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M Neutra

Publications and source records attributed to M Neutra.

12 recordsLinked to original sources
PubMed2003

A newborn mouse model for the study of intestinal pathogenesis of shigellosis.

Shigella infection is characterized by the induction of acute inflammation, which is responsible for the massive tissue destruction of the intestinal mucosa. A murine model would be a valuable tool for gaining a better understanding of the physiopathology of shigellosis and the host immune response to Shigella infection, but adult mice do not develop disease upon oral inoculation. We therefore attempted to develop a model of infection in newborn mice. Four-day-old mice inoculated with 50 microl of 5 x 10(9) invasive wild-type Shigella flexneri 5a were susceptible to bacterial infection, but mice inoculated with the non-invasive strain BS176 were not. Histologically, 4-day-old mice infected with the invasive strain presented intestinal lesions and inflammation similar to those described in patients with shigellosis. Moreover, cytokine and chemokine responses consistent with inflammation were observed. Lower bacterial inocula induced less severe intestinal damage. In contrast, 5-day-old mice inoculated with either the invasive or the non-invasive strain were not infected. We have thus established a mouse model that is suitable for the study of the pathogenesis of intestinal Shigella infection.

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PubMed2001

Early immunologic events in mucosal and systemic lymphoid tissues after intrarectal inoculation with simian immunodeficiency virus.

The pathogenesis of human immunodeficiency virus transmission via the rectal route remains poorly understood. By use of the simian immunodeficiency virus (SIV)-rhesus macaque model and intrarectal inoculation with pathogenic SIVmac251, a significant increase was found in the percentage of CD11b(+) monocyte lineage cells expressing HLA-DR and/or B7-2 in local and peripheral immune inductive sites, but not in mucosal effector sites, as early as 7 days after inoculation and up to 50 days after inoculation. Moreover, at 21 and 50 days after inoculation, not only the gut but also the lung mucosa were depleted of CD4(+) T cells, which suggests that early loss of CD4(+) T cells may be a common feature of mucosal effector sites. These data suggest that, after intrarectal inoculation with SIV, early activation occurs within the monocyte lineage cell population at immunologic inductive sites, which is followed by a loss of CD4(+) T cells at local and distant mucosal effector sites.

Animals↗
PubMed1999

Mucin-related epitopes distinguish M cells and enterocytes in rabbit appendix and Peyer's patches.

The biochemical composition of the apical membranes of epithelial M cells overlying the gut-associated lymphoid tissues (GALT) is still largely unknown. We have prepared monoclonal antibodies (MAbs) directed against carbonate-washed plasma membranes from epithelial cells detached with EDTA from rabbit appendix, a tissue particularly rich in GALT. As determined by immunofluorescence microscopy, several MAbs specifically recognized either M cells or enterocyte-like cells of the domes from rabbit appendix, sacculus rotundus, and Peyer's patches. M cells were identified by their large ventral pocket containing lymphoid cells and by specific labeling with antivimentin. Among various characterized MAbs, MAb 104 recognized rabbit immunoglobulins and was used as an apical marker for M cells in the rabbit appendix, MAb 58 selectively stained an integral membrane glycoprotein of greater than 205 kDa located at the apex of M cells, and MAb 214 stained a smaller soluble glycoprotein associated with the apical surfaces from neighboring enterocytes. In addition, both MAbs 58 and 214 also labeled luminal mucus and secretory granules in goblet cells. The selective association of mucin-related molecules at the surfaces of either M cells or enterocyte-like cells of the follicle-associated epithelium suggests that specific carbohydrate antigens are differentially expressed by epithelial cells and could account for the differential binding properties of pathogens.

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PubMed1994

Bovine colostrum ultrafiltrate: an effective supplement for the culture of mouse-mouse hybridoma cells.

