Hydrobionts as reservoir hosts for infectious agents of bacterial sapronoses

Data on parasitism of the infectious agents of sapronoses in hydrobionts (protozoans, crustaceans, worms, mollusks, echinoderms, and fishes) are considered from the population-ecological viewpoint. The symbiotic relationships between populations of pathogenic bacteria and protozoans are of the host-parasite type. An ultrastructural analysis demonstrates that phagocytosis is incomplete both in planktonic forms and in biofilms formed by bacteria and protozoa. This provides for long-term survival of infectious agents in the environment. The migration of Yersinia pseudotuberculosis along trophic chains from the lowest to the highest level has been simulated experimentally. The long-term survival of pathogenic bacteria in aquatic animals and the ability of bacteria to migrate along trophic chains, reaching soil animals and humans, provide evidence that comprehensive studies on the routes of circulation of pathogens in natural ecosystems are highly relevant from the ecological and epidemiological viewpoints.     

Pseudomonads as parasites of protozoa]

The experimental study of the interaction of Tetrahymena pyriformis with different microorganisms of the genus Pseudomonas, isolated from the soil, was made. The study revealed that T. pyriformis phagocytosed some Pseudomonas pigment-forming species (P. cepacia, P. putida, P. fluorescens, P. pirkettii). The most pronounced cytopathogenic effect was produced by P. cepacia. The dynamic observations of the ultrastructural features of interaction between P. cepacia and protozoa were made. Even at early stages of this interaction some types of parasitiferous phagosomes containing both intact bacteria capable of multiplication by binary division and Pseudomonas cells exhibiting different degrees of destruction were registered. In several phagosomes morphologically intact bacteria differing in their cell-wall profiles and the density of their cytoplasm and nucleotide were present simultaneously. More dense cells with sinuous cell-wall membranes were more virulent. By hour 18 one giant parasitiferous vacuole was formed by fusion of smaller phagosomes, which subsequently broke up, liberating a new generation of bacteria. In infected cells disturbances in the structure of their mitochondria and macronucleus appeared. During the first 2 days of the joint cultivation of P. cepacia and T. pyriformis the accumulation of bacteria occurred due to the selection and multiplication of digestion-resistant bacterial cells, which ensured the resistance of this Pseudomonas population in association with protozoa.     

Do inflammatory mediators influence the contribution of airway smooth muscle contraction to airway hyperresponsiveness in asthma?

It is now accepted that a host of cytokines, chemokines, growth factors, and other inflammatory mediators contributes to the development of nonspecific airway hyperresponsiveness in asthma. Yet, relatively little is known about how inflammatory mediators might promote airway structural remodeling or about the molecular mechanisms by which they might exaggerate smooth muscle shortening as observed in asthmatic airways. Taking a deep inspiration, which provides relief of bronchodilation in normal subjects, is less effective in asthmatic subjects, and some have speculated that this deficiency stems directly from an abnormality of airway smooth muscle and results in airway hyperresponsiveness to constrictor agonists. Here, we consider some of the mechanisms by which inflammatory mediators might acutely or chronically induce changes in the contractile apparatus that in turn might contribute to hyperresponsive airways in asthma.     

Changes in the reactivity of microvessels of the pia mater system of rats during ontogenesis

Changes in microvascular reactivity in pia mater system have been studied under conditions of bilateral occlusion of common carotid arteries in rats of different age groups. The studies were performed on the 7th, 30th, 45th and 90th day of the postnatal development. The occlusion of common carotid arteries lasted 6 min in week-old animals and 9 min in rats of other age groups. The phase character of microvascular reactivity has been determined. It has been found that dilation of arterioles depends on the age of the animal. So dilation of precortical arterioles averaged 20-25% of the initial level in 7-day-old animals and increased to 60-75% in 30- and 45-day-old animals. It has been determined that the smaller is the diameter of the vessels the more expressed is their reactivity. It has been shown that a steady reaction of compensatory adaptation in microvessels in characteristic only of adult animals.     

Characterization of the dominant halophilic archaea in a bacterial bloom in the dead sea

Abstract A mass bloom of halophilic archaea developed in the Dead Sea in the summer of 1992, with peak densities of more than 3 × 10⁷ cells/ml, imparting a red coloration to the water. Microscopical examination showed a numerical dominance of pleomorphic, flat cells. Attempts to identify the dominant type of halophilic archaea by means of growth experiments, both on agar plates and by dilution in liquid media, were unsuccessful, as viable counts obtained were two or more orders of magnitude lower than the total microscopic counts. Analysis of the polar lipids in the Dead Sea biomass during the bloom showed one major glycolipid to be present in the extracts, corresponding with the sulfated diglycosyl diether lipid (S-DGD-1) characteristic of the genus Haloferax . No indications were found for the presence of significant amounts of other glycolipids that indicate the presence of large numbers of Dead Sea archaea such as Halobacterium sodomense or Haloarcula marismortui , or Halobacterium species such as H. halobium, H. salinarium and H. saccharovorum . Thus, the numerically dominant organisms in the bloom is probably a difficult to culture, not yet isolated, representative of the genus Haloferax .