1,720,958 research outputs found
ULTRASTRUCTURAL-CHANGES IN THE GANGLIA OF VIVIPARUS-ATER FOLLOWING EXPERIMENTAL LEAD-INTOXICATION
No full textUltrastructural damage in the ganglia of Viviparus ater specimens exposed to short-term staticpollution by lead (1,2,5, and 10 mgiliter for 24,48, and 96 hr) was studied. In polluted samples theneurons inside the ganglia are not regularly arranged in layers in the superficial zone of the gangliabut are irregularly scattered. Neuron structure appears particularly affected by lead exposure: thecell swells and the axon hillock is poorly distinguishable; the nucleus also frequently swells and thechromatin appears particularly dispersed; Nissl bodies appear disassembled and the ribosomes arenot generally linked to the vesicle membranes; the mitochondria are also swollen, cristae practicallydisappear, and the matrix becomes homogeneous and electron transparent; and a noticeableincrease in the number and size of secondary lysosomes was observed. 8 1990 Academic PXSS, I~IC
The digestive gland of Viviparus ater (Mollusca, Gastropoda, Prosobranchia): An ultrastructural and histochemical study
No full textThe digestive gland of Viviparus ater was studied using histochemical and ultrastructural methods. Only one cell type was observed in the tubule epithelium of the gland. The cells are involved in an endocytotic process mediated by clathrin-coated vesicles and in the intracellular digestion of food materials (thus they can be regarded as digestive cells). The different stages of digestion and exocytotic extrusion of residual bodies into the tubule lumen were shown by electron microscopy. Very few, small myocytes are scattered among the digestive cells. Calcium concretions, glycogen-containing cells and endocrine cells are scattered in the area of connective tissue present among the digestive tubules
IMMUNOCYTOCHEMICAL DETECTION OF ENDOCRINE-CELLS IN THE GUT OF VIVIPARUS ATER (MOLLUSCA, GASTROPODA)
No full textThe presence of endocrine cells was investigated by immunocytochemical procedures in the gut and salivary gland of Viviparus ater, a freshwater prosobranch gastropod. The endocrine cells were scanty and both of closed and open cell type. Most of them were located in the esophagus (immunostaining with antigastrin, anti-insulin, anti-serotonin and anti-substance P antisera), very few in the stomach (immunoreactive only to anti-gastrin antibody) and in proximal part of the intestine (immuno-reactive to anti-serotonin and anti-substance P antibodies). In the salivary glands, occasional endocrine cells scattered among the glandular cells in the adenomera stained with anti-neuropeptide Y, anti-pancreatic polypeptide and anti-somatostatin sera were detected
EFFECTS OF LEAD ON HEPATOCYTE ULTRASTRUCTURE IN CARASSIUS-CARASSIUS (L) VAR AURATUS
No full textSubcellular modifications in hepatocytes of Carassius carassius var. auratus subjected to 24 hr and 48 hr sublethal acute lead (5mg.1(1)) exposure were studied by electron microscopy. Cytological alterations were observed after 24 hr of treatment and became more evident after 48 hr. Lead induced an increase in nuclear heterochromatin and alterations in mitochondria, endoplasmic reticulum and Golgi complex ultrastructure. Glycogen granula decreased, and secondary lysosomes and lipid droplets increased. Furthermore, intracytoplasmic lumina with microvilli-bearing surfaces and numerous autophagic vacuola were observed after 48 hr of exposure
GILL MORPHOLOGY AND ATPASE ACTIVITY IN THE GOLDFISH CARASSIUS-CARASSIUS VAR AURATUS EXPOSED TO EXPERIMENTAL LEAD-INTOXICATION
No full textThe effect of acute lead intoxication (5 mg l-1) on the structure and function of the gills in Carassius carassius var. auratus was studied. The gills absorbed Pb very quickly and the storage increased progressively in the longest treated specimens. Light and electron microscopy observations on gill filaments from unexposed fish showed in organization similar to that described for other teleosteans. Gill histological and cytological alterations induced by lead were detected after 24 h of treatment and became more evident after 48 h. The salient changes were the following: 1) free parts of secondary lamellae increased in length and had irregular outlines; 2) an increased number of mucocytes, prevalently distributed over the superficial layer of the primary epithelium; 3) chloride and epithelial cell ultrastructure were particularly damaged; the degenerating chloride cells were more numerous; 4) K+-NPPase activity was not particularly affected; on the contrary, Ca2+-ATPase increased particularly in chloride cells
EFFECTS OF LOW-POWER 632 NM RADIATION (HENE LASER) ON A HUMAN CELL-LINE - INFLUENCE ON ADENYLNUCLEOTIDES AND CYTOSKELETAL STRUCTURES
No full textHeNe (632 nm) irradiation (5, 15 and 30 min) of an embryonal human cell line (EUE) was used to study the short-term effects on energy charge and the rapid, energy-dependent, remodelling processes of cytoskeletal and adhesion structures. The adenosine triphosphate (ATP) concentration, tested by luminometric and high performance liquid chromatography (HPLC) procedures, is constant after 15 and 30 min of HeNe treatment; the lower phosphorylated nucleotides, i.e. adenosine diphosphate (ADP) and adenosine monophosphate (AMP), change after 30 min in opposite directions: the ADP concentration decreases by 39% whilst that of AMP increases about sixfold. The adenylate energy charge (AEC) decreases by 21.7% in treated EUE cells (AEC = 0.65) in comparison with untreated EUE cells (AEC = 0.83). In HeNe-treated cells, the remodelling of cytoskeletal and adhesion molecules becomes evident after 15 min of treatment. The following events are important: (1) modification of stress fibre assembly and increase in vinculin-containing adhesion plaques; (2) assembly and bundling of intermediate filaments; (3) increase in laminin and L-cell adhesion molecules (L-CAM) expression. The lowered energy charge in irradiated cells is related to the increase in AMP production at the expense of ADP. ATP is dynamically constant despite its requirement in short-time remodelling processes of the cytoskeletal network which are enhanced in irradiated cells
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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