Mucosal defense against gastrointestinal nematodes: responses of mucosal mast cells and mouse mast cell protease 1 during primary strongyloides venezuelensis infection in FcRgamma-knockout mice

A possible role for the gamma subunit of immunoglobulin Fc receptors (FcR) in mucosal defenses against intestinal nematode parasites was studied using age-matched FcRgamma-knockout (FcRgamma(-/-)) and wild-type (FcRgamma(+/+)) C57BL/6 mice. Mice were infected subcutaneously with 3,000 infective larvae of Strongyloides venezuelensis, and the degree of infection was monitored by daily fecal egg counts and adult worm recovery on days 8 and 13 postinfection. Mucosal mast cell (MMC) responses were assayed by in situ intestinal mast cell counts in stained histological sections of the jejunum and by measuring mouse mast cell protease 1 (MMCP-1) release in serum using sandwich enzyme-linked immunosorbent assay. FcRgamma(-/-) mice had significantly higher egg counts (P<0.01) and numbers of adult worms (P<0.05) than FcRgamma(+/+) mice, but mastocytosis and serum MMCP-1 release were comparable. It was concluded that MMCP-1 release may be spontaneous, does not depend on mast cell degranulation via the FcRgamma signaling system, and appears to play no role in the expulsion of S. venezuelensis. The delay in worm expulsion in the FcRgamma(-/-) mice might be related to inability of the MMC to degranulate and release effector molecules other than MMCP-1, since FcRgamma deletion abrogates mast cell degranulative responses.     

Dose- and time-dependent responses for micronucleus induction by X-rays and fast neutrons in gill cells of medaka (Oryzias latipes)

Medaka fish (Oryzias latipes) were exposed to various doses of X-rays or fast neutrons, and the frequency of micronucleated cells (MNCs) was measured in gills sampled at 12- or 24-hr intervals from 12 to 96 hr after exposure. The resulting time course of MNC frequency was biphasic, with a clear peak 24 hr after exposure, irrespective of the kind of radiation applied and the dose used. The half-life of MNCs induced in the gill tissues by the two exposures fluctuated around 28 hr, with no significant dose-dependent trend for either X-ray- or neutron-exposed fish. As assayed 24 hr after exposure, the MNC frequency increased linearly over the control level with increasing doses of both X-rays and fast neutrons. The relative biological effectiveness (RBE) of fast neutrons to X-rays for MNC induction was estimated to be 4.3 +/- 0.6. This value is close to the RBE value of 5.1 +/- 0.3 reported for fast neutron induction of somatic crossing-over mutations in Drosophila melanogaster that arise from recombination repair of DNA double-strand breaks. These results and other data support our conclusion that the medaka gill cell micronucleus assay is a reliable short-term test for detecting potential inducers of DNA double-strand breaks.     

Virulence of Rhodococcus equi isolates from patients with and without AIDS.

Rhodococcus equi is an emerging opportunistic pathogen of human immunodeficiency virus-infected patients. Thirty-nine isolates of R. equi from immunocompromised patients with and without AIDS were analyzed for the presence of virulence plasmid DNA, expression of 15- to 17-kDa antigens, and their pathogenicities in mice. Of the human isolates, eight contained an 85-kb virulence plasmid, expressed 15- to 17-kDa antigens, and were virulent in mice. Nineteen isolates carried cryptic plasmids of various sizes, and the remaining 12 isolates did not contain any plasmids. These 31 isolates did not express virulence-associated antigens and were not virulent in mice. The results suggested that opportunistic infections in immunocompromised patients could be caused by both virulent and avirulent R. equi strains and that the pathogenesis of R. equi infection in immunocompromised patients appears to be different from that which occurs in foals.     

Purification and hemagglutinating properties of egg drop syndrome 1976 virus

Summary We purified three populations of virus particles, F7, F9 and F17, with buoyant densities of 1.34, 1.33 and 1.29 g/ml, respectively, in CsCl equilibrium density gradients from cultures of chick embryo liver cells infected with the H-162 strain of the virus of egg drop syndrome 1976. F9 particles were infectious complete virions and most F17 particles were empty particles. F7 particles were less infectious, and had little capacity of hemagglutination (HA). HA titers were the same at 4° and 37° C and maximal between pH 6.4 and 8.4 and ionic strength from 0.14 to 0.54m of NaCl. HA titer was inversely proportional to erythrocyte concentration. Potassium periodate destroyed markedly the infectivity of the virus and partially its HA activity at 37° C. HA activity was stable at 56° C or lower temperatures and destroyed at 80° C. Trypsin, -chymotrypsin, papain, ficin and neuraminidase had no effect on HA activity. Alpha-chymotrypsin destroyed the receptor for the virus on chicken erythrocytes, whereas trypsin and neuraminidase did not affect the receptor.With 2 Figures     

Hepatitis B surface antigen particles of subtypes adw and adr, and compound subtype (adwr) in symptom-free carriers in Japan.

