No abstract

Entry of opsonized pathogens into phagocytes may benefit or, paradoxically, harm the host. Opsonization may trigger antimicrobial mechanisms such as reactive oxygen or nitric oxide (NO) production but may also provide a safe haven for intracellular replication. Brucellae are natural intramacrophage pathogens of rodents, ruminants, dogs, marine mammals, and humans. We evaluated the role of opsonins in Brucellamacrophage interactions by challenging cultured murine peritoneal macrophages with Brucella melitensis 16M treated with complement-and/or antibody-rich serum. Mouse serum rich in antibody against Brucella lipopolysaccharide (LPS) (aLPS) and human complement-rich serum (HCS) each enhanced the macrophage uptake of brucellae. Combinations of suboptimal levels of aLPS (0.01%) and HCS (2%) synergistically enhanced uptake. The intracellular fate of ingested bacteria was evaluated with an optimal concentration of gentamicin (2 g/ml) to control extracellular growth but not kill intracellular bacteria. Bacteria opsonized with aLPS and/or HCS grew equally well inside macrophages in the absence of gamma interferon (IFN-␥). Macrophage activation with IFN-␥ inhibited replication of both opsonized and nonopsonized brucellae but was less effective in inhibiting replication of nonopsonized bacteria. IFN-␥ treatment of macrophages with opsonized or nonopsonized bacteria enhanced NO production, which was blocked by N G -monomethyl L-arginine (MMLA), an NO synthesis inhibitor. MMLA also partially blocked IFN-␥-mediated bacterial growth inhibition. These studies suggest that primary murine macrophages have limited ability to control infection with B. melitensis, even when activated by IFN-␥ in the presence of highly opsonic concentrations of antibody and complement. Additional cellular immune responses, e.g., those mediated by cytotoxic T cells, may play more important roles in the control of murine brucellosis.Brucella spp., short, nonmotile, nonsporulating, nonencapsulated, gram-negative aerobic rods, are important facultative intracellular pathogens of humans and livestock. Brucella melitensis usually infects sheep, goats, and camels and is the most pathogenic species for humans (1). Like other facultative intracellular pathogenic bacteria (e.g., Francisella tularensis, Listeria monocytogenes, Mycobacterium spp., and Legionella pneumophila), clearance of Brucella infection relies on both cellmediated immunity (1,3,7,12,20,21,27,30,38) and humoral responses (10,22,29,35). The interplay of these two arms of the immune response, however, is not well understood.Successful infection of the host by Brucella reflects the ability of the bacterium to establish itself in an intracellular environment favorable for its replication. The presence of complement or antibody in the extracellular fluid favors killing of some Brucella strains (35,38). Opsonization by these humoral factors also enhances uptake by phagocytic cells that shelter the bacteria. The intracellular fate of brucellae may depend on the bacterial species or the kind of ph...

No abstract

The sugar composition of the unfermented sap from oil palm (Elaeis guinensis) trees growing in the plantations of the Nigerian Institute for Oil Palm Research, Benin City, has been determined. While sucrose concentration ranges from 9.59 to 10.59% (w/v) in the pure unfermented sap, that of either glucose or fructose is much less than 1% (w/v) (0.13-0.73% w/v). Raffinose occurs in traces only (0.13-0.35 w/v). These results were derived from our improved methods which eliminate completely, or reduce to a bare minimum, fermentation of the sap during collection. The variation with time of storage of the individual sugars in the sap during fermentation to form palm wine reveals that, as sucrose steadily decreases, fructose reaches a peak at 1.51% (w/v) at the 9th hour, and thereafter declines, while glucose and raffinose remain continuously low; all sugars disappear beyond the 33rd hour. Concomittantly, pH decreases from pH 6.60 at zero time and stabilizes at pH 3.30 after 48 h, while titrable acidity increases continuously up until the 96th hour. These changes account for the variations in the quality of palm wine during storages.

No abstract