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Gut Lumen (gut + lumen)
Selected AbstractsUltrastructure and functional features of midgut of an adult water mite Teutonia cometes (Koch, 1837) (Hydrachnidia: Teutoniidae)ACTA ZOOLOGICA, Issue 2 2010Andrew B. Shatrov Abstract Shatrov, A. B. 2010. Ultrastructure and functional features of midgut of an adult water mite Teutonia cometes (Koch 1837) (Hydrachnidia: Teutoniidae). ,Acta Zoologica (Stockholm) 91: 222,232 The midgut of the adult water mite Teutonia cometes (Koch 1837) (Hydrachnidia: Teutoniidae) was investigated by means of transmission electron microscopy and on semi-thin sections. The midgut is represented by a blind sac composed of the narrow ventriculus, two proventricular lateral diverticula and three pairs of postventricular caeca. A single-layered epithelium consists of one type of endodermal digestive cells of quite different shape and size, which may form protrusions into the midgut lumen. The large nuclei are frequently lobed and contain one to three nucleoli. The apical cell membrane forms short scarce microvilli, between their bases the pinocytotic vesicles of unspecific macropinocytosis as well as the narrow pinocytotic canals are formed and immersed into the cell. The intracellular digestion of the food ingested into the midgut after extraintestinal digestion is predominant. The pinocytotic vesicles fuse with small clear vesicles of proposed Golgi origin to form secondary lysosomes. The digestive cells also contain small amounts of rough endoplasmic reticulum, variously structured heterolysosomes, residual materials in the form of both the small electron-dense bodies and the large variously granulated substances, reserve nutritive materials such as lipid and glycogen, as well as clear vacuoles. Residual materials are obviously extruded from the cells into the gut lumen. [source] Molecular and morphological characterization of the association between bacterial endosymbionts and the marine nematode Astomonema sp. from the BahamasENVIRONMENTAL MICROBIOLOGY, Issue 5 2007Niculina Musat Summary Marine nematode worms without a mouth or functional gut are found worldwide in intertidal sandflats, deep-sea muds and methane-rich pock marks, and morphological studies show that they are associated with endosymbiotic bacteria. While it has been hypothesized that the symbionts are chemoautotrophic sulfur oxidizers, to date nothing is known about the phylogeny or function of endosymbionts from marine nematodes. In this study, we characterized the association between bacterial endosymbionts and the marine nematode Astomonema sp. from coral reef sediments in the Bahamas. Phylogenetic analysis of the host based on its 18S rRNA gene showed that Astomonema sp. is most closely related to non-symbiotic nematodes of the families Linhomoeidae and Axonolaimidae and is not closely related to marine stilbonematinid nematodes with ectosymbiotic sulfur-oxidizing bacteria. In contrast, phylogenetic analyses of the symbionts of Astomonema sp. using comparative 16S rRNA gene sequence analysis revealed that these are closely related to the stilbonematinid ectosymbionts (95,96% sequence similarity) as well as to the sulfur-oxidizing endosymbionts from gutless marine oligochaetes. The closest free-living relatives of these gammaproteobacterial symbionts are sulfur-oxidizing bacteria from the family Chromatiaceae. Transmission electron microscopy and fluorescence in situ hybridization showed that the bacterial symbionts completely fill the gut lumen of Astomonema sp., suggesting that these are their main source of nutrition. The close phylogenetic relationship of the Astomonema sp. symbionts to known sulfur-oxidizing bacteria as well as the presence of the aprA gene, typically found in sulfur-oxidizing bacteria, indicates that the Astomonema sp. symbionts use reduced sulfur compounds as an energy source to provide their hosts with nutrition. [source] Improving M cell mediated transport across mucosal barriers: do certain bacteria hold the keys?IMMUNOLOGY, Issue 1 2004Angela L. Man Summary Specialized microfold (M) cells of the follicle-associated epithelium (FAE) of the mucosal-associated lymphoid tissue (MALT) in gut and the respiratory system play an important role in the genesis of both mucosal and systemic immune responses by delivering antigenic substrate to the underlying lymphoid tissue where immune responses start. Although it has been shown that dendritic cells (DC) also have the ability to sample antigens directly from the gut