Quantitative ultrastructural features of maturing mononuclear phagocytes in rat peritoneal fluids.

Ultrastructural features of the in vivo transformation of macrophage congeners in resident and adjuvant-induced peritoneal populations are evaluated by sterological methods. Maturation involves an increase in cell size by the differential hypertrophy of subcellular compartments, notably remaining cytoplasm, nucleus and lysosome-like granules. Larger cells have more and larger granules, more mitochondria and a greater plasmalemmal surface. In contrast, adjuvant activation tends to produce fewer granules and a nett loss of surface membrane.     

Secretory phenomenon of the adenohypophyseal cells viewed with the scanning electron microscope

Summary Exocytosis from rat adenohypophyseal cells, probably somatotrophic, was studied in the scanning electron microscope after freeze fracturation of the glands. This technique permitted the distinguishing of a clearly delimited exoplasm interrupted by the passage of the secretory granules. It was postulated that the exoplasm could be involved in the control of the release of secretory granules in the endocrine cells studied. At the basal cell surface a simultaneous discharge of several secretory granules has been detected.With the technical assistance of Mr P.-A. Milliquet.     

Presence of presumptive interdigitating cells in the spleen of the natterjack,Bufo calamita

Summary The periphery of splenic lymphoid follicles, an area rich in reticulum fibers, contains presumptive interdigitating cells characterized by low electron density, scantiness of cytoplasmic organelles, abundant surface foldings and, sometimes, electrondense granules of unknown significance.     

Preparing the lethal hit: interplay between exo- and endocytic pathways in cytotoxic T lymphocytes

Cytotoxic T lymphocytes patrol our body in search for infected cells which they kill through the release of cytotoxic substances contained in cytotoxic granules. The fusion of cytotoxic granules occurs at a specially formed contact site, the immunological synapse, and is tightly controlled to ensure specificity. In this review, we discuss the contribution of two intracellular compartments, endosomes and cytotoxic granules, to the formation, function and disassembly of the immunological synapse. We highlight a recently proposed sequential process of fusion events at the IS upon target cell recognition. First, recycling endosomes fuse with the plasma membrane to deliver cargo required for the docking of cytotoxic granules. Second, cytotoxic granules arrive and fuse upon docking in a SNARE-dependent manner. Following fusion, membrane components of the cytotoxic granule are retrieved through endocytosis to ensure the fast, efficient serial killing of target cells that is characteristic of cytotoxic T lymphocytes.     

The subcommissural organ of the lizardLacerta s. sicula raf. ultrastructure during the winter

Summary The secretory activity of the SCO cells ofLacerta s.sicula Raf. is strongly reduced during the winter. Such reduction is documented by the decrease of the number of secretory granules type A and B described in previous papers in the summer SCO cells. Also the sacks of RER filled with electron-dense material (type C secretion) are very few; in their place there are, in the basal region of the cells, large vacuoles. In the distal region of the cells, at the free cell surface, a pronounced increase in the number of microvilli is noticed.     

Control of the behaviour of leaf-cutting ants by their ‘symbiotic’ fungus

There is an obligatory relationship between leaf-cutting ants of the generaAtta andAcromyrmex (Hymenoptera; Attini) and the fungus,Attamyces bromatificus Kreisel, for which they provide a substrate of cut plant material. We show that the ants learn to reject plant material that contains chemicals injurious to the fungus. After an initial period of acceptance, ants from laboratory nests stopped harvesting granular bait containing a fungicidal agent (cycloheximide) and orange peel. This rejection was maintained for many weeks. These colonies also rejected control bait containing no cycloheximide. Some generalisation of the response was observed; colonies rejecting orange granules also rejected grapefruit granules, although they still accepted blackcurrant granules. Rejection of fungicidal bait by colonies in the field was restricted to ants on foraging trails exposed to experimental bait. We conclude that a semiochemical from the fungus, circulated by trophallaxis and grooming, regulates the selection of plant material by foragers. The fungus gains more advantages from the symbiotic relationship than is often realised. The ants provide the fungus with housing, sanitation, defence against disease and predators, pre-selected food, and a means of dissemination, at the cost to itself of providing food for the ant brood.     

