Ultrastructure of endocrine cells in the stomach of two teleost fish Perca fluviatilis L. and Ameiurus nebulosus L.

Summary In the gastric mucosa of two teleost species, the perch (Perca fluviatilis) and the catfish (Ameiurus nebulosus) three endocrine cell types were found, located predominantly between the mucoid cells of the gastric mucosa. A fourth cell type is present in the gastric glands of catfish. Each cell type was defined by its characteristic secretory granules. Type-I cells were predominant in both fish. These cells contained round or oval granules with a pleomorphic core. The average diameter of granules was 400 nm for the perch and 270 nm for the catfish. Type-II cells of both species displayed small, highly osmiophilic granules about 100 nm in diameter. The secretory granules of type-III cells (260 nm in the perch and 190 nm in the catfish) were round or slightly oval in shape and were filled with a finely particulate electron-dense material. Type-IV cells of the catfish were found in the gastric glands only. Their cytoplasm was filled with homogeneous, moderately electron-dense granules averaging 340 nm in diameter. The physiological significance of these different morphological types of gastric endocrine cells requires further investigation.     

Elderberry latent virus: its relationship to Pelargonium ringspot virus and its identification as a distinct member of the genus Carmovirus, family Tombusviridae

The properties of Elderberry latent virus (ELV) and Pelargonium ringspot virus (PelRSV) were compared. The viruses were largely indistinguishable in herbaceous host range and symptomatology, particle morphology, sedimentation coefficient and RNA profiles and size. They were also very closely related serologically with SDI differences in agarose gel double‐diffusion tests of 1 to 3. Purified virus particle preparations of each virus contained isometric particles c. 30 nm in diameter that sedimented as a major component with an s^O_20W of 112–115S. Purified virus particle preparations contained a major and a minor ssRNA species that in polyacrylamide gel electrophoresis (PAGE) had estimated sizes of c. 3.8 kb and c. 1.6 kb respectively. Plants of Chenopodium quinoa infected with ELV or PelRSV each contained three dsRNA species of c. 3.8, 2.6 and 1.8 kbp, although the smallest of these species was not evident in all preparations. Protein from purified virus particle preparations contained a major polypeptide that, in SDS‐PAGE, had an estimated M^r of 40 000 (40K). However, after storage of purified virus particles for 7–10 days, protein preparations from PelRSV particles also contained an additional major polypeptide of estimated M^r of 37 000 that is probably derived by degradation of the 40K protein; this additional component was not observed in freshly prepared preparations of ELV. Neither virus was found to be related serologically to 16 other viruses with isometric particles and similar properties. These data, together with the recent finding by other researchers that the smallest RNA species is a sub‐genomic RNA, suggests that both viruses are members of the genus Carmovirus, and that PelRSV is a minor variant of ELV. However, the taxonomic status of these two viruses is discussed in relation to recent brief reports comparing the nucleotide and amino acid sequences of these two viruses.     

Morphometric studies on lipoprotein particles in developing rat liver and their corticosteroid-induced changes during the late gestational period

Summary Changes in lipoprotein particles in hepatocytes of the fetal rat liver have been studied morphometrically from days 15–21 of gestation. On all these days, distinct lipoprotein particles are found within the cisternae of the RER, Golgi complexes and Golgi-derived secretory vesicles. Their mean diameter is 30–31 nm. The number of Golgi complexes per hepatocyte, the lipoprotein particle number per Golgi complex and the volume density of the latter remain unchanged within the developmental period examined. The volume density of lipid droplets, however, shows a significant decrease during this time.Following corticosteroid treatment, the mean diameter of lipoprotein particles, the number of lipoprotein particles per Golgi complex, the volume density of the Golgi complex, and that of the lipid droplets increase significantly within the examined period, whereas the number of Golgi complexes per hepatocyte is reduced. These data support the view that triglyceride production in the fetal liver is directly or indirectly stimulated by corticosteroids administered to the pregnant rat, thus giving rise to larger amounts of hepatic lipoproteins and lipids.Abbreviations LP lipoprotein - VLDL very low density lipoproteins (d< 1.006 g/ml) - RER rough endoplasmic reticulum - ER endoplasmic reticulum     

