Small Electron-dense Bodies Research Articles

The common ABCA3E292V variant disrupts AT2 cell quality control and increases susceptibility to lung injury and aberrant remodeling.

ATP-binding cassette class A3 (ABCA3) is a lipid transporter that plays a critical role in pulmonary surfactant function. The substitution of valine for glutamic acid at codon 292 (E292V) produces a hypomorphic variant that accounts for a significant portion of ABCA3 mutations associated with lung disorders spanning from neonatal respiratory distress syndrome and childhood interstitial lung disease to diffuse parenchymal lung disease (DPLD) in adults including pulmonary fibrosis. The mechanisms by which this and similar ABCA3 mutations disrupt alveolar type 2 (AT2) cell homeostasis and cause DPLD are largely unclear. The present study, informed by a patient homozygous for the E292V variant, used an in vitro and a preclinical murine model to evaluate the mechanisms by which E292V expression promotes aberrant lung injury and parenchymal remodeling. Cell lines stably expressing enhanced green fluorescent protein (EGFP)-tagged ABCA3 isoforms show a functional deficiency of the ABCA3E292V variant as a lipid transporter. AT2 cells isolated from mice constitutively homozygous for ABCA3E292V demonstrate the presence of small electron-dense lamellar bodies, time-dependent alterations in macroautophagy, and induction of apoptosis. These changes in AT2 cell homeostasis are accompanied by a spontaneous lung phenotype consisting of both age-dependent inflammation and fibrillary collagen deposition in alveolar septa. Older ABCA3E292V mice exhibit increased vulnerability to exogenous lung injury by bleomycin. Collectively, these findings support the hypothesis that the ABCA3E292V variant is a susceptibility factor for lung injury through effects on surfactant deficiency and impaired AT2 cell autophagy.

Transmission and Scanning Electron Microscopy of the Accessory Cells and Chorion During Development of Ciona intestinalis Type B Embryos and the Impact of Their Removal on Cell Morphology.

Spawned ascidian oocytes are surrounded by a membrane called the chorion (or vitelline coat) and associated with two populations of maternally-supplied cells. Outside the chorion are follicle cells, which may affect the buoyancy of eggs. Inside the chorion are test cells, which during oogenesis provision the egg and which after fertilisation contribute to the larval tunic. The structure of maternal cells may vary between species. The model ascidian Ciona intestinalis has been recently split into two species, currently named type A and type B. The ultrastructure of extraembryonic cells and structures from type A embryos has been reported. Here we describe the ultrastructure of follicle and test cells from C. intestinalis type B embryos. Test cells are about 5 µm in diameter and line the inside of the chorion of developing embryos in a dense sheet. Follicle cells are large (> 100 µm long) and spike-shaped, with many large vesicles. Terminal electron dense granules are found towards the tips of spikes, adjacent to cytoplasm containing numerous small electron dense bodies connected by filaments. These are probably vesicles containing material for the terminal granules. Removal of maternal structures and cells just after fertilisation, as commonly used in many experiments manipulating C. intestinalis development, has been reported to affect embryonic patterning. We examined the impact of this on embryonic ectoderm cells by scanning electron microscopy. Cells of embryos that developed without maternal structures still developed cilia, but had indistinct cell boundaries and a more flattened appearance than those that developed within the chorion.

Histological and biochemical study on the protective effect of losartan on rat renal cortex in experimentally induced liver failure

