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A D Befus

Publications and source records attributed to A D Befus.

At least 109 records · Page 6Linked to original sources
PubMed1985

Intestinal mucosal mast cells: isolation from rat lamina propria and purification using unit gravity velocity sedimentation.

Mucosal mast cell (MMC) suspensions obtained from the rat intestinal lamina propria by collagenase digestion (35.2 +/- 3.2% MMC) were enriched to 65.5 +/- 5.2% MMC by the use of a discontinuous gradient (30%/80%) of Percoll. Further purification to 95.7 +/- 1.3% MMC was achieved using velocity sedimentation at unit gravity (Sta-Put). Analysis of the cells throughout the purification procedure confirms that the purified MMC are representative of the MMC in the initial isolated cell suspension. No differences were seen in terms of size, histamine content, protease content and responsiveness to secretagogues among the initial isolated population, the Percoll-enriched population and the Sta-Put-purified population. This study represents a major advance in mast cell research in that, for the first time, mast cells isolated from a homogeneous in vivo mucosal source have been obtained at levels of purity sufficient for specific biochemical characterization. Such characterization will aid in the interpretation of the role of MMC in disease and will provide a firm basis of knowledge of the form and function of intestinal MMC for comparison with mast cells derived from other mucosal sites or cultured in vitro from various organs.

Animals↗
PubMed1985

Number and affinity of receptors for IgE on enriched populations of isolated rat intestinal mast cells.

Recently, particular attention has been paid to a unique subpopulation of mast cells located in the intestinal mucosa of rodents and man (Befus et al., 1982a, b; Strobel, Busuttil & Ferguson, 1983; Ruitenberg et al., 1982). These cells, presently referred to as mucosal mast cells (MMC), are morphologically, histochemically and functionally distinct from the more extensively studied connective tissue mast cells (Befus et al. 1982b; Pearce et al., 1982). Our ability to characterize the MMC more fully has been markedly enhanced by the development of techniques to enrich populations of this cell to purities of over 60% (mean 65.6 +/- 5.2%) using density centrifugation over discontinuous Percoll gradients. In this communication, we report the results of our studies to determine the number and affinity characteristics of IgG Fc (Fc epsilon) receptors on enriched MMC isolated from the intestine of rats with parasite-induced mast cell hyperplasia.

Animals↗
PubMed1985

Activation of alveolar macrophages following infection with the parasitic nematode Nippostrongylus brasiliensis.

Alveolar macrophages (AM) of rats infected with 3000 Nippostrongylus brasiliensis infective larvae for 2, 8 or 32 days (D2, D8 or D32 AM) quantitatively surpassed AM from uninfected rats in one or more of IgG- or C3-dependent phagocytosis indices, beta-D-glucuronidase release, or spontaneous release of thymocyte activating factor (interleukin-1, IL-1) and hepatocyte stimulation factor (HSF). These observations suggest that N. brasiliensis infection results in the activation of AM. We have reported previously that a greater proportion of AM from infected rats expressed C3 receptors and were helminthocidal in vitro in the presence of complement than normal AM which were not helminthocidal. The acquisition of the activated state by AM during infection may play a role in vivo lung resistance against migrating helminth parasites.

Animals↗
PubMed1984

The influence of endorphins on peritoneal and mucosal mast cell secretion.

