Degranulation and histamine release from murine mast cells sensitized with dengue virus-immune sera

Mice were immunized with dengue type 2 virus (DEN 2) under a schedule favoring the production of IgE antibody. The antibody obtained could sensitize peritoneal resident mast cells both in vitro and in vivo so that the sensitized cells were degranulated and released histamine on challenge with the DEN 2 antigen. It was also demonstrated that the antibody was cytophilic and heat-labile. The above observations suggest that the present experimental system can be used to detect anti-DEN 2 IgE antibody in mice.     

Concurrent Bursty Behavior of Social Sensors in Sporting Events

The advent of social media expands our ability to transmit information and connect with others instantly, which enables us to behave as “social sensors.” Here, we studied concurrent bursty behavior of Twitter users during major sporting events to determine their function as social sensors. We show that the degree of concurrent bursts in tweets (posts) and retweets (re-posts) works as a strong indicator of winning or losing a game. More specifically, our simple tweet analysis of Japanese professional baseball games in 2013 revealed that social sensors can immediately react to positive and negative events through bursts of tweets, but that positive events are more likely to induce a subsequent burst of retweets. We confirm that these findings also hold true for tweets related to Major League Baseball games in 2015. Furthermore, we demonstrate active interactions among social sensors by constructing retweet networks during a baseball game. The resulting networks commonly exhibited user clusters depending on the baseball team, with a scale-free connectedness that is indicative of a substantial difference in user popularity as an information source. While previous studies have mainly focused on bursts of tweets as a simple indicator of a real-world event, the temporal correlation between tweets and retweets implies unique aspects of social sensors, offering new insights into human behavior in a highly connected world.     

The flaFIX gene product of Salmonella typhimurium is a flagellar basal body component with a signal peptide for export.

flaFIX, the structural gene for the periplasmic P ring of the flagellar basal body of Salmonella typhimurium, was cloned. Two gene products with apparent molecular weights of 38,000 and 40,000 were identified by minicell analysis. Data from pulse-chase and membrane fractionation experiments and data on the inhibitory effect of the proton ionophore carbonyl cyanide m-chlorophenylhydrazone all indicated that the 40-kilodalton protein was a precursor form which, after export across the cytoplasmic membrane accompanied by cleavage of a signal peptide, gave rise to the mature protein in the periplasm. The N-terminal amino acid sequence of the FlaFIX protein, predicted from the DNA sequence, conformed well to known signal peptide sequences. The results indicate that the P-ring protein of the basal body (unlike flagellin and possible some other external flagellar components) crosses the cytoplasmic membrane in a conventional signal peptide-dependent manner.     

Identification of flagellar hook and basal body gene products (FlaFV, FlaFVI, FlaFVII and FlaFVIII) in Salmonella typhimurium.

The flagellar genes flaFV, flaFVII, and flaFVIII of Salmonella typhimurium were cloned, and their presence on a given plasmid was verified by complementation of Escherichia coli mutants defective in the homologous genes. The gene products were identified by radiolabeling in a minicell system as being proteins of the following molecular masses: FlaFV, 42 kilodaltons (kDa); FlaFVI, 32 kDa; FlaFVII, 30 kDA; and FlaFVIII, 27 kDa. These data, together with isoelectric focusing data, confirm gene product assignments of flagellar components made indirectly from mutant studies. Flagellar components are transported by either a signal peptide-dependent or a flagellar-specific pathway. Consistent with its location in the outer membrane ring of the basal body, protein FlaFVIII seems to use the signal peptide-dependent pathway, since it was synthesized in a precursor form and processed, presumably by peptide cleavage, to a mature form; the maturation process was inhibited by addition of a proton ionophore. Proteins synthesized in minicells were localized as follows: FlaFVI was localized to the soluble fraction (cytoplasm); pre-FlaFVIII and FlaFVIII were localized to the particulate fraction (membrane or high-molecular-weight aggregate); FlaFV and FlaFVII were localized to both fractions. The significance of these locations in terms of known or suspected roles in the flagellar apparatus is discussed.     

