Ant assemblage composition explains high predation pressure on artificial caterpillars during early night

1. Predator–prey interactions, especially those involving herbivorous insects, are of great importance in maintaining biodiversity. Predation pressure varies temporally in response to prey availability and activity. However, little is known about the patterns and drivers of fluctuations in predation pressure at fine temporal scales. 2. Artificial caterpillars (placed on plant leaves at breast height) were used to assess changes in predation pressure across four time intervals of the day in a monsoonal tropical rainforest in south-west China. The study examined how assemblage composition of arboreal ants, the dominant predators, changed across the same time intervals. The potential linkages between biotic (arboreal ants) and abiotic (temperature and light intensity) factors with predation rate were evaluated. 3. Predation rate on caterpillars during the early part of the night (19.00–01.00 hours) was significantly higher than in the morning, afternoon, or late night. Ant assemblage composition, rather than species richness or total abundance, best explained the variations in predation rate on artificial caterpillars. 4. The results help to strengthen understanding of trophic interactions by demonstrating that predation pressure fluctuates at finer timescales than previously tested, and that a particular set of ant species may play major roles in predation on caterpillars and possibly other organisms.     

MicroRNA-351 Regulates Two-Types of Cell Death,Necrosis and Apoptosis,Induced by 5-fluoro-2'-deoxyuridine

Cell-death can be necrosis and apoptosis. We are investigating the mechanisms regulating the cell death that occurs on treatment of mouse cancer cell-line FM3A with antitumor 5-fluoro-2''-deoxyuridine (FUdR): necrosis occurs for the original clone F28-7, and apoptosis for its variant F28-7-A. Here we report that a microRNA (miR-351) regulates the cell death pattern. The miR-351 is expressed strongly in F28-7-A but only weakly in F28-7. Induction of a higher expression of miR-351 in F28-7 by transfecting an miRNA mimic into F28-7 resulted in a change of the death mode; necrosis to apoptosis. Furthermore, transfection of an miR-351 inhibitor into F28-7-A resulted in the morphology change, apoptosis to necrosis, in this death-by-FUdR. Possible mechanism involving lamin B1 in this miR-351’s regulatory action is discussed.     

The importance of chemical environmental cues for juvenile Lethrinus nebulosus Forsskål (Lethrinidae, Teleostei) when settling into their first benthic habitat

A commercially important coral-reef fish, the spangled emperor Lethrinus nebulosus, settles into seagrass beds at the end of its pelagic larval phase, but the mechanism for locating these beds is unknown. To investigate this mechanism we first used a wide-choice, ex situ setup to examine the ability of captivity-reared naïve L. nebulosus settlers to select their first benthic habitat by reference to chemical cues. Second, we examined the morphology and ultrastructure of the nasal olfactory organ in settling L. nebulosus juveniles. We obtained the first evidence of a tropical seagrass-settling coral reef fish that can use chemical environmental cues in selecting its first benthic habitat at ranges up to at least 2 m. The L. nebulosus settlers exhibited a well developed pair of nasal olfactory organs, positioned in nares on the dorsal side of the head. These organs were elliptical radial rosettes, one in each of the olfactory chambers, and each comprised 12 lamellae, six on each side of a midline raphe, which were totally covered with sensory and non-sensory cilia, except for the margins. This type of cilia distribution is thought to indicate an acute sense of smell. The olfactory epithelium contained mature and immature ciliated receptor neurons bearing three to five cilia, and a second type of receptor neuron bearing six to eight microvilli.     

Aggregatibacter actinomycetemcomitans induces detachment and death of human gingival epithelial cells and fibroblasts via elastase release following leukotoxin‐dependent neutrophil lysis

Aggregatibacter actinomycetemcomitans is considered to be associated with periodontitis. Leukotoxin (LtxA), which destroys leukocytes in humans, is one of this bacterium's major virulence factors. Amounts of neutrophil elastase (NE), which is normally localized in the cytoplasm of neutrophils, are reportedly increased in the saliva of patients with periodontitis. However, the mechanism by which NE is released from human neutrophils and the role of NE in periodontitis is unclear. In the present study, it was hypothesized that LtxA induces NE release from human neutrophils, which subsequently causes the breakdown of periodontal tissues. LtxA‐treatment did not induce significant cytotoxicity against human gingival epithelial cells (HGECs) or human gingival fibroblasts (HGFs). However, it did induce significant cytotoxicity against human neutrophils, leading to NE release. Furthermore, NE and the supernatant from LtxA‐treated human neutrophils induced detachment and death of HGECs and HGFs, these effects being inhibited by administration of an NE inhibitor, sivelestat. The present results suggest that LtxA mediates human neutrophil lysis and induces the subsequent release of NE, which eventually results in detachment and death of HGECs and HGFs. Thus, LtxA‐induced release of NE could cause breakdown of periodontal tissue and thereby exacerbate periodontitis.     

Regulation of angiotensin converting enzyme activity in cultured human vascular endothelial cells

Angiotensin converting enzyme (ACE) of vascular endothelial cells is suggested to control vascular wall tonus through the conversion of angiotensin I (AI) to angiotensin II (AII) and the degradation of bradykinin. To obtain more insight into the pathophysiological significance of ACE of vascular endothelial cells, we studied the regulation of ACE produced by cultured human umbilical vein endothelial cells (EC). Phorbol 12-myristate 13-acetate (PMA) increased the cellular and medium ACE activity, accompanied by a marked morphological change in EC. N'-O'-dibutylyladenosine 3';5'-cyclic monophosphate (db-cAMP) increased only the cellular ACE activity and not the medium ACE activity. The effect of isoproterenol with 0.1mM theophylline mimicked that of db-cAMP. These findings suggest that PMA and cAMP-related agents participate in the control of vascular wall tonus through the positive regulation of ACE produced by vascular endothelial cells.     

