Ilan Hammel

Learn More
Secretory vesicles express a periodic multimodal size distribution. The successive modes are integral multiples of the smallest mode (G(1)). The vesicle content ranges from macromolecules (proteins, mucopolysaccharides and hormones) to low molecular weight molecules (neurotransmitters). A steady-state model has been developed to emulate a mechanism for the(More)
Morphometric evidence derived from studies of mast cells, pancreatic acinar cells and other cell types supports a model in which the post-Golgi processes that generate mature secretory granules can be resolved into three steps: (1) fusion of small, Golgi-derived progranules to produce immature secretory granules which have a highly constrained volume; (2)(More)
Cellular communication depends on membrane fusion mechanisms. SNARE proteins play a fundamental role in all intracellular fusion reactions associated with the life cycle of secretory vesicles, such as vesicle-vesicle and vesicle plasma membrane fusion at the porosome base in the cell plasma membrane. We present growth and elimination (G&E), a birth and(More)
The inventory of secretory granules along the plasma membrane can be viewed as maintained in two restricted compartments. The release-ready pool represents docked granules available for an initial stage of fast, immediate secretion, followed by a second stage of granule set-aside secretion pool, with significantly slower rate. Transmission electron(More)
The size distribution of vesicles exocytosed from secretory cells displays quantal nature, vesicle volume is periodic multi-modal, suggesting that these heterogeneous vesicles are aggregate sums of a variable number of homogeneous basic granules. Whether heterogeneity is a lumping-together artifact of the measurement or an inherent intra-cell feature of the(More)
The delivery of newly-formed secretory content to the granule inventory occurs through direct fusion of recently formed granules and mature granules. The introduction of knockout mice allowed us to investigate the characteristics of the delivery process and to determine the core protein machinery required for granule growth. The SNARE machinery mediates(More)
It has been suggested that reserpine blocks expression of delayed hypersensitivity in mice because it depletes stores of the vasoactive amine serotonin in mast cells. To determine whether mast cell serotonin or other mast cell-derived mediators are essential for delayed hypersensitivity, responses to contact sensitizers in mast cell-deficient W/Wv or Sl/Sld(More)
GTP-binding protein(s) recognized by antibodies against the alpha-subunits of Gi- and Go-proteins were detected in crude nuclei isolated from rat brain stem and cortex. Immunohistochemical staining indicated that in the cortex these proteins are perinuclear, or are embedded in the nuclear membrane. Evidence is presented for an endogenous ADP-ribosylation of(More)
Lesch-Nyhan syndrome (LNS), caused by the complete deficiency of hypoxanthine phosphoribosyltransferase (HPRT), is characterized by a neurological deficit, the etiology of which is still unclear. Evidence has accumulated indicating that it reflects dopamine deficiency associated with defective arborization of dopaminergic dendrites. We monitored the(More)
Gap junctions are thought to grow in size by the incorporation of single connexons and by the fusion of connexon aggregates but the relative importance of these two growth mechanisms, particularly in the formation of large gap junctions, remains unclear. We have used a quantitative approach to distinguish between these two growth mechanisms and present(More)