Toxin profiles of Vibrio cholerae non-O1 from environmental sources in Calcutta, India.

A collection of Vibrio cholerae non-O1 isolated from the aquatic environs of Calcutta, a cholera-hyperendemic area, were examined for the production of cholera toxin (CT), Shiga-like toxins (Vero toxins), heat-stable enterotoxin, and hemolysins. Two (0.5%) V. cholerae non-O1 isolates produced CT. The DNA from both these isolates also hybridized with a DNA probe containing sequences encoding the A subunit of CT. None of the strains produced Shiga-like toxins or heat-stable enterotoxin. Hemolytic activity was observed in 89.7% of the strains, of which 36.1% exhibited biological activity in the suckling mouse. However, none of them produced a hemolysin that cross-reacted with the thermostable direct hemolysin of Vibrio parahaemolyticus. It appears from this study that a small percentage of environmental V. cholerae non-O1 strains do possess the potential for causing cholera-like diarrhea.     

Oligomycin-insensitive incorporation of 32P into chloroplast protein by illumination

³²P incorporation into the protein fraction of chloroplast fragmentsby short illumination was investigated under various phosphorylatingconditions. ³²P incorporation was generally accompanied by cyclic and non-cyclicphotophosphorylations and also by formation of a high energyintermediate "X_E". However, the addition of a DPIP-ascorbatecouple caused inhibition of ³²P incorporation, while ATP formationproceeded. Effects of inhibitors and uncouplers of photophosphorylationon the formation of protein-bound ³²P were generally similarto those on ATP formation. AT³²P was not utilized for protein-bound ³²P formation in thedark by chloroplast fragments, but its radioactivity was transferredinto the chloroplast protein fraction in the light. Oligomycininhibited ATP formation but did not inhibit protein-bound ³²Pformation. m-Cl-CCP blocked both reactions. This suggests thatprotein-bound ³²P is not an actual intermediate in the phosphorylativeprocess leading to formation of ATP. It is probably formed ona side pathway from an intermediate of ATP formation. Analyses of protein-bound ³²P after digestion with proteaseand lipase showed that the ³²P incorporated was bound to peptidesin chloroplast lamellae. The possible form of this bound ³²Pis discussed. (Received November 22, 1971; )     

Electron transfer and energy dependent reactions in glutaraldehyde-fixed chloroplasts

The effects of GA fixation on electron transfers in photosystemsI and II in photosynthesis and energy dependent reactions ofchloroplasts, such as changes in light scattering, H⁺ uptakeand 515-nm absorbance, were investigated. Fixation of chloroplastswith GA resulted in a lowering of the DCIP and MV photoreductions.DCIP photoreduction activity in fixed chloroplasts was not restoredin the presence of DPC, an electron donor to photosystem II,but was significantly stimulated by DPC when chloroplasts werefixed after aging. The results suggest that the inhibitory effectof GA fixation on photosystem II differs in its mechanism fromthose of treatments such as heating, Tris-washing and aging.The oxidation-reduction reaction of P700 was depressed by GAfixation. Energy dependent reactions in fixed chloroplasts were more markedlydepressed than were electron transfers. Fixed chloroplasts showeda slight conformational response in the presence of PMS. Analysis of the emission spectrum and the induction of chlorophylla fluorescence in fixed chloroplasts suggested that the twopigment systems were partially disordered and that the correspondingprimary photochemical processes were inhibited. (Received November 21, 1972; )     

Prostaglandins antagonize fibroblast proliferation stimulated by tumor necrosis factor

