γ-Radiation induces apoptosis via sarcoplasmatic reticulum in guinea pig ileum smooth muscle cells

We investigated the effects of γ-radiation on cells isolated from the longitudinal smooth muscle layer of the guinea pig ileum, a relatively radioresistant tissue. Single doses (up to 50 Gy) reduced the amount of sarcoplasmatic reticulum and condensed the myofibrils, as shown by electron microscopy 3 days post-irradiation. After that, contractility of smooth muscle strips was reduced. Ca2+ handling was altered after irradiation, as shown in fura-2 loaded cells, with elevated basal intracellular Ca2+, reduced amount of intrareticular Ca2+, and reduced capacitive Ca2+ entry. Radiation also induced apoptosis, judged from flow cytometry of cells loaded with proprium iodide. Electron microscopy showed that radiation caused condensation of chromatin in dense masses around the nuclear envelope, the presence of apoptotic bodies, fragmentation of the nucleus, detachment of cells from their neighbors, and reductions in cell volume. Radiation also caused activation of caspase 12. Apoptosis was reduced by the administration of the caspase inhibitor Z-Val-Ala-Asp-fluoromethyl-ketone methyl ester (Z-VAD-FMK) during the 3 day period after irradiation, and by the chelator of intracellular Ca2+, 1,2-bis(o-aminophenoxy)-ethane-N,N,N′,N′-tetraacetic acid (BAPTA), from 1 h before until 2 h after irradiation. BAPTA also reduced the effects of radiation on contractility, basal intracellular Ca2+, amount of intrareticular Ca2+, capacitative Ca2+ entry, and apoptosis. In conclusion, the effects of gamma radiation on contractility, Ca2+ handling, and apoptosis appear due to a toxic action of intracellular Ca2+. Ca2+-induced damage to the sarcoplasmatic reticulum seems a key event in impaired Ca2+ handling and apoptosis induced by γ-radiation. © 2008 Elsevier B.V. All rights reserved.

Structural and ultrastructural characteristics of interrenal gland and chromaffin cell of matrinxa, Brycon cephalus Gunther 1869 (Teleostei-Characidae)

This work presents the structure and ultrastructure of the interrenal gland and chromaffin cells, as well as the morphology of the head kidney of Brycon cephalus, the head kidney is composed of fused bilateral lobes located anterior to the swim bladder and ventrolateral to the spinal column, the parenchyma revealed lympho-haematopoietic tissue, melano-macrophage centres, interrenal gland and chromaffin cells. The interrenal gland consisted of cords or strands of cells grouped around the posterior cardinal vein and their branches. Chromaffin cells are found in small groups, closely associated with the interrenal gland and/or under the endothelium of the posterior cardinal vein. So far, the ultrastructural analysis has revealed only one interrenal cell type which contained abundant smooth endoplasmic reticulum and numerous mitochondria with tubulo-vesicular cristae, characteristic of steroid-producing cells. Two types of chromaffin cells were observed. The first type was characterized by the presence of vesicles with round, strongly electron-dense granules, which were eccentrically located, Such cells were interpreted as noradrenaline cells, Meanwhile, cells which contained smaller vesicles and electron-lucent granules, with a small halo separating the granule from the vesicular limiting membrane, were identified as adrenaline cells.

Increased pancreatic islet mass is accompanied by activation of the insulin receptor substrate-2/serine-threonine kinase pathway and augmented cyclin D(2) protein levels in insulin-resistant rats

It is well known that glucocorticoids induce peripheral insulin resistance in rodents and humans. Here, we investigated the structural and ultrastructural modifications, as well as the proteins involved in beta-cell function and proliferation, in islets from insulin-resistant rats. Adult male Wistar rats were made insulin resistant by daily administration of dexamethasone (DEX; 1mg/kg, i.p.) for five consecutive days, whilst control (CTL) rats received saline alone. Structure analyses showed a marked hypertrophy of DEX islets with an increase of 1.7-fold in islet mass and of 1.6-fold in islet density compared with CTL islets (P < 0.05). Ultrastructural evaluation of islets revealed an increased amount of secreting organelles, such as endoplasmic reticulum and Golgi apparatus in DEX islets. Mitotic figures were observed in DEX islets at structural and ultrastructural levels. Beta-cell proliferation, evaluated at the immunohistochemical level using anti-PCNA (proliferating cell nuclear antigen), showed an increase in pancreatic beta-cell proliferation of 6.4-fold in DEX islets compared with CTL islets (P < 0.0001). Increases in insulin receptor substrate-2 (IRS-2), phosphorylated-serine-threonine kinase AKT (p-AKT), cyclin D(2) and a decrease in retinoblastoma protein (pRb) levels were observed in DEX islets compared with CTL islets (P < 0.05). Therefore, during the development of insulin resistance, the endocrine pancreas adapts itself increasing beta-cell mass and proliferation, resulting in an amelioration of the functions. The potential mechanisms that underlie these events involve the activation of the IRS-2/AKT pathway and activation of the cell cycle, mediated by cyclin D(2). These adaptations permit the maintenance of glycaemia at near-physiological ranges.

