Electron-dense Globules Research Articles

Histochemical and immunohistochemical characterization of foamy histiocytes (muciphages and xanthelasma) of the rectum.

Despite being relatively common in the rectum, foamy histiocytes have received scant attention as to the antecedent lesion that causes them to form or their histologic characterization on the types of muco-substances they accumulate. One-hundred consecutive tissue sections of the rectum from an equal number of patients were reviewed for the presence of foamy histiocytes, evaluated for their associated histologic features, and examined histochemically for five types of mucin. Immunohistochemical and electron microscopic studies were performed. Forty (40%) of the rectal biopsy tissues contained foamy histiocytes. Patients presented with diarrhea, hematochezia, intestinal habit change, constipation, hemorrhoids, and abdominal pain. Endoscopically, 19 patients were thought to have rectal nodules or polyps. Histologically, 25 of the patients had regenerative changes in the adjacent mucosa and 14 had hyperplastic changes. In 36 patients (90%), the foamy histiocytes were located superficially in the lamina propria. Associated changes indicated that they are found in areas that are subject to an injury that is in a healing phase. These changes included mild fibrosis and chronic inflammation of lamina propria with mild architectural distortion. Thirty-five (88%) cases showed staining for D-PAS, Alcian blue stain pH 2.5, and the cocktail Alcian blue stain/PAS. Mucicarmine was positive in 25 (63%) cases. The Alcian blue stain pH 1.0 was positive in 19 (59%) of 32 cases. Ultrastructural studies showed electron-dense globules. Two cases were histologically identical to the other 38 but they did not stain for any mucin. Ultrastructural features disclosed clear vacuoles and thus represent a xanthelasma of the rectum. The foamy cells in all cases were confirmed to be histiocytes by immunohistochemistry and electron microscopy. Although muciphages and xanthelasma of the rectum may mimic polyps endoscopically, they are not related to any specific symptom or clinical finding, despite the fact that they probably represent remnants of a previous injury. Muciphages contain neutral, weakly acidic or strongly acidic mucin. The main type of acidic mucin is sialomucin with a smaller component of sulfated mucin.

Ultrastructural alterations in response to zinc and nickel stress in the root cells of pigeonpea

Ultrastructure of root cortical cells of two genotypes of pigeonpea ( Cajanus cajan), namely LRG30 and ICPL87, were grown under different concentrations of zinc and nickel. Growth reduction was found in roots. Electron micrographs of the root cortex cells of the two pigeonpea genotypes exposed to zinc and nickel showed alterations both at the cellular and the organelle level. At the lower concentrations, appearance of unusual deposition of electron dense globules in the vacuoles of the root cortical cells suggests that they may be involved in metal detoxification. Some of the cortical cells showed two nucleoli. The ultrastructural alterations are discussed in relation to the tolerance indices of the two genotypes.

Ultrastructural aspects of damage to leaves of Eucalyptus camaldulensis by the psyllid Cardiaspina retator

The ultrastructural changes to leaf mesophyll cells in River Red Gum, Eucalyptus camaldulensis Dehnh., which occur during feeding by nymphs of Cardiaspina retator Frogatt were characterised using Transmission Electron Microscopy. Image analysis of micrographs revealed that the sap-sucking nymphs of C. retator cause a condition in mesophyll cells that closely resembles the cell degeneration described for senescing leaves of deciduous trees. The most conspicuous change was the breakdown of the thylakoid membranes in chloroplasts coupled with a massing of electron-dense globules (plastoglobuli). For psyllid-affected River Red Gums, as for senescing leaves of deciduous plants, this change appears to be related to the mobilisation of lipids and proteins. Results were compared to mesophyll cells of naturally senescing leaves of E. camaldulensis which had been abscised. These cells showed whole-scale breakdown with the chloroplasts remaining intact and functional the longest as judged by the presence of large starch grains. There was no accumulation of plastoglobuli. Mesophyll cells from senescing leaves appeared to suffer from severe water stress, indicated by the deformation of the cell wall and separation of the plasmalemma from the wall.

Morphological differences in nuclear materials released from hamster sperm heads at an early stage of incorporation into immature oocytes, mature oocytes, or fertilized eggs.