Introduction Hepatic ischemia/reperfusion (I/R) injury is an unavoidable problem during liver surgery that often results in acute liver failure, with its complications. Losartan may be beneficial in such conditions. Objectives This study was designed to investigate the histological and biochemical alterations that could occur in the renal cortex in case of liver cell failure and to assess the possible protective role of losartan. Materials and methods Thirty male albino rats were equally divided into three groups: group I (control) was equally subdivided into sham operated-untreated (Ca) and sham-operated, losartan-treated (Cb) subgroups. In group II (operated), rats were subjected to experimentally induced I/R. In group III (losartan treated), rats were subjected to a surgical procedure and treated with losartan (5 mg/kg body weight). At the end of the experiment, blood samples were obtained for the biochemical assay. The liver was processed for assessment of antioxidant markers and for light microscope examination. Both kidneys were processed for light and electron microscope examinations. The results were morphometrically and statistically analyzed. Results Light microscope examination of the operated group indicated shrunken glomeruli with wide Bowman’s space. Some tubules were distorted with cytoplasmic vacuoles and cellular casts, whereas others were dilated. The interstitium contained an acidophilic material, increased collagen fibers, cellular infiltration, and congested blood vessels. Ultrastructurally, podocytes had small electron-dense nuclei and fused foot processes. Some renal tubules had small heterochromatic nuclei, mitochondria with disrupted cristae, and small electron-dense bodies. The biochemical results of the same group showed the occurrence of oxidative stress and deterioration in liver and kidney functions. The treated group showed preserved structure of the renal corpuscles and tubules. Conclusion Liver I/R adversely affected the renal cortex histologically and biochemically. Losartan could be promising as an adjuvant therapy before hepatic surgery for rescuing the kidney from hepatic I/R injury.

Utrastructural observations on Goussia metchnikovi (Laveran, 1897) in the spleen of gudgeon, Gobio gobio L.

The ultrastructure of gamonts and sporulated oocysts of Goussia metchnikovi in the spleen of gudgeon, Gobio gobio from the river Lee, England is described. In developing microgamonts, small amylopectin granules were grouped centrally and nuclei were often arranged peripherally, close to the surface membrane. Nuclear chromatin condensed into peripheral dense portions that became the nuclei of flagellated microgametes, released to the parasitophorous vacuole. The cytoplasm of macrogametes had larger, scattered amylopectin granules, lipid globules and small electron-dense bodies, but no obvious wall forming bodies; peripheral vesicular structures with the appearance of mitochondria were also present and the parasitophorous vacuole contained flocculent material, but was otherwise free of structures. Sporulated oocysts contained four sporocysts and oocyst walls appeared to consist of a single membrane. Sporocyst walls showed a dehiscence suture, characteristic of the genus Goussia, which had filamentous extensions in places. The sporocyst wall comprised a dense inner layer and a thin outer layer with a fuzzy coat, separated by an electron lucent layer. Groups of oocysts were encapsulated by fibrous layers and inflammatory cells, and many sporocysts and their contained sporozoites showed evidence of elimination by the host.

The ultrastructure of the subcommissural organ ependyma of the goat.

The cells of pseudostratified columnar ciliated ependyma of the subcommissural organ in the goat were classified into two types on the basis of the distribution of chromatin material and nuclear clefts. Amongst the cell organelles the endoplasmic reticulum was highly developed and formed three types of Nebenkerne systems. The type-I Nebenkerne had spiral concentric lamellae and was associated with round lipid droplets. The type-II Nebenkerne, with widely spaced coils, was expanded towards its central and peripheral parts. The type-III Nebenkerne, composed of a meshwork of lamellae, was modified into a vacuolated form. The concentration of mitochondria was greatly increased towards the basal processes of the ependymal cells. The inclusion bodies included small electron-dense bodies, osmiophilic asteroid droplets, large round to spherical bodies and large round osmiophilic bodies with inner structures.

Changes in intestinal villi, cell area and intracellular autophagic vacuoles related to intestinal function in chickens

