Zsolt Pálfia

Morphological aspects of ionizing radiation response of small intestine

Knowledge of the acute and late ionizing radiation exposure damage to the gastrointestinal tract, particularly injury of the small intestine, is of great significance in radiotherapy, as is management of accidental radiation exposure. Irradiation (X-ray, neutron, cobalt gamma) induces a series of events in this rapidly renewing tissue resulting in the well-known symptoms of the gastrointestinal (GI) radiation syndrome, such as GI haemorrhage, endotoxemia, bacterial infection, anorexia, nausea, vomiting, diarrhoea, and loss of electrolytes and fluid. In spite of the significant advances that have occurred in research on underlying mechanisms over the last two decades, the overall etiology and pathogenesis of the GI-syndrome still remains unclear. Currently, to our knowledge, these symptoms are probably due to a rapid modification of the intestinal motility and to the structural alteration of the intestinal mucosa (cell loss and altered crypt integrity). Several evidences suggest that radiation-induced dysfunctions and structural changes of this organ (either changes in subcellular, cellular, and histological structure) are mediated by concerted and interrelated changes of a plethora of various extracellular mediators and their intracellular messengers. The aim of this review is to summarize our current knowledge about the pathomorphology and cell biology of the ionizing radiation response of the GI tract with a focus on the small intestine.

Sequestration revisited: Integrating traditional electron microscopy, de novo assembly and new results

Electron microscopy analysis of the autophagic sequestration membrane (SM) in various metazoan cell types after different fixation methods shows that: (1) the growing SM cannot derive from preformed rough surfaced endoplasmic reticulum (RER) membranes by transformation; (2) the empty cleft between the two layers of the SM after aldehyde fixation is an artifact of sample preparation; (3) the SM emerges from and grows de novo in cytoplasmic areas where membranous precursors cannot be identified by traditional electron microscopy; (4) the growing SM consists of two tightly packed membrane layers with a sharp bend at the edge; (5) changes in the environment of the growing SM participate in the determination of the size and shape of the autophagosome.

Qualitative and quantitative characterization of autophagy in Caenorhabditis elegans by electron microscopy.

Caenorhabditis elegans has been introduced relatively late into the field of autophagy with no previous results by classical methods. Therefore, it has to be studied in parallel with both traditional electron microscopy and modern molecular approaches. In general, correct identification of autophagic elements by electron microscopy is indispensable to establish a firm basis for our understanding of the process. The principles and the method for identification, applied also for C. elegans, are summarized first in this article, to facilitate their utilization both for further studies and the analysis of new cell types and to support researchers new to electron microscopy techniques. Studying autophagy in the worm by electron microscopy has required the development of special handling and sampling techniques in addition to overcoming the general technical difficulties due to the nature of C. elegans samples. These are described in detail, together with some initial qualitative and quantitative results obtained by them. The feasibility of the presented method is supported by data which show that in continuously fed worms the autophagic compartment is in the lower range of the 10(-2)% order of magnitude of the cytoplasmic volume, while immediately after molting or upon starvation in the second larval period, usually more than a 10-fold increase can be measured. In dauer larvae, individual variation of the autophagic compartment is very high. The predauer stage in daf-2 mutants does not seem to show significant constitutive autophagic activity. Some autophagy-related gene mutants show characteristic ultrastuctural features, such as autophagosomes with membrane abnormalities (unc-51/Atg1) or the hypertrophy of multivesicular bodies (let-512/Vps34, bec-1/Atg6).

Dynamics of vinblastine-induced autophagocytosis in murine pancreatic acinar cells: Influence of cycloheximide post-treatments

Accumulation of autophagic vacuoles (AVs) was monitored by electron microscopic morphometry in murine pancreatic acinar cells during the 5-hr period after a single injection of vinblastine (VBL). The expansion of the autophagic compartment (AC) occurred in two waves. AVs accumulated in the first 90 min and regressed in the next hour, but thereafter AC expanded again, and 5 hr following the VBL injection, as much as 5.3% of the cytoplasmic volume was found sequestered into the AC. The high rates of accumulation of AVs indicated that VBL stimulated AV formation (segregation) during both expansion phases. To have a deeper insight into the dynamics of the process segregational inhibitor cycloheximide (CHI) was given 1 and 3 hr after VBL and the subsequent regression of the AC and its subcompartments (i.e., early, advanced, and late AVs) were measured during the next 90 min. We found that regression of AVs was fast in the first expansion and slowed down in the second expansion phase during which only early AVs regressed. CHI proved to be a fast and effective inhibitor of autophagic segregation, whether it was given before, simultaneously, or after the VBL injection. The aforementioned results argue for a dual mode of action of VBL (i.e., a prompt stimulation of segregation and a delayed retardation of AV maturation). The two effects of the alkaloid prevail differently along the time course. A further analysis of the behavior of the AC subcompartments showed that CHI perhaps inhibits segregational step(s) occurring prior to the actual formation of the autolysosomes.

Introduction to the Atlas

Studying 0.5–1 cm thick, unstained slices of different fixed animal carcasses by the unaided eye, with a magnifying glass or a dissecting stereo microscope (sectional anatomy) might be of great help in supporting traditional anatomical studies, in gaining true and detailed spatial perception. The sectional anatomic approach is useful also, because it provides information that is usually lost between the dimensions of normal anatomic (dissectional) and histologic (microscopic) dimensions.