To elucidate the effects of ooplasmic factors on the early morphological changes in hamster sperm heads within the ooplasm, immature ovarian oocytes at the germinal vesicle stage (GV oocytes), ovulated fully mature oocytes, and fertilized eggs at anaphase II or the pronuclear stage (PN eggs) were examined in detail 15-30 min after insemination or reinsemination. Thin-sectioning studies demonstrated distinct materials released from the sperm nucleus over the entire postacrosomal nuclear surface immediately after disappearance of the sperm nuclear envelope. The release occurred in all of the oocytes and eggs prior to or even in the absence of subsequent chromatin decondensation. Depending upon the stage of the penetrated oocyte or egg, however, the materials varied in morphology: several hemispherical projections of amorphous material within mature oocytes; a number of electron-dense globules within GV oocytes and PN eggs; and both forms within eggs at anaphase II-telophase II. These observations and the fact that only the release of the amorphous material was accompanied by sperm chromatin decondensation indicate that this release was the initial process of chromatin decondensation, whereas the release of the globules resulted from a deficiency or lack of ooplasmic factors affecting the sperm nucleus. Restriction of the release in both forms of material to the late meiotic phase suggests changes in the factors associated with progression of meiosis. To approach an understanding of the mechanism of successful decondensation of sperm chromatin, the ooplasmic factors considered responsible for the stage-dependent release of nuclear materials are discussed.

An Ultrastructural Study of the Centrosome and Centrioles in Gametogenesis and Early Embryogenesis of Lymnaea stagnalis L. : II. Centrosome and Centrioles in Oogenesis and Early Embryogenesis

The fine structure of astral poles during both meiotic and early mitotic divisions of Lymnaea stagnalis eggs is studied. It is shown that both meiosis 1 spindle poles contain single centrioles due, apparently, to uncoupling of the nuclear and centriolar cycles before meiosis: DNA replication proceeds, but reduplication of the centrioles is absent. The outer pole of the meiosis II spindle also possesses one centriole and the inner pole contains a sperm basal body. The inner pole centrosome of the meiosis II spindle reveals a complex structure. Its periphery is formed as a result of transformation of the inner pole centrosome of the meiosis I spindle, and the center includes the sperm basal body. Thus, the zygote centrosome is a hybrid consisting of both maternal and paternal material. Both poles of the first mitosis spindle contain single centrioles. At the proximal end of each centriole an electron-dense globule is found. The sperm basal body has not been found. Therefore, formation of the centrioles de novo during the first interphase may be proposed. At the second mitosis a pair of centrioles is observed at each spindle pole. Two rounds of centriole duplication appear to occur during the second interphase. As a result, the correlation between DNA content and number of centrioles typical for proliferating animal cells is restored. Later, such a correlation is maintained: at the third mitosis each spindle pole contains a diplosome.

Ultrastructure of growing oocytes and accessory cells in Austrognathia (Gnathostomulida, bursovaginoidea)

The ovary of Austrognathia cf. riedli consists of 4–6 oocytes which are located in the mid-body region between the epidermis and the gut epithelium. The ovary is not enveloped by a tunica and each growing oocyte is surrounded by one or more accessory cells, the function of which is hypothesized in this study. Oogenesis is not synchronous and can be subdivided into a previtellogenic phase and a vitellogenic phase. Previtellogenic oocytes undergo a number of cell differentiations which consist mainly of an increase in size of the nucleus and nucleolus and the appearance in the cytoplasm of chromatoid bodies, annulate lamellac and short cisternae of rough endoplasmic reticulum (RER). Vitellogenic oocytes are characterized by the increase of RER, the appearance of numerous Golgi complexes and the accumulation of electron-dense globules, glycogen and lipid droplets. The electron-dense globules have been interpreted as yolk on the basis of both their localization and composition. Yolk synthesis occurs mainly by an endogenous mechanism and, to a lesser extent, by micropinocytosis. No shell-granules have been identified in the oocytes. The present ultrastructural findings are discussed in comparison with those from other lower metazoans.

Ultrastructure of Ascospore Ontogeny in Aleuria, Octospora, and Pulvinula (Otideaceae, Pezizales)

Ultrastructural studies were used to help resolve questions as to the recognition and limits of the heterogeneous family Otideaceae (Pezizales). Ascospore ontogeny was examined in species of Aleuria, Octospora, and Pulvinula and compared with that of other members of the order. Stages of ascosporogenesis, including primary wall formation, were similar to those found in other pezizalean genera. An accumulation of electron-dense globules appeared early in the perisporic sac of species of Aleuria and Octospora and contributes directly to formation of the epispore layer. In Pulvinula, there was a late accumulation of small electron-dense granules that was deposited onto the primary wall to form the epispore. A pronounced development of dense granules occurred in the perispore of Aleuria that condensed onto the epispore to form prominent ornaments. In Octospora, the granules degenerated and formed a loose secondary wall separated from the primary wall by an electron-translucent zone. A secondary wall did not develop in Pulvinula, and the epispore layer became the outer spore wall. We conclude that there was not a close correlation in spore ontogeny among the tribes of Otideaceae currently recognized on the basis of light-microscope data.