1. Morphological changes in the intestinal villi, cell area and cell mitosis number in the duodenal epithelial cells were compared in cockerels fasted for 1, 2 and 3 d, and also when refed for 1 and 2 d after 3 d of fasting, to demonstrate whether these morphological changes are related to intestinal function. Alterations in the fine structure of vacuoles in epithelial cells were also examined in each group to investigate whether the vacuolar changes are associated with these morphological changes, and to obtain an index for judging the nutritional condition of the chicken intestine. 2. Fasting induced decreases in villus height, cell area and cell mitosis number, which recovered rapidly after refeeding, suggesting that these parameters are related to changes in intestinal function and may be useful for assessing intestinal function. 3. At 1 d of fasting, small electron-dense bodies appeared in the absorptive epithelial cells, some of them fusing with each other. As the fasting period increased, these small bodies developed to moderate-sized nascent autophagic vacuoles containing various kinds of electron-dense contents and finally became large autophagic vacuoles with electron-lucent contents. Some vacuoles showed positive acid phosphatase reactions, which indicated that they were lysosomal autophagic vacuoles containing hydrolytic enzymes. 4. After 1 d of refeeding the large autophagic vacuoles seen after 3 d fasting rapidly decreased to the small electron-dense bodies seen after 1 d of fasting. 5. These findings suggest that intestinal epithelial cells have the ability to digest their own cell components to supply nutrients during fasting by means of lysosomal active autophagic transport mechanisms; after refeeding, the epithelial cells return to the absorption of nutrients. 6.The present results demonstrate that the autophagic vacuolar changes are correlated with changes in intestinal villus height, cell area and cell mitosis number induced by fasting and refeeding; this indicates that autophagic vacuoles are a useful index of the nutritional condition of chicken intestine. The greater the number of electron-lucent vacuoles there are in the duodenal absorptive cells, the lower the nutritional condition of the chicken intestine.

Lipocortin 1 (annexin 1) in patches associated with the membrane of a lung adenocarcinoma cell line and in the cell cytoplasm.

Lipocortin 1 (annexin I) is a calcium- and phospholipid-binding annexin protein which can be externalised from cells despite the lack of a signal sequence. To determine its cellular distribution lipocortin 1 in A549 human lung adenocarcinoma cells was localised by light- and electron-microscopic immunocytochemistry and by cell fractionation and western blotting. Lipocortin 1 immunoreactivity is concentrated in prominent patches associated with the plasma membrane. The intensity of these patches varied with the confluence and duration of the culture and was not detectably diminished by an EDTA wash before fixation. Tubulin and cytokeratin 8 were colocalized with lipocortin 1 in the patches. Within the cells lipocortin 1 was distributed throughout the cytoplasm. Electron microscopy revealed prominent immunoreactivity along the plasma membrane with occasional large clusters of gold particles in contact with the membrane surface of the cells; within the cytoplasm the membrane of some vesicle/vacuole structures and some small electron-dense bodies was immunoreactive, but no immunogold particles were associated with the multilamellar bodies. Subcellular fractionation, extraction and western blotting showed that lipocortin 1 in the membrane pellet was present as two distinct fractions; one, intimately associated with the lipid bilayer, which behaved like an integral membrane protein and one loosely attached which behaved like a peripheral membrane protein. The results show that a substantial amounts of lipocortin 1 is concentrated in focal structures associated with and immediately beneath the plasma membrane. These might form part of the mechanism by which lipocortin 1 is released from the cells.

Spermatozoon structure and spermiogenesis inNassarius kraussianus(Gastropoda, Prosobranchia, Nassariinae)

Summary The testis of Nassarius kraussianus (Nassariinae) produces two types of spermatozoa, a motile euspermatozoon and a non-motile paraspermatozoon. The euspermatozoon is filiform and about 95/μm long. The elongated head (40 μm long) is comprised of a slender nucleus (about 0.5 μm diameter) which is penetrated throughout by an intranuclear canal housing the anterior portion of the axoneme. A short (about 2 μm long) conical acrosome surmounts the nucleus anteriorly. The mid-piece (23 μm in length) consists of six to seven modified mitochondria which are helically arranged around the axoneme. Posterior to the mid-piece the tail is composed of a short glycogen piece and an end piece. The paraspermatozoon is spindle-shaped (about 50 μm long) and contains multiple (16–20) axonemes the basal bodies of which fuse anteriorly. Posteriorly, numerous small mitochondria and electron-dense bodies lie between the axonemes. Structural changes during eu- and paraspermiogenesis mirror those described for other species ...

Intraerythrocytic schizogony of Theileria sergenti in cattle.

