Presence Of Electron-dense Granules Research Articles

Spermatological characteristics of the enigmatic monogenean Dictyocotyle coeliaca Nybelin, 1941 (Monopisthocotylea: Monocotylidae) reveal possible adaptation to endoparasitism.

Spermatological characters of Dictyocotyle coeliaca Nybelin, a unique endoparasitic monogenean from the body cavity of the ray Amblyraja radiata (Elasmobranchii: Rajidae), was investigated by means of scanning and transmission electron microscopy for the first time. The process of the spermatozoon formation begins with the appearance of the differentiation zone which contains two centrioles. Subsequently developed two free flagella rotate to lie parallel before their fusing. After fusion, both the mitochondrion and nucleus migrate alongside the axonemes. Spermatids are formed within parallel cytoplasmic canals. During late spermiogenesis, an electron-dense spiral end-piece is formed proximally to the centriolar region of some spermatids. At the end of spermiogenesis, this end-piece is separated by a plasma membrane from the late spermatid and remains in the residual cytoplasm when spermatozoa are released into the testis lumen. The mature spermatozoon of D. coeliaca contains two parallel axonemes with the 9 + "1" trepaxonematan pattern, mitochondrion, nucleus, parallel cortical microtubules, and electron-dense granules. Especially the presence of electron-dense granules, occurring frequenly in the spermatozoa of endoparasitic flatworms, may indicate an adaptation to endoparasitic lifestyle in D. coeliaca. The anterior extremity of the male gamete contains one centriolar derivative, a small component of the second centriolar derivative and anterior extremity of the mitochondrion. The posterior extremity of the mature spematozoon exhibits tubular elements of the disorganized axoneme. Variations of the spermatozoon ultrastructural characters within monocotylid monogeneans and possible evolutionary significance of glycogen in sperm to the endoparasitic habit are discussed.

Acanthamoeba culbertsoni: Electron-Dense Granules in a Highly Virulent Clinical Isolate.

The virulence of various amoebic parasites has been correlated with the presence of electron-dense granules (EDGs) in the cytoplasm of trophozoites. Here, we report the finding by transmission electron microscopy of a large number of EDGs in a recent culture of Acanthamoeba culbertsoni, isolated from a severe case of human keratitis. When this isolate was maintained in culture for 6mo, the granules almost disappeared. However, after induction of mice brain lesions with the long-term cultured isolate, recovered amoebas had abundant EDGs. Trophozoites of the original isolate, or those recovered from experimental lesions, secreted EDGs into the medium when incubated with MDCK cells. To analyze a possible cytotoxic effect the conditioned medium was incubated with MDCK monolayers. After 5h, the media containing EDGs produced opening of the tight junctions; at 24h, cell viability was compromised, and at 48h most of the cells were detached from the monolayer. In contrast, trophozoites in long-term cultures did not release EDGs to the medium during incubation with MDCK cells, and the corresponding conditioned medium did not have any effect on MDCK monolayers. Our observations further support the hypothesis that EDGs play a role in the cytopathogenic mechanisms of A.culbertsoni.

Linking root traits to copper exclusion mechanisms in Silene paradoxa L. (Caryophyllaceae)

Copper is one of the most important pollutants in mine-contaminated soils. This study tests the response in a sensitive population vs a tolerant one of the model species Silene paradoxa in order to understand the general mechanisms of tolerance at the micromorphological and ultrastructural level. Two populations of Silene paradoxa were grown in hydroponics and exposed to different CuSO4 treatments. The roots were investigated with light, fluorescence and transmission electron microscope. Callose and lignin were spectrophotometrically determined. The tolerant population constitutively possessed a higher amount of mucilage and was able to reduce the length of the zone between the apex and the first lignified tracheids. Callose production decreased. It did not show remarkable copper-induced ultrastructural modifications, apart from the presence of precipitates in the tangential walls. The sensitive population showed huge nucleoli with a spongy periphery in the central cylinder together with the presence of electrondense granules in the mitochondria. Plastids were rarely observed and generally very electrondense and elongated. n the copper tolerant population of S. paradoxa some of the root traits concurring to generate metal-excluding roots were suggested to be mucilage and lignin production and the reduction of the subapical root zone.

CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a dominantly inherited small artery disease that leads to dementia and disability in mid-life. The clinical presentation of CADASIL is variable between and within affected families and is characterized by symptoms including migraine with aura, subcortical ischemic events, mood disturbances, apathy, and cognitive impairment. The mean age at onset of symptoms is 45 years, with variable duration of the disease ranging from 10 to 40 years. In 1996, linkage studies mapped and identified mutations in the NOTCH3 gene on chromosome 19 as causative in CADASIL. Head magnetic resonance imaging (MRI) is always abnormal in participants with NOTCH3 mutations after age 35. Magnetic resonance imaging shows on T2-weighted images or fluid attenuation inversion recovery (FLAIR) sequence, widespread areas of increased signal in the white matter associated with focal hyperintensities in basal ganglia, thalamus, and brainstem. The pathologic hallmark of CADASIL is the presence of electron-dense granules in the media of arterioles that can be identified by electron microscopic evaluation of skin biopsies.

Functional Morphology of Femoral Glands in the Tegu Lizard,Tupinambis merianae

Several lizards have femoral glands, which have an influence in various reproductive behaviors. In this paper we describe the morphological organization of the femoral glands in the Tegu, Tupinambis merianae, by means of light and electron microscopy. Even though these glands are present in both genders, secretions during the reproductive period can only be found in males. The glandular parenchyma, which is organized in numerous secretory units, consists of keratinocyte-like cells and granular cells. The holocrine secretion is constituted from both cells, which lose their integrity and become a semi-amorphous material, reinforced by keratin sheets. The discharges of each unit merge together into a solid cylinder of secretion, surrounded by epithelial cells, that is extruded to the exterior. The keratin sheets and epithelial layers that surround both the complete and partial secretions form a sort of structural support suitable for the type of territorial demarcation characteristic of the species. The granular cells, supposedly the producers of pheromones, are characterized by the presence of electron-dense granules and multilaminar membranous bodies that show ultrastructural changes of unknown function. The free granules in the secretion cylinder may act as pheromone deposits.

Ultrastructural characterization of CD133+ stem cells bound to superparamagnetic nanoparticles: possible biotechnological applications

CD133 antigen is an integral membrane glycoprotein that can bind with different cells. Originally, however, this cellular surface antigen was expressed in human stem cells and in various cellular progenitors of the haematopoietic system. Human cord blood has been described as an excellent source of CD133(+) haematopoietic progenitor cells with a large application potential. One of the main objectives of the present study is to describe for the first time the ultrastructural characteristics of CD133(+) stem cells using transmission electronic microscopy. Another objective of the manuscript is to demonstrate through transmission electronic microscopy the molecular image of magnetic nanoparticles connected to the stem cells of great biotechnological importance, as well as demonstrating the value of this finding for electronic paramagnetic resonance and its related nanobioscientific value. Ultrastructural results showed the monoclonal antibody anti-CD133 bound to the superparamagnetic nanoparticles by the presence of electrondense granules in cell membrane, as well as in the cytoplasm, revealing the ultrastructural characteristics of CD133(+) cells, exhibiting a round morphology with discrete cytoplasmic projections, having an active nucleus that follows this morphology. The cellular cytoplasm was filled up with mitochondrias, as well as microtubules and vesicles pinocitic, characterizing the process as being related to internalization of the magnetic nanoparticles that were endocyted by the cells in question. Electronic paramagnetic resonance analysis of the CD133(+) stem cells detected that the signal (spectrum) generated by the labelled cells comes from the superparamagnetic nanoparticles that are bound to them. These results strongly suggest that these CD133(+) cells can be used in nanobiotechnology applications, with benefits in different biomedical areas.

