Formation Of Dense Bodies Research Articles

Increased intra-mitochondrial lipofuscin aggregates with spherical dense body formation in mitochondrial myopathy

Lipofuscin aggregation may result from incomplete degradation of damaged mitochondria by autophagy-lysosome pathway, and intra-mitochondrial lipofuscin aggregation may exacerbate mitochondrial abnormalities in mitochondrial myopathy (MM) and mitochondrial disease. We examined vastus lateralis muscle biopsies from 24 patients with pathologically diagnosed MM and clinically diagnosed chronic progressive external ophthalmoplegia, in comparison to the biopsies from 3 other groups:10 patients with inclusion body myositis (IBM), 11 younger adults, and 10 older subjects with no to minimal myopathic changes. Lipofuscin aggregation in muscle fibres was assessed on autofluorescence microscopy, some histochemical stains, and electron microscopy (EM). EM analyses demonstrated intra-mitochondrial lipofuscin aggregates, spherical dense bodies (SDBs), and paracrystalline inclusions (PCIs) which were semi-quantitatively assessed. Intra-mitochondrial lipofuscin aggregates showed no significant differences between groups of MM patients and older subjects or IBM patients, but significant differences between groups of younger adults and others with associated age-related changes. Intra-mitochondrial SDBs were significantly more in MM patients than in older subjects, IBM patients, and younger adults. There was a significant positive correlation between intra-mitochondrial lipofuscin aggregates and SDBs. These findings suggest that intra-mitochondrial formation of lipofuscin SDBs is more in MM and contributing to the pathophysiology of mitochondrial disease.

The enigmatic meiotic dense body and its newly discovered component, SCML1, are dispensable for fertility and gametogenesis in mice.

Meiosis is a critical phase in the life cycle of sexually reproducing organisms. Chromosome numbers are halved during meiosis, which requires meiosis-specific modification of chromosome behaviour. Furthermore, suppression of transposons is particularly important during meiosis to allow the transmission of undamaged genomic information between generations. Correspondingly, specialized genome defence mechanisms and nuclear structures characterize the germ line during meiosis. Survival of mammalian spermatocytes requires that the sex chromosomes form a distinct silenced chromatin domain, called the sex body. An enigmatic spherical DNA-negative structure, called the meiotic dense body, forms in association with the sex body. The dense body contains small non-coding RNAs including microRNAs and PIWI-associated RNAs. These observations gave rise to speculations that the dense body may be involved in sex body formation and or small non-coding RNA functions, e.g. the silencing of transposons. Nevertheless, the function of the dense body has remained mysterious because no protein essential for dense body formation has been reported yet. We discovered that the polycomb-related sex comb on midleg-like 1 (SCML1) is a meiosis-specific protein and is an essential component of the meiotic dense body. Despite abolished dense body formation, Scml1-deficient mice are fertile and proficient in sex body formation, transposon silencing and in timely progression through meiosis and gametogenesis. Thus, we conclude that dense body formation is not an essential component of the gametogenetic program in the mammalian germ line.