An ultrafiltrate fraction (UF) of bovine colostrum has been successfully used as a cell culture supplement for growth and monoclonal IgG antibody production of cultured mouse-mouse hybridomas derived from spleen cells. In this study we compared the ability of UF to support growth and antibody production of IgA hybridomas derived from Peyer's patch cells with that of an IgG hybridoma cell line. One IgG (LPC2) and two IgA hybridoma cell lines (RB3 and P2E7) were used as models. The optimal UF concentration for Ig production and cell growth for both the IgA hybridoma RB3 and the IgG hybridomas was 5-10%. Initial plating density was found to be a critical factor for IgA hybridoma cell growth: the IgA hybridomas required a seeding density of at least 70,000 cells/ml to grow compared to 15,000 IgG hybridoma cells/ml (Pakkanen et al., 1992). The addition of small amounts (up to 2%) of FBS in 10% UF supplemented medium did not enhance IgA production or cell growth. RB3 and LPC2 cells seeded at equal density and grown in 10% UF for 8 days attained maximum cell densities at 3-4 days that were 58% (RB3) or 34% (LPC2) lower than those in 10% FBS, but the total amounts of monoclonal antibody produced were 73% and 83%, respectively, of that in 10% FBS. Thus, Ig production per cell was 22-27% higher in 10% UF than in 10% FBS. Hybridoma cells could be cultured for at least 5 weeks without any reduction in growth rates, if medium was partially but not completely replaced twice a week. This suggests that hybridoma cells maintained in UF supplemented medium secrete growth promoting factors. Cells maintained in UF for up to 5 weeks sustained similar monoclonal antibody production rates as in short term culture. These results show that UF can be used as an economical and effective hybridoma culture supplement for the production of both IgG and IgA antibodies.

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PubMed1990

Convergence of apical and basolateral endocytic pathways at apical late endosomes in absorptive cells of suckling rat ileum in vivo.

Absorptive cells of the intestinal epithelium endocytose proteins from both apical and basolateral membrane domains. In absorptive cells of suckling rat ileum, luminal protein tracers first enter an apical tubulovesicular endosomal system, then enter larger apical endosomal vesicles and multivesicular bodies (MVB), and finally are delivered to a giant supranuclear lysosomal vacuole. To determine whether proteins endocytosed from the basolateral domain in vivo enter the same endosomal or lysosomal compartments as those taken up from the apical side, we simultaneously applied cationized ferritin (CF) apically (by intra-luminal injection) and horseradish peroxidase (HRP) basally (by intravenous injection), and examined absorptive cells after 3 min to 60 min using light, electron and fluorescence microscopy. At early times, CF and HRP entered separate endosomal compartments at apical and basolateral poles. At no time did HRP enter the apical tubulovesicular system, and CF never entered early basolateral endosomes. After 15 min, however, both tracers appeared together in large late endosomes and MVB located apically, above the giant vacuole. From 15 to 60 min both tracers accumulated in the giant vacuole. Membranes of some apical late endosomes, all apical MVB, the giant vacuole, and occasional sub-nuclear vesicles contained immunoreactive Igp120, a glycoprotein specific to late compartments of the endosome-lysosome system. These results show that highly polarized intestinal epithelial cells have separate apical and basolateral early endosomal compartments, presumably to maintain distinct membrane domains while allowing endocytosis and recycling of membrane from both surfaces. Apical and basolateral endocytic pathways, and presumably vesicles delivering hydrolytic enzymes and lysosomal membrane components, converge at the apical late endosome.

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PubMed1986

Uptake and transepithelial transport of nerve growth factor in suckling rat ileum.

Nerve growth factor (NGF) is necessary for the development of sympathetic and some sensory neurons. Milk may be a source of NGF for suckling young, but sites of intestinal absorption of the protein have not been identified. To determine whether NGF is transported across the absorptive epithelium of suckling rat ileum, we assessed binding, uptake, and transport of 125I-NGF by light microscopy and EM autoradiography. Blood and tissue extracts were analyzed by biochemical and immunological methods to determine whether NGF was taken up structurally intact. NGF binding sites were identified on microvilli and apical invaginations of ileal absorptive cells in vitro. Injected into ileal loops in vivo, NGF radioactivity retained by fixation was evident after 20 min in apical regions of absorptive cells, in endocytic tubules (which mediate the uptake of membrane-bound ligands), in vesicles (which mediate nonspecific endocytosis), and in the supranuclear lysosomal vacuole. At 1 and 2 h, radiolabel in these compartments increased and silver grains were evident at the basal cell surface, and in cells, matrix, and vessels of the lamina propria. In blood and liver, radiolabeled molecules that were immunologically and electrophoretically indistinguishable from NGF and that co-eluted with NGF on gel filtration columns were detected, confirming that some NGF was transported across the epithelium structurally intact. Thus, absorptive cells of suckling rat ileum can take up NGF by both receptor-mediated and nonspecific endocytosis, and direct NGF either to the lysosome for degradation, or into a transepithelial transport pathway.

