Legionella natural biofilms and their role in epidemiology of the infection: methods of study and modelling

Ability of Legionella species to form biofilms in association with other microorganisms is the key factor of their spreading in potentially dangerous water systems. Ability of different strains of Legionella to form monospecies biofilms as well as biofilms in association with Pseudomonas aeruginosa in constant conditions was analyzed. It was shown that ability of Legionella strains to form monospecies biofilms correlates with their ability to persist in biofilms formed by P. aeruginosa.     

Nitric oxide-induced membrane tubulovesicular extensions (cytonemes) of human neutrophils catch and hold Salmonella enterica serovar Typhimurium at a distance from the cell surface

Nitric oxide (NO) plays an important role in host defense against bacterial infections such as salmonellosis. NO and 4-bromophenacyl bromide (BPB) induce the formation of long tubulovesicular extensions (TVE, cytonemes, membrane tethers) from human neutrophils. These TVE serve as cellular sensory and adhesive organelles. In the present study, we demonstrated that in the presence of the NO donor, diethylamine NONOate or BPB human neutrophils bound and aggregated Salmonella enterica serovar Typhimurium bacteria extracellularly by TVE. In contrast, inhibition of NO-synthase activity by N ^ω-nitro- l -arginine methyl ester stimulated neutrophil phagocytosis (ingestion) of bacteria. Neutrophil TVE consisted of membrane-covered cytoplasm as was shown by the fluorescent cytoplasmic dye 2',7'-bis(2carboxyethyl)-5,(6)-carboxyfluorescein, and the fluorescent lipid, BODIPY-labeled sulfatide. Disruption and shedding of TVE were accompanied by the appearance of specific invaginations (porosomes) on neutrophil cell bodies. These invaginations corresponded to the variations in diameter of TVE (160–240 nm). We hypothesized that TVE represented protrusions of neutrophil exocytotic trafficking through special structures on the neutrophil surface. In conclusion, we propose a novel mechanism by which NO-induced TVE formation enables neutrophils to bind and aggregate bacteria at a distance.     

Rice resistance to blast caused by leaf surface moistening prior to inoculation

Effect of water droplets placed onto rice (Oryza sativa L.) leaves before inoculation with blast fungus Magnaporthe grisea (Hebert) Barr on disease severity and superoxide radical generation by the leaves was investigated. The leaves were inoculated by placement of spore suspension droplets. One day before, droplets of distilled water were placed to the same sites as an inoculum. It was found, that such a pretreatment decreased frequency of susceptible-type lesions by 2 to 2.5 times and increased that of symptomless outcome by 1.5 times in comparison with the nontreated control. Besides, the pretreatment enhanced superoxide radical generation in diffusates of healthy leaves of susceptible cultivar and in diffusates of infected leaves of resistant cultivar one day post inoculation. It is suggested that water contacting with the leaf surface for a rather long time washes out from its cells compounds possessing properties of plant endogenous elicitors. The latter induce superoxide radical formation by plants and, as a consequence, their disease resistance. This may be interpreted as plant adaptation to high humidity, which usually favors infections.     

Exit of GPI‐Anchored Proteins from the ER Differs in Yeast and Mammalian Cells

Previous studies have shown that yeast glycosylphosphatidylinositol‐anchored proteins (GPI‐APs) and other secretory proteins are preferentially incorporated into distinct coat protein II (COPII) vesicle populations for their transport from the endoplasmic reticulum (ER) to the Golgi apparatus, and that incorporation of yeast GPI‐APs into COPII vesicles requires specific lipid interactions. We compared the ER exit mechanism and segregation of GPI‐APs from other secretory proteins in mammalian and yeast cells. We find that, unlike yeast, ER‐to‐Golgi transport of GPI‐APs in mammalian cells does not depend on sphingolipid synthesis. Whereas ER exit of GPI‐APs is tightly dependent on Sar1 in mammalian cells, it is much less so in yeast. Furthermore, in mammalian cells, GPI‐APs and other secretory proteins are not segregated upon COPII vesicle formation, in contrast to the remarkable segregation seen in yeast. These findings suggest that GPI‐APs use different mechanisms to concentrate in COPII vesicles in the two organisms, and the difference might explain their propensity to segregate from other secretory proteins upon ER exit.     

