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Midgut Lumen (midgut + 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] Fluorescence in situ hybridization (FISH) analysis of the interactions between honeybee larvae and Paenibacillus larvae, the causative agent of American foulbrood of honeybees (Apis mellifera)ENVIRONMENTAL MICROBIOLOGY, Issue 6 2008Dominique Yue Summary American foulbrood (AFB) is a bacterial disease of honeybee larvae caused by the spore-forming bacterium Paenibacillus larvae. Although AFB and its aetiological agent are described now for more than a century, the general and molecular pathogenesis of this notifiable disease is poorly understood. We used fluorescence in situ hybridization (FISH) performed with P. larvae -specific, 16S rRNA-targeted oligonucleotide probes to analyse the early steps in the pathogenesis of American foulbrood. The following chain of events could be demonstrated: (i) the spores germinate in the midgut lumen, (ii) the vegetative bacteria massively proliferate within the midgut before, and (iii) they start to locally breach the epithelium and invade the haemocoel. The paracellular route was shown to be the main mechanism for invasion contrasting earlier hypotheses of phagocytosis of P. larvae. Invasion coincided with the death of the host implicating that the penetration of the midgut epithelium is a critical step determining the time of death. [source] Storage and secretion of the peritrophic matrix protein Ag-Aper1 and trypsin in the midgut of Anopheles gambiaeINSECT MOLECULAR BIOLOGY, Issue 4 2004M. Devenport Abstract The gene Ag-Aper1 encodes a peritrophic matrix (PM) protein from the mosquito Anopheles gambiae. Ag-Aper1 gene expression and protein localization in the mosquito midgut were studied during the course of a blood meal. Ag-Aper1 mRNA abundance does not change appreciably during the course of blood ingestion and digestion. Prior to a blood meal, the protein is stored in secretory vesicles of midgut epithelial cells. Moreover, Ag-Aper1 colocalizes to the same secretory vesicles as trypsin, indicating that these proteins use a common secretory pathway. Blood feeding triggers the secretion of vesicle contents into the midgut lumen, after which Ag-Aper1 is incorporated into the PM. Newly synthesized Ag-Aper1 protein was again detected within the midgut epithelial cells at 60 h after blood ingestion. [source] Degenerative and regenerative processes involved in midgut pseudotumor formation in the stick insect (Carausius morosus)JOURNAL OF MORPHOLOGY, Issue 12 2009Paul Hoffmann Abstract Spontaneous and experimentally induced pseudotumor formation in Carausius morosus impairs the midgut tissue homeostasis. Spontaneous pseudotumor formation begins by the break down of a single or a small group of columnar cells (CCs) and is followed by the degeneration of neighboring CCs. There are not only marked similarities but also decisive differences between normal dying CCs in healthy specimens and the degeneration of CCs leading to pseudotumors: in both cases, the apical cell parts with the nucleus are extruded into the midgut lumen, but only during of pseudotumor formation an "amorphous substance" originates from the basal parts of the CCs. Hemocytes are attracted to this substance and form a nodule-like aggregation, which is responsible for the phenotype of pseudotumors. Pseudotumor infestation has also an impact on the midgut nidi, which consist of an intestinal stem cell and several CC progenitor cells. In healthy specimens only one progenitor cell per nidus differentiates at a time, but, several to all progenitor cells differentiate simultaneously in pseudotumor-infested specimens. Extirpation of the ingluvial ganglion in healthy specimens results in an immediate onset of pseudotumor formation and a dramatic acceleration of pseudotumor growth. Importantly, the ultrastructural characteristics of spontaneous and experimentally induced pseudotumors are identical. This supports the idea that the stomatogastric nervous system plays an integral role in the maintenance of midgut tissue homeostasis. J. Morphol., 2009. © 2009 Wiley-Liss, Inc. [source] Factors affecting proliferation and differentiation of lepidopteran midgut stem cells,ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 1 2010Marcia J. Loeb Midgut stem cells of last instar larvae and pupae of Heliothis virescens, Lymantria dispar and several other Lepidopteran species have been cultured in vitro and have been induced to proliferate using low titers of ecdysteroids and the 77-Kda peptide fragment, ,-arylphorin, isolated and identified from pupal fat body tissue. The insulin-related hormone, Bombyxin, also induced mitosis in cultured midgut stem cells; it appeared to be fast-acting and quickly inactivated, while ,-arylphorin was slower to act and had a longer lasting effect in vitro, indicating different functions for these proliferation agents. Changes in Calcium ion concentration within or outside the cells discretely affected stem cell differentiation, indicating a role for second messenger participation in peptide regulation of this process. Four different peptides (MDFs 1,4) that induced midgut stem cells to differentiate to mature midgut cell types in vitro were isolated and characterized from conditioned media and hemolymph of H. virescens and L. dispar. However, platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and all-trans retinoic acid (RA) from vertebrate sources induced differentiation to non-midgut cell types as well. MDF1 was located in basal areas of columnar cells of midgut epithelium, although MDF2 was observed in all of the cytoplasm of columnar cells and in droplets of antibody positive material in the midgut lumen, suggesting a digestive function as well for this peptide. Anti-MDF-3 stained the central areas of cultured midgut columnar cells and the bases of columnar cells of midgut epithelium in vivo. Midgut secretory cells stained with anti-MDF-4; streams of MFD-4-positive material were observed extending from secretory cells facing the epithelial lumen, and as a layer on the hemolymph-facing side, suggesting an endocrine or paracrine function for this or an immunologically similar peptide. Published 2010 Wiley Periodicals, Inc. [source] Toxicity and disruption of midgut physiology in larvae of the European corn borer, Ostrinia nubilalis, by anion transporter blockersARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2009Dhana Raj Boina Abstract In this study, four blockers of anion transporters (ATs) belonging to four different classes of organic acids, including DIDS (4, 4'-diisothiocyanatostilbene-2, 2'- disulfonic acid; a stilbene disulfonic acid), NPPB [(5-nitro-2-(3-phenylpropylamino) benzoic acid; an anthranilic acid)], 9-AC (anthracene-9-carboxylic acid; an aromatic carboxylic acid), and IAA-94 (indanyloxy acetic acid; an indanyloxy alkanoic acid), were tested for their toxicity against the European corn borer (ECB), Ostrinia nubilalis. All the AT blockers inhibited the growth of larvae, increased the developmental time, and decreased survival compared to controls, when second-instar ECB larvae were fed for seven days on treated diet. In general, DIDS and NPPB were the most active compounds, with the rank order of activity being DIDS>NPPB>IAA-94>9-AC. All the AT blockers decreased the midgut alkalinity in fifth-instar larvae when fed for 3,h on treated diet. Effective concentrations required for 50% decrease in midgut alkalinity (EC50) ranged between 29.1 and 41.2,ppm and the rank order of activity was NPPB>DIDS>IAA-94>9-AC. Similarly, all the tested AT blockers inhibited 36Cl, uptake from the midgut lumen in fifth-instar larvae when fed for 3,h on treated diet. Concentrations required for 50% inhibition of 36Cl, uptake (IC50) ranged between 7.4 and 11.0,ppm and the rank order of activity was DIDS>NPPB>9-AC >IAA-94. Modest to highly strong positive correlations observed among growth, midgut alkalinity, and midgut Cl, ion transport in AT blocker,fed larvae suggested that these effects are causally related to each other. Finally, AT blockers have the potential to become good candidates for development of insecticides with a unique mode of action. © 2009 Wiley Periodicals, Inc. [source] | ||||||||||