Immuno-electronmicroscopic study of human EA rosettes

Summary The immuno-electronmicroscopic study of human EA rosettes, using ferritin-labelled anti-human IgG antiserum, showed clusters of ferritin granules at the points of contact between erythrocytes and lymphoid cells, indicating that the links between Fc fragment of IgG on the surface of erythrocytes and specific receptor on the surface of lymphoid cell correspond to the sites of morphological interaction between the 2 cell types.recipient of a Grant of the Italian Consiglio Nazionale Ricerche.     

Immuno-electronmicroscopic study of human EA rosettes.

The immuno-electronmicroscopic study of human EA rosettes, using ferritin-labelled anti-human IgG antiserum, showed clusters of ferritin granules at the points of contact between erythrocytes and lymphoid cells, indicating that the links between Fc fragment of IgG on the surface of erythrocytes and specific receptor on the surface of lymphoid cell correspond to the sites of morphological interaction between the 2 cell types.     

Modifications ultrastructurelles provoquées par quelques médicaments sur les terminaisons nerveuses adrénergiques et sur la médullaire surrénale

Summary It has been shown that reserpine and guanethidine deplete granules containing catecholamine in sympathetic nerve endings of both the pineal gland and the vas deferens. This effect is blocked by iproniazid. Bretylium is not able to deplete these granules but it modifies their aspect. It has also been observed that granules of the adrenal medulla are depleted less easily than those of sympathetic nerve endings.     

Identification of hemolytic granules isolated from human myocardial cells

Human myocardial cells from fresh autopsy material contained granules which possessed hemolytic activity against guinea pig and rabbit erythrocytes. The hemolytic granules, which had a density of 1.02 and a diameter of 200-300 nm, were recovered as a microsome fraction from subcellular homogenates of human myocardial cells by differential centrifugation in 300 mM sucrose containing 0.1 mM PMSF and 10 mM EDTA. The membrane lesions caused by the granules were ring-like structures with an internal diameter of about 10-17 nm, analogous to that caused by perforin- and complement-induced lysis. However, the requirement for divalent cation differed from that for perforin-induced lysis, since the microsome-mediated lysis occurred in the presence of EDTA.     

Identification of hemolytic granules isolated from human myocardial cells

Summary Human myocardial cells from fresh autopsy material contained granules which possessed hemolytic activity against guinea pig and rabbit erythrocytes. The hemolytic granules, which had a density of 1.02 and a diameter of 200–300 nm, were recovered as a microsome fraction from subcellular homogenates of human myocardial cells by differential centrifugation in 300 mM sucrose containing 0.1 mM PMSF and 10 mM EDTA. The membrane lesions caused by the granules were ring-like structures with an internal diameter of about 10–17 nm, analogous to that caused by perforin- and complement-induced lysis. However, the requirement for divalent cation differed from that for perforin-induced lysis, since the microsome-mediated lysis occurred in the presence of EDTA.     

Relationship between lectin-affinity granules in anuran embryos and formation of primordial germ cells

Embryos of the anuran, Rana nigromaculata, contained granules with a specific affinity for Con A and GS-I. Larvae derived from embryos injected with these lectins had a noticeable reduction in both the number and size of primordial germ cells (PGCs). This observation suggests that the granules are somehow involved in the formation of PGCs.     

Ultrastructure of neurosecretory granules in the sinus gland of Palaemon serratus Pennant]

Five types secretory granules are distinguished in the sinus gland of Palaemon serratus on the basis of differences in their diameter and their electron density. Variations in the density of the acoplasm and of the granules are observed for three of these granule types.     

Relationship between lectin-affinity granules in anuran embryos and formation of primordial germ cells

Summary Embryos of the anuran,Rana nigromaculata, contained granules with a specific affinity for Con A and GS-I. Larvae derived from embryos injected with these lectins had a noticeable reduction in both the number and size of primordial germ cells (PGCs). This observation suggests that the granules are somehow involved in the formation of PGCs.     