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PubMed1981

Submandibular glands in mice with muscular dystrophy: studies with nerve growth factor.

Experiments have been carried out to examine the submandibular glands in mice with hereditary muscular dystrophy. Radioimmunoassay data confirm biological studies which show that submandibular glands in mice with muscular dystrophy contain less nerve growth factor (NGF) than glands of normal animals. Male dystrophics have half as much submandibular NGF as unafflicted mice, while females have only 10% of control levels. Gel filtration and electrophoretic studies detect no differences in the molecular properties of NGF in gland extracts from normal and dystrophic mice. Furthermore, NGF from both sources show equal activity in the sensory ganglion bioassay. Together, these results suggest that NGF deficits in submandibular glands of dystrophic mice are not due to measurement artifacts arising from alterations in the structure of the molecule. Morphological studies have uncovered a cytological basis for chemical deficits within submandibular glands of dystrophic mice. Stereological analysis of light and electron microscopic sections revealed that growth factor containing granular tubule cells (GTC) take up a smaller portion of the total gland volume, are smaller in size, and contain fewer secretory granules than comparable cells in glands from controls. Furthermore, the ultrastructure of GTC in dystrophic animals suggests that the cells are less active in producing secretory protein than GTC in glands from normal animals. These results are consistent with the idea that growth factor deficits arise from cellular abnormalities in the granular tubule segment of the gland.

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PubMed1966

Synthesis of the carbohydrate of mucus in the golgi complex as shown by electron microscope radioautography of goblet cells from rats injected with glucose-H3.

It is known that colonic goblet cells utilize glucose to synthesize the carbohydrate portion of mucus glycoprotein. To determine the intracellular site of this synthesis, glucose-H(3) was injected into 10-g rats. At 5, 20, 40 min, 1, 1(1/2), and 4 hr after injection, segments of colon were fixed and prepared for electron microscope radioautography. By 5 min after injection, label had been incorporated into substances present in the flattened saccules of the Golgi complex. At 20 min, both Golgi saccules and nearby mucigen granules were labeled. By 40 min, mucigen granules carried almost all detectable radioactivity. Between 1 and 4 hr, these labeled granules migrated from the supranuclear region to the apical membrane; here, they were extruded singly, retaining their limiting membrane. The evidence indicates that the Golgi saccule is the site where complex carbohydrate is synthesized and is added to immigrant protein to form the complete glycoprotein of mucus. The Golgi saccule, distended by this material, becomes mucigen granules. It is roughly estimated that one saccule is released by each Golgi stack every 2 to 4 min: a conclusion implying continuous renewal of Golgi stacks. It appears that the Golgi synthesis, intracellular migration, and release of mucus glycoprotein occur continually throughout the life of the goblet cell.

Amylases↗
PubMed1966

Radioautographic comparison of the uptake of galactose-H and glucose-H3 in the golgi region of various cells secreting glycoproteins or mucopolysaccharides.

The radioautographic distribution of the label of galactose-H(3) was compared with that of glucose-H(3) in a series of secretory cells of the rat. Whereas the glucose label appeared in all mucous cells, the galactose label was incorporated only into certain mucous cells. Whenever either label was incorporated, however, it was located first in the Golgi region and later in the secretion product, mucus. Several lines of evidence, including extraction of glucose label with peracetic acid-beta glucuronidase, indicated that the material synthesized in the Golgi region was glycoprotein in nature. In chondrocytes, both the galactose and the glucose label appeared first in the Golgi region and later in cartilage matrix; extraction of glucose label with hyaluronidase indicated that much of it consisted of mucopolysaccharide. In all secretory cells, the extraction of glycogen by amylase had no effect on Golgi radioactivity. Such extraction did not eliminate the scattered cytoplasmic label also seen after glucose-H(3) injection, but completely eliminated that seen after galactose-H(3). Consequently, the galactose-H(3) label in the Golgi region stood out more clearly, and was detected in many cells: pancreas, liver, epididymis, and intestinal columnar cells. In the latter, label later appeared in the surface coat. Thus, radioautography after injection of galactose-H(3), as after glucose-H(3), indicates that synthesis of complex carbohydrates takes place in the Golgi region of many secretory cells.

Amylases↗