Particle purification and properties of cassava Ivorian bacilliform virus

A virus found in cassava from the north-west of the Ivory Coast was transmitted by inoculation with sap extracts to herbaceous species in six plant families. Chenopodium quinoa was used as a propagation host and C. murale was used for local lesion assays. The virus particles are bacilliform, c. 18 nm in diameter, with predominant lengths of 42,49 and 76 nm and a structure apparently similar to that found in alfalfa mosaic virus. Purified preparations of virus particles had A₂₆₀/A₂₈₀ of 1.7 ±0.05, contained one protein of M_rc. 22 000, and yielded three species of RNA with M_r (× 10^-6) of c. 0.7, 0.8 and 1.2. Although the virus particles were poorly immunogenic, an antiserum was produced and the virus was detected by enzyme-linked immunosorbent assay (DAS-ELISA) in leaf extracts at concentrations down to c. 6 ng/ml. Four other field isolates were also detected, including a strain which caused only mild systemic symptoms in C. quinoa instead of necrosis. The naturally infected cassava source plants were also infected with African cassava mosaic virus (ACMV) but when the new virus was cultured in Nicotiana benthamiana, either separately or together with ACMV, its concentration was the same. The new virus did not react with antisera to several plant viruses with small bacilliform or quasi-bacilliform particles, and alfalfa mosaic virus reacted only weakly and inconsistently with antiserum to the cassava virus. The new virus, for which the name cassava Ivorian bacilliform virus is proposed, is tentatively classified as the second member of the alfalfa mosaic virus group.     

Host range, purification and some properties of rubus Chinese seed-borne virus

A previously undescribed virus, for which the name rubus Chinese seed-borne virus (RCSV) is proposed, was isolated from a single, symptomless plant of an unidentified Rubus species grown from seed collected in the wild in the People's Republic of China, Experimentally RCSV infected 23 out of 39 spp. in six out of eight families. The virus was seed-transmitted in Chenopodium quinoa (100%) and Nicotiana bigelowii (27%). RCSV was not transmitted by the nematodes Xiphinema diversicaudatum or X. index. The particles of RCSV were isometric, c. 30 nm in diameter with some penetrated by negative stains. In thin sections particles were found in double walled tubular structures with an outer membrane enclosing one or more tubules. In crude extracts some particles were found within single-walled tubules. Two virus-associated bands were seen in sucrose density gradients of purified preparations. The upper band was not infective and consisted of penetrated particles apparently devoid of nucleic acid. The lower, infective band was resolved into two components, of density 1.452 and 1.461 g/ml, in caesium chloride isopycnic gradients. There were two polypeptides (mol. wts c. 47 000 and 25 200 daltons) and two nucleic acid species (one of mol. wt c. 1.4 × 10⁶ daltons; the second was poorly defined by the methods used but was of higher molecular weight). RCSV was distantly related serologically (6–7 SDI) to the type isolate of strawberry latent ringspot virus (SLRV) and also reacted with antisera to serologicaly distinct grape and olive isolates of SLRV. It did not react with antisera to 10 other isometric viruses.     

Light and electron microscopic study on the endocrine cells of the pancreas in a marine teleost,Fugu rubripes rubripes

Summary The pancreatic endocrine tissue of Fugu rubripes rubripes consists of numerous round principal islets (Brockmann bodies) of various sizes scattered around the gall-bladder. The endocrine cells are divided into A-, B-, D-, and F_f-cells. Each cell type was identified by comparing thick and thin sections in both light and electron microscopy. Aldehyde-fuchsin positive B-cells contain numerous round secretory granules (average diameter 300 nm) each of which has a round compact core of moderate density; a narrow space exists between this core and the limiting membrane. Grimelius' silver positive A cells contain round secretory granules (average diameter 360 nm) with a hexagonal or tetragonal crystalline core (average diameter 170 nm) of high density; the silver grains preferentially appear in the space between the limiting membrane and the core. The crystalline core of each -granule often contains an appendix-like structure of variable shape. D cells blackened by the silver impregnation method of Hellman and Hellerström (1960) have round secretory granules (average diameter 320 nm) filled with a flocculent material of low density. The fourth cell type (F_f-cell) has a clear cytoplasm after differential staining for light microscopy. By electron microscopy, this cell has elongated fusiform secretory granules (520 nm average length × 230 nm average width) filled with numerous filaments arranged in parallel with the longitudinal axis. Figures suggesting granule formation in the sacs of the Golgi apparatus were obtained in all of islet cell types. Equivalents of emiocytotic release of secretory granules were encountered in the A and F_f cells.     

