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Journal of Biochemistry Aug 1982We studied the effect of intestinal microorganisms on the synthesis of membrane-associated glycoproteins in the upper small intestine by intraperitoneally administering...
We studied the effect of intestinal microorganisms on the synthesis of membrane-associated glycoproteins in the upper small intestine by intraperitoneally administering L-[3H]fucose, D-[14C]glucosamine, or L-[3H]leucine to germ-free mice and mice exposed to microorganisms for 4 weeks (conventionalized). The incorporation of the labeled compounds into sucrase-isomaltase complex and maltase was determined by immunoprecipitating Triton X-100-solubilized microvillus membranes with their antibodies. Purified microvillus membranes from germ-free and conventionalized mice differed in the activities of some marker enzymes but not in the number and mobility of the components on SDS-polyacrylamide gel electrophoresis. Maximal incorporation of [3H]fucose and [14C]glucosamine into the microvillus membrane and two enzymes was reached 2-3 h post-injection in both groups, however, the amounts incorporated were larger in conventionalized mice. There was little difference in [3H]leucine incorporation into the total glycoproteins of microvillus membranes between the two groups. Our results suggest that the introduction of microorganisms stimulates the synthesis of sugar chains of microvillus membrane-associated glycoproteins. The enhanced in vitro fucosyltransferase activity in conventionalized mice partly supports this suggestion.
Topics: Animals; Chemical Precipitation; Epithelium; Female; Fucose; Germ-Free Life; Glucosamine; Glycoproteins; In Vitro Techniques; Intestine, Small; Leucine; Mice; Mice, Inbred ICR; Microvilli
PubMed: 7130148
DOI: 10.1093/oxfordjournals.jbchem.a133943 -
Cellular and Molecular Gastroenterology... 2024Microvillus inclusion disease (MVID) is a rare condition that is present from birth and affects the digestive system. People with MVID experience severe diarrhea that is... (Review)
Review
Microvillus inclusion disease (MVID) is a rare condition that is present from birth and affects the digestive system. People with MVID experience severe diarrhea that is difficult to control, cannot absorb dietary nutrients, and struggle to grow and thrive. In addition, diverse clinical manifestations, some of which are life-threatening, have been reported in cases of MVID. MVID can be caused by variants in the MYO5B, STX3, STXBP2, or UNC45A gene. These genes produce proteins that have been functionally linked to each other in intestinal epithelial cells. MVID associated with STXBP2 variants presents in a subset of patients diagnosed with familial hemophagocytic lymphohistiocytosis type 5. MVID associated with UNC45A variants presents in most patients diagnosed with osteo-oto-hepato-enteric syndrome. Furthermore, variants in MYO5B or STX3 can also cause other diseases that are characterized by phenotypes that can co-occur in subsets of patients diagnosed with MVID. Recent studies involving clinical data and experiments with cells and animals revealed connections between specific phenotypes occurring outside of the digestive system and the type of gene variants that cause MVID. Here, we have reviewed these patterns and correlations, which are expected to be valuable for healthcare professionals in managing the disease and providing personalized care for patients and their families.
Topics: Humans; Mucolipidoses; Microvilli; Malabsorption Syndromes; Phenotype; Animals; Myosin Type V; Mutation; Genetic Predisposition to Disease
PubMed: 38307491
DOI: 10.1016/j.jcmgh.2024.01.015 -
Veterinary Medicine and Science Sep 2021The cellular mechanisms involved in the development of proximal tubules are not only associated with morphogenesis in fetal life, but also with restoration of damaged...
BACKGROUND
The cellular mechanisms involved in the development of proximal tubules are not only associated with morphogenesis in fetal life, but also with restoration of damaged tubules in adulthood. Knowledge about morphological features of cell differentiation and proliferation along the developing tubule is insufficient, which hinders identification of the cellular origin.
OBJECTIVES
This study aimed to investigate ultrastructures of the proximal tubule at different stages of nephrogenesis.
METHODS
Electron microscopy was used and guided by computer-assisted tubular tracing to identify the cellular structures.