Juxtaligamental cells in the arm of the brittlestar Amphipholis kochii Lütken, 1872 (Echinodermata: Ophiuroidea)

We found that ligaments connecting the skeletal elements in the arm of the brittlestar Amphipholis kochii, consisted of mutable collagenous tissue (MCT), whose basichistological character is that of numerous processes of juxtaligamental cells penetrating the extracellular matrix. These cells are located in the hyponeural neuroepithelium associated with hyponeural nerves, and were also recorded in the spine ganglia and basiepithelial nervous plexus in the coelomic epithelium. The distinctive feature of juxtaligamental cells is the presence of electron-dense granules in their cytoplasm and a well developed synthetic apparatus. Based on personal and literature data it is concluded that juxtaligamental cells are a part of the nervous system, and their basic function is related to providing MCT with innervation.

Euglena gracilis as a model for the study of Cu 2+ and Zn 2+ toxicity and accumulation in eukaryotic cells

We have observed the effect of copper and zinc on the biology of Euglena gracilis. The cells displayed different sensitivities to these metals, as the apparent LC 50 for Cu 2+ was 0.22 mM, and for Zn 2+ it was 0.88 mM. While Zn 2+ was able to increase cell proliferation even at 0.1 mM, the minimal CuCl 2 concentration tested (0.02 mM) was sufficient to impair cell division. Higher concentrations of these metals not only inhibited cell division in a concentration-dependent manner, but also interfered with the metabolism of E. gracilis. A higher accumulation of proteins and lipids per cell was observed at the DI 50 concentration for metal-treated cells. These results suggest that the test concentration of both metals leads to a failure in completing cell division. Ultrastructural analysis indicated a chloroplast disorganization in copper-treated cells, as well as the presence of electron dense granules with different shapes and sizes inside vacuoles. Microanalysis of these granules indicated an accumulation of copper, thus suggesting a detoxification role played by the vacuoles. These results indicate that E. gracilis is an efficient biological model for the study of metal poisoning in eukaryotic cells. They also indicate that copper and zinc (copper being more poisonous) had an overall toxic effect on E. gracilis and that part of the effect can be ascribed to defects in the structure of chloroplast membranes.

In vivo secretory responses of submandibular glands in streptozotocin-diabetic rats to sympathetic and parasympathetic nerve stimulation.

Submandibular gland responses to sympathetic and parasympathetic nerve stimulation were studied in streptozotocin-diabetic rats. Morphologically, the acinar cells in control glands were relatively uniform in size and contained electron-lucent granules. The granular ducts were distinguished by the presence of electron-dense granules. With the exception of intracellular lipid droplets and the presence of a few autophagosomes in diabetic glands, no consistent differences in acinar cell structure were observed. In contrast, the diameter of the granular ducts and the granule content of their cells were less in diabetic glands. At 3 weeks sympathetic flow rate, salivary protein concentration, and total protein output were unaffected by diabetes. Sympathetic flow rate was greater at 3 months, and the concentration of protein in the saliva was lower. In 6-month diabetic rats flow rate remained increased, but protein concentration and total protein output were reduced. The decrease in salivary protein concentration at 3 and 6 months was accompanied by a reduction in secretory granule release from acinar and granular duct cells. No consistent differences in flow rate, protein concentration, protein output, or secretory granule release were observed following parasympathetic stimulation. We conclude that the effects of diabetes on nerve-stimulated flow rate and protein release depend on the duration of diabetes and the type of stimulation, and are independent of one another.