The characteristics of developing intraerythrocytic stages of T. sergenti were studied by light and transmission electron microscopy. The parasites with many ribosomes, acristate mitochondria, cytostome, and food vacuoles were morphologically regarded as the trophozoite stage. Although this type of parasites was frequently detected, intraerythrocytic merozoite stage with electron dense cisternae, rhoptries and small electron dense bodies was rarely observed in high parasitaemia. The intraerythrocytic stages of T. sergenti were divided mainly into four daughters by schizogony, and alternatively into two by binary fission. The daughter parasites in each division had the same ultrastructural features as of merozoites. As a result, it was suggested that T. sergenti trophozoites multiplied by schizogony to four organisms or by binary fission in the peripheral erythrocyte, and differentiated to the merozoites which acquired penetrating ability into the erythrocytes.

Ultrastructure of Epidermis and Sperm of the Turbellarian Syndisyrinx-Punicea (Hickman, 1956) (Rhabdocoela, Umagillidae)

Syndisyrinx punicea has an epidermis with intraepidermal nuclei, a thick basal lamina, and microvilli containing an array of densely packed filaments and, in the widened tips, an electron-dense cap. The epidermal cilia posess a widened cytoplasmic portion close to the base and vertical and horizontal cross-striated rootlets; the latter are anchored in the adjacent matrix by means of transverse bars. Basal bodies have a distinct spike opposite the horizontal rootlet. In the tips of epidermal cilia, one of the microtubules disappears first in doublets 7-9 and 1, and gradually all peripheral doublets disappear; there is no electron-dense rod along the central microtubules, but cilia have a terminal electron-dense cap. Spermatozoa have two flagella, much shorter than the sperm (and not incorporated in it); axonemes are of the 9+'1' type; an elongate nucleus, numerous small mitochondria and electron-dense bodies are surrounded by a single peripheral row of microtubules in the thicker parts of the sperm, in the thinner parts (apparently close to the ends) microtubules are also found in the interior; some electron- dense bodies were also seen free between sperm, indicating their secretory function. Ultrastructural evidence does not support the view that Umagillidae (as well as Temnocephalida) are particularly closely related to the Neodermata, the major parasitic groups of Platyhelminthes.

Infectious Crystalline Keratopathy

A 73-year-old man developed a crystalline stromal keratopathy in one eye following his second corneal transplant. Despite aggressive treatment with antibiotics and antifungal agents, the lesion increased in size. A corneal transplant was performed and histopathologic studies were performed using both light and transmission electron microscopy. The characteristic trilamellar structure of a bacterial cell wall was found. The organisms were present only anteriorly. Small electron-dense bodies with needle-like projections were found. These bodies may be responsible for the crystalline appearance of this keratopathy. The appearance of a crystalline keratopathy should alert clinicians to the possibility of a low-grade bacterial infection. After appropriate cultures, we advise early and aggressive therapy with appropriate antibiotics.

Endocytosis in alveolar type II cells: effect of charge and size of tracers.

The type II cell of the alveolar epithelium of adult rats has been studied by electron microscopy to determine its ability to endocytose electron-dense tracers of differing molecular charge and size. The tracers studied were native (anionic) ferritin, cationic ferritin, 70-kilodalton dextran, and colloidal carbon. Alveolar macrophages ingested all tracers in large amounts, while type II cells took up significant amounts of cationic ferritin only. This tracer was observed, in sequence, within small pinocytic vesicles, large electron-lucent multivesicular bodies, small electron-dense multivesicular bodies, and, by 30 min after instillation, within the nonlamellar matrix of lamellar bodies. By 2 hr all lamellar bodies in any labeled cell contained cationic ferritin. Cationic ferritin also appeared to be transported from alveoli to interstitium by vesicles of type II, but not type I, cells. Native ferritin and dextran were observed in the same organelles as cationic ferritin but in much smaller amounts; colloidal carbon was not taken up by type II cells. These tracers were not observed in the alveolar interstitium. Type II cells therefore appear to internalize preferentially the tracer that binds to the cell membrane. Once within the cell, the tracer may enter a pathway that terminates in a lamellar body or, in the case of cationic ferritin, may be ferried across the cell.

