Alan Curry

Light- and Electron-Microscopic Studies on Multinucleated Giant Cells in Sarcoid Granuloma: New Aspects of Asteroid and Schaumann Bodies

Ultrastructural studies using transmission, analytical, electron, and light microscopy were performed on epithelioid granulomata in 4 lymph nodes from a case of sarcoidosis, emphasizing the organization of asteroid and Schaumann bodies in multinucleated giant cells and the deposition of chemical elements. Serial sectioning at semithin level showed a single multinucleated giant cell can contain up to 4 asteroid and 1 Schaumann body. Microtubules and centrioles were not found in asteroid bodies, although a centriolar field was present in 1 giant cell close to the plasma membrane, completely unrelated to the asteroid body. In 1 asteroid body, tubulelike structures were observed in a focus showing filament dissociation. A principal ultrastructural finding is intimate envelopment of radiating filamentous arms of the asteroid body by myelinoid membranes, extensive forms of which are also present between the arms. Elemental analysis revealed a definite peak of calcium and a probable phosphorus peak in relation to the asteroid body and associated myelinoid membranes. Calcium and phosphorus with smaller quantities of aluminum and iron were found in Schaumann bodies. Our studies indicate that organization of the asteroid body is more complex than hitherto described, independent of the centriolar and microtubular systems. Evidence for the possible developmental pathway of the Schaumann body is provided by morphological changes within myelinoid figures intimately related to the asteroid body.

Spindle cell and pleomorphic lipoma: an ultrastructural study.

Spindle cell and pleomorphic lipoma are rare benign tumors of adipose tissue. Their histogenesis is poorly understood and pleomorphic lipoma has not previously been studied ultrastructurally. This study describes the morphology and ultrastructure of 6 cases of spindle cell and pleomorphic lipoma. Both spindle cell and pleomorphic lipomas showed similar ultrastructural features with an interrupted basal lamina, occasional non-membrane-bound lipid vacuoles and abundant rER. In all the cases mast cells were conspicuous and were intimately related to both spindle and pleomorphic cells. It is proposed that both the spindle and pleomorphic multinucleated cells that characterize these tumors are prelipoblastic mesenchymal cells. The possible significance of an interaction between these cells and mast cells is discussed.

Stromal cells in the human gut show ultrastructural features of fibroblasts and smooth muscle cells but not myofibroblasts

The free spindled cells of the lamina propria of the gut have been reported as showing fibroblastic, smooth‐muscle and myofibroblastic differentiation. A precise understanding of the differentiation of these cells is essential for appreciating their functions, and this paper addresses this question using ultrastructural analysis. Histologically normal samples from different areas of the gastrointestinal tract were studied. Both subepithelial stromal cells, lying immediately beneath the basal lamina, and the deeper interstitial stromal cells, were studied. Subepithelial and interstitial cells had comparable features, reinforcing the idea that these formed a single reticulum of cells. Two major cell types were identified. Some were smooth‐muscle cells, on the basis of abundant myofilaments with focal densities, glycogen, an irregular cell surface, focal lamina and multiple attachment plaques alternating with plasmalemmal caveolae. Some cells had a lesser expression of these markers, especially of myofilaments, and were regarded as poorly differentiated smooth‐muscle cells and descriptively referred to as ‘myoid’. Other cells were fibroblastic to judge by prominent rough endoplasmic reticulum, an absence of myofilaments and lamina, but presence of focal adhesions. The fibronexus junctions of true myofibroblasts were not seen. The study emphasises that the smooth‐muscle actin immunoreactivity in this anatomical site resides in smooth‐muscle cells and not in myofibroblasts, a view consistent with earlier ultrastructural and immunostaining results. The recognition that these cells are showing smooth‐muscle or fibroblastic but not true myofibroblastic differentiation should inform our understanding of the function of these cells.

Bacteria-like endobionts of the suctorian,Discophrya sp.

SummaryIndividuals ofDiscophrya sp. contain approximately 11,000 endobionts, interpreted as gram-positive bacteria. Treatment with the antibiotic rifampin resulted in destruction of the bacteria, but with an accompanying gigantism, loss of reproductive capacity and a restricted lifespan of the suctorian. Treatment with penicillin G resulted in a reduction of the bacterial population and gigantism. A subsequent increase in the number of bacteria coincided with a reduction in cell size of the suctorian. Copper ions were also found to destroy the bacteria. The possible existence of a symbiotic relationship between the two organisms is discussed.