Mast cell tryptase,a still enigmatic enzyme

Tryptases constitute a subfamily of trypsin-like proteinases, stored in the mast cell secretory granules of all mammalian organisms. These enzymes are released along with other mediators into the extracellular medium upon mast cell activation/degranulation. Among the trypsin-like enzymes, tryptases are unique: they are present as active enzymes in the mast cell granules, but display activity only extracellularly, and have a specificity which is much more restricted than trypsin. Tryptases are mostly tetrameric, and in only few organisms (not in humans) are they inhibited by endogenous inhibitors in vitro. The enzymatic and molecular properties of tryptases are far better characterized that any of their plausible biological functions. On the basis of its structural and functional features it could be predicted that tryptase would not degrade a large number of proteins in vivo due to low accessibility to the tetramer central pore where the active sites face inwards. Although their biological function has not yet been clarified, tryptases seem to be involved in a number of mast cell-mediated allergic and inflammatory diseases. In particular, the involvement of tryptase in asthma, an inflammatory disease of the airways often caused by allergy, has been proposed. Here we review the present knowledge on the structure-function relationship of tryptases from different organisms, with special emphasis on human enzymes, and on their role in a variety of pathophsyiological processes.Received 29 October 2003; received after revision 3 December 2003; accepted 11 December 2003     

Reinterpretation of the ultrastructure of cartilage matrix.

The epiphyseal cartilage from new-born mouse was treated with collagenase in two ways: either before fixation or after glutaraldehyde fixation. The electron dense granules of the matrix were not seen in the micrographs of cartilage treated with collagenase before fixation. It is concluded that collagen plays a definite role in the formation of the granules at the time of tissue fixation and that the granules are fixation artifacts.     

Giant granules in adrenaline-secreting chromaffin cells of lizard adrenal glands after metyrapone administration

Summary Secretory granules of extraordinary size, some of them bigger than the cell nucleus, abound in the adrenaline cells of lizard adrenals after metyrapone injections during 7 days. In these granules, the bounding membrane is studded with ribosomes, and the core is formed by rounded small subunits. Some granules of this type are also found in noradrenaline cells. They may represent an exceptionally increased elaboration and storage of adrenaline, induced by metyrapone probably through its action on steroidogenic tissue.This research forms part of project No. 31.26.S1-1154 supported by the Consejo Nacional de Investigaciones Científícas y Tecnológicas.     

Peroxidase activity of neutrophil granules in two cases of congenital myeloperoxidase deficiency]

The neutrophils and monocytes of two patients with hereditary myeloperoxidase deficiency lacked myeloperoxidase activity as determined by light and electron microscopic cytochemical staining. Using Graham-Karnovsky media, azurophils of neutrophils were devoid of peroxidase whereas all eosinophilic and basophilic granules exhibited normal peroxidase activity. After incubation in alkaline diaminobenzidine media which stains the catalase of microperoxisomes, some small granules were seen to be strongly stained in both immature and mature neutrophils. These small granules were distinct from all other neutrophilic granules which lacked a positive reaction. Only, in the presence of cyanide or aminotriazole, peroxidatic activity was also detected in some ellipsoid azurophils. This observation suggests that these substances activated an oxidase whose nature is discussed.     

Reinterpretation of the ultrastructure of cartilage matrix

Summary The epiphyseal cartilage from new-born mouse was treated with collagenase in two ways: either before fixation or after glutaraldehyde fixation. The electron dense granules of the matrix were not seen in the micrographs of cartilage treated with collagenase before fixation. It is concluded that collagen plays a definite role in the formation of the granules at the time of tissue fixation and that the granules are fixation artifacts.Commonwealth Academic Staff Fellow. Permanent address: Department of Zoology, University of Poona, Poona 411007, India.     

Regulation of centriolar satellite integrity and its physiology

Centriolar satellites comprise cytoplasmic granules that are located around the centrosome. Their molecular identification was first reported more than a quarter of a century ago. These particles are not static in the cell but instead constantly move around the centrosome. Over the last decade, significant advances in their molecular compositions and biological functions have been achieved due to comprehensive proteomics and genomics, super-resolution microscopy analyses and elegant genetic manipulations. Centriolar satellites play pivotal roles in centrosome assembly and primary cilium formation through the delivery of centriolar/centrosomal components from the cytoplasm to the centrosome. Their importance is further underscored by the fact that mutations in genes encoding satellite components and regulators lead to various human disorders such as ciliopathies. Moreover, the most recent findings highlight dynamic structural remodelling in response to internal and external cues and unexpected positive feedback control that is exerted from the centrosome for centriolar satellite integrity.