The histamine-releasing effect of certain opiate drugs prompted a survey of endogenous opiates for mast cell-secretagogue activity. Since intestinal mucosal mast cells (MMC) differ from connective tissue mast cells in their response to a variety of secretagogues and anti-allergic compounds, we have examined the influence of several endogenous opiate peptides on histamine secretion from the two mast cell types in the rat. MMC hyperplasia was induced in rats infected with the nematode Nippostrongylus brasiliensis and MMC were isolated by collagenase digestion from the small intestine. Connective tissue mast cells from the peritoneal cavity (PMC) were isolated by peritoneal lavage. Dynorphin, alpha-neoendorphin, and beta-endorphin had a concentration-dependent secretagogue effect (10(-6)M to 10(-4)M) on PMC that was temperature and energy dependent, but MMC from the same animals were unresponsive to these agents. Differences between PMC and MMC did not appear to be attributable to the MMC isolation procedure since PMC treated similarly remained responsive to endorphin. Endorphin-induced histamine secretion from PMC was partially inhibited by the anti-allergic agent disodium cromoglycate. Inhibition with the opiate antagonist naloxone was nonspecific, occurring only at concentrations that also inhibited antigen-induced mediator release. Mast cell secretion induced by certain opiate peptides may therefore be nonreceptor mediated and relate to a direct membrane effect by basic peptides.

Animals↗
PubMed1984

Mucosal mast cells. III. Effect of quercetin and other flavonoids on antigen-induced histamine secretion from rat intestinal mast cells.

Quercetin, a naturally occurring flavonol structurally related to the antiallergic drug disodium cromoglycate inhibits anaphylactic histamine release from MMC isolated from the small bowel LP of the rat previously infected with the nematode Nippostrongylus brasiliensis. This contrasts with our previous observation that cromoglycate is inactive in this system. The present effect is immediate and does not decrease on preincubation with the drug. The flavonoids acacetin , apigenin , chrysin , and phloretin also demonstrate significant activity but are less potent than quercetin. Catechin, flavone, morin, and taxifolin are inactive. These results resemble those previously reported for the human basophil. In contrast, all compounds with the possible exception of taxifolin demonstrate significant activity against rat PMC. Acacetin and chrysin are the most effective inhibitors and are more active than quercetin. Rutin (the glycane of quercetin) and phlorezin (the glycane of phloretin) are inactive in both systems. These results are discussed in terms of the functional heterogeneity of mast cells from different sources and identify a group of compounds other than doxantrazole (reported previously), which inhibit histamine secretion by MMC.

Animals↗
PubMed1984

Mast cell heterogeneity.

Increasing evidence for the existence of inter- and intra-species mast cell heterogeneity has expanded the potential biological role of this cell. Early studies suggesting that mast cells at mucosal sites differ morphologically and histochemically from connective tissue mast cells have been confirmed using isolated intestinal mucosal mast cells in the rat and more recently in man. These studies also established that mucosal mast cells are functionally distinct from connective tissue mast cells. Thus, mucosal and connective tissue mast cells differ in their responsiveness to a variety of mast cell secretagogues and antiallergic agents. Speculation about the therapeutic use of antiallergic drugs in disorders involving intestinal mast cells cannot, therefore, be based on extrapolation from studies of their effects on mast cells from other sites. Regulatory mechanisms for mast cell secretion may also be heterogeneous since mucosal mast cells differ from connective tissue mast cells in their response to a variety of physiologically occurring regulatory peptides. The development of techniques to purify isolated mast cell subpopulations will facilitate future analysis of the biochemical basis of the functional heterogeneity of mast cells.

Animals↗
PubMed1984

Isolation and characteristics of small intestinal lamina propria cells from normal and nematode (Nippostrongylus brasiliensis)-infected rats.

Intestinal lamina propria (LP) cells were isolated from normal or nematode (Nippostrongylus brasiliensis)-infected rats. At certain times after infection (days 11-17), viable cell recoveries from infected rats were lower, whereas at other times (days 20-50), they were significantly greater than those from normal rats. The frequencies of lymphocytes, plasma cells, eosinophils, mast cells and macrophages from LP differed between normal and infected rats, and the histamine content did also. However, spontaneous 3H-uridine and 3H-thymidine incorporation and the number of cells with cytoplasmic immunoglobulin were similar. LP cells from normal rats were unresponsive to the mitogens phytohemagglutinin, concanavalin A and pokeweed. 125I-deoxyuridine-radiolabeled LP lymphoblasts from normal rats were widely distributed in recipients 22-24 h after transfer and showed no selective predilection to return to the intestine. The isolation procedure can be used to study intestinal LP cells from normal or diseased animals.