Tumor necrosis factor (TNF) is known to be a mitogen for human diploid FS-4 fibroblasts. We have shown in an earlier study (Hori et al. (1989) J. Cell. Physiol. 141, 275-280) that indomethacin further enhances the cell proliferation stimulated by TNF. Since indomethacin inhibits the activity of cyclooxygenase, the role of prostaglandins in TNF-stimulated cell growth was examined. Cell growth stimulated by TNF and indomethacin was inhibited by exogenously added prostaglandins (PGE2, PGF2 alpha, and PGD2), among which PGE2 caused the greatest inhibition of cell growth. Treatment of FS-4 cells with 10 ng/ml TNF resulted in the release of prostaglandins (PGE2, 6-keto-PGF1 alpha, PGA2, PGD2, and PGF2 alpha) 2 to 4 fold over that of untreated cells. The amount of all these prostaglandins increased in a time-dependent manner over 6 h after treatment. In both TNF-treated and control cells, PGE2 was released as the predominant prostaglandin. Furthermore, when PGE2 production and DNA synthesis were determined in FS-4 cells treated with increasing doses of indomethacin, these two cellular responses were inversely affected by indomethacin. These data show that prostaglandins induced by TNF antagonize growth stimulatory action of TNF.     

Adsorption of gamma-globulin, a model protein for antibody, on colloidal particles

The effect of surface properties on the adsorption of bovine gamma-globulin, a model protein for antibody, was studied. Polystyrene latex (PS), hydrophilic copolymer lattices of styrene/2-hydroxyethyl methacrylate [P(S/HEMA)], styrene/ methacrylic acid [P(S/MAA)] and methyl methacrylate/ 2-hydroxyethyl methacrylate [P(MMA/HEMA)], and colloidal silica were used. The adsorption isotherms of gamma-globulin on these colloidal particles were measured as a function of pH and ionic strength. The hydrophilic particles showed low affinities for gamma-globulin at alkaline pH, while PS showed high affinities for gamma-globulin over the whole range of pH and ionic strength. The gamma-globulin adsorption on hydrophilic particles was highly reversible with respect to the pH and ionic strength compared with that on PS. These differences indicate that the dominant driving forces of adsorption are related to the hydrophilicity of particles. The adsorption isotherms of all colloidal particles showed the plateau values, and the order of maximum values of plateau adsorption was P(S/MAA) > PS or P(S/HEMA), silica > P(MMA/HEMA). Thus, they were also affected by the charged groups and the hydrophilicity of the surfaces. On the other hand, the plateau values of all colloidal particles were more or less symmetrical with a maximum at around the isoelectric point of gamma-globulin at an ionic strength of 0.01. This behavior is attributed to the important role of the lateral interaction between the adsorbed molecules at low ionic strength.     

Requirement of the conformational stability of a Salmonella ribosomal vaccine for its mouse protection

The 43-kDa non-O antigenic component isolated from the crude ribosomal fraction of Salmonella typhimurium [9] was further purified by affinity chromatography (43-kDa protein: 43-kDp). Immunization with 43-kDp did not induce complete mouse protection in CF1 mice to 500 LD50 of S. typhimurium, although it elicited a substantial IgG antibody response. The 43-kDp exhibited the mitogenicity to splenocytes (CF1 and C3H/HeJ) and B cell-rich populations (CF1). Complexing 43-kDp with the compact ribosomes of Streptococcus pyogenes by formaldehyde (complex vaccine: CV) elicited both IgM and IgG antibodies to 43-kDp. CV induced a boosting effect to enhance IgG antibody response. Moreover, CV generated delayed-type hypersensitivity to salmonella antigens and also conferred complete protection against 500 LD50 challenge of S. typhimurium to CF1 mice. These abilities of CV were reduced or impaired by RNase digestion. CV was able to induce partial or complete protection in inbred mouse strains (C3H/HeN, C3H/HeJ, DBA/2 and A/J). These data, in addition to other reports, suggest that conformational stability between ribosomes and contaminating substances such as 43-kDp or O-antigens might be required for the overall effects of the ribosomal vaccine.     