Clinicopathologic study of sinonasal inflammatory myofibroblastic tumor

To study the clinicopathologic features, immunophenotype and ultrastructural features of sinonasal inflammatory myofibroblastic tumors (IMT). The clinical and histologic features of 5 cases of sinonasal IMT were reviewed. Immunohistochemical study for vimentin, MSA, SMA, calponin, h-caldesmon, desmin, ALK, fibronectin, CK, S-100 and Ki-67 was carried out. Ultrastructural examination was also performed in two of the cases. The patients age ranged from 28 to 62 years (mean = 43 years). The male-to-female ratio was 2:3. The clinical presentation included nasal obstruction, nasal discharge, nasal bleeding, facial pain, facial swelling, toothache and tear overflow. All of the 5 patients suffered from disease relapses; and 4 of them had recurrences for more than 5 times. One patient had lymph node metastasis and 3 patients died of the disease. Histologically, the tumor cells were arranged in interlacing fascicles and sometimes haphazard in fashion. They were spindly in shape, cytoplasm eosinophilic with mild nuclear atypia and a low mitotic activity. The intervening stroma was myxoid in appearance accompanied by lymphocyte and plasma cell infiltration, abundant blood vessels and focal collagenized areas. In 3 of the recurrent cases, the tumor cells displayed increased nuclear atypia and mitotic activity (average about 5 to 6 per 10 high-power fields), accompanied by patchy necrosis, less inflammatory cell infiltration and focal sarcomatous changes. Immunohistochemical study showed that the tumor cells were diffusely positive for vimentin. SMA, MSA, calponin and fibronectin were variably expressed. Desmin was weakly positive in 1 case. The staining for h-caldesmon, ALK, S-100 and CK was negative. The Ki-67 proliferation index increased with tumor recurrences. Electron microscopy revealed abundant rough endoplasmic reticulum and dense body formation in the cytoplasm. There were an increased amount of collagen fibers in the stroma. IMT rarely occurs in nasal cavity and paranasal sinuses. The tumor is prone to local invasion and recurrences, with subsequent progression to frank malignancy and distant metastasis, resulting in high mortality and poor prognosis. Complete surgical resection remains the main modality of treatment.

A Syd-1 homologue regulates pre- and postsynaptic maturation in Drosophila

Active zones (AZs) are presynaptic membrane domains mediating synaptic vesicle fusion opposite postsynaptic densities (PSDs). At the Drosophila neuromuscular junction, the ELKS family member Bruchpilot (BRP) is essential for dense body formation and functional maturation of AZs. Using a proteomics approach, we identified Drosophila Syd-1 (DSyd-1) as a BRP binding partner. In vivo imaging shows that DSyd-1 arrives early at nascent AZs together with DLiprin-alpha, and both proteins localize to the AZ edge as the AZ matures. Mutants in dsyd-1 form smaller terminals with fewer release sites, and release less neurotransmitter. The remaining AZs are often large and misshapen, and ectopic, electron-dense accumulations of BRP form in boutons and axons. Furthermore, glutamate receptor content at PSDs increases because of excessive DGluRIIA accumulation. The AZ protein DSyd-1 is needed to properly localize DLiprin-alpha at AZs, and seems to control effective nucleation of newly forming AZs together with DLiprin-alpha. DSyd-1 also organizes trans-synaptic signaling to control maturation of PSD composition independently of DLiprin-alpha.

Cappuccino mutation in an autoimmune‐prone strain of mice suggests a role of platelet function in the progression of immune complex crescentic glomerulonephritis

Crescent formation in the renal glomerulus is a typical manifestation of progressive glomerulopathy associated with fatal renal failure; therefore, its prevention is of clinical importance. Little is known about the pathogenic mechanism for crescent formation. This study was undertaken in an attempt to identify the events that are critical for crescent formation in immune complex crescentic glomerulonephritis (CGN) by analyzing a novel mutant strain of mice. A spontaneous mutant strain of mice was isolated from the autoimmune-prone strain EOD, which stably develops fatal CGN. The mutant phenotypes were assessed histopathologically, hematologically, and immunologically. The mutation was searched for with positional cloning using microsatellite markers. Compared with wild-type EOD (WT-EOD) mice, mutant EOD (mut-EOD) mice showed marked improvement in CGN in conjunction with an improvement in spontaneous mortality. In WT-EOD mice, an inverse correlation between blood urea nitrogen concentration and blood platelet count and massive accumulation of platelets in the glomerulus were evident, suggesting that an accumulation of platelets in the glomerulus contributes to the progression of CGN. The mutant platelets showed an abnormal aggregation in response to collagen and thrombin, associated with a bleeding tendency in mut-EOD mice. Genetic analysis revealed a deleterious mutation in the cappuccino gene (cno), which encodes a protein that belongs to a complex called the biogenesis of lysosome-related organelle complex 1 and is profoundly involved in platelet function. Morphologic examination revealed a partial defect in dense body formation in the delta-granule of platelets. The present findings suggest that platelet functions have a critical role in crescent formation in autoimmune GN.

