Biomedical subjects
Publications and source records attributed to D Mateos.
It is shown that a IIA superstring carrying D0-brane charge can be "blown up," in a Minkowski vacuum background, to a (1/4)-supersymmetric tubular D2-brane, supported against collapse by the angular momentum generated by crossed electric and magnetic Born-Infeld fields. This "supertube" can be viewed as a world-volume realization of the sigma-model Q lump.
The biochemical properties, virulence for mice and trout, and the extracellular virulence factors at 28 degrees and 37 degrees C of 11 environmental and nine human strains of Aeromonas hydrophila were compared. All the environmental isolates and four of the human group were virulent for trout at 3 x 10(7) cfu, but only human strains were able to cause death or lesions in mice by the intramuscular route. Extracellular virulence factors such as haemolysins, cytotoxins and proteases were also investigated in supernatant fluids of cultures grown at 28 degrees C and 37 degrees C. The production of haemolysins, caseinases, elastases and growth yields of environmental strains decreased sharply during cultivation at 37 degrees C but cytotoxins were produced to the same extent, or slightly less, than at 28 degrees C. The human strains differed from the environmental strains in response to growth temperatures: protease activity decreased at 37 degrees C, although growth yield was not affected, but more haemolysins and cytotoxins were produced by the virulent strains at this temperature than at 28 degrees C. Sodium caseinate SDS-PAGE of culture supernatant fluids of selected human strains revealed that temperature selectively inhibited the production of certain proteases.
Seventy-four strains of Aeromonas hydrophila isolated from water and sediments of the River Porma (León, N.W. Spain) were characterized biochemically and biologically. Fifty-seven strains (77.02%) were virulent for rainbow trout (Salmo gairdneri) by intramuscular challenge but showed differing degree of pathogenicity which could not be associated with the source. A lack of correlation between caseinase, haemolytic and cytotoxic activities of the strains and their isolation source was also observed. Only two surface characters, acriflavine 0.2% agglutination and non-agglutinating SP-/PAB-phenotypes, were significantly associated with water and sediment strains, respectively.
Aeromonas virulence is thought to depend on multigenic functions. The gene for an extracellular protease from Aeromonas hydrophila SO2/2 was cloned in Escherichia coli C600-1 by using pIJ860, bifunctional plasmid, as a vector. The gene encodes for a temperature-labile serine protease (P2) with a molecular mass of approx. 68 kDa which is highly inhibited by PMSF. The gene was expressed in Streptomyces lividans 1326 by transforming protoplasts with the original clone pPA2. We were also able to transfer and express the prt P2 gene in Pseudomonas putida by mating experiments. The protein P2 was secreted into the periplasms of both P. putida and E. coli C600-1 being identical in properties to one of the proteases secreted into the culture supernatant by A. hydrophila SO2/2.