Summary. Cholera toxin (CT) and prostaglandin E, (PGE,) increased the synthesis of 3',5'-cyclic adenosine monophosphate (CAMP) in rabbit intestinal mucosa, which appeared to be responsible for inducing the release of 5-hydroxytryptamine (5-HT) from enterochromaffin cells into the intestinal lumen. With isolated intestinal cells, CT induced the synthesis of PGE, more efficiently from epithelial cells than from lamina propria cells ; however, the basal amount of this eicosanoid produced by lamina propria cells was approximately six-fold more than that formed by the epithelial cells. The CT-induced stimulation of arachidonate metabolism appeared to be generalised in nature, as PGF,, and leukotrienes were synthesised in addition to PGE,. Injection of dibutyryl cAMP into the intestinal lumen in viuo markedly reduced both basal levels of PGE,, as well as CT-induced levels of PGE,, released into the luminal fluid. Similarly, when biopsy samples of tissue from rabbit intestinal loops, challenged in vivo with dibutyryl CAMP, were washed and incubated in vitro, the amount of PGE, synthesis remained below basal levels. In contrast, when biopsy samples of normal small intestinal tissue were exposed in vitro to dibutyryl CAMP, PGE, synthesis increased. Thus, cAMP appeared to down-regulate the levels of intestinal eicosanoids in vivo, despite its innate capacity to evoke PGE, synthesis from mucosal tissue in vitro. Thus, the data indicate that CT-induced mediators exhibit interactive effects that alter their cellular concentrations, that in turn could affect the biological responses.

Basic fibroblast growth factor (bFGF) has shown a neuroirophic effect in the neurons of several CNS areas. In vivo, it contributes to restore neurochcmical and morphological deficits in different rodent models of brain damage, including rats with brain damage induced by hypoxia/ischemia when FGF was intramuscularly (i.m.) administered. Toxicological and immunological studies performed in rats, mice and volunteers showed no evidence of side‐effects. Bovine FGF was i.m. administered in children with mental retardation caused by perinatal hypoxia, aged 1–15 years, at dosages of 0–4 or 0–28 μ.g kg−1, once or twice a month, over 7–12 months. Group A [n= 12; 6 treated (T), 6 controls (Ct)], group B (n= 16; 8 T, 8 Ct) and group C (n = 67; 45 T, 22 Ct) were evaluated with the P. A. R. scale, the WISC‐RM and the Gesell scale, respectively. Development increased significantly in treated children from groups A (P < 0.02) and C (P < 0.001), and IQrose by more than 10 points (P < 0.001) in group B patients.

Cholera toxin (CT) increases intestinal secretion of water and electrolytes and modulates the mucosal immune response by stimulating cellular synthesis of arachidonic acid (AA) metabolites (e.g., prostaglandin E2), as well as the intracellular second messenger cyclic AMP (cAMP). While much is known about the mechanism of CT stimulation of adenylate cyclase, the toxin’s activation of phospholipase A2, which results in increased hydrolysis of AA from membrane phospholipids, is not well understood. To determine whether CT activation of AA metabolism requires CT’s known enzymatic activity (i.e., ADP-ribosylation of GSα), we used native CT and a mutant CT protein (CT-2*) lacking ADP-ribose transferase activity in combination with S49 wild-type (WT) and S49 cyc− murine Theta (Th)1.2-positive lymphoma cells deficient in GSα. The experimental results showed that native CT stimulated the release of [3H[AA from S49 cyc− cells at a level similar to that for S49 WT cells, indicating that GSα is not essential for this process. Further, levels of cAMP in the CT-treated cyc− cells remained the same as those in the untreated control cells. The ADP-ribosyltransferase-deficient CT-2* protein, which was incapable of increasing synthesis of cAMP, displayed about the same capacity as CT to evoke the release of [3H]AA metabolites from both S49 WT and cyc− cells. We concluded that stimulation of arachidonate metabolism in S49 murine lymphoma cells by native CT does not require enzymatically functional CT, capable of catalyzing the ADP-ribosylation reaction. These results demonstrated for the first time that stimulation of adenylate cyclase by CT and stimulation of AA metabolism by CT are not necessarily coregulated. In addition, the B subunits purified from native CT and CT-2* both simulated the release of [3H]AA from S49 cyc− cells and murine monocyte/macrophage cells (RAW 264.7), suggesting a receptor-mediated cell activation process of potential importance in enhancing immune responses to vaccine components.

Each year cholera epidemics occur in various places around the world. Though there is no effective vaccine against cholera, people who recover from an infection usually have prolonged immunity to the disease. Sera from convalescent patients contain antibodies to a number of outer membrane proteins (OMPs) of V. cholerae. We isolated several OMPs (43, 42, 30, and 22 kDa) from V. cholerae V86 E1 Tor Inaba, sequenced their amino-termini, and generated hyperimmune sera against them in rabbits. Antisera to the 43-, 42-, and 22-kDa OMPs, but not the preimmune sera, significantly reduced V. cholerae-induced fluid secretion seen in rabbit intestinal loops challenged with the homologous strain. In addition, a combination of antisera to the different OMPs reduced the fluid secretion induced by challenge with heterologous V. cholerae Ogawa and O139 strains. These results have significance in the development of vaccines to V. cholerae, as the hyperexpression of these OMP encoding genes in vaccine strains may improve the efficacy of cholera vaccines.