Increased iron content in the putamen of patients with striatonigral degeneration.

We measured the total content of iron, copper, zinc and manganese in the putamen of four patients with striatonigral degeneration (SND) and age- and gender-matched normal controls. The iron content in the SND patients was five times greater than in the controls. Electron microscopic histochemistry revealed the iron reaction products in the pigments showing a triphasic pattern of coarse, electron-dense globules, fine granular and fibrillary materials, and lamellated structures. These findings suggest that increased iron deposition may be related to pigment formation in the putamen of SND.

STRUCTURAL CORRELATES OF IMBIBITIONAL INJURY IN TYPHA POLLEN

The ultrastructure of Typha latifolia pollen was examined as a function of pollen moisture content and incubation temperature, in order to identify possible lesions induced by imbibitional chilling. A syndrome of structural traits was found which characterizes damaged grains. Compared to viable grains, the protoplast of damaged pollen has a higher proportion of its volume occupied by vesicles, and less volume occupied by cytoplasm. Damaged grains also tend to have dilated cisternae of endoplasmic reticulum, larger starch grains and lipid bodies, poorly preserved mitochondria and membranes, and, sometimes, numerous electron-dense globules associated with membranes. The percentage of grains exhibiting this damage syndrome correlates closely with the number of ungerminated grains in most samples, regardless of moisture content or incubation temperature. Injury due to rapid imbibition from the dry state or to imbibitional chilling appear to be similar structurally, regardless of whether the stresses are imposed singly or together. The injury is not confined to one cell component (e.g., mitochondria), but may involve a generalized disruption of membranes. These results suggest that similar stress responses are elicited by imbibition from the dry state and by imbibitional chilling.

Ultrastructure of altered rat enamel beneath fluoride-induced cysts.

The effect of a single injection of sodium fluoride (60 mg/kg) on the development of rat molar enamel beneath fluoride-induced subameloblastic cysts was studied by transmission electron microscopy using undecalcified sections. Three bands of altered enamel were identified and defined as the cyst surface band, the hypoplastic band, and the hypercalcified band. The irregular cyst surface band, not previously described, was found to have two components: electron-dense enamel globules and organic spherules. The electron-dense globules consisted of small, randomly arranged crystals (confirmed by selected area electron diffraction) occurring within a stippled organic matrix. The organic spherules have staining properties similar to stippled material and lack a crystalline component. They may be a form of organic material being extruded from the underlying developing enamel. The critical role of normal matrix production and ameloblast Tomes' process structure on the development of the crystal orientation and rod pattern is discussed.

The aboral haemal system of the sea star, Asterias rubens (Echinodermata, Asteroidea): An ultrastructural and histochemical study

The aboral parts of the haemal system of the sea star Asterias rubens are described, based on light and electron microscopy. These parts are (1) the mesenteric strands along the pyloric caeca and the pyloric stomach, (2) the gastric haemal tufts, and (3) the aboral haemal ring. The mesenteric haemal strands are very limited in size and distribution and, therefore, do not seem to have a major function in nutrient translocation. The myoepithelial cells of the gastric haemal tufts have the typical features of choanocytes; their ultrastructural characteristics corroborate the possible absorptive role of the gastric haemal tufts. The myoepithelial cells of the aboral haemal ring often show distinct apical bulbs of cytoplasm suggesting apocrine secretion of PAS-positive materials which are found in the surrounding aboral coelomic ring. These cells contain large stores of particulate glycogen and typical 1–2 μm electrondense globules. The ground substance of the haemal tissues, which contains collagen fibers, reticular fibrils, and numerous amoeboid phagocytes, has been analyzed histochemically. Sulfated glycosaminoglycans are almost completely absent; the predominant components are polysaccharides, proteins, and/or glycoproteins. Lipids have not been demonstrated. The possible functions of the haemal tissues and associated coelomic channels are discussed.