Changes in the chromatin structure of lymphoid cells under the influence of low-intensity extremely high-frequency electromagnetic radiation against the background of inflammatory process

Using the alkaline single cell gel electrophoresis technique (comet assay), changes in chromatin structure of peripheral blood leukocytes and peritoneal neutrophils have been studied in mice exposed to low-intensity extremely high-frequency electromagnetic radiation (42.2 GHz, 0.1 mW/cm2, 20 min at 1 h after induction of inflammation) against the background of the systemic inflammatory process. It was revealed that the exposure of mice with the developing inflammation leads to a pronounced decrease in the level of DNA damage to peripheral blood leukocytes and peritoneal neutrophils. It is supposed that the changes in the chromatin structure of lymphoid cells have a genoprotective character in the inflammatory process and can underlie the mechanisms of realization of antiinflammatory effects of the electromagnetic radiation.     

Immunohistochemical investigation of Bcl-2 and p53 levels in rat hypothalamus after sleep deprivation

On Wistar rats in view of electrophysiological parameters after sleep deprivation (SD; awake by gentle handling method) and the subsequent postdeprivative sleep (PDS) immunohistochemical investigation of Bcl-2 and p53 peptides optical density levels in neurons of paraventricular (PVN), supraoptic (SON) and median (MnPN) hypothalamus nuclei was carried out. The Bcl-2 was increased in all nuclei both after SD and PDS. The level of p53 was increased in PVN and SON after SD and PDS, but in MnPN only on PDS. Any morphological attributes of apoptosis in the nuclei was not revealed. Obtained data testify an active role of p53 and Bcl-2 peptides in regulation of neuronal activity in hypothalamus at change of a cycle wakefulness-sleep.     

Absorption of 241Am in the gastrointestinal tract

In experiments with rats a study was made of a number of factors influencing the resorption of 241Am from the gastrointestinal tract (GIT). The resorption of 241Am from GIT was found to be 120-245 times more intensive in neonatal rats, during the first 21 days after birth (a milk diet), than in adult animals. A milk diet for adult rats produced a 5-fold increase in the resorption of 241Am from GIT. The additional administration of digestive enzymes, as a homogenate from pancreas and small intestine, produced a 7--9-fold increase in the rate of 241Am resorption from GIT.     

Effect of temperature on thrombin- and trypsin-catalyzed hydrolysis of synthetic substrates

A comparative analysis of the temperature effect on the thrombin- and trypsin-catalyzed hydrolysis of synthetic substrates which are derivatives of A(alpha)-chain of fibrinogen has been carried out. The substrates have general formula: Tos-P2-Arg-OCH3 and Tos-P3-P2-Arg-OCH3, where P2-Gly, Val, MeVal; P3 = Gly, Sar. The activation parameters delta G not equal to, delta H not equal to and delta S not equal to are determined. Thrombin is shown to split the most effectively tripeptide containing amino acids sequence Gly-Gly at the subsites of P3 and P2. It is suggested to be caused by an ability of the above compound to take a bent conformation at the active site of thrombin.     

Peculiarities of Leukocytic Formula of Peripheral Blood of Green Frogs under Conditions of Anthropogenic Load

Changes of the total number of leucocytes and the leucocytic formula of peripheral blood were studied and stability of development was evaluated by the indicator of fluctuating asymmetry of populations of green frogs Rana lessonae Cam. and Rana ridibunda Pall. inhabiting city reservoirs of Nizhni Novgorod and the Nizhegorodskaya Province. The revealed changes in the amphibians white blood depending on the degree of anthropogenic effects in the studied reservoirs can be divided into two types. In the first type (the level of stability of development of populations is 2 scores according to Zakharov) there were revealed neutropenia, increased content of eosinophils, and total leucopenia. In the second type, a more intensive anthropogenic effect and deviation of the organism state from normal conditions, estimated by 3 scores (Zakharov), the leucograms of frogs were characterized by more pronounced negative alterations. Leucocytosis accompanied by neutropenia, eosinophilia, basophilia, and a decrease of the total number of lymphocytes has been established. In the absence of deviations of the stability of development from the conditionally normal state, there was revealed the balance of leucogram indicators, close to norm. An increase of the number of lymphocytes and young forms of neutrophils in the amphibian peripheral blood indicates stimulation of the processes providing the organism protective reaction. Cross-correlation between the integral indicator of stability of development, the content of eosinophils and lymphocytes has been established in individuals from populations of green frogs inhabiting the studied reservoirs.