RESULTS
Renal vesicles and S-shaped bodies revealed more proliferative features, such as densely-packed fusiform-shaped cells with numerous protein-producing organelles than membrane specializations typical for mature tubules. At the capillary-loop stage the proximal tubules demonstrated all characteristics of the mature tubules, but not as developed, including shorter but densely packed microvilli, fewer lateral processes with cell-cell contacts, lower basal membrane infoldings, and lower mitochondrial volume density. However, they exhibited an elaborated endocytic system above the nucleus, indicating a membrane transport is being established. Abundant free- and endoplasmic reticulum-adhered ribosomes and Golgi complexes reflected active protein synthesis for cell growth and proliferation. Interestingly, electron dense cells were occasionally intermixed with electron lucent cells characterized by various organelles in less cytosol and a larger nucleus with abundant euchromatin, which is a feature of active proliferation.
CONCLUSIONS
These ultrastructures indicate that the morphogenesis of the developing proximal tubule corresponds to the gradually established physiological activities. The two different cellular electron densities may suggest distinctive differentiation of the cells along the tubule.
Topics: Animals; Imaging, Three-Dimensional; Kidney Tubules, Proximal; Microscopy, Electron; Microvilli
PubMed: 34236772
DOI: 10.1002/vms3.558 -
Current Biology : CB Jun 1995Transfection studies provide supporting evidence for the proposed role of villin and fimbrin in bundling the core actin filaments of microvilli. (Review)
Review
Transfection studies provide supporting evidence for the proposed role of villin and fimbrin in bundling the core actin filaments of microvilli.
Topics: Actin Cytoskeleton; Actins; Animals; Carcinoma; Carrier Proteins; Cell Line; Chickens; Colonic Neoplasms; Cytoskeletal Proteins; Humans; Kidney; Membrane Glycoproteins; Microfilament Proteins; Microvilli; Phosphoproteins; Swine; Tumor Cells, Cultured
PubMed: 7552163
DOI: 10.1016/s0960-9822(95)00117-5 -
Development (Cambridge, England) Dec 2021The intestinal brush border is made of an array of microvilli that increases the membrane surface area for nutrient processing, absorption and host defense. Studies on...
The intestinal brush border is made of an array of microvilli that increases the membrane surface area for nutrient processing, absorption and host defense. Studies on mammalian cultured epithelial cells have uncovered some of the molecular players and physical constraints required to establish this apical specialized membrane. However, the building and maintenance of a brush border in vivo has not yet been investigated in detail. Here, we combined super-resolution imaging, transmission electron microscopy and genome editing in the developing nematode Caenorhabditis elegans to build a high-resolution and dynamic localization map of known and new brush border markers. Notably, we show that microvilli components are dynamically enriched at the apical membrane during microvilli outgrowth and maturation, but become highly stable once microvilli are built. This new toolbox will be instrumental for understanding the molecular processes of microvilli growth and maintenance in vivo, as well as the effect of genetic perturbations, notably in the context of disorders affecting brush border integrity.
Topics: Animals; Caenorhabditis elegans; Enterocytes; Microvilli
PubMed: 34704594
DOI: 10.1242/dev.200029 -
ACS Nano Oct 2021The cellular uptake of nanoparticles (NPs) represents a critical step in nanomedicine and a crucial point for understanding the interaction of nanomaterials with...
The cellular uptake of nanoparticles (NPs) represents a critical step in nanomedicine and a crucial point for understanding the interaction of nanomaterials with biological systems. No specific mechanism of uptake has been identified so far, as the NPs are generally incorporated by the cells through one of the few well-known endocytotic mechanisms. Here, an alternative internalization route mediated by microvilli adhesion is demonstrated. This microvillus-mediated adhesion (MMA) has been observed using ceria and magnetite NPs with a dimension of <40 nm functionalized with polyacrylic acid but not using NPs with a neutral or positive functionalization. Such an adhesion was not cell specific, as it was demonstrated in three different cell lines. MMA was also reduced by modifications of the microvillus lipid rafts, obtained by depleting cholesterol and altering synthesis of sphingolipids. We found a direct relationship between MAA, cell cycle, and density of microvilli. The evidence suggests that MMA differs from the commonly described uptake mechanisms and might represent an interesting alternative approach for selective NP delivery.