Atypical Lung Carcinoid with GFAP Immunoreactive Cells

A case of atypical carcinoid with peculiar histological and ultrastructural pattern and immunohistochemical phenotype is presented. The neoplasm is composed of three types of cells. Type 1 cells are small to medium sized, fusiform, with scarce cytoplasm and are arranged in fascicles. Type 2 cells are cuboidal and line acinar structures. Type 3 cells have more abundant eosinophilic cytoplasm, larger nuclei and are arranged in fascicles intersecting with fascicles of type 1 cells, and sometimes surround acinar structures. The three cell types are present both in the primary lesion and in its lymph node metastases. Immunohistochemistry demonstrates immunoreactivity of all cell types for general neuroendocrine markers. Cytokeratin immunoreactivity is more prominent in type 1 and 2 cells, and is only focally expressed in type 3 cells. Type 3 cells are also immunoreactive for glial fibrillary acidic protein (GFAP), alpha-actin, S-100 protein, vimentin. Electron microscopic examination confirms the neuroendocrine nature of the cells, and show that type 3 cells have prominent bundles of intermediate filaments, electron-dense granules and junctional complexes. To our knowledge, this is the first case of atypical lung carcinoid with GFAP immunoreactivity. The nature of type 3 GFAP positive cells is unclear. There are some clues pointing to their sustentacular nature, and other ones pointing to a myoepithelial origin, but the data are inconclusive. Type 3 cells may be the malignant counterpart of sustentacular cells seen in typical carcinoids, but their GFAP positivity and the presence of electron-dense granules are very unique features, which differentiates them from sustentacular cells. Alternatively, their unusual GFAP + immunohistochemical phenotype may be due to aberrant expression of cytoskeletal proteins.

Aortic calcification in chronic fluoride poisoning: Biochemical and electronmicroscopic evidence

Fluoride is known to cause ectopic calcification. The biochemical mechanism(s) involved in the initiation of calcification is not understood and the accompanying ultrastructural changes remain to be elucidated. Therefore, certain relevant parameters have been investigated in the aorta of rabbits administered fluoride, 10 mg NaF/kg body wt, every 24 hr for 17 and 24 months. The significant findings are: (i) degeneration of smooth muscle fibers in the tunica media of the aorta, (ii) presence of electron-dense granules in the mitochondria and on the inner surface of the plasma membrane of smooth muscle cells, (iii) presence of matrix vesicles with electron-dense deposits, (iv) enhanced calcium content and the Ca/P ratio, and (v) increased total glycosaminoglycan (GAG) content with reduced dermatan sulfate. The presence of electron-dense granules in the mitochondria, on the plasma membrane and matrix vesicles is suggestive of the process of calcification. The enhanced calcium content as well as the Ca/P ratio supports the view that the aorta is undergoing mineralization. The total GAG is enhanced, possibly due to an increase in the content of GAGs other than isomers of chondroitin. The observation that conveys an important message is that the dermatan sulfate normally known to exist in high concentrations in soft tissues begins to decrease as the process of calcification sets in. This perhaps would hold true and may serve as an index in the process of ectopic calcification.

The arrangement of collagen fibrils in the lymphatic sinus wall of the rabbit appendix.

The lymphatic sinus of the rabbit appendix was examined by scanning and transmission electron microscopy. Luminal surfaces of the sinus were lined by squamous endothelial cells, some of which, however, were blebby in surface relief due to the presence of electron dense granules in the cytoplasm. Many clusters of lymphocytes were present on the endothelial surface, mainly along the blood vessels of the trabeculae and of the sinus wall. Regional differences in collagen fibrillar arrangement of the sinus wall were demonstrated after the removal of the endothelial cells by the NaOH maceration method (OHTANI, 1987). In the upper region of the sinus and the lymphatic plexus of the internodular thymus dependent area (TDA), the fibrillar layer was a delicate network of interwoven thin fibrils. Furthermore, transmission electron microscopy revealed frequent transmural passages of lymphocytes, which suggest the existence of pores or fenestrations in the fibrillar layer of these regions. The fibrillar layer in the lateral and basal sinus was formed by densely interwoven thick bundles or sheets which consisted of thin collagen fibrils. No obvious space was seen between fibrils. These observations suggest that the upper region of the sinus and the lymphatics in the TDA may be active sites of cell migration from the reticular tissue.