Ultrastructural and ultrahistochemical studies on ventricular endocardial cells in teleosts (Pisces)

The ultrastructure of the ventricular endocardial cells in 17 bony‐fish species representing eight families, is described. In species of Characidae, Cobitidae, Cyprinidae, and Gyrinocheilidae these cells are flat (1–2 µm at nucleus) and contain numerous ribosomes, some few bristle‐coated vesicles (BCV) and small (0.243 pm) electron dense inclusion bodies. However, in species of Cichlidae, Gadidae, and Poeciliidae most endocardial cells appear relatively thicker (2–5 µm at nucleus) and contain numerous BCV, tubules of agranular endoplasmic reticulum, and large (0.5‐1.5 µm) moderately electron dense bodies (MDB). In the MDB occur a number of small (20–150 nm) electron dense granules. Within the family Anabantidae, most endocardial cells seem to be of the first type in Colisa laliu and Trichogaster leeri. whereas in Helosioma iemmincki there are numerous cells of the second type. When glutaraldehyde/tannic acid fixed heart tissue of Pollachius virens is treated with ferrous chloride, ferric chloride, or osmium tetroxide, and grid stained by uranyl and lead solutions, damaged endocardial cells appear highly electron dense, whereas undamaged ones are electron lucent. Further, when glutaraldehyde fixed tissue is treated with osmium tetroxide/potassium ferrocyanide the subendocardial space is filled by a highly electron dense material. The methods described in this study make it possible to distinguish between those endocardial vacuoles having structural contact with the cell membrane, and those lacking such contact, and also to determine whether the lumen of the former is continuous with the subendocardial space, or with the intertrabecular lumen.

Alveolar pre-type II cells from the fetal rabbit lung isolation and characterization

A method for preparing a homogeneous population of undifferentiated cells from the fetal rabbit lung is described. This method utilizes enzymatic digestion, differential adhesion to remove fibroblasts and centrifugation on a discontinuous metrizamide gradient. Cells isolated by this procedure replicate in vitro in medium supplemented with carbon-stripped fetal bovine serum. Mitosis can also be stimulated by heat-inactivated medium conditioned by fetal lung fibroblasts. After confluence, exposure of these cells to 0.55 or 55 nM dexamethasone significantly increased the incorporation of [ 14C]choline into phosphatidylcholine. Lower concentrations of the drug also increased incorporation, but not significantly so. Addition of heat-inactivated fibroblast-conditioned medium produced a 25% increase in choline incorporation, but this was not significant. Furthermore, the presence of conditioned medium tended to reduced the response of the cells to dexamethasone. After confluence, lamellar inclusion bodies were present in more than 90% of those cells exposed to dexamethasone. These organelles were not observed in cell monolayers not exposed to the steroid. These cells did contain a few small electron-dense bodies. The latter may be immature multivesicular bodies.

Structure and Ultrastructure of the Cotyledon of Date Palm (Phoenix dactylifera L.)

The cotyledon of the embryo of the date palm (Phoenix dactylifera L.) is composed of three cell types with similar ultrastructure. These three types-the parenchyma, protoderm, and procambium-can be distinguished on the basis of position, size, and shape within the embryo. The procambial strands in the cotyledon consist of a ring of sympodia that diverged from the hypocotyl; each sympodium bifurcates two to three times to form 49 or more separate bundles at the distal end of the embryo, where they are situated very close to the cotyledon surface. Although the most prominent organelles are protein and lipid bodies, all cells also contain crystalline protein fibers and small electron-dense bodies bound in vacuoles. The amount of water in the fixative affected several structural features of the cells, primarily the appearance of the plasmalemma. It was determined, from both the rate of hydration and the amount of extractable water in the tissue, that the most realistic primary fixation was obtained with 2% formaldehyde in 80% glycerol. This study provides a structural basis for studies of palm germination.