Cell adhesion receptors in C. elegans.

C. elegans has numerous putative cell adhesion receptors, many of which have vertebrate homologues. The simple body plan of C. elegans , its optical transparency and genetic tractability make it well suited for the study of adhesion receptors and their associated complexes (reviewed by Cox and

Electron-dense chains and clusters in platelets from patients with storage pool-deficiency disorders

Human platelets are known to contain inherently electron-opaque dense bodies, the storage sites for adenine nucleotides and serotonin, which can be identified under the electron microscope without fixation or staining. Recently we have reported that platelets also contain chains and clusters that are also opaque when examined by the whole-mount technique. The possibility that the newly described structures might be stages in the development of dense bodies requires consideration. The present study examined platelets from patients with Hermansky-Pudlak syndrome, Chediak-Higashi syndrome and platelet storage pool disease, whose cells are markedly deficient or lack dense bodies. Platelets from these individuals contained the same frequency of chains and clusters as found in platelets from normal controls. Thus, chains and clusters do not appear related to formation of dense bodies.

Effect of ovariectomy followed by administration of ovarian steroid hormones on the pig pinealocyte ultrastructure

The ultrastructure of female pig pinealocytes was studied after ovariectomy alone and ovariectomy followed by administration of estradiol, progesterone, or both. Administration of estradiol as well as a combination of estradiol and progesterone induced qualitative ultrastructural changes in pinealocytes relative to Golgi apparatus and cytoplasmic dense bodies as well as quantitative ones, such as a decrease in relative volume of cytoplasmic dense bodies and lysosomes. Administration of progesterone caused the formation of dense bodies and a decrease in the relative volume of lysosomes. The results point to a relationship between the pineal gland and gonads in the pig and suggest that gonadal steroids, particularly estradiol, could be involved in a feedback mechanism of the hypothalamichypophyseal-gonadal system to the pineal gland.

Ubiquitin, PGP 9.5 and dense body formation in trimethyltin intoxication: differential neuronal responses to chemically induced cell damage.

Ubiquitin in normal cells may be important in degrading or transferring short-lived or aberrant proteins to lysosomal dense bodies. To examine its role in degrading proteins produced by a chemical insult, changes in the distribution of ubiquitin and the carboxy-terminal hydrolase, PGP 9.5, have been studied in rat hippocampal neurons and cerebellar Purkinje cells in trimethyltin intoxication. Here tubulovesicular dense bodies (TVBs) form from 12h onwards associated with vacuolation of the Golgi apparatus. Striking accumulations of lysosomal dense bodies follow in hippocampal pyramidal cells but not in cerebellar Purkinje cells; many of the hippocampal neurons later die, while the Purkinje cells generally survive. Ubiquitin immunoreactivity was diffusely increased in hippocampal pyramidal and Purkinje cells 6 h after dosing. By 12 h both diffuse and granular ubiquitin immunoreactivity was present that intensified over 24 and 48 h. Both by light and electron microscopy TVBs showed ubiquitin immunoreactivity, but dense bodies in hippocampal perikarya did not stain with an anti-ubiquitin antibody. PGP 9.5 immunoreactivity was not altered in hippocampal cells at any time, while Purkinje and Golgi cell dendrites and perikarya showed intensified labelling at 3 h that reached a peak of 12 h. At 48 h Western blot analysis of hippocampal homogenates showed significant increases in high molecular weight (HMW) ubiquitin conjugates, while cerebellar homogenates showed an increase in ubiquitin-histone conjugates. Northern blot analyses showed no change in ubiquitin or PGP9.5 gene expression in hippocampus or cerebellum. These findings suggest that the material in the TVBs in hippocampal cells is not being degraded by the ubiquitin system but passes ubiquitinated into the lysosomal system, while material in Purkinje cell TVBs is degraded by the ubiquitin system, suggesting it may have a different composition in each type of neuron.