Secretory cells in the clitellar epithelium of Eisenia foetida (Annelida,Oligochaeta): A histochemical and ultrastructural study

Eight secretory cell types are identified in the clitellar epithelium of Eisenia foetida, of which five have been described in detail previously (i.e., the large granular, fine granular, metachromatic, orthochromatic, and small granular proteinacecus cells). The remaining three secretory cell types are mucus-producing cells specific to the clitellar epithelium (type 3), cells associated with the chaetal follicles (type 4), and cells that occur exclusively in the tubercula pubertatis (type 5). Type 3 cells secrete a mucus containing neutral and acid mucosubstances. Ultrastructurally, type 3 cells are characterized by membrane-bound globules 0.4 to 3.7 μm in diameter. The contents of the globules have a finely reticulate appearance. The secretion of type 4 cells contains a collagenlike protein and neutral and sulfated acid mucosubstances. Type 4 cell secretory granules are membrane bound and range in diameter from 0.8 to 1.6 μm. They contain large, electron-dense, spheroid cores which are surrounded by parallel orientated microfibrils 14 nm in diameter. Type 5 cells give variable responses to the histochemical techniques used in the present study. An elastinlike protein is detected in about half of the type 5 cells and acid and neutral mucosubstances in the remainder. At the ultrastructural level the secretory granules vary in shape from spheroid to polygonal. Their finely, electron-dense contents exhibit progressive swelling which results in the eventual rupture of the limiting membranes of the granules. The necks of types 3, 4, and 5 cells contain a peripheral ring of microtubles (20 ± 1 nm in diameter).     

Isolation and characterization of basil mosaic virus in Egypt

Different viral infection symptoms were observed on leaves of basil plants (Ocimum basilicum L.), growing at El-Monofia Governorate, Egypt, during 2015–2016. The majority of these symptoms were mosaic and leaf malformation. The pathogenic agent of this disease is known as basil mosaic virus (BsMV). The sensitive hosts to BsMV are Chenopodium amaranticolor and Phaseolus vulgaris cv. (brown beans). The biological properties of BsMV were found to be 10^?4, 6 days and 66 °C for dilution end point, longevity in vitro and thermal inactivation point, respectively. The electron micrograph of the isolated virus indicated this virus was found to be isometric particles of approximately, 50 nm in diameter and could be classified as tentative member of the Fabavirus. Real-time PCR detection by the Fab primer pairs was confirmed at Ct value = 25.44 for the total cDNA isolated from infected Basil plants and 27.94 for the cDNA of purified virus particles, while CMV primer pairs showed no amplification for both samples. According to the available reports this seems to be the first record for basil mosaic virus in Egypt.     

Classifications of somatotropes, lactotropes and corticotropes in the mouse adenohypophysis with immunohistochemistry

Somatotropes, lactotropes and corticotropes of adult male mice were identified with immunohistochemistry in the adenohypophysis fixed by OsO4 alone. Somatotropes were classified into type I somatotropes that contain large (350 nm in diameter) round secretory granules and type II somatotropes that contain small (100-200 nm in diameter) round secretory granules. Most somatotropes were type I somatotropes. Lactotropes were also classified into type I lactotropes that contain irregularly shaped secretory granules and type II lactotropes containing small (100-200 nm in diameter) round secretory granules. Corticotropes are irregular stellate or slender cells with little cytoplasm. They contain round solid secretory granules in various densities along the cell periphery. Most of these are low-density granules (200-300 nm in diameter) and a few are high-density granules (200-250 nm in diameter). These data were compared with the classical data of mouse adenohypophysial cells that were fixed in OsO4 alone and identified only by conventional electron microscopy.     

