawings, photos of the essential equipment, tables of hazards and instructions for handling hazardous chemicals (e.g. milk powder is a handy absorbent for mopping up fixative spillages). Handy tips are given in the tables showing how to prepare fixatives, buffers and embedding media as well as the schedules of fixation, dehydration, infiltration and embedding. In addition, the reader is referred to other original publications and additional books for further reading at the end of each chapter.The fledgling electron microscopist may well be dazzled by Glauert and Lewis and might find it easier to read a more practical electron microscopy book (e.g. Ref. 1xPractical Electron Microscopy: A Beginner’s Illustrated Guide. Hunter, E.E. CrossrefSee all ReferencesRef. 1). The reader should also refer to books about microorganisms (e.g. Ref. 2xElectron Microscopy in Microbiology. Hoppert, M. and Holzenburg, A. See all ReferencesRef. 2); articles about pre-embedding immunolabelling (e.g. Ref. 3xHumbel, B.M. et al. Microscopy Research and Technique. 1998; 42: 43–58Crossref | Scopus (45)See all ReferencesRef. 3); and more electron microscopy methods (e.g. Ref. 4xElectron Microscopy Methods and Protocols. Hajibagheri, N. CrossrefSee all ReferencesRef. 4). However, almost all you could wish to know about fixation, dehydration, and embedding is in this book, making it a useful asset.