Bimodal effect of humic acids on the LPS-induced TNF-alpha release from differentiated U937 cells.

Humic substances (HS) have been reported to possess anti-inflammatory as well as pro-inflammatory properties. The anti-inflammatory activity was demonstrated in the rat paw edema model and we found a preliminary explanation in the 5-lipoxygenase inhibitory effect of humic acids (HA). The pro-inflammatory activity is reflected by the production and release of pro-inflammatory cytokines in HA-treated neutrophilic granulocytes. With regard to the potential use of HA as antiviral and UV-protective agents it appears advisable to investigate the role of HS in the inflammation process in more detail. Hence we tested four different HS preparations - two naturally occurring HA from the Altteich peatland in Germany, one fulvic acid (FA) preparation from a Finnish spruce forest and a synthetic HA-like polymer (caffeic acid oxidation product, KOP) for their influence on the lipopolysaccharide (LPS)-induced TNF-alpha release in human U937 cells. In addition, the cytotoxicity of HS was determined. The results demonstrate a concentration-dependent bimodal effect of HA on the TNF-alpha release of differentiated LPS-stimulated U937 cells for both the natural black peat HA from the Altteich peatland and the HA-like polymer KOP. Low HA concentrations (10-80 microg/ml) enhanced the TNF-alpha release by up to threefold (pro-inflammatory activity), while HA concentrations >100 microg/ml reduced it about 10-fold (anti-inflammatory activity). FA failed to enhance TNF-alpha release, but reduced it at higher concentrations (>200 microg/ml) by the half. Brown water HA did not exert any significant effect on TNF-alpha release. No HS-stimulated TNF-alpha release was also observed in the absence of exogenously supplied LPS. This means that HS, unlike endotoxin, are no inflammation-causing agents for LPS-untreated cells. Differences in the effect of individual HS on TNF-alpha release are discussed in connection with the polyanionic character of HS, their molecular mass distribution and the hitherto imperfectly known chemical structure.

The development and evaluation of ultrasound for the treatment of bacterial suspensions. A study of frequency, power and sonication time on cultured Bacillus species.

Some species of bacteria produce colonies and spores which agglomerate in spherical clusters (Bacillus subtilis) and this serves as a protection for the organisms inside against biocidal attack. Flocs of fine particles e.g. clay can entrap bacteria which can also protect them against the biocides. It is because of problems such as these that alternative methods of disinfecting water are under active investigation. One such method is the use of power ultrasound, either alone or in combination with other methods. Ultrasound is able to inactivate bacteria and deagglomerate bacterial clusters or flocs through a number of physical, mechanical and chemical effects arising from acoustic cavitation. The aim of this study was to investigate the effect of power ultrasound at different powers and frequencies on Bacillus subtilis. Viable plate count techniques were used as a measure of microbial activity. Results showed a significant increase in percent kill for Bacillus species with increasing duration of exposure and intensity of ultrasound in the low-kilohertz range (20 and 38 kHz). Results obtained at two higher frequencies (512 and 850 kHz) indicated a significant increase in bacteria count suggesting declumping. In assessing the bacterial kill with time under different sonication regimes three types of behaviour were characterized: High power ultrasound (lower frequencies) in low volumes of bacterial suspension results in a continuous reduction in bacterial cell numbers i.e. the kill rate predominates. High power ultrasound (lower frequencies) in larger volumes results in an initial rise in cell numbers suggesting declumping of the bacteria but this initial rise then falls as the declumping finishes and the kill rate becomes more important. Low intensity ultrasound (higher frequencies) gives an initial rise in cell numbers as a result of declumping. The kill rate is low and so there is no significant subsequent decrease in bacterial cell numbers.