Topics: Biological Transport; Endocytosis; Microvilli; Nanomedicine; Nanoparticles
PubMed: 34585565
DOI: 10.1021/acsnano.1c03151 -
The Journal of Pathology Mar 2021Apical microvilli of polarized epithelial cells govern the absorption of metabolites and the transport of fluid in tissues. Previously, we reported that tall and dense...
Apical microvilli of polarized epithelial cells govern the absorption of metabolites and the transport of fluid in tissues. Previously, we reported that tall and dense basal microvilli present on the endothelial cells of pancreatic cancers, a lethal malignancy with a high metabolism and unusual hypomicrovascularity, contain nutrient trafficking vesicles and glucose; their length and density were related to the glucose uptake of pancreatic cancers in a small-scale analysis. However, the implications of basal microvilli on pancreatic cancers are unknown. Here, we evaluated the clinical implications of basal microvilli in 106 pancreatic cancers. We found that basal microvilli are a dominant change in pancreatic cancers. The presence of longer and denser basal microvilli on the microvessels in pancreatic cancer tissues positively correlated with increased glucose uptake and higher metastatic (or invasive) and proliferative potentials of neoplastic cells and vice versa. Clinically, postoperative patients with longer and denser basal microvilli were more prone to unfavorable pathological characteristics and dismal prognoses. They were even more refractory to adjuvant therapy than those with shorter and thinner basal microvilli were. Our findings show that basal microvilli define the metabolic capacity and lethal phenotype of pancreatic cancers. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.
Topics: Adult; Aged; Endothelium, Vascular; Female; Humans; Image Interpretation, Computer-Assisted; Male; Microvessels; Microvilli; Middle Aged; Pancreatic Neoplasms; Phenotype; Positron Emission Tomography Computed Tomography; Prognosis
PubMed: 33159698
DOI: 10.1002/path.5588 -
PloS One 2022We imaged the carbohydrate-selective spatial binding of 8 lectins in the ampullary organs (AOs) of electroreceptors on the rostrum of freshwater paddlefish (Polyodon...
We imaged the carbohydrate-selective spatial binding of 8 lectins in the ampullary organs (AOs) of electroreceptors on the rostrum of freshwater paddlefish (Polyodon spathula), by fluorescence imaging and morphometry of frozen sections. A focus was candidate sites of secretion of the glycoprotein gel filling the lumen of AOs. The rostrum of Polyodon is an electrosensory appendage anterior of the head, covered with >50,000 AOs, each homologous with the ampulla of Lorenzini electroreceptors of marine rays and sharks. A large electrosensory neuroepithelium (EN) lines the basal pole of each AO's lumen in Polyodon; support cells occupy most (97%) of an EN's apical area, along with electrosensitive receptor cells. (1) Lectins WGA or SBA labeled the AO gel. High concentrations of the N-acetyl-aminocarbohydrate ligands of these lectins were reported in canal gel of ampullae of Lorenzini, supporting homology of Polyodon AOs. In cross sections of EN, WGA or SBA labeled cytoplasmic vesicles and organelles in support cells, especially apically, apparently secretory. Abundant phalloidin+ microvilli on the apical faces of support cells yielded the brightest label by lectins WGA or SBA. In parallel views of the apical EN surface, WGA labeled only support cells. We concluded that EN support cells massively secrete gel from their apical microvilli (and surface?), containing amino carbohydrate ligands of WGA or SBA, into the AO lumen. (2) Lectins RCA120 or ConA also labeled EN support cells, each differently. RCA120-fluorescein brightly labeled extensive Golgi tubules in the apical halves of EN cells. ConA did not label microvilli, but brightly labeled small vesicles throughout support cells, apparently non-secretory. (3) We demonstrated "sockets" surrounding the basolateral exteriors of EN receptor cells, as candidate glycocalyces. (4) We explored whether additional secretions may arise from non-EN epithelial cells of the interior ampulla wall. (5) Model: Gel is secreted mainly by support cells in the large EN covering each AO's basal pole. Secreted gel is pushed toward the pore, and out. We modeled gel velocity as increasing ~11x, going distally in AOs (toward the narrowed neck and pore), due to geometrical taper of the ampulla wall. Gel renewal and accelerated expulsion may defend against invasion of the AO lumen by microbes or small parasites. (6) We surveyed lectin labeling of accessory structures, including papilla cells in AO necks, striated ectoderm epidermis, and sheaths on afferent axons or on terminal glia.