Toxicidade da mitomicina C ao endotélio da córnea de coelhos

Purpose: To evaluate corneal endothelium alterations after applying mitomycin C to the sclera using transmission and scanning electron microscopy, correlating alterations with time, concentration, and evaluation methods. Methods: The corneal endothelium of both eyes of 32 albino rabbits was evaluated and distributed into four groups of 8. Mitomycin C was applied under a scleral flap in the right eye for 5 minutes. Mitomycin C concentrations were 0.5 mg/ml for G1 and G2 and 0.2 mg/ml for G3 and G4. Examinations were performed 15 days after application to G1 and G3, and 30 days after application to G2 and G4. Four cornea in each group were prepared for transmission electron microscopy and four for scanning electron microscopy. Left eyes of all animals were used as controls. Results: Transmission electron microscopy showed corneal endothelium alterations in all groups: rarefied cytoplasm, dilation and fragmentation of rough endoplasmic reticulum cisternae, Golgi apparatus with cisternal dilation, reduced vacuoles, and irregularities of internal membrane more noticeable in G1 and G2. Scanning electron microscopy revealed alterations in all groups except G1: changes in the shape and size of cells and longer filopodial projections. Conclusions: 1-Corneal endothelium alterations were seen at both 0.5 and 0.2 mg/ml concentrations and at 15 and 30 days after mytomicin C application; 2 - Alterations were more intense with higher mytomicin C concentration by transmission electron but not by scanning electron microscopy; 3 - The alterations correlated with time by scanning electron microscopy but not by transmission electron microscopy.

The central repeat domain 1 of Kaposi's sarcoma-associated herpesvirus (KSHV) latency associated-nuclear antigen 1 (LANA1) prevents cis MHC class I peptide presentation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ultrastructure of spermatogonia and primary spermatocytes of C57BL6J mice

The three types of spermatogonia were confirmed. Type A spermatogonia have a large nucleus and loose chromatin and are poor in endoplasmic reticulum. The second type, B spermatogonia, have rounded and smaller nuclei filled with more electron-dense nucleoplasmic material. The endoplasmic reticulum has the aspect of round or elongated cisterns that are free in the cytoplasm or close to the basement membrane. In contrast, intermediate spermatogonia present chromatin material with intermediate condensation compared with the two previous cell types. Primary spermatocytes are characterized by the presence of intercellular bridges and a synaptonemal complex. In the late pachytene stages, the synaptonemal complex was found to be enveloped by chromatin material.

Evaluation of the ethanol intake on the Calomys callosus seminal vesicle structure

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ultrastructure and cytochemistry of the pearl gland in Piper regnellii (Piperaceae)

Pearl glands are scattered throughout the lamina of developing leaves and rarely found on adult leaves of Piper regnellii (Piperaceae). The pearl gland is a bicellular secretory trichome composed of a short broad basal cell and a spatula-like, semiglobular apical cell. Four different stages of the pearl grand were determined during its ontogenesis: origin, pre-secretory, secretory and post-secretory. During the pre-secretory stage, mitochondria, ribosomes, dictyosomes, rough endoplasmic reticulum, and plastids with electron dense inclusions were present in the cytoplasm of the apical cell. During the secretory stage, the most remarkable characteristics of the apical cell are the proliferation of dictyosomes and their vesicles, rough endoplasmic reticulum, and modified plastids. At this stage, electron-dense oil drops occur in the plastids as well as scattered within the cytoplasm, proteins and polysaccharides are seen in the plastids, vesicles, and vacuoles. Only polysaccharides are present in the periplasmic space, wall cavities, and on the surface of the apical cell. The polysaccharides are one of the main components of the mucilagenous exudate that covers the developing leaf structures. The apical cell of the senescing trichomes undergoes a progressive degeneration of its cellular components, the plastids being the first organelles to undergo lysis.

Zinc iodide-osmium tetroxide (ZIO) reactive sites in the extrafloral nectary of Citharexylum mirianthum Cham. (Verbenaceae)

This paper reports on a study of the zinc iodide-osmium tetroxide method (ZIO) applicability to formaldehyde-glutaraldehyde prefixed extrafloral nectary tissues of Citharexylum mirianthum Cham. (Verbenaceae). The ZIO solution impregnates the dictyosome stacks and adjacent vesicles, smooth endoplasmic reticulum, nuclear envelope, multivesicular bodies, and peroxisomes. The use of this method greatly facilitates the observation and recognition of organelles in each nectary region. it also allows the correlation between structure and function in nectariferous cells. (C) 2001 Harcourt Publishers Ltd.