Characteristics of secondary flow in steady and pulsatile flows through a symmetrical bifurcation

Steady and pulsatile flow in a glass model simulating an arterial bifurcation was investigated by flow visualization techniques. Secondary flow generated at the bifurcation has a similar pattern to a vortex, called the horseshoe vortex, produced around a wall-based protuberance in a circular tube. The same flow disturbance was clearly observed during the decelerating phase of pulsatile flow. The vortex produces a stagnation point on the top and bottom wall just upstream from the bifurcation apex. When aluminium dust was suspended in the test fluid perfusing the blood vessel model, particles deposited over an area spreading from the stagnation point to the lateral corners of the bifurcation. Comparison between the present results and topographical patterns of atherosclerosis reported in the literature suggests that it is in such low shear regions that lipid deposition tends to occur most.     

Protection of mice against Sendai virus pneumonia by non-neutralizing anti-F monoclonal antibodies

Nine monoclonal antibodies (MAbs) directed to F protein of Sendai virus were obtained and characterized for their protective ability against Sendai virus infection in mice. None of the MAbs showed hemagglutination-inhibition (HI), hemolysis-inhibition (HLI), or neutralization (NT) activities in vitro when assayed by standard methods. Some of the MAbs, however, showed complement-requiring NT (C-NT) and complement-requiring hemolysis (C-HL) activities when assayed in the presence of complement. Passive immunization experiments revealed that the MAbs with higher C-NT and C-HL activities showed protective activity against Sendai virus pneumonia in mice, and that some MAbs with IgG1 isotype having neither C-NT nor C-HL activity also showed the protective activity. Digestion of the MAbs with pepsin which split immunoglobulin molecules into F(ab')2 and Fc fragments greatly suppressed the protective activity. These results suggest that not only complement-mediated immunological responses such as immune virolysis but also antibody-dependent cellular cytotoxicity (ADCC) and/or immune phagocytosis, in which complement system is not necessarily involved, play an important role in the protection of mice from Sendai virus infection.     

Correlation between the virulence ofFrancisella tularensis in experimental mice and its acriflavine reaction

Correlation between the virulence of Francisella tularensis in experimental mice and its acriflavine reaction was studied. The cultures derived from all four strains (Ebina, CMB2, Schu, and N9) that had long been subcultured on agar media yielded two types of colonies, i.e., acriflavine reaction-positive (acf+) and acriflavine reaction-negative (acf-) colonies. All acf+ colonies, regardless of their parent strains, were shown to be low virulent in mice. Acf- colonies were shown to be either high (Ebina, CMB2) or low (Schu, N9) virulent. The low-virulent acf- colonies gained virulence during several passages in mice, whereas the acf+ colonies remained low virulent even after the animal passages.     

Inhibition of ATPase Activity in Pea Plasma Membranes In Situ by a Suppressor from a Pea Pathogen, Mycosphaerella pinodes

A pathogenic fungus of pea, Mycosphaerella pinodes, secretesa so-called "suppressor" in its pycnospore germination fluid.The suppressor blocks the defense responses and induces localsusceptibility (accessibility) in pea plants to agents thatare not pathogenic in pea. The suppressor nonspecifically inhibitsthe ATPase activity in plasma membranes prepared from pea, soybean,kidney bean, cowpea and barley plants. However, cytochemicalstudies by electron microscopy indicate that the suppressorspecifically inhibits the ATPase in pea cell membranes, butnot in those of four other plant species tested. That is, thespecificity of the suppressor appears at the cell and/or tissuelevel, but is not evident in vitro. Furthermore, the inhibitoryeffect of the suppressor is temporary because the ATPase activityrecovers 9 h after the treatment. A similar effect was observedafter inoculation with M. pinodes but not with a nonpathogenof pea, M. ligulicola. The role of the suppressor in host-parasitespecificity is discussed. (Received April 9, 1991; Accepted August 6, 1991)