Morphology of the minipig kidney.

The minipig has a multilobar kidney with a wide cortex and short papilla. The vascular bundles are of a simple type. Although short and long looped nephrons are both present, the short looped kind predominates. The minipig has many morphological similarities to dog and human kidneys. One particularly unique feature of the minipig papillary collecting duct cells, however, is the presence of electron-dense granules in the basal cytoplasm which appear to be secreted into the lateral intercellular spaces, perhaps forming a water-tight seal in a manner analogous to membrane-coating granules found in the epidermis of skin.

Subcellular localization of oxytocin in the ovine corpus luteum.

The subcellular localization of oxytocin within the corpus luteum of sheep was investigated using differential and density gradient centrifugation. Oxytocin was associated with a particulate fraction which sedimented to a density of 1.054-1.061 g/mL. The exclusion of [3H]oxytocin from this particulate fraction is indicative that particulate oxytocin represents endogenous compartmentalization. Particulate oxytocin, incubated in buffered medium at 37 degrees C, was stable for up to 1 h and the release of oxytocin was not affected by the pH of the incubation medium, over the range 5.5-8.5. Oxytocin release, however, was stimulated by incubating particle-bound oxytocin in buffered medium of low osmolality (less than 200 mosmol). These data are similar to the physicochemical properties reported for peptide-containing neurohypophysial secretory granules. Ultrastructural analysis of oxytocin-containing fractions revealed the presence of electron-dense granules (diameter, 200-250 nm). These data are suggestive that oxytocin, in the corpus luteum of sheep, is contained within a population of secretory granules which occur in high numbers during the midluteal phase of the oestrous cycle.

Ultrastructural characteristics of human T cell clones with various cytolytic activities.

Fifteen T cell clones with different (specific, antibody-dependent or natural killer-like) cytolytic activity were derived from mixed lymphocyte culture activated T cells and analyzed for their morphological characteristics and, in some instances, for their surface markers. All of the five cytolytic clones analyzed by electron microscopy possessed numerous electron-dense granules and in some instances multivesicular bodies, with or without an electron-dense matrix, that are the putative precursors of the granules. In addition, light microscopy examination of semithin sections of other ten cytolytic clones showed that the large majority of the cells in each clone had numerous toluidine blue-stained cytoplasmic granules. It is of note that nine clones without detectable cytolytic activity analyzed by electron microscopy did not possess granules and presented the features of large agranular blasts. Ten cytolytic clones were analyzed for different surface markers including rosette formation with sheep erythrocytes (E rosettes), receptors for the Fc portion of IgG or IgM ((Fc gamma R and Fc mu R) and a group of antigens recognized by monoclonal antibodies including Ia, 4F2, OKT8 or OKT4. All the clones were E-rosette+, Ia+ and 4F2+. Expression of Fc gamma R was restricted to the clones active in antibody-dependent cell-mediated cytotoxicity. Expression of OKT8 and OKT4 antigens was variable; in particular, five clones were OKT8+/OKT4-, whereas the other five expressed the OKT8-/OKT4+ phenotype. It is noteworthy that the ultrastructural features of cytolytic T cell clones are similar to those of large granular lymphocytes, known to be the only lymphoid cells in normal peripheral blood which possess cytolytic activity. Thus, it is possible that the presence of electron-dense granules may represent a morphological marker for all human cytolytic lymphocytes.

Ascospore development in the fission yeasts Schizosaccharomyces pombe and S. japonicus.