Ovary peltate trichomes of Zeyheria montana (Bignoniaceae): Developmental ultrastructure and secretion in relation to function

center dot Background and Aims Nectar production in the Bignoniaceae species lacking a nectariferous functional disc is ascribed to trichomatic glands around the ovary base and/or on the inner corolla wall. Nevertheless, knowledge about the secretion and function of these glands is very incomplete. The purpose of this paper is to study, from a developmental viewpoint, the ultrastructure, histochemistry and secretory process of the peltate trichomes on the ovary of Zeyheria montana, a species in the Bignoniaceae which has a rudimentary disc.center dot Methods Samples of the gynoecium at various developmental stages were fixed and processed for light and electron microscopy. Histochemistry and cytochemistry tests were performed to examine the chemical composition of exudates. Thin layer chromatography was used to determine the presence of alkaloids and terpenes in gynoecium and fruit extracts, and in fresh nectar stored in the nectar chamber.center dot Key Results Peltate trichomes at different developmental stages appear side by side from floral budding up to pre-dispersal fruit. Large plastids with an extensive internal membrane system consisting of tubules filled with lipophilic material, abundant smooth endoplasmic reticulum, few Golgi bodies, lipophilic deposits in the smooth endoplasmic reticulum and mitochondria, and scattered cytoplasmic oil droplets are the main characteristics of mature head cells. The secretion which accumulates in the subcuticular space stains positively for hydrophilic and lipophilic substances, with lipids prevailing for fully peltate trichomes. Histochemistry and thin layer chromatography detected terpenes and alkaloids. Fehling's test to detect of sugars in the secretion was negative.center dot Conclusions the continuous presence and activity of peltate trichomes on the ovary of Z. montana from early budding through to flowering and fruiting set, and its main chemical components, alkaloids and terpenes, suggest that they serve a protective function and are not related to the floral nectar source or to improving nectar quality.

Ontogenesis, structure and ultrastructure of Hymenaea stigonocarpa (Fabaceae : Caesalpinioideae) colleters

The genus Hymenaea is characterized by a great diversity of secretory structures, but there are no reports of colleters yet. The objectives of this study are to report the occurrence and describe the origin and structure of colleters in Hymenaea stigonocarpa Mart. ex Hayne. Shoot apex samples were collected, fixed, and processed for light microscopy, scanning electron microscopy, and transmission electron microscopy as per usual methods. Colleters occur predominantly on the stipule's adaxial side. These structures are found at the base on a narrow strip, corresponding to the median vein up to half the length of the stipule. When present on the abaxial side, they are concentrated at the base and restricted to the margins. Colleters develop from the protoderm; they are elongate and club-shaped. Their body has no stratification; their surface cells differ from the inner cells only in position and presence of cuticle. Colleter cells have thin walls, dense cytoplasm, large nuclei, many mitochondria, rough endoplasmic reticulum, and abundant dictyosomes. Histochemical tests with Ruthenium red showed pectic compounds in the cytosol. In H. stigonocarpa, colleter arrangement is compatible with the hypothesis that they protect shoot apex. In this species, protection is reinforced by the sheath formed by the stipule pairs.

The oleoresin secretory system in seedlings and adult plants of copaiba (Copaifera langsdorffii Desf., Leguminosae-Caesalpinioideae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Can sieve-element plastids in Panicum maximum (Poaceae) leaves act in the blockage of injured sieve-tube elements?

The ultrastructural features and the plastid changes caused by sample preparation were studied in sieve elements of Panicum maximum leaves. Samples of expanded leaves, taken near the ligule region, were fixed and processed by common light and transmission electron microscopy methods. In mature sieve-tube elements, the protoplast is electron-translucent and plastids are the most frequent organelles. Mitochondria and smooth endoplasmic reticulum segments are also visible and occupy a parietal position within the cell. The plastids are globular and show electron-dense proteinaceous inclusions in the stroma. The protein crystals are predominantly cuneate, but thin crystalloids and amorphous and/or filamentous proteins also occur. The presence of intact plastids plus others in different phases of plastid envelope rupture were interpreted as evidence that this rupture is a normal event in response to injury. This plastid envelope rupture is possibly activated by the release of pressure in the sieve-tube element. After plastid membrane vesiculation, the stroma and the protein crystals are dispersed within the sieve-element ground cytoplasm. The vesicles originating from the plastid envelope move to one cell pole, while protein crystalloids move to the opposite pole and agglomerate in the sieve-plate region. Our findings indicate that these protein crystalloids, which deposit in the sieve plate, may act in sieve-plate pores occlusion, preventing the release of phloem sap, similar to the role of P-protein in dicotyledons. (c) 2008 Elsevier GmbH. All rights reserved.

Leaf glands act as nectaries in Diplopterys pubipetala (Malpighiaceae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)