Topics: Animals; Lectins; Fishes; Bodily Secretions; Microvilli; Epithelial Cells
PubMed: 36395118
DOI: 10.1371/journal.pone.0276854 -
The Journal of Physiology Aug 2017Light intensities (photons s μm ) in a natural scene vary over several orders of magnitude from shady woods to direct sunlight. A major challenge facing the visual... (Review)
Review
Light intensities (photons s μm ) in a natural scene vary over several orders of magnitude from shady woods to direct sunlight. A major challenge facing the visual system is how to map such a large dynamic input range into its limited output range, so that a signal is neither buried in noise in darkness nor saturated in brightness. A fly photoreceptor has achieved such a large dynamic range; it can encode intensity changes from single to billions of photons, outperforming man-made light sensors. This performance requires powerful light adaptation, the neural implementation of which has only become clear recently. A computational fly photoreceptor model, which mimics the real phototransduction processes, has elucidated how light adaptation happens dynamically through stochastic adaptive quantal information sampling. A Drosophila R1-R6 photoreceptor's light sensor, the rhabdomere, has 30,000 microvilli, each of which stochastically samples incoming photons. Each microvillus employs a full G-protein-coupled receptor signalling pathway to adaptively transduce photons into quantum bumps (QBs, or samples). QBs then sum the macroscopic photoreceptor responses, governed by four quantal sampling factors (limitations): (i) the number of photon sampling units in the cell structure (microvilli), (ii) sample size (QB waveform), (iii) latency distribution (time delay between photon arrival and emergence of a QB), and (iv) refractory period distribution (time for a microvillus to recover after a QB). Here, we review how these factors jointly orchestrate light adaptation over a large dynamic range.
Topics: Animals; Biomimetics; Diptera; Light; Microvilli; Photons; Photoreceptor Cells, Invertebrate; Stochastic Processes
PubMed: 28369994
DOI: 10.1113/JP273614 -
Respiratory Physiology & Neurobiology Jan 2016To verify the hypothesis that by enmeshing lubricants, microvilli reduce the coefficient of kinetic friction (μ) of pleural mesothelium, μ was measured during...
To verify the hypothesis that by enmeshing lubricants, microvilli reduce the coefficient of kinetic friction (μ) of pleural mesothelium, μ was measured during reciprocating sliding of rabbit's visceral against parietal pleura before and after addition of hyaluronan, and related to the morphological features of the microvillar network. Because no relation was found between μ or μ changes after hyaluronan and microvillar characteristics, the latter are not determinants of the frictional forces which oppose sliding of normal mesothelial surfaces under physiological conditions, nor of the effects of hyaluronan. Addition of hyaluronan increased μ slightly but significantly in normal specimens, probably by altering the physiological mix of lubricants, but decreased μ of damaged mesothelia, suggesting protective, anti-abrasion properties. Indeed, while sliding of an injured against a normal pleura heavily damaged the latter and increased μ when Ringer was interposed between the surfaces, both effects were limited or prevented when hyaluronan was interposed between the injured and normal pleura before onset of sliding.
Topics: Animals; Epithelium; Friction; Hyaluronic Acid; Isotonic Solutions; Lubricants; Microscopy, Electron, Transmission; Microvilli; Pleura; Rabbits; Respiration; Ringer's Solution
PubMed: 26376001
DOI: 10.1016/j.resp.2015.09.003