Evolution of the intracellular changes in neurons caused by trimethyltin.

Rats have been given a single dose of trimethyltin (10 mg/kg) and the intracellular events have been followed particularly in hippocampus, cerebral cortex, cerebellum and spinal ganglion cells. The earliest change visible occurs 12 h after this dose and is found to be dense membrane-bound bodies, probably derived from branching tubulo-vesicular smooth endoplasmic reticulum formations. These occur in close connection with rought endoplasmic reticulum and polyribosomes and appear also to have some association with the Golgi complex. At 24 h there is a general vacuolation of Golgi cisterns and SER membranes, and the membrane-bound dense body formation is greatly increased. SER abnormalities are particularly conspicuous in Purkinje cells. In spinal ganglion cells, while vacuolation of Golgi cisterns is intense, dense bodies are inconspicuous and are replaced by increased autophagosomes, often of great complexity. By 48 h vacuolation of Golgi cisterns has waned, but accumulation of dense bodies and secondary lysosomes has steadily increased. In spinal ganglion cells autophagosomes only are increased as the Golgi vacuolation declines. At later times steady increases of lysosomal dense bodies is seen generally accompanied in hippocampal pyramidal cells and dentate fascia cells by abundant cell death. The suggestion is put forward that the Golgi complex may be the seat of the critical metabolic lesion and disturbances to protein transfer and protein synthesis follow. No explanation for the selective loss of hippocampal h1-5 (CA1-CA4 except Sommer's sector) pyramidal cells and of small dentate fascia neurons can be derived from these conclusions.

Extraneuronal effects of 6-hydroxydopamine and extraneuronal uptake of noradrenaline

6-hydroxydopamine (6-OHDA) was shown to cause ultrastructural changes in adrenocortical cells of lizards and rats. These changes comprised the formation of dense bodies with lamellar and crystalloid patterns, a decrease in the number of mitochondria and structural alterations of mitochondria. Alterations in adrenomedullary cells were not affected as a rule. Only in young animals did 6-OHDA cause deposits of an electron-dense material in medullary cells. An attempt was made to obtain information on amine uptake into cortical cells using the Falck-Hillarp technique to analyse the in-vivo and in-vitro uptake of noradrenaline (NA) into the adrenal cortex in adult rats. Extraneuronal uptake into heart and spleen was studied as well. Our results suggest that NA is taken up into cortical cells, particularly into nuclei, after exposure to 10(-4) gm/ml in-vitro indicating that uptake of 6-OHDA is also likely. Investigations using labelled 6-OHDA is also likely. Investigations using labelled 6-OHDA are required for further elucidating its extraneuronal uptake.

Fine structure of the male genital tract and kidney in the Anura Xenopus laevis Daudin, Rana temporaria L. and Bufo bufo L. under normal and experimental conditions.

