Volatile fatty acids as indicators of process imbalance in anaerobic digestors

In continuously stirred tank reactor experiments, with manure as substrate at thermophilic temperatures, the use of volatile fatty acids (VFA) as process indicators was investigated. Changes in VFA level were shown to be a good parameter for indicating process instability. The VFA were evaluated according to their relative changes caused by changes in hydraulic loading, organic loading or temperature. Butyrate and isobutyrate together were found to be particularly good indicators. Butyrate and isobutyrate concentrations increased significantly 1 or 2 days after the imposed perturbation, which makes these acids suitable for process monitoring and important for process control of the anaerobic biological system. In addition it was shown in a batch experiment that VFA at concentrations up to 50 mM did not reduce the overall methane production rate. This showed that VFA accumulation in anaerobic reactors was the result of process imbalance, not the cause of inhibition, thus justifying the use of VFA as process indicators.     

Nonspecific and antigen-specific adhesiveness of circulating lymphocytes in dysentery patients undergoing combined therapy using thymalin and indomethacin

Nonspecific adhesiveness of lymphocytes to polyacrylonitrile fiber and the antigen-specific adhesiveness of T-lymphocytes to Shigella flexneri pellicular immunosorbent have been studied in dysentery patients. Short courses of treatment with indomethacin, but not with thymalin (the preparation of thymic hormones), used for immunomodulation, have accelerated the normalization of nonspecific lymphocyte adhesiveness during regression of the disease, while indomethacin, in contrast to thymalin, inhibits antigen-specific T-lymphocyte adhesiveness which increases with the development of immune response.     

Studies on thymocyte subpopulations in guinea pigs. Differences in cell volume and proliferative ability in vitro of two populations separated by density gradient centrifugation with Percoll

Thymus cells from guinea pigs were separated according to buoyant density by centrifugation with PVP-coated colloidal silica particles (Percoll). By creating an S-shaped density gradient, two populations (referred to as peak-I and peak-II cells) were obtained which differed in size as well as ability to spontaneous proliferation in vitro. Peak I contained low density cells of large size and was highly enriched with DNA-synthesizing cells. These continued to proliferate in culture for at least 30 h as demonstrated by mitotic studies in the intervals 0-10 and 20-30 h. In order to grow in vitro, however, the cycling cells of peak I depended on the medium (RPMI 1640) being supplemented with L-alanine. The high density cells of peak II constituted 70% of the thymocytes and had a small and uniform volume. This population was depleted of proliferating cells. The simple and rapid separation of these two major populations is considered a useful first step for the further characterization of thymocyte subpopulations. We suggest that peak I primarily includes proliferating precursor cells from the cortex as well as mature, immunocompetent cells. Peak II consists largely of small cortical cells.