lumen, M cells certainly remain the most important antigen-sampling cell to be investigated in order to devise novel methods to improve mucosal delivery of biologically active compounds. Recently, novel information on the interactions between bacteria and FAE have come to light that unveil further the complex cross-talk taking place at mucosal interfaces between bacteria, epithelial cells and the immune system and which are central to the formation and function of M cells. In particular, it has been shown that M cell mediated transport of antigen across the FAE is improved rapidly by exposure to certain bacteria, thus opening the way to identify new means to achieve a more effective mucosal delivery. Here, these novel findings and their potential in mucosal immunity are analysed and discussed, and new approaches to improve antigen delivery to the mucosal immune system are also proposed. [source] Molecular cloning and immunolocalization of a diuretic hormone receptor in rice brown planthopper (Nilaparvata lugens)INSECT MOLECULAR BIOLOGY, Issue 5 2004D. R. G. Price Abstract RNA extracted from guts of rice brown planthopper, Nilaparvata lugens, was used to clone cDNA predicted to encode a diuretic hormone receptor (DHR). The DHR, a member of the calcitonin/secretin/corticotropin-releasing factor family of G-protein-coupled receptors, contains seven transmembrane domains and a large N-terminal extracellular domain potentially involved in hormone binding. The N-terminal domain was expressed as a recombinant protein, purified and used to raise antibodies. Anti-DHR IgG bound specifically to Malpighian tubules in immunolocalization experiments using dissected guts, and to a putative DHR polypeptide from N. lugens gut on Western blots. Anti-DHR IgG delivered orally to insects was not detected in the haemolymph, and showed no binding to gut or tubules, confirming that DHR N-terminal hormone-binding domain is not exposed to the gut lumen. [source] Endotoxin translocation in two models of experimental acute pancreatitisJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 4 2003C. Vasilescu Abstract To test the hypothesis that endotoxin is absorbed from the gut into the circulation in rats with experimental acute pancreatitis we studied two different animal models. In the first model necrotizing pancreatitis was induced by the ligation of the disatl bilio-pancreatic duct while in the second, experimental oedematous acute pancreatitis was induced by subcutaneous injections of caerulein. In both experiments, in the colon of rats with acute pancreatitis endotoxin from Salmonella abortus equi was injected. Endotoxin was detected by immunohistochemistry in peripheral organs with specific antibodies. The endotoxin was found only in rats with both acute pancreatitis and endotoxin injected into the colon and not in the control groups. The distribution of endotoxin in liver at 3 and 5 days was predominantly at hepatocytes level around terminal hepatic venules, while in lung a scattered diffuse pattern at the level of alveolar macrophages was identified. A positive staining was observed after 12 hours in the liver, lung, colon and mesenteric lymph nodes of rats with both caerulein pancreatitis and endotoxin injected into the colon. We conclude that the experimental acute pancreatitis leads to early endotoxin translocation from the gut lumen in the intestinal wall and consequent access of gut-derived endotoxin to the mesenteric lymph nodes, liver and lung. [source] Biosynthesis of fatty acid amide elicitors of plant volatiles by insect herbivores ,ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2005James H. Tumlinson Larvae of several species of Lepidoptera produce fatty acid amide elicitors that induce the plants on which they feed to synthesize and release volatile organic compounds. The volatiles released by the plants act as cues that aid in host location by natural enemies of the herbivorous larvae. The elicitors are synthesized in the larvae by enzymes embedded in the membranes of the crop and anterior midgut tissues. The fatty acid precursors of the elicitors are obtained from the plants on which the caterpillars feed, while the amino acid moieties appear to be obtained from pools within the insects. The fatty acid amide elicitors are rapidly hydrolyzed in the midgut and hindgut by enzymes in the gut lumen. The role of these fatty acid amides in caterpillar metabolism is not yet understood. Arch. Insect Biochem. Physiol. 58:54,68, 2005. © 2005 Wiley-Liss, Inc. [source] | |||||||||||||