The ultrastructure of the main cellular components of testicular interstitial spaces in three Anuran species was studied during two short periods of the seasonal cycle and after treatment with 5- and 6-hydroxydopamine (5- and 6-OHDA). In early December when seminiferous tubules are completely filled with resting spermatozoa in Rana, Leydig cells display a well developed smooth- and rough-surfaced ER, numerous granular vesicles being untypical of Mammalian Leeydig cells, metochondria with tubular cristae and only few lipid droplets. In late April shortly after spermiation has occurred in most animals studied Leydig cell exhibit a low degree of activity as shown by the presence of numerous large lipid inclusions, reduced amounts of ER and granular vesicles, but increased numbers of dense bodies. In addition, a few rather undifferentiated cells are observed. In principle, the same differences between winter and late spring Leydig cells are seen in Bufo, although the smooth-surfaced ER which is partly arranged in whorls is much more pronounced in this species whereas granular vesicles are lacking. In December intertubular spaces display a few mitotic figures of Leydig cells. In Xenopus no obvious seasonal changes are observed in Leydig cells. As in Rana, there are numerous granular vesicles. The agranular ER is moderately developed. Intratesticular seminal excretory ducts consist in all three species studied of very low differentiated cells being almost completely filled with filaments (equivalent-100 A). Seasonal changes do not seem to occur. Morphological equivalents for secretory or resorptive processes are neither observed in early December nor in late April around the time of spermiation (in Rana and Bufo). At the connections site of seminiferous tubules and excretory ducts a basal laminal labyrinth is commonly observed. In Xenopus smooth muscle cells from an incomplete sheath around seminiferous tubules and are also uniformly distributed in the intertubular spaces without any obvious relationships to vessels. Rana and Bufo lack a peritubular contractile cell layer. After application of 5- and 6-OHDA (5-OHDA: three injections of 200 mg/kg at 12 hr intervals; 6-OHDA: three doses of 100-150 mg/kg on three consecutive days) cytoplasmic inclusion bodies with lamellar and crystalloid internal patterns develop in Leydig cells from lysosome-like structures. In addition, formation of dense bodies from mitochondria is seen in a few instances. The significance of these alterations is discussed.

Ultrastructure of the midgut epithelial cells in the fly Calliphora erythrocephala

The present paper concerns the organization of the epithelium in three histologically different parts of the midgut, each possibly having a specific function in the process of digestion. Three cell types can be distinguished: The columnar or absorptive cells resemble those described in other insects, but show structural characteristics depending on their location in the epithelium. An attempt was made to determine whether there is a relationship between these characteristics and functional specializations. The occurrence of apical cytoplasmic extrusions is considered to reflect a process of degeneration. In some cases fixation artifacts may be misleading. Special attention was paid to membrane configurations believed to play a part in the formation of dense bodies. Regenerative cells also occur; their relative numbers were determined in relation to their location. A third type of cell, characterized by the presence of electron dense granules, is described.

Observations on “Dense-body” Structure in Nerve Cells with Special Reference to Scrapie

SUMMARY Examination of nerve cells of sheep affected with scrapie under natural conditions has shown (a) nerve cells with large numbers of slit-like spaces in their cytoplasm with adjacent accumulation of ribosomc-like particles; and (b) apparent formation of dense-bodies from degenerating mitochondria. Within these are filamentous structures showing a helical, or stacked disc appearance, with a central rod-like core. These filaments are about 120 A wide and the turns of the helix (or discs) about 50 A apart. Small numbers of such macromolecular structures can be seen in normal sheep neurone dense-bodies, but their frequency in scrapie is much greater. Their significance is discussed in the light of the association of the scrapie infective agent with mitochondrial fractions and the demonstration of DNA in mitochondria.

Massive pyritic deposits related to volcanism, and possible methods of emplacement

Deposits of massive pyrite and pyrrhotite-pyrite occur mainly in volcanic rocks and particularly in the uppermost pyroclastic parts of submarine volcanic piles. Large deposits of massive pyrite and pyrite-sulfur have formed in the recent past and are forming now around fumaroles and volcanic hot springs in Japan and Taiwan. The older but undeformed massive pyrite deposits of Cyprus appear to have formed in the same manner, but largely under submarine conditions. Deposits in deformed rocks, as those at Rio Tinto, Spain, and Shasta county, California, give less positive evidence of origin but appear to be of the same type. Material in volcanic emanations is thought to be in both a molecularly dispersed and a colloidally dispersed state where emanations enter a near-surface submarine environment. Rapid flocculation of colloids and rapid precipitation of material in solution are postulated to occur in sea water or in sea-water-soaked pyroclastic rocks and sediments. Several mechanisms for formation of dense bodies of massive sulfide are suggested, but filtration of the flocculated and precipitated material, with accompanying replacement, appears to be a probable process.