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A study on the measurement of visibility by the use of light scattering has been carried out. The basis for the research was the optical forward-scatter sensor, Mira visibility sensor, developed and produced by Aanderaa Instruments. The focus of the study was on how to measure correct visibility at different weather situations e.g.fog, rain, haze and snow and how a sensor can provide information on the type of particlesdrops which are causing reduced visibility. Optical scatter measurement of airborne dust was also investigated. The work includes theoretical calculations and experimental work. The correlations between scatter measurements and both visibility and the concentration of airborne dust are studied. A short introduction to the subject of visibility measurement is also included.

ExoT is a type III secreted effector protein found in almost all strains of Pseudomonas aeruginosa and is required for full virulence in an animal model of acute pneumonia. It is comprised of an N-terminal domain with GTPase activating protein (GAP) activity towards Rho family GTPases and a C-terminal ADP ribosyltransferase (ADPRT) domain with minimal activity towards a synthetic substrate in vitro. Consistent with its activity as a Rho family GTPase, ExoT has been shown to inhibit P. aeruginosa internalization into epithelial cells and macrophages, disrupt the actin cytoskeleton through a Rho-dependent pathway, and inhibit wound repair in a scrape model of injured epithelium. We have previously shown that mutation of the invariant arginine of the GAP domain to lysine (R149K) results in complete loss of GAP activity in vitro but only partially inhibits ExoT anti-internalization and cell rounding activity. We have constructed in-frame deletions and point mutations within the ADPRT domain in order to test whether this domain might account for the residual activity observed in ExoT GAP mutants. Deletion of a majority of the ADPRT domain (residues 234 to 438) or point mutations of the ADPRT catalytic site (residues 383 to 385) led to distinct changes in host cell morphology and substantially reduced the ability of ExoT to inhibit in vitro epithelial wound healing over a 24-h period. In contrast, only subtle effects on the efficiency of ExoT-induced bacterial internalization were observed in the ADPRT mutant forms. Expression of each domain individually in Saccharomyces cerevisiae was toxic, whereas expression of each of the catalytically inactive mutant domains was not. Collectively, these data demonstrate that the ADPRT domain of ExoT is active in vivo and contributes to the pathogenesis of P. aeruginosa infections.

ABSTRACTExoT is a type III secreted effector protein found in almost all strains of Pseudomonas aeruginosaand is required for full virulence in an animal model of acute pneumonia. It is comprised of an N-terminal domain with GTPase activating protein (GAP) activity towards Rho family GTPases and a C-terminal ADP ribosyltransferase (ADPRT) domain with minimal activity towards a synthetic substrate in vitro. Consistent with its activity as a Rho family GTPase, ExoT has been shown to inhibit P. aeruginosainternalization into epithelial cells and macrophages, disrupt the actin cytoskeleton through a Rho-dependent pathway, and inhibit wound repair in a scrape model of injured epithelium. We have previously shown that mutation of the invariant arginine of the GAP domain to lysine (R149K) results in complete loss of GAP activity in vitro but only partially inhibits ExoT anti-internalization and cell rounding activity. We have constructed in-frame deletions and point mutations within the ADPRT domain in order to test whether this domain might account for the residual activity observed in ExoT GAP mutants. Deletion of a majority of the ADPRT domain (residues 234 to 438) or point mutations of the ADPRT catalytic site (residues 383 to 385) led to distinct changes in host cell morphology and substantially reduced the ability of ExoT to inhibit in vitro epithelial wound healing over a 24-h period. In contrast, only subtle effects on the efficiency of ExoT-induced bacterial internalization were observed in the ADPRT mutant forms. Expression of each domain individually in Saccharomyces cerevisiaewas toxic, whereas expression of each of the catalytically inactive mutant domains was not. Collectively, these data demonstrate that the ADPRT domain of ExoT is active in vivo and contributes to the pathogenesis of P. aeruginosainfections.

A large number of harp seals invaded the Norwegian coast in 1987 and 1988, when approximately 80 000 animals were drowned in the gillnet fisheries. The diet had the same composition and geographical variation as described for the previous invasion in 1902 and 1903, i.e. a dominance of cod and capelin in Finnmark, saithe in the Norwegian Sea, and herring in the Lofoten fjords. A physiological model is developed to study the sensitivity to variation in those parameters which are poorly known. An average seal is estimated to have consumed 4 ± 1 kg day^-1 on the meagre diet (4.5% fat) during the invasion. In 1987 the harp seals consumed 215 000 ± 50 000 tonnes off Norway. Our estimate of the impact on the 1985 year-class of cod and the 1985 and 1986 year-classes of saithe is 110 000 000 ± 25 000 000 individuals eaten. This order of predation agrees well with the observed sudden decline of these three year-classes. Copyright 1993, 1999 Academic Press