Assessment of faba bean (Vicia faba) response to inoculation with Rhizobium leguminosarum in clay loam Nile Delta soil.

A field experiment was conducted to assess the response to inoculation with rhizobia in a clay loam soil of the Nile Delta using faba bean (Vicia faba) for two successive winter seasons (1985/6 and 1986/7). Three selected strains of Rhizobium leguminosarum, TAL 634, NRC 65 and TAL 1400, were used singly or in combination as peat-based inocula in 1985/6 winter season. Strain TAL 1400 was replaced by strain F9 in the 1986/7 winter season. A significant seed yield response was obtained only with strain TAL 1400, in the 1985/6 season. In the 1986/7 season, no significant yield response was observed with any of the strains. The serotyping of nodules collected in the 1985/6 season showed that strain TAL 1400 was more competitive than either the indigenous rhizobia or the two inoculant strains. However, the majority of nodules formed in the 1986/7 season were formed from strains other than the inoculant ones.

Colonic mucosal T lymphocytes in ulcerative colitis: expression of CD7 antigen in relation to MHC class II (HLA-D) antigens.

T-cell subsets and their activation state were examined by double-label immunofluorescence of cryostat tissue sections of the colon from 21 patients with ulcerative colitis (UC) and 30 histologically normal controls. Expression of MHC class I (HLA-A, B, C) and class II (HLA-D) antigens was studied in parallel. In the normal colonic mucosa, the CD4:CD8 ratio in the epithelial compartment approximated 1:1, and in the lamina propria, 2.55:1. Of the CD8+ (cytotoxic/suppressor) subset, approximately half did not express the CD5 "pan-T" marker in either compartment. Virtually no Leu8+ cells were observed, implying that the CD4+ subset consisted of helper, rather than suppressor-inducer cells. Classical markers of T-cell activation (CD25, HLA-D) and proliferation were absent, and strong expression of the CD7 "immunostimulation" marker was approximately equal in both CD4 and CD8 subsets. The epithelium was uniformly negative for class II antigens, but positive for class I. In UC, there were no significant alterations in CD4:CD8 ratios in either compartment, and there were no changes with respect to phenotype of the subsets. In 11 of 19 patients (mainly with total colitis), enterocytes were HLA-D+. In this HLA-D+ group, there was an increase in the percentage of CD4+ cells coexpressing CD7; this difference was significant (P less than 0.02) in the lamina propria. Increased expression of CD7 was also found by the CD6+ T cell subset (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Local immunity in ulcerative colitis: evidence for defective secretory IgA production.

To investigate local humoral immunity in ulcerative colitis (UC), immunoglobulin (Ig) contents and net Ig production in vitro was assessed using organ cultures of colonic biopsies from 21 patients with quiescent disease and 11 controls. Ig was estimated by enzyme linked immunoassay (ELISA) for IgA, secretory IgA (sIgA), IgM, and IgG. In parallel, numbers of IgA plasma cells were estimated by indirect immunoperoxidase staining of tissue sections for IgA. IgA was the dominant Ig isotype found pre-existing in colonic mucosae, and secreted in vitro. In UC patients, preformed tissue IgA and IgA produced in vitro were significantly increased compared with controls. There was no concomitant increase in amounts of sIgA synthesised in culture, however, although numbers of IgA plasma cells were increased in UC patients by an amount comparable with the increased in vitro IgA production. These results directly show a dysfunction of transepithelial IgA secretion in quiescent ulcerative colitis. Despite a significantly raised concentration of tissue IgG in UC patients, little was produced in vitro in patient and control groups alike, suggesting that mucosal IgG was serum derived, and not linked to local IgA production.

T lymphocytes of the human colonic mucosa: functional and phenotypic analysis.

Normal human colonic lymphocyte populations were isolated for both phenotypic analysis by double-label immunofluorescence and assessment for regulatory effects on Ig production by co-culture with responder cells from colonic mucosa and peripheral blood. Mean CD4:CD8 ratios for colonic intraepithelial lymphocytes (IEL) and lamina propria lymphocytes (LPL) were comparable to values obtained from tissue sections. IEL alone did not produce Ig in vitro and were without effect on Ig production when co-cultured with LPL. However, T-enriched LPL had a marked helper effect for T-depleted LPL. Maximal help was for IgA production, increasing with numbers of T-enriched cells. In colonic LPL T-depleted and T-enriched co-cultures, pokeweed mitogen (PWM) had no significant effect. By contrast, in co-cultures of T-enriched and T-depleted peripheral blood mononuclear cells, Ig production was PWM-dependent. In all experiments with colonic mucosal responder cells, IgG production was low. The effects of unfractionated colonic biopsy lymphocytes on T-depleted peripheral blood mononuclear cells were additive for IgM production and synergistic for IgA synthesis, although almost no IgG was produced. Moreover, PWM had helper effects for IgM, but was suppressive for IgA production. These data suggest that colonic mucosal regulatory cells reside in the lamina propria, and predominantly provide help for IgA and IgM synthesis. The data further suggest the existence of a pre-stimulated IgA-specific T helper cell population.

Kinetics and properties of L-glutaminase and L-asparaginase activities of Pseudomonas ovalis.

Pseudomonas ovalis produces L-glutaminase and L-asparaginase activities simultaneously upon induction by L-glutamine or L-asparagin in the growth medium. Both activities are confined to the cell during active growth and are not released into the medium. The apparent Km values are 1.4 X 10(-2) M and 6 X 10(-3) M for L-glutamine and L-asparagine substrates, respectively. Induction of both activities is substantially favoured in media with initial pH values higher than 7. In buffered yeast extract L-asparagine medium, significant amounts of L-glutaminase and L-asparaginase activities appeared towards the end of the exponential phase and along the stationary phase. The process of enzyme formation showed a firm link to the cell active growth, as evidenced by the use of growth inhibitors.

Characterization and microbiological evaluation of the red compounds, associated with red rot idsease of sugar cane.

The red coloured compounds, isolated from sugar cane tissues infected with red rot, were phenolic and included a mixture of flavonoid compounds. Two of these compounds were purified and partially characterized. Neither the mixture of the coloured compounds nor any of its individual compounds exhibited in vitro activity against the causal organism Physalospora tucumanensis. One of the purified compounds showed in vitro activity against Bacillus subtilis. The role of the red coloured compounds in the mechanism of disease resistance is discussed.