The AtXTH28 Gene, a Xyloglucan Endotransglucosylase/Hydrolase, is Involved in Automatic Self-Pollination in Arabidopsis thaliana

Successful automatic self-pollination in flowering plants isdependent on the correct development of reproductive organs.In the stamen, the appropriate growth of the filament, whichlargely depends on the mechanical properties of the cell wall,is required to position the anther correctly close to the stigmaat the pollination stage. Xyloglucan endotransglucosylase/hydrolases(XTHs) are a family of enzymes that mediate the constructionand restructuring of xyloglucan cross-links, thereby controllingthe extensibility or mechanical properties of the cell wallin a wide variety of plant tissues. Our reverse genetic analysishas revealed that a loss-of-function mutation of an ArabidopsisXTH family gene, AtXTH28, led to a decrease in capability forself-pollination, probably due to inhibition of stamen filamentgrowth. Our results also suggest that the role of AtXTH28 inthe development of the stamen is not functionally redundantwith its closest paralog, AtXTH27. Thus, our finding indicatesthat AtXTH28 is specifically involved in the growth of stamenfilaments, and is required for successful automatic self-pollinationin certain flowers in Arabidopsis thaliana.     

Enhancement of the growth of human osteosarcoma cells by human interferon-gamma.

It is well known that interferons inhibit cell growth. However, we found that human interferon-gamma (HuIFN-gamma) enhanced the growth of human osteosarcoma cells, HOS-Y1 cells, in a dose-dependent manner. This enhancing effect was found only under the following conditions: when the cells were precultured for 2 or 3 days and then treated with HuIFN-gamma for 2, 3, or 4 days, and when the cells were seeded at a density of 1,000 or 2,000 cells/well. The degree of enhancement of cell growth was maximum when the cells were precultured at a density of 1,000 cells/well for 3 days and then treated with HuIFN-gamma for 2 days. The enhancing effect of HuIFN-gamma disappeared in the presence of anti-HuIFN-gamma antibody. In addition, it was found that the conditioned medium from HOS-Y1 cells enhanced the growth of HOS-Y1 cells, and that the conditioned medium from HOS-Y1 cells cultured with HuIFN-gamma enhanced the cell growth more than that from cells cultured without HuIFN-gamma. Epidermal growth factor (EGF), acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF), and transforming growth factor-beta 1(TGF-beta 1) did not enhance the growth of HOS-Y1 cells. These results suggest that HuIFN-gamma enhanced the cell growth by augmenting the production of unknown growth factor(s) in HOS-Y1 cells via an autocrine mechanism.     

Immunogenic dialyzable factor derived from a ribosomal fraction of Salmonella typhimurium III. Analysis of resistance induced by dialyzable factors

Dialyzable factors (DF) were prepared from ribosomal fractions of several organisms including rough mutants of Salmonella typhimurium LT2, salmonella species of different serogroups, other enteric bacteria and gram-positive organisms, and tested for their immunogenicity against S. typhimurium infection in mice. All of them conferred local resistance on mice challenged intramuscularly with S. typhimurium LT2 in the early stage of immunization before the establishment of delayed-type hypersensitivity (DTH) to salmonella antigens. Although DFs of enteric bacteria including rough mutants of S. typhimurium induced DTH to salmonella antigens, only DF of a two-heptose mutant of S. typhimurium LT2 afforded significant mouse protection but others only prolonged the mean time to death. DF of Listeria monocytogenes induced the cross-reacting immunity which afforded the low level of mouse protection as well as an increase in mean time to death without inducing DTH. Passive transfer of anti-O antibody did not enhance the mouse protection provided by each DF. Resistance conferred by DF of S. typhimurium LT2 consisted of two phases: (i) nonspecific macrophage activation resulting in reduction of organisms at the infected site, which became active in the early stage of immunization and (ii) salmonella-specific immunity capable of preventing systemic infection, which became active in the late stage of immunization.     

Changes in Lysozyme due to Interaction with Vaporized Hexanal

In order to elucidate the mechanism of the alteration of proteins induced by vaporized aldehydes, unmodified and chemically-modified lysozymes were exposed in the solid state to vaporized hexanal at 50°C and 5.8 or 75% relative humidity (RH). On exposure at 75%RH, the unmodified lysozyme exhibited polymerization, browning, loss of solubility, fluorescence production and impairment of lysine, tryptophan and methionine residues. Methionine residues seemed to be oxidized to methionine sulfoxide residues. The polymerization did not proceed at 5.8RH. All the above alterations were almost completely prevented by the removal of oxygen from the reaction cells. Acetylation of lysozyme retarded these alterations fairly well except that the impairment of tryptophan residues was unaffected.

On the basis of all the results it is suggested that at the first step the concerned reaction essentially requires hexanal derivatives such as peroxyhexanoic acid and/or related radicals induced through the reaction with oxygen. The second step seems to consist at least of two routes which are independent of each other and require water. One route is assumed to be an amino-carbonyl reaction involving lysine residues. The other route seems responsible for the attack on tryptophan and methionine residues through oxidation involving the radicals.