Untersuchungen zur Verdauung beim Ciliaten Nassula aureaEhrenberg

Summary The digestion of food in the ciliate Nassula aurea Ehrenberg is studied using transmission electron microscopy. During the food uptake numerous vesicles fuse with the food vacuole and secrete a flocculent material into it. This process causes the degradation of the cell walls of the food, the blue-green alga Phormidium autumnale. The digestion of the algal cytoplasm starts at a later time. After desintegration of the food, numerous longish folds become visible around the periphery of the food vacuole. These folds might facilitate the resorption of the nutrients. In starved cells many vacuoles filled with electron dense globules are encountered. The fate of the globules remains obscure because these cells will die very soon. Several anomalies in the mitochondrial ultrastructure are related to starvation.

Rotary replication of lens gap junctions

We have further characterized the structure of chick lens gap junctions by rotary-shadowed freeze-etch electron microscopy. The crystalline gap junctions, seen in lens epithelial cells and differentiating cells, had connexons arranged in hexagonal clusters separated by particle-free aisles. These connexons measured 7–8 nm in diameter and had center-to-center spacing of 8.5 to 9.5 nm. The noncrystalline gap junctions seen in lens fibers had connexons that were nonordered. Connexons of these gap junctions measured 8–9 nm in diameter and had center-to-center spacing of 8 to 15 nm. Two distinct populations of connexons were seen in these two types of lens gap junctions. One population displayed a central, electron-luscent zone surrounded by six electrondense globules that represented the metal caps of rotary-shadowed subunits of connexons. The second population had a similar ultrastructure but, in addition, contained a central electron-dense core measuring 1.5–2.0 nm that corresponded to the metal cap deposited over the rotary-shadowed central pore of the connexon. This ultrastructure closely resembled that seen previously in rotary-shadowed gap junctions of other epithelial cells and was consistent with the Unwin and Zampighi (1980) model of liver gap junction structure. These results demonstrate that lens gap junctions have the ultrastructure that clearly characterizes gap junctions in other tissues.

Ca2+-binding sites and Ca2+-ATPase activity in barley root tip cells

Different cytochemical methods were employed to demonstrate the existence of Ca2+-binding sites (Ca2+-bs) at the membranes of barley root tip cells, involving addition of CaCl2 (10 mM or 1 mM) to all aqueous solutions used for tissue processing for electron microscopy, treatment of ultrathin sections by Ca-chelating agents, enzymic digestion of ultrathin sections and modification of Wachstein-Meisel procedure for localization of Ca2+-dependent ATPase activity. Addition of 10 mM CaCl2 to the fixatives and rinsing solutions causes electron-dense globules (EDG) to be formed in a variety of cells, those in cortical cells being associated mainly with the plasma membranes, in root cap cells with the plasmalemma as well as with majority of intracellular membranes. The obligatory presence of EDG at the membranes of Golgi vesicles and secretory vesicles approaching plasmalemma was revealed in the secreting root cap cells. Besides, electron opaque connecting material was found between the plasmalemma and adjacent secretory vesicle membranes. In true meristematic cells Ca-supplemented solutions induce formation of EDG localized at the ER membranes, and nuclear and plastid envelopes. In root cells of seeds germinated in the presence of 1 mM CaCl2 electron opaque deposits were found only in local areas of plasmalemma collars around plasmodesmata neck regions, contacting the terminals of subsurface ER channels. In control speciemens (germination, fixation and washing without added CaCl2) EDG were absent in cortical and ground meristem cells, but present in root cap cells, although their number and average size were greatly reduced. Treatment of thin sections by 10mM EGTA or EDTA led to complete removing of EDGs, electron-transparent holes replacing them. Digestion by a variety of proteolytic enzymes and by phospholipase A induced partial destruction of EDG matrices, confirming the presence of protein as well as of phospholipid membrane components. Visualization of electron-dense granular product of cytochemical Ca-ATPase reaction at the same membrane areas where EDG were located suggests that one of the Ca-binding proteins in EDG may represent Ca-ATPase. It is proposed that EDG at plant cell membranes have a certain resemblance to the Ca2+-bs revealed by the same method on plasma membrane of a variety of animal cells. The data obtained are discussed regarding possible regulatory roles of calcium ions in plant cells, especially in exocytotic secretion.

Ultrastructural studies of the free zoospore of the rumen phycomycete Neocallimastix frontalis.