The fine structure of ascospore formation in the fission yeasts Schizosaccharomyces pombe and Schizosaccharomyces japonicus var. japonicus was studied by serial thin-sectioning and electron microscopy. The morphogenetic events were almost the same in both species. Ascospore development was initiated by the formation of the forespore membrane on the cytoplasmic side of the differentiated nucleus-associated organelle (NAO) in the interval between meiosis I and II in S. pombe, or during the post-meiotic nuclear division in S. japonicus, and the process proceeded almost synchronously through the two or four nuclei in the ascus. The forespore membrane developed by fusion of the cytoplasmic vesicles and this was clearly demonstrated in S. japonicus where the behaviour of vesicles involved in the forespore membrane development could be traced as they were marked by the presence of electron-dense granules. The staining technique, by phosphotungustic acid--chromic acid (PTA-CA) after treatment with periodic acid, was used to attempt to elucidate the origin and the nature of the forespore membrane. The method specific to plasmalemma-type membranes stained both ascus and ascospore plasmalemmas; the forespore membrane was not stained at first but developed the same affinity for stain as the plasma membrane in the course of ascospore development. The results suggest that the forespore membrane did not come directly from the ascus plasma membrane, but from another membrane system such as the endoplasmic reticulum. Spore wall material was deposited in the space between the inner and outer leaflets of the forespore membrane.

Early Pathologic Features of Hereditary Nephritis: A Clinicopathologic Correlation

The histologic, immunofluoresence and electron microscopic features of renal biopsies from twelve patients having hereditary nephritis were examined and correlated with the clinical data. In ten patients with normal renal function, light microscopy showed similar but nonspecific glomerular abnormalities consisting of mild focal and segmental hypercellularity and thickening of capillary walls. Biopsies from two patients with azotemia had diffuse lesions of the glomeruli and associated interstitial fibrosis. There were no characteristic findings on immunofluorescence. Electron microscopy revealed alterations in thickness and density of the glomerular capillary basal lamina in all patients. However, lamellation of the basement membrane and the presence of electron dense granules were present only in the two patients with renal functional impairment. These findings support the view that hereditary nephritis is a form of glomerular disease in which ultrastructural changes in the basal lamina of glomerular capillaries are the earliest and most consistent lesions. However, the morphologic spectrum of these ultrastructural abnormalities is broader than previously recognized.

Ultrastructure of the muscles of the dorsal diaphragm in Locusta migratoria.

The alary muscles of Locusta migratoria adults make up the major tissue of the dorsal diaphragm which separates pericardial and perivisceral sinuses in the abdomen. The alary muscles are striated with a sarcomere at rest measuring about 9 microns. The Z-line has a staggered-beaded arrangement with A-bands and I-bands readily discernable. Thick myofilaments are surrounded by 10 or more thin filaments. The sarcoplasm has few mitochondria near the area of the Z-line, dyads are present and sarcoplasmic reticulum is poorly developed. Axons which innervate the alary muscle are either contained within invaginated folds of the sarcolemma of the muscle cells or the muscle cells send finger-like projections to envelop the axons. The synaptic terminals contain synaptic vesicles between 40 and 45 nm in diameter and a few electron-dense granules near or less than 170 nm in diameter. Away from synaptic terminals the axon profiles show few or no granules. The axons are accompanied everywhere by well-developed glial cells. This then is not typical neurosecretomotor innervation, however, the presence of electron-dense granules suggests the possibility of peptidergic neurotransmission.

The pars intermedia of the mink, Mustela vison. Fluorescence, light and electron microscopical studies.

The pars intermedia of intact and experimental female minks has been studied by light, electron and fluorescence microscopy. The general structure of the mink intermediate lobe is described. Two main cell types are recognized. One, termed glandular cell, predominates in number and is characterized by the presence of electron-dense granules about 200 nm in diameter and numerous large vesicles up to 300 nm in diameter. The other, termed stellate cell, is devoid of cytoplasmic vesicles and granules and possesses microfilaments, junctional complexes and elongated processes inserted between the glandular cells. Different treatments (photostimulation and administration of hypertonic saline and metopirone) induced morphological reactions in the glandular cells. The significance of these changes and the possibility of a functional relation between the pars intermedia and ACTH secretion are 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.