Research
Mast cell biology
Mast cells are present in almost all major organs and tissues of the mammalian body. These cells play a role in the immunopathology of immediate hypersensitivity reactions and in some inflammatory reactions. Mast cells also play a critical role in the expression of host resistance to certain parasites, depending on factors such as parasite species and the infection site. A wide variety of important chemical mediators, in both health and disease, are stored within and secreted from specific cytoplasmic granules in mast cells. The secretory granules can be released into the extracellular space, thereby mediating important physiological and pharmacological processes. The quantitative morphologic correlation between mast cell structure and secretory activity are the major interests of our group.
Ginsburg H, Nir I, Hammel I, Eren R, Weissman BA, and Naot Y. Differentiation and activity of mast cells following immunization, in cultures of lymph node cells. Immunology 1978; 35:485-502.
Ginsburg H, Ben-Sachar D, Hammel I, and Ben-David E. Degranulation capacity of mast cells grown in cell culture in the presence of histamine releaser. Nature 1979; 280:151-153.
Galli SJ, and Hammel I. Unequivocal delayed hypersensitivity in mast cell deficient and beige mice. Science 1984; 226: 710-713.
Hammel I, Shilo-Rabinovich H and Nir I. Two populations of mast cells on fibroblast monolayers: correlation of quantitative microscopy and functional activity. J. Cell Sci. 1988; 91: 13-19.
Hammel I, Lagunoff D and Krüger P-G. Recovery of rat mast cells after secretion: A morphometric study. Exp. Cell Res. 1989; 184: 518-523.
Hammel I, Arizono N and Galli SJ. Mast cells in rat dermis and jeujunal lamina propia show a five-fold difference in unit granule volume. Cell Tissue Res. 1991; 265:329-334.
Hammel I, Alroy J, Goyal V and Galli SJ. Ultrastructure of human mast-cells in 29 different lysosomal storage diseases. Virchows Archiv B - Cell Pathology including Molecular Pathology. 1993,64:83-89.
Skutelsky E, Shoichetman T, Hammel I. An histochemical approach to characterization of anionic constituents in mast cell secretory granules. Histochem. Cell. Biol. 1995; 104:453-458.
Amihai D, Trachtenberg S, Terkel J, Hammel I. The structure of mast cell secretory granules in the blind mole rat (Spalax ehrenbergi). J Struct Biol 2002; 136:96-100.
Unit Granule formation
The classical model of secretory granule formation holds that proteins are transported from the rough endoplasmic reticulum (RER) to the Golgi zone where they can undergo post-transitional modification. They are then packaged for secretion by concentration within membrane-bound condensing vacuoles. The contents of the condensing vacuoles are then concentrated further, forming mature secretory granules of quantal size distribution (the unit granule model). The Golgi complex is an organelle which is usually located near the cell centriole and in close proximity to the rough endoplasmic reticulum. The transportation of secretory proteins occurs in a vectorial way. The newly synthesized proteins in the RER are moved, probably via a vesicular transport, to the proximal side of the Golgi cisternae, the cis Golgi side. While moving through the Golgi cisternae the proteins undergo many modifications; most of the steps of which have not yet been resolved. The processed proteins are packed into vesicles which bud off the Golgi cisternae. The elucidation of this sequence of protein synthesis, packaging and secretion constitutes a major contribution to cell biology, and the overall scheme is still regarded as correct and virtually considered dogma. It is well documented that granules in various cellular systems increase in size as time passes. For example, after degranulation is induced in either mast cells or mouse pancreatic acinar cells, granules start to accumulate. If the cell is not re-sensitized, the granule size distribution becomes broader (namely, the coefficient of variation is increased) and the mean granule size is increased. We have demonstrated that the unit granule volume is conserved, indicating that the granule size increase is probably due to granule-granule fusion. The mechanism of polymerization was theoretically and experimentally investigated in chemical processes. It was found that two major mechanisms may lead to polymerization. The first one was defined as unit addition mechanism, while the second one was defined as a random addition process. In the unit addition mechanism polymer size may be increased only by the addition of a basic monomer M1 + Mn -> M1+n. Such a mechanism has a Poisson-like distribution. The alternative process, random addition mechanism, assumes that polymer of any size may react with any other polymer Mm + Mn -> Mm+n. The random polymerization has a geometric distribution and its main characteristic is that the smaller the polymer unit, the more frequent it is [namely P(n)>P(n+1)]. The monomer is the most frequent unit, whereas in a Poisson distribution the mean polymer size defines the value of the most frequent polymer as well. Using such an approach we have demonstrated that the pancreatic acinar cell and mast cell granule size distribution is better fitted to the unit addition model rather than the random addition model. The Chediak-Higashi syndrome is an example of a random mechanism of granule growth.
