Methylene blue (MB) and its derivatives azure A, B, C and thionine are photoactive and, in principle, are suitable for photodynamic virus inactivation of blood and blood products, such as therapeutic plasma. Methylene blue was selected for plasma decontamination because it is being clinically used and because of its known toxicological and other properties. The standard procedure for photodynamic treatment of single units of fresh plasma involves illumination with visible light at an MB concentration of 1 microM. Polymerase chain reaction analysis revealed that, in addition to model viruses, the bloodborne viruses hepatitis B virus, hepatitis C virus, human immune deficiency virus-1 and probably also the nonenveloped parvovirus B19 are sensitive to MB/light treatment. The procedure is further improved when the fluorescent tubes routinely used for illumination are replaced by more intense light sources, e.g. light-emitting diodes or low-pressure sodium lamps. Surprisingly, the improved virus kill is accompanied by reduced damage to plasma proteins.
Mycoplasma mobile, a new gliding mycoplasma isolated from the gills of a fish, was capable of positive rheotaxis; the cells glided upstream in a moving fluid. To our knowledge this is the first demonstration of rheotactic behavior among the procaryotes.Despite its diminutive size and simple organization, Mycoplasma mobile 163K (3), which has been isolated from the gills of a freshwater fish (5), exhibits some peculiar properties: it has a differentiated cell shape with a specialized terminal structure (5, 6), can attach strongly to glass and plastic as well as to animal cells (5, 6), can glide with remarkably high speed on inert surfaces (6, 8) and on erythrocytes (2), and exhibits chemotactic behavior in response to a range of attractants (4). The last property indicates that M. mobile is able to sense changes in concentrations of specific chemical substances and can consequently direct its motion in preferred directions. Here we report another sensory-response system of this gliding mycoplasma. We found that M. mobile is also able to respond to the mechanical stimuli of flow velocity gradients by moving preferentially upstream.M. mobile was cultivated in modified Hayflick medium (4, 8). Exponentially growing cells were centrifuged for 5 min at 3,000 x g and resuspended in fresh culture medium at a concentration of approximately 108 CFU/ml. The gliding motion of M. mobile in fluid streams was investigated by a test procedure similar to that described for chemotaxis (4).Briefly, flow chambers were prepared by placing a glass cover slip (21 by 26 mm) over a 2-,ul drop of a freshly prepared mycoplasma cell suspension on a glass slide and sealing the 26-mm edges of the cover slip with paraffin. Before being sealed, the cover slip was firmly pressed to the slide to minimize the thickness of the liquid layer, thus allowing fresh medium to flow through from one open end of the chamber to the other by capillary action. The chambers were incubated for at least 5 min in petri dishes lined with dampened filter paper to allow the mycoplasma cells to establish contact either with the undersurface of the cover slip or with the top of the slide. This was important, since only attached cells exhibit gliding movement. The preparations were examined with a Zeiss photomicroscope equipped with Nomarski interference optics and coupled to a microcinematographic system, as well as with a Leitz photomicroscope equipped with dark-field optics. The microscope image was focused in the plane of the attached cells, and an appropriate observation field with an adequate number of gliding organisms (10 to 20 cells) was selected. A current velocity gradient across the chamber was induced by placing microdrops of medium along one open end of the chamber. While this technique did not generate a stable current velocity gradient along the direction of flow, it did permit the calculation of local current velocity values. Furthermore, it * Corresponding author. was possible to change the slope of the current velocity gradient and the absolute local ...
A preparation of three C-terminal fragments of the platelet protein beta-thromboglobulin was previously described to have immunomodulatory properties on phagocytic cells. One of the components is obviously identical to the recently described neutrophil-activating peptide 2 (NAP-2). In further investigations on this protein preparation (called factor C) we are able to show an additional influence on the tumour-cytolytic activities of mononuclear cells. Total neutralization of the factor C effect, by treating a factor C preparation with specific monoclonal antibody C24 prior to application in cell culture, proved that the effect is really restricted to factor C proteins. If factor C is given in combination with natural interleukin-2 (IL-2) a dose-dependent suppression of IL-2-mediated natural killer lymphokine-activated killer activity can be measured, which is first detectable 72 h after addition of factor C. Suppression does not occur if the both factors are added within a time interval of more than 12 h. Depletion of monocytes from mononuclear cells has no effect on factor-C-mediated cytotoxicity, demonstrating that factor C acts directly on lymphoid cells.
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