Antibacterial activity in hemocytes of the squat lobster,
Galathea strigosa, the Norway lobster,
Nephrops norvegicus, the common shrimp,
Crangon crangon, and the giant Antarctic isopod,
Glyptonotus ...antarcticus, was investigated
in vitro. For all species, the marine bacterium,
Psychrobacter immobilis, was used as the test organism, although with
G. antarcticus, the Gram positive bacteria,
Planococcus citreus and BS 68 (an isolate from Antarctic waters), were also used. Hemocyte lysate supernatants (HLS) from all four species reduced the viable count of test bacteria over a period of 4 hr showing that their hemocytes contain factors able to neutralize bacteria
in vitro. However, comparison of responses produced by serially diluted samples of HLS from
G. strigosa,
N. norvegicus and
C. crangon, revealed that activity (per unit protein) is weaker than for
Carcinus maenas. Using
G. antarcticus, positive activity was also observed against
P. citreus and BS 68; with the response effective against all of the bacteria at both 0°C and 20°C. These results show that: (1) the hemocytes from a range of crustacean species contain factor(s) able to neutralize bacteria
in vitro; (2) antibacterial potency varies from species to species; and (3) antibacterial immunity in at least one polar invertebrate functions at low temperature.
The antimicrobial defenses of anthozoans were investigated in vitro by extracting amoebocytes from the mesenteric filaments of the beadlet anemone, Actinia equina, and testing for their ability to ...phagocytose and kill the gram-negative bacterium Psychrobacter immobilis. Only the hyaline amoebocytes exhibited phagocytosis in vitro, with about 40% seen to ingest one or more bacteria over 45 min. Mixed cultures of viable amoebocytes were further found to produce O2- ions and other reactive oxygen species (ROS) after stimulation with phorbol myristate acetate or lipopolysaccharide. Co-incubation of viable amoebocytes with P. immobilis for 3 h in vitro resulted in reduced growth of the bacterium compared to saline-incubated bacteria, but because the growth of P. immobilis was also impaired by lysed control amoebocytes, the contribution made to bacterial killing by ROS could not be evaluated. Instead, as confirmed by additional experiments using lysate supernatants of the amoebocytes, it appears that the cells contain soluble bactericidal factors. The nature of these agents is at present unknown, although preliminary tests indicate that killing is not mediated by lysozyme.
Reactive thermostatistical search (RTS) is used within this paper to optimise parameter settings for discrete event simulation problems; the performance of its implementation within the Witness ...discrete event simulation package is benchmarked against that of the optimiser used within the ProModel package. RTS is a new technique, based upon simulated annealing, which incorporates elements of tabu search into the SA process, by learning from its experience of the problem domain and modifying its search strategy accordingly.
An introduction to the approaches used to discretise continuous database features is given, together with a discussion of the potential benefits of such techniques. These benefits are investigated by ...applying discretisation algorithms to two large commercial databases; the discretisations yielded are then evaluated using a simulated annealing based data mining algorithm. The results produced suggest that dramatic reductions in problem size may be achieved, yielding improvements in the speed of the data mining algorithm. However, it is also demonstrated under certain circumstances that the discretisation produced may give an increase in problem size or allow overfitting by the data mining algorithm. Such cases, within which often only a small proportion of the database belongs to the class of interest, highlight the need both for caution when producing discretisations and for the development of more robust discretisation algorithms.
The Omega RICH in the CERN hyperon beam experiment Müller, U.; Beusch, W.; Boss, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/1999, Letnik:
433, Številka:
1
Journal Article
Recenzirano
The Omega RICH, a large-aperture detector for identification of secondary pions, kaons, and (anti) protons was in operation at the CERN Omega spectrometer facility between 1984 and 1994. Cherenkov ...photons from a 5 m long radiator were detected in drift chambers with quartz windows, using TMAE-loaded counting gases. The RICH was used by experiments WA69 and WA82, until 1988. It was then equipped with new drift chambers and mirrors and was in use since 1990 in experiments WA89 and WA94. The setup in the WA89 hyperon beam experiment is described in more detail and efficiencies, resolutions, and physics results are discussed.
Solitary ascidians possess a wide range of antimicrobial agents in their bloodand other tissues. A number have been purified and characterised with a view to developing novel pharmacological or ...commercially useful products. The most well known are the didemnins isolated from whole body homogenates of Caribbean ascidians belonging to the genus
Trididemnum. Others include the halocyamines from
Halocynthia roretzi, piclavines from
Clavelina picta and lissoclinotoxins from
Lissoclinum perforatum. For most species, however, little is known about the spectrum of activity, tissue location or mode of action of these compounds, and no details have been forthcoming about their biosynthesis, release or internal regulation. Recent work on
Ciona intestinalis has shown that potent antibacterial activity against a range of Gram positive and Gram negative bacteria resides within the circulating blood cells, principally the morula cells. Activity is constitutive, unrelated to lysozyme and does not involve agglutination or direct lysis of the bacterial cell wall. Instead, it appears to be clue to at least two proteins with molecular masses of ca 8–12 kDa and 60–70 kDa respectively. Since the morula cells are known to participate in a variety of cellular host defence responses, there can be little doubt that these proteins aid in the neutralisation of bacterial, and possibly other micro-organisms, which may gain access to the tissues. However, in some ascidian species, peptides with antibiotic properties
in vitro have been shown to have other biological effects; for example protection against predation, digestion or prevention of surface epibiosis. There is great scope for finding further novel antimicrobial proteins in the ascidian group, and areas where further research is needed include an analysis of their biochemical and phylogenetic relationship to other biologically active peptides, an understanding of their induction and modulation in vivo and an assessment of the ways they exert their biological effects on susceptible micro-organisms
in vitro.
The construction is described of a molecular probe to P virus, a double stranded RNA virus belonging to the Reoviridiae, which is an endemic pathogen of swimming crabs in British coastal waters and ...the Mediterranean. The probe hybridises to the P virus genome and can be easily produced in large quantities by PCR. It may be used by dot blotting or in situ hybridisation to specifically detect P virus in tissues and cells of natural or experimentally infected animals. Analyses of tissue samples with this probe show that the virus infects connective tissues of gills and hepatopancreas. This is the first gene probe to be constructed for a native viral pathogen of temperate water brachyurans and it will be useful to study virus ecology and virus–host interactions in vivo and in vitro. An understanding of these processes is essential to control and manage disease and, ultimately, to identify immune effectors capable of destroying viral pathogens.
PDF