Animals↗
PubMed1984

The acute phase response in parasite infection. Nippostrongylus brasiliensis in the mouse.

Systemic inflammatory reactions are a prominent feature of many parasitic infections and the cellular and humoral components of the acute phase reaction may have an impact on the host-parasite relationship. We examined serum changes of four acute phase reactants: alpha 1-proteinase inhibition (alpha 1Pi); complement C3; serum amyloid A protein (SAA); and serum amyloid P component (SAP), in mice undergoing a primary infection with Nippostrongylus brasiliensis. SAA and SAP showed changes within the first 2 days of infection indicating the presence of an acute phase response associated with inflammation in the lung. Alpha 1Pi and C3 serum levels were not altered. However, all four acute phase reactants were synthesized in greater amounts by primary cultures of hepatocytes taken from infected animals at this time. Subsequently, as parasite-mediated inflammatory changes occur in the gut, both serum and hepatocyte cultures demonstrate an acute inflammatory response in all four reactants. It is proposed that the early reaction between parasites and macrophage/monocyte lead to the release of a mediator of inflammation which initiates the hepatocyte response. In this infection, at least one of the APR is shown to localize to the site of inflammation influencing the host-parasite relationship.

Acute Disease↗
PubMed1982

Characteristics of natural killer cells in the murine intestinal epithelium and lamina propria.

Highly purified populations of lymphocytes were obtained from the murine intestinal mucosa using EDTA-collagenase isolation procedures in combination with discontinuous density centrifugation. Intraepithelial lymphocytes (IEL) were separated from lamina propria lymphocytes (LPL) and, within these two populations, fractions enriched or depleted in gut granular lymphocytes (gGL) were obtained. Using these cells in cytotoxic assays, it was shown that both IEL and LPL possess natural killer (NK) activity, and this was associated with gGL. The major effector cells of gut NK activity appeared to be Thy-1.2+, Lyt-1.1-, and Lyt-2.1-. The susceptibility of gut NK cells to anti-Thy-1.2 plus complement (C) was significantly higher than that of splenic NK cells. In contrast, anti-asialo GM1 and anti-NK-1.2 plus C only slightly affected the gut NK activity. Thus, the phenotype of the gut NK cells appears to be different from the splenic one and provides further evidence for NK heterogeneity and establishes the compartmentalization of one NK subpopulation. Beige mice, deficient in splenic NK activity, also had very low gut NK activity. W/Wv mice, which lack mast cell precursors, had normal numbers of gGL and diminished, but still present, gut and splenic NK activity. This deficiency did not segregate with the genes responsible for the basic hemopoietic stem cell defect, and these results argue against a close ontogenetic relationship between IEL, gGL, and intestinal mucosal mast cells. The relevance of these observations to the cell lineage of the effector cell of gut NK activity is discussed.

Animals↗
PubMed1982

Unique functional characteristics of mucosal mast cells.

Mast cells have been isolated from the intestine (IMC) of rats previously infected with the nematode, Nippostrongylus brasiliensis. Functional studies on IMC have shown that they are responsive to antigen and possess surface IgE but, in contrast to peritoneal mast cells (PMC), IMC are unresponsive to the basic secretagogues, 48/80 and bee venom peptide 401, and hyporesponsive to ionophores. Furthermore, sodium cromoglycate, AH9679 and theophylline inhibited secretion by PMC but not IMC, whereas doxantrazole inhibited secretion by both cells. Histochemical investigations established that there is mast cell heterogeneity in the human intestine as well as in the rat. Since GALT and BALT are important in intestinal mastocytosis it is important to determine whether the distinct functional properties of IMC reflect a distinct precursor population, inducer cell, or other factors in GALT or BALT.

Animals↗