Of sera from 1,878 Japanese blood donors who carried hepatitis B surface antigen (HBsAg), 420 were subtyped as adw (22.4%) and 1,443 as adr (76.8%); only 15 (0.8%) contained HBsAg of subtype ayw or ayr. Sera with HBsAg/adr had higher HBsAg titres than those with HBsAg/adw (geometric mean of haemagglutination titre: 10.1 +/- 2.4 vs. 9.7 +/- 2.4, p less than 0.01), and a higher prevalence of hepatitis B e antigen (24% vs. 13%, p less than 0.001). Carriers of HBsAg/adr progressively predominated over those of HBsAg/adw with increasing age. Of sera from 1,863 carriers of HBsAg/adw or HBsAg/adr, 182 (9.8%) contained HBsAg particles with both subtypic determinants in the w/r allele. The presence of w and r determinants on the same particles was ascertained by sandwiching them between monoclonal antibody with the specificity for w and that with the specificity for r. HBsAg particles of compound subtype (adwr) were found more often in sera with hepatitis B e antigen than those without it (145/403 [36.0%] vs. 37/1,460 [2.5%], p less than 0.001). Sera with HBsAg/adwr particles had HBsAg titres higher than those without them (12.4 +/- 1.9 vs. 9.7 +/- 2.3, p less than 0.001). HBsAg/adwr particles arise from phenotypic mixing of the S-gene product of wild-type virus and that of mutants with point mutations for subtypic changes. The results obtained indicated that HBV strains of subtype adr have a higher replicative activity than those of adw, and suggested that mutations in the S gene for subtypic changes would be associated with an active replication of hepatitis B virus.     

Multiple downstream signalling pathways from ROCK, a target molecule of Rho small G protein, in reorganization of the actin cytoskeleton in Madin-Darby canine kidney cells

BACKGROUND: In Madin-Darby canine kidney cells, Rho small G protein regulates formation of stress fibres, focal adhesions, and peripheral bundles through reorganization of the actin cytoskeleton. There are two morphologically distinguishable types of Rho-regulated stress fibres: parallel and stellate. Of these, effects of Rho small G protein, mDia1 regulates the formation of parallel stress fibres, whereas ROCK regulates the formation of stellate stress fibres, peripheral bundles and focal adhesions. Both mDia1 and ROCK are direct downstream targets of Rho small G protein. RESULTS: The ROCK-induced formation of stellate stress fibres is regulated mainly through the myosin light chain kinase-dependent phosphorylation of myosin light chain and the LIM-kinase-dependent phosphorylation of cofilin. The ROCK-induced formation of focal adhesions is mainly regulated through a downstream pathway of ROCK other than myosin light chain and cofilin. The ROCK-induced formation of peripheral bundles is regulated at least through ERM proteins, but not through the myosin light chain or cofilin. CONCLUSION: Our present and previous findings suggest the presence of multiple downstream signalling pathways from ROCK to reorganization of the actin cytoskeleton in Madin-Darby canine kidney cells.     

Role of nectin in organization of tight junctions in epithelial cells

BACKGROUND: In polarized epithelial cells, cell-cell adhesion forms specialized membrane structures comprised of claudin-based tight junctions (TJs) and of E-cadherin-based adherens junctions (AJs). These structures are aligned from the apical to the basal side of the lateral membrane, but the mechanism of this organization remains unknown. Nectin is a Ca2+ independent immunoglobulin-like cell-cell adhesion molecule which localizes at AJs. Nectin is associated with E-cadherin through their respective cytoplasmic tail-binding proteins, afadin and catenins, and involved in the formation of AJs in cooperation with E-cadherin. We show here that nectin is also involved in the formation of TJs. RESULTS: During the formation of the junctional complex consisting of AJs and TJs in Madin-Darby canine kidney (MDCK) cells, claudin and occludin accumulated at the apical sites of the nectin-based cell-cell adhesion sites. This accumulation of claudin and occludin was inhibited by inhibitors acting on the trans interaction of nectin. The barrier function of TJs was also impaired by the nectin inhibitors. It has been shown that a phorbol ester promotes the formation of a TJ-like structure in an E-cadherin-independent manner. This phorbol ester-induced formation of the TJ-like structure was also inhibited by the nectin inhibitors. CONCLUSIONS: These results suggest a role of the nectin-afadin system in the organization of TJs as well as AJs in epithelial cells.