Hormonal regulation of soluble immune response suppressor (SIRS): a possible role of SIRS in the maintenance of pregnancy

This study was conducted to investigate the effects of sex hormones upon the nature of soluble immune response suppressor (SIRS) produced by concanavalin A-stimulated Lyt-2+ T cells. Conventional SIRS affected IgM PFC only. However, SIRS made with progesterone (20-400 ng/ml or Prog-SIRS) suppressed IgM PFC, one-way MLR, and generation CTL; and SIRS made with estrogen (0.2-50 ng/ml or Est-SIRS) enhanced these responses. The factor(s) (MW 40,000-55,000) to stimulate macrophages to produce the second soluble factor (M phi-SF) was isolated from all preparations by gel filtration. Furthermore, Est-SIRS contained a factor(s) (MW 10,000-30,000) to enhance IgM PFC, MLR, and mitogen-induced blastogenesis of both T and B cells; and Prog-SIRS possessed the suppressive factor(s) to IgM PFC, MLR, and mitogen-induced T-cell proliferation. These activities were not impaired by 2-mercaptoethanol. Moreover, the suppressive activity of Prog-SIRS was completely absorbed by T cells only, but the enhancing activity of Est-SIRS was not completely absorbed by a single-cell population. These data suggest that progesterone can contribute to the suppression of allograft rejection through soluble factors, and estrogen can enhance host responses which may be affected by several soluble factors during pregnancy.     

Suppression of Pisatin Production and ATPase Activity in Pea Plasma Membranes by Orthovanadate, Verapamil and a Suppressor from Mycosphaerella pinodes

A pea pathogen, Mycosphaerella pinodes, secretes both an elicitorand a suppressor for the accumulation of pisatin, a major phytoalexinof pea, into the spore germination fluid. The effects of theelicitor and the suppressor on the ATPase activity in pea plasmamembranes was examined. The ATPase was sensitive to orthovanadateand dicyclohexylcarbodiimide but insensitive to nitrate andazide; it was unaffected by the elicitor but was markedly inhibitedby the suppressor (50µg.ml^–1, bovine serum albuminequivalents) or verapamil (1OOµM). The accumulation ofpisatin induced by the elicitor was delayed for 3 to 6 h inthe presence of orthovanadate or verapamil to an extent similarto that in the presence of the suppressor. The relationshipbetween the inhibition of plasma membrane ATPase activity andthe suppression of the active defense reaction that involvesthe production of pisatin in the pea plant is discussed. (Received April 16, 1990; Accepted September 6, 1990)     

Exogenous nitric oxide donor and arginine provide protection against short-term drought stress in wheat seedlings

Nitric oxide (NO) is an important plant signaling molecule that has a vital role in abiotic stress tolerance. In the present study, we assessed drought-induced (15 and 30% PEG, polyethylene glycol) damage in wheat (Triticum aestivum L. cv. Prodip) seedlings and mitigation by the synergistic effect of exogenous Arg (0.5 mM l-Arginine) and an NO donor (0.5 mM sodium nitroprusside, SNP). Drought stress sharply decreased the leaf relative water content (RWC) but markedly increased the proline (Pro) content in wheat seedlings. Drought stress caused overproduction of reactive oxygen species (ROS) and methylglyoxal (MG) due to the inefficiency of antioxidant enzymes, the glyoxalase system, and the ascorbate-glutathione pool. However, supplementation with the NO donor and Arg enhanced the antioxidant defense system (both non-enzymatic and enzymatic components) in drought-stressed seedlings. Application of the NO donor and Arg also enhanced the glyoxalase system and reduced the MG content by increasing the activities of the glyoxalase system enzymes (Gly I and Gly II), which restored the leaf RWC and further increased the Pro content under drought stress conditions. Exogenous NO donor and Arg application enhanced the endogenous NO content, which positively regulated the antioxidant system and reduced ROS production. Thus, the present study reveals the crucial roles of Arg and NO in enhancing drought stress tolerance in wheat seedlings by upgrading their water status and reducing oxidative stress and MG toxicity.