Hammel I, Lagunoff D, Bauza M, and Chi E. Periodic, multimodal distribution of mast cell granule volumes. Cell Tissue Res 1983; 228: 51-59.
Dvorak AM, Hammel I, Schulman ES, Peters SP, MacGlashan DW jr., Schleimer RP, Newball HH, Pyne K, Dvorak HF, Lichtenstein LM, and Galli SJ. Differences in behaviour of cytoplasmic granules and lipid bodies during human mast cell degranulation. J. Cell Biology 1984; 99: 1678-1687.
Hammel I, Dvorak AM, Peters SP, Schulman ES, Dvorak HF, Lichtenstein LM and Galli SJ. Differences in the volume distribution of human lung mast cell granules and lipid bodies: Evidence that the size of these organelles is regulated by distinct mechanisms. J. Cell Biology 1985; 100: 1488-1492.
Hammel I, Dvorak AM and Galli SJ. Defective cytoplasmic granule formation I. Abnormalities affecting tissue mast cells and pancreatic acinar cells of beige mice. Lab. Invest. 1987; 56: 321-328.
Weintraub H, Abramovici A, Amichai D, Eldar T, Ben-Dor L, Pentchev PG and Hammel I. Morphometric studies of pancreatic acinar granule formation in NCTR-Balb/c mice. J. Cell Sci. 1992; 102:141-147.
Lew S, Hammel I and Galli SJ. Cytoplasmic granule formation in mouse pancreatic acinar cells. Evidence for formation of immature granules (condensing vacuoles) by aggregation and fusion of progranules of unit size, and for reductions in membrane surface area and immature granule volume during granule maturation. Cell Tissue Res. 1994; 278:327-336.
Hammel I, Dvorak AM, Fox P, Shimoni E and Galli SJ. Defective cytoplasmic granule formation. II. Differences in patterns of radiolabeling of secretory granules in beige versus normal mouse pancreatic acinar cells after [3H]-glycine administration in vivo. Cell Tissue Res. 1998; 293:445-452.
Hammel I, Shor-Hazan O, Eldar T, Amihai D and Lew S. Morphometric studies of secretory granule formation in mouse pancreatic acinar cell. Dissecting the early structural changes following pilocarpine injection. J. Anat. 1999; 194:51-60.
Quantitative microscopy
A common morphometric problem is the determination of an estimate of the size of biological particles obtained from measurements made on a sample of profiles observed in sections. Results are typically reported in terms of mean caliper diameter or mean volume of the particle. Much of the emphasis has been on measurements of unique objects rather than populations. Our investigations have been confined to populations of spheres and ellipsoids. We have concentrated on practical considerations of section thickness and Gausssian distributions of particle size in order to provide guidelines for using the various estimators for objects that are consistent with the models we have used. Based on our results, we think that Monte Carlo simulations deserve a place in the armamentarium of stereologists even if only for practical ends.
Hammel I. Progression of errors in morphometry. Estimation of particle number density. J. Histocem. Cytochem. 1986; 34: 941-944.
Elmalek M and Hammel I. Estimation of the mean caliper, a new approach. J. Elect. Microsc. Techniq. 1988; 8: 173-177.
Kalina M, Elmalek M and Hammel I. Intragranular processing of pro-opiomelanocortin in the intermediate lobe of the rat pituitary glands. A quantitative immunocytochemical approach. Histochemistry 1988; 89: 193-198.
Hammel I and Kalina M. Morphometric analysis of gold particles in low-label cellular compartments. J. Histocem. Cytochem. 1991; 39:131-133.
Trachtenberg S, Hammel I. The rigidity of bacterial flagellar filaments and its relation to filament polymorphism. J. Structural Biol. 1992; 109:18-27.
Hammel I, Lagunoff D. Determination of mean particle volume, a Monte Carlo simulation. Comput Biol Med 1997; 27:283-291.
Shoichetman T, Skutelsky E, Lew S, Hammel I. Changes in the distribution of anionic constituents in secretory granules of mouse pancreatic acinar cells after pilocarpine-induced degranulation. J Histochem Cytochem; 2001; 49:1199-1204.
Hammel I, Lagunoff D. A Monte Carlo simulation of the determination of mean particle volume using the Cavalieri estimator. Cytometry 2002; 47: 138-141.
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