The structure of the free zoospores of Neocallimastix frontalis has been examined by electron microscopy of thin-sectioned and negatively stained preparations. There are up to 15 flagella arranged in two rows. The free end of each flagellum is narrow and its tip does not contain microtubules. The flagella and the cell body are coated with distinct surface layers composed of regular arrays of particles and fibrils, respectively. The cell body contains a variety of inclusions. Near to the flagellar pole there are numerous membrane-bound electron-dense globules about 0.2 to 0.7 mum in diameter, between which are microtubules, particles and small vesicles. In the region of the centrally placed nucleus are arrays of helices of ribosome-like particles. These particles also occur in the form of globular aggregates, each partially enclosed within a membrane. The remainder of the cytoplasm is filled with material resembling glycogen. The zoospores stain positively for glycogen and contain ribonuclease-sensitive particulate material which is stained by toluidine blue. Scanning electron microscopy shows that the zoospores attach to the substrate by the flagellar pole.

Mitochondrial alterations in the spinal ganglion neurons in ageing rats.

An ultrastructural study of the mitochondria was performed in the 3-, 24-, and 32-month-old rats. Accumulation of "unusual" substances or structures was the most striking characteristic in senescent neuron mitochondria. Tubular or filamentous inclusions, modifications in matrix density, deposit of glycogen particles and electron-dense globules were observed. The various nature of these alterations and their different situation in the cristae or in the matrix, suggested that they could be the result of some specific oxidative metabolism dysfunctions associated with ageing.

The tubular exine ofLauraceae andHernandiaceae, a novel type of exine structure in seed plants

The pollen grains ofLauraceae andHernandiaceae are characteristic in having a tubular exine of ± microfibrillar structure. This is coated with a layer of medium electron-dense globules and very peculiar spines, made up of a substance differing from that of the exine. Such a pollen wall structure is otherwise unknown in seed plants and thus adds to the list of odd features erratically present in various taxa of the Ranalean complex.

The structure of plasma low density lipoproteins: experimental facts and interpretations--a minireview.

From data on size and chemical composition, low density lipoprotein (LDL) can be described as a spherical particle having cholesteryl esters and triglycerides contained in a spherical core covered by the closely packed hydrophobic ends of phospholipids and unesterified cholesterol, while the head groups of the phospholipids, together with protein, occupy the surface. Such a model is compatible with early small angle X-ray and neutron scattering studies which, by prostulating spherical symmetry, assigned the LDL constituents to locations predicted from the radial electron density distribution. However, the concept of spherical symmetry, as applied to LDL structure, was recently challenged by results obtained from freeze-etching electron microscopy and small angle X-ray scattering experiments. Novel interpretations of these data suggest that the surface of LDL contains 4 electron-dense globules, located at tetrahedral positions, which have a capacity for structural remodeling at least as a function of the 2 temperatures studied (21C and 41C). It is reasonable to presume that the LDL protein (apo LDL) plays a role in the organization of the surface and overall LDL structure. However, until the chemical properties of apoLDL, and its behavior in solution and at the water-lipid interface are better understood, the validity of the proposed models cannot be assessed.

Ultrastructure of potato tubers infected with potato virus X

The ultrastructure of Katahdin tubers infected with potato virus X (PVX) is compared with PVX-free tubers by electron microscopy. Electron-dense globules surrounding the inner periphery of the tonoplast were observed in PVX-infected tubers, while PVX-free tubers did not show such bodies. Other organelles were comparable in PVX-infected and PVX-free tubers

THE FINE STRUCTURE OF THE NEURONES IN THE MID-DORSAL LOBES OF THE VISCERAL GANGLION OF THE LAMELLIBRANCH MOLLUSC <italic>SCROBICULARIA PLANA</italic> (DA COSTA)

Yellow-pigmented, concentrically-laminated and small electron-dense globules are three kinds of globule present in different neurones of the mid-dorsal lobes of the visceral ganglion of Scrobicularia plana . The yellow globules originate from vesicles formed by Golgi cisternae and the other kinds are derived from concentric membranes. Multiglobular bodies consisting of fused yellow globules occupy most of the somata of glial cells. The contents of the globules and the multiglobular bodies are released into extracellular spaces or blood sinuses byexocytosis. Multivesicular organelles resembling modified mitochondria which form elementary (neurosecretory) granules are found in some perikarya and axons. Glomeruli are present and resemble those of arthropods. The large central axons and their collaterals contain an intricate system of neurotubules; numerous lysosomes and various unidentified inclusions are present in the central axons. A few myelinated axons are present in the mid-dorsal lobes. These axons have 30–50 layers of electron-dense membranes. Axo-somatic and axo-axonal synapses are present in glomeruli