Plate-shaped nuclear pole bodies in the monothalamous foraminiferKibisidytes sp.

In the monothalamous foraminiferKibisidytes sp. a pair of flat small electron dense bodies of 0.6 μm in length can be demonstrated at the nuclear envelope of interphase nuclei. During karyokinesis these extranuclear bodies enlarge to plate-shaped nuclear pole bodies with a diameter of about 2 μm. They are located at the poles within a depression of the persisting nuclear envelope and in cross section they show an asymmetrical structure.

SOME CHANGES IN THE SUBCELLULAR STRUCTURE OF ROOT CELLS OF PHASEOLUS VULGARIS AS A RESULT OF CESSATION OF AERATION IN THE ROOT MEDIUM

Following cessation of aeration of the nutrient solution several effects could be observed in cells of the root tips of bean plants: Starch grains disappeared from the amyloplasts; small electron dense bodies, probably lipids, were formed and the rough endoplasmatic reticulum showed concentric arrangements. The internal structure of the mitochondria seemed unaffected.

Ultrastructural study of the normal mucosa-adenoma-cancer sequence in the development of familial polyposis coli.

Ultrastructural changes that occurred in the colon epithelia of patients with familial polyposis coli were investigated. Criteria of gradation of the crescendo changes from the mucosa in the controls, through the "normal" mucosa between polyps and adenomas in various stages of dedifferentiation, to invasive carcinoma were established. Our criteria were based on the following requirements: a) vesiculation and increasing numbers of small electron-dense bodies (secretory granules) and lysosomes in the mature and immature absorptive cells, b) presence of immature and undifferiated cells, c) variation in the globlet cells and appearance of atypical secretory cells, and d) nuclear changes. The results illustrated the adenoma-carcinoma sequence and added strong evidence to support its occurrence. Furthermore, this ultrastructural study revealed cellular changes that preceded adenomatous growth and may be of value as markers of early stages of cancer. However, this study also revealed a close link between the function and morphology of the mucosal epithelium.

Proliferative kidney disease in rainbow trout Salmo gairdneri Richardson

Abstract. Two entirely separate outbreaks of PKD are described in an attempt to properly define the condition and enable it to be differentiated from other diseases of a similar nature. Losses of up to 75% of fingerling rainbow trout were recorded in one outbreak, illustrating the potentially serious nature of the disease. Although the kidneys showed the most obvious pathological changes, other organs were also affected. The host response was granulomatous in type, the foci of each cellular reaction being 5‐20 μm eosinophilic cells considered to be parasitic. The cytoplasm of these cells contained numerous electron dense bodies some with a tail, but each with an electron lucent bar always orientated at right angles to the plasmalemma whenever they were near it. The most obvious cytoplasmic inclusion of these ‘parasites’ were other cells numbering up to five or six, each with its own nucleus and nucleolus, but devoid of any of the small electron dense bodies. The significance of either of these inclusions is unknown.A limited differential diagnosis is given, and the argument presented that the condition PKD is the result of infection by a parasite, possibly an amoeba, in combination with poor quality water.

Ultrastructural features of the colonic epithelium in familial polyposis coli.

Colectomy specimens from 6 cases of familial polyposis coli (FPC) were examined. Macroscopically normal mucosa between polyps was taken at intervals along the ascending, transverse and descending colons and studied at EM level. All three regions show the same cell populations varying only in their ratio and height of the epithelium. The same cell types seen in the normal crypt epithelium are present in the mucosa from FPC. As in the normal, 'intermediate' cells are present in FPC but they are less conspicuous than in the mucosa adjacent to colonic carcinoma. However, there are ultrastructural features which distinguish the "normal" mucosa in FPC from the true normal: (a) the presence of "clear columnar" cells; (b) increased vesiculation in the absorptive cells; (c) large number of lysosomes; and (d) the presence of small electron-dense bodies. The ultrastructure of the "clear columnar" cells suggests their being incompletely differentiated cells, thus raising the possibility that their presence in the upper crypt and surface epithelium may represent an early stage in the process of polyp and cancer formation.