Cell types of the endocrine pancreas in the shark Scyliorhinus stellaris as revealed by correlative light and electron microscopy

Summary In the pancreas of Scyliorhinus stellaris large islets are usually found around small ducts, the inner surface of which is covered by elongated epithelial cells; thus the endocrine cells are never exposed directly to the lumen of the duct. Sometimes, single islet cells or small groups of endocrine elements are also incorporated into acini. Using correlative light and electron microscopy, eight islet cell types were identified:Only B-cells (type I) display a positive reaction with pseudoisocyanin and aldehyde-fuchsin staining. This cell type contains numerous small secretory granules (Ø280 nm). Type II- and III-cells possess large granules stainable with orange G and azocarmine and show strong luminescence with dark-field microscopy. Type II-cells have spherical (Ø700 nm), type III-cells spherical to elongated granules (Ø450 × 750 nm). Type II-cells are possibly analogous to A-cells, while type III-cells resemble mammalian enterochromaffin cells. Type IV- cells contain granules (Ø540 nm) of high electron density showing a positive reaction to the Hellman-Hellerström silver impregnation and a negative reaction to Grimelius' silver impregnation; they are most probably analogous to D-cells of other species. Type VI-cells exhibit smaller granules (Ø250 × 500 nm), oval to elongated in shape. Type VI-cells contain small spherical granules (Ø310 nm). Type VII-cells possess two kinds of large granules interspersed in the cytoplasm; one type is spherical and electron dense (Ø650 nm), the other spherical and less electron dense (Ø900 nm). Type VIII-cells have small granules curved in shape and show moderate electron density (Ø100 nm). Grimelius-positive secretory granules were not only found in cell types II and III, but also in types V, VI, and VII. B-cells (type I) and the cell types II to IV were the most frequent cells; types V to VII occurred occasionally, whereas type VIII-cells were very rare.This work was supported by a fellowship from the Ministry of Education of Japan and the Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg (La 229/8)     

Crystalloid Inclusions in Species of Leucocytozoon,Parahaemoproteus, and Plasmodium*†

Cytoplasmic vacuoles seen in methanol-fixed, Giemsa's-stained ookinetes of Leucocytozoon simondi, Parahaemoproteus fringillae and Plasmodium gallinaceum, when studied with the electron microscope, were found to correspond with crystalloid inclusions of similar structure, particle size, and arrangement. Cytochemical examination of these “crystalloids” revealed their lipid-protein nature. Morphologically similar inclusions were found also in ookinetes of Leucocytozoon ziemanni and Parahaemoproteus velans. In L. simondi, crystalloid is formed rapidly after fertilization, from amorphous electron dense material seen in mature macrogametocytes. The arrangement and distribution of crystalloids in the zygote, ookinete, oocyst, and sporozoite are described. On the basis of differences in structure and particle size, it is proposed that the crystalloid inclusions in Haemosporina be divided into 2 types. Type I—lipid-protein in nature, characterized by electron dense irregularly spherical particles, 25–40 nm in diameter, with individual particles not invested by membrane. Type II—probably virus, characterized by electron dense, irregularly spherical, membrane-bounded particles, with a diameter usually greater than 40 nm.     

Licht- und elektronenmikroskopische Untersuchung des Corpus cardiacum der Eintagsfliege Ephemera danica Müll. (Ephemeroptera: Ephemeridae) während der Metamorphose*