Asexual reproduction in the suctorianDiscophrya collini

SummaryDiscophrya collini reproduces asexually through the formation of a ciliated swarmer by evaginative budding. This process is initiated by the repeated replication of a single subcortical kinetosome to form a kinetosome field. The epiplasm of the multilayered cortex covering this field becomes reduced in thickness and the whole cortex invaginates to produce an internal embryonic cavity. The kinetosomes become organised into rows, and each produces a cilium which projects into the cavity. On completion of the embryonic cavity its walls are extruded through the cavity opening to form an external ciliated swarmer connected to the parent by a thin bridge of cytoplasm. It is suggested that this evagination is induced by a rapid breakdown of supporting microtubules in the cavity wall and the subsequent hydrostatic pressure exerted by the body cytoplasm. The connecting bridge shows no specialised ultrastructural features and separation of swarmer from parent probably is achieved by the active movement of the swarmer. The cytoplasm of the swarmer is similar in structure to that of the adult cell but contains a number of primordia of tentacle axonemes. The infraciliature resembles that of other suctorian swarmers. On settling, the cilia of the swarmer are lost, at least some by resorption, a stalk may be secreted and the axoneme primordia are extended to form functional tentacles.

Quality Standards for Diagnostic Electron Microscopy

Transmission electron microscopy (TEM) continues to play a critical role in diagnostics; [1] however, due to a combination of economic and staffing issues, diagnostic TEM is currently at a significant crossroads. In some countries rationalization of TEM facilities is resulting in laboratory closures and dedicated electron microscopists are retiring; both are processes that will result in a serious loss of skill, knowledge, and experience. Furthermore, the staffing profile of many units is changing; the scientific and technical staff responsible for diagnostic TEM are increasingly likely to be multiskilled rather than TEM specialists. In such an environment, attention to quality to maintain standards and ensure a rapid and reliable diagnostic service is essential. To ensure quality, two strategies are available. First, it is essential to underpin good practice with clear guidelines that define ‘‘quality standards’’ for laboratory operations (processes and outcomes). Second, it is advisable to participate in an external quality assurance program (EQAP) that audits laboratory processes and outputs; ideally the EQAP should also function as an educational tool. The second strategy has been addressed; two EQAPs for general diagnostic transmission electron microscopy (TEM) are currently available. The Royal College of Pathologists Australasia (RCPA), through the RCPA Quality Assurance Programs Pty Ltd (RCPA QAP), successfully initiated an internationally accredited (ILAC G13) program in 2006. Also, in the United Kingdom (UK) the Association of Clinical Electron Microscopists (ACEM) has initiated an informal quality assurance program for ACEM members. In fact, it is the first strategy that requires additional action. Quality control in the histopathology laboratory, much of which applies to TEM, has been described [2] and a range of activities that support quality practices in TEM facilities are in place. Some TEM laboratories have quality processes for viral screening and many facilities have standard operating procedures (SOPs). Indeed, in some countries (such as Australia and the UK) ‘‘controlled’’ manuals describing SOPs and a record of processing details for auditing purposes are mandatory for laboratory accreditation. Laboratory accreditation also requires the documentation of staff training, another process that supports quality practice when used to define the competence, range, and level of duties permitted for each member of staff. Finally, while a laboratory might not have ‘‘published’’ quality standards, it must be said Received 17 July 2007; accepted 2 July 2007.

Diagnostic Electron Microscopy - A Practical Guide to Interpretation and Technique: Stirling/Diagnostic Electron Microscopy - A Practical Guide to Interpretation and Technique

Diagnostic Electron Microscopy: A Practical Guide to Interpretation and Technique summarises the current interpretational applications of TEM in diagnostic pathology. This concise and accessible volume provides a working guide to the main, or most useful, applications of the technique including practical topics of concern to laboratory scientists, brief guides to traditional tissue and microbiological preparation techniques, microwave processing, digital imaging and measurement uncertainty.

Unusual Organelles in an Epithelioid Angiosarcoma

We recently encountered unusual organelles in a tumor from a 75-year-old white British female presenting with a scalp lesion which histologically was a poorly differentiated malignant neoplasm (Fig. 1). On the basis of histology and immunohistochemistry [positive staining for factor Vlll-related antigen (Fig. 2), JC70A (CD31),1 and Ulex europaeus agglutinin 1] the tumor was diagnosed as an epithelioid angiosarcoma. An unexpected finding was that some unambiguous tumor cells were positive for S100 protein. Occasional S100 protein-positive dendritic cells, interpreted as reactive Langerhans cells, were also present. To confirm a confidently held diagnosis, but one which was nevertheless uncertain because of the S100 protein staining, electron microscopy was conducted. Not unexpectedly, Weibel-Palade bodies were not identified,2 but the rough endoplasmic reticulum, polyribosomes, aggregates of haphazardly arranged intermediate filaments, and a well developed lamina were seen as being consistent with epitheli...