Kaiser, H. 1980. Licht- und elektronenmikroskopische Untersuchung des Corpus cardiacum des Eintagsfliege Ephemera danica Müll. (Ephemeroptera: Ephemeridae) während der Metamorphose. [Light- and electron microscopic investigation on the corpus cardiacum in the mayfly Ephemera danica Müll. (Ephemeroptera: Ephemeridae) during metamorphosis.] (Zoologisches Institut der Universität Basel, Schweiz.) — Acta zool. (Stockh.) 61(2): 93–103. The corpus cardiacum (cc) of Ephemera danica is an unpaired organ in the dorsal wall of the aorta. During the last four instars there has been no significant change in the volume of the cc of the males. In the females, however, the cc enlarges in the final nymphal instar due to a thickening of the organ. Owing to a shortening prior to the subimaginal moult the volume has diminished in the subimagines and imagines. In the electron microscope different types of axons and secretory granules could be observed. The type a axons contain electron opaque granules with a mean diameter of 125 nm. The granules in the axons of type b are smaller (mean diameter 85 nm) and are more or less electron opaque, and the type c axons are filled with less electron opaque secretory droplets with mean diameters of 170 nm. In the fourth type of axons (d) the granules are approximately the same size as those of the type a but are more irregular in shape. In addition to the different axons two cell types—interstitial and secretory cells—are described, and the probable mechanism of the release of neurosecretory material is discussed. During metamorphosis only minor changes were apparent at the ultrastructural level.     

Association of different kinds of bacilliform particle with vein chlorosis and mosaic diseases of raspberry (Rubus idaeus)

Thin sections of diseased raspberry (Rubus idaeus) were examined by electron microscopy. Plants of the cv. Baumforth's B and of an aphid (Amphorophora rubi)-resistant breeding selection (6820/54), both infected with raspberry vein chlorosis virus (RVCV) but not with other detectable viruses, contained large bacilliform particles c. 430 × 65 nm. Particles occurred in the cytoplasm and perinuclear space of a small proportion of xylem parenchyma cells. They had an inner core c. 25–30 nm in diameter with cross-banding of periodicity 4·5 nm, and were bounded by an outer membrane. They are probably the particles of RVCV. Plants of cv. Mailing Jewel and of a selection (M14) both showing symptoms of raspberry mosaic (veinbanding) disease contained smaller bacilliform particles c. 125 × 30 nm, which occurred singly or in clusters in the cytoplasm of a small proportion of vascular parenchyma cells. It is not known which, if any, of the viruses associated with raspberry mosaic are represented by the particles.     

The Ultrastructure of the Endocrine Pancreas of the Grass Lizard,Mabuya quinquetaeniata*

Four endocrine cell types were identified ultrastructurally in the pancreas of the grass lizard, Mabuya quinquetaeniata. These cells were similar in shape, location and frequency to the previously described B-, A-, D- and PP-cells. The secretory granules of the B-cells were round or oval in profile, with an internal core of variable shape. The mean diameter of the B-cell granules was 780 nm (range 350–1000 nm). The A-cell granules were round, oval or irregular in shape and highly electron dense, with a narrow electron lucent space between the core and the limiting membrane. The mean diameter of these granules was 450 nm (range 200–750 nm). The D-cell granules were round, oval or irregular and of moderate electron density, with an average diameter of 340 nm (range 200–500 nm). The limiting membrane was closely apposed to the core or separated from it by a narrow lucent space. PP-cell granules were round with high electron density and with a narrow space between the core and the limiting membrane, and their average diameter was 150 nm (range 50–350 nm); these secretory granules accumulated at the cytoplasmic process. Tracing of the cytoplasmic processes of PP-cells in serially cut ultrathin sections revealed that most of these processes ended in the vicinity of blood capillaries, indicating that the PP-cells were endocrine rather than paracrine.     

A Virus Infection in the Marine Brown Alga Ectocarpus siliculosus (Phaeophyceae)

Laboratory cultures of Ectocarpus siliculosus originating from New Zealand showed a defect in gametangium formation. Nuclear divisions in gametangium initials are not followed by cell wall formation. In the resulting multinucleate cells nuclear DNA increases dramatically, and nuclear membranes disintegrate. Eventually, the entire structure is filled with hexagonal particles of approximately 130 nm diameter. These were isolated and shown by EM to consist of a dense core surrounded by a 3-layered shell. They are released into the culture medium when the host cells burst. Ectocarpus gametes from healthy cultures could be infected by these particles. The resulting partheno-sporophytes developed pathological symptoms, suggesting that the particles are viruses. The expression of the defect is temperature dependent. At 10°C all gametangia are abnormal, while between 15 and 20 °C defective and normal gametangia and gametes are formed on the same plant. Partheno-sporophytes developing from such gametes carry the viral particles expressed in deformed unilocular and plurilocular sporangia.     

Ultrastructural Comparison of the Vacuolar and Mitochondrial H+-ATPases of Daucus carota

Eukaryotic vacuolar H⁺-ATPases (V-ATPases) are related to the F₀F₁-ATPases of chloroplasts and mitochondria and are believed to be organized into peripheral and integral membrane complexes. Vacuolar membranes isolated from purified carrot (Daucus carota) root vacuoles were observed to be coated with F₁-like particles after negative staining with phosphotungstic acid. The F₁-like particles formed typical “ball and stalk” structures, about 9.4 nm in diameter and 13.6 nm in height. The head portion frequently had a characteristic bifurcation or cleft at the apex and appeared to be composed of subunits. Such “V₁” complexes were frequently associated with smaller stalked particles emerging near the base. In contrast, negatively-stained carrot mitochondrial F₁ complexes averaged 8.7 nm in diameter and 11.7 nm in height. The head groups of the mitochondrial F₁s were nearly always spherical, and had no other smaller structures associated with them. The V₁ complexes of carrot are thus similar in form to the V₁ complexes of Neurospora (Bowman et al. J. Biol. Chem. 264 (1989) 15606–15612).     

Characterization of Maize Chlorotic Mottle Virus Associated with Maize Lethal Necrosis Disease in China

A maize lethal necrosis disease was observed in Yunnan province of China. Isometric virus particles 30 nm in diameter were found in infected maize leaf tissues. Using DAS‐ELISA, diseased maize plant samples reacted positively with the antiserum of Maize chlorotic mottle virus (MCMV). The complete nucleotide sequence (4436 nt) of a Yunnan isolate of MCMV was determined; it shares 97% nucleotide sequence identity with previously reported MCMV isolates. This is the first report of MCMV occurring in China.     

Freeze-fracture characteristics of the ocellar retina of the honeybee,Apis mellifica carnica pollm. (Hymenoptera : Apidae)

Freeze-fracture electron microscopy has been utilized to investigate membrane specializations in the dark-adapted retina of the ocellus of worker honeybee, Apis mellifica (Hymenoptera : Apidae).The distal segment of the photoreceptor cell is unilaterally composed of short microvilli, termed rhabdomeres. All microvilli are oriented in the same direction. Transversally fractured rhabdomerss show the typical hexagonal arrangement of the microvillar profiles. The plasma membrane limiting each microvillus, is rich in particles (4000/μm² on the protoplasmic (P) face). Two kinds of P-face particles are seen: one type is about 4nm in diameter and the other has diameters of 8 – 10nm. Because of their size and density, these particles may mainly correspond to photopigments. Plaques of exoplasmic (E) face particles present in the glial cells sheathing the photoreceptor cells, are thought to represent gap junctions. Special differentiations of the smooth endoplasmic reticulum (ER) are found in the perirhabdomeric cytoplasm closely associated with microvilli. The membranes of the ER are wound up to form large concentric bodies. These bodies may play an important role in formation of new microvilli. Furthermore, conspisuous bodies with stomata are found in the perirhabdomeric cytoplasm.     

First evidence for the existence of pennate diatom viruses

Diatoms are considered the most successful and widespread group of photosynthetic eukaryotes. Their contribution to primary production is remarkably significant to the earth''s ecosystems. Diatoms are composed of two orders: Centrales and Pennales. Thus far, viruses infecting centric diatom species have been isolated and characterized; however, viruses infecting pennates have not been reported. Here, we describe the first isolations and preliminary characterizations of two distinct pennate diatom viruses, AglaRNAV (31 nm in diameter, accumulates in the host cytoplasm) and TnitDNAV (35 nm in diameter, accumulates in the host nuclei) infecting Asterionellopsis glacialis and Thalassionema nitzschioides, respectively. Their genomes contain a single-stranded RNA of approximately 9.5 kb, and a closed, circular single-stranded DNA of approximately 5.5 kb harboring a partially double-stranded region, respectively. Further analysis of these viruses may elucidate many aspects of diatom host–virus relationships.