Cell wall-lytic activity in Chlorella fusca

The soluble fraction of homogenates of synchronous Chlorella fusca was tested for carbohydrate-lyzing activities. With isolated cell walls and beta-1,4-mannan or carboxymethyl cellulose as substrates, a sharp increase in activity occurred shortly before release of the daughter cells followed by a decline during release. The lytic activities were partially purified by ammonium sulphate precipitation and analyzed by gel filtration on a calibrated column. Apparent molecular weights were 27,000 for cell wall autolysin(s) and beta-1,4-mannanase, 36,000 for carboxymethyl cellulase and gE70,000 for another beta-1,4-mannanase. Incubation of isolated cell walls with an enzyme preparation purified by ammonium sulphate precipitation resulted in release of up to 70% of the cell wall carbohydrate as monosaccharide, predominantly mannose and glucose. The carbohydrate released in vivo into the culture medium shortly before and during liberation of the daughter cells consisted largely of polymeric material with rhamnose, fucose and mannose as main constitutents. Upon poisoning the cells with NaN3 or carbonyl cyanide p-trifluoromethoxy-phenylhydrazone, however, a monosaccharide fraction consisting of mannose and glucose was predominant in the medium. It is suggested that the major products of cell wall lysis in vivo are monosaccharides which are rapidly taken up and metabolized by the developing daughter cells in an energy-dependent manner

Changes in nasal specific IgE to mites after periods of allergen exposure-avoidance: a comparison with serum levels

Variations of serum and nasal specific IgE to Dermatophagoides pteronyssinus (Der p) during alternate periods of antigen avoidance-exposure have been evaluated with an open design in a group of allergic children with asthma and rhinitis at the residential house Istituto Pio XII (Misurina, BL, Italy), at 1756 m, in the Italian Dolomites. A method based on direct incubation of allergen coupled substrate on the nasal mucosa has been employed to evaluate the levels of nasal IgE. Serum specific IgE decreased respectively from (median) 117-89.3 kU/l (P < 0.001) during an initial period of 3 months of allergen avoidance and from 88.2 to 78.4 kU/l (P < 0.0002) during a subsequent period of allergen avoidance. No significant increase in serum specific IgE was, in contrast, observed during two periods, 22 and 9 days, of antigen exposure, changing respectively from 89.3 to 88.2 and from 78.4 to 89.1 kU/l. In contrast, nasal IgE has been significantly influenced by the alternate periods of antigen exposure-avoidance, showing a decrease from 19.75 to 4.01 kU/l (P < 0.0001) after the initial period of avoidance, followed by an increase to 9.95 kU/l (P < 0.0001) after 22 days of exposure. A significant decrease to a value of 2.37 kU/l (P < 0.0001) was also observed during the subsequent period of avoidance, followed again by an increase to 7.87 kU/l (P < 0.002) after 9 days of exposure. The evaluation of the kinetics of changes in nasal specific IgE revealed a significant decrease (P < 0.01) as soon as antigen avoidance was implemented for 3 days.(ABSTRACT TRUNCATED AT 250 WORDS

Studies on the carbohydrases in the digestive tract of the milkfish Chanos chanos

SEAFDEC Contribution no. 71.Crude extracts from various regions of the digestive tract of pond grown milkfish were tested forttheir ability to catalyze the hydrolysis of various carbohydrates. The most active carbohydrases were those involved in the hydrolysis of agr-glucosidic bonds. Maltose, trehalose, dextrin, starch and glycogen were rapidly hydrolyzed in the presence of crude extracts from the intestines and the pyloric caeca. High amylase activity was observed in extracts from the intestines, pancreas, pyloric caeca and liver. The intestinal amylase had optimum activity at pH 6.2 and at a temperature of about 50°C. It was active at a chloride concentration of 10 to 40 ppt. The amylase activity in the intestines consistently peaked daily at about noon when the milkfish gut was full. In contrast, enzyme activity was significantly lower at 0030 hrs when the gut was empty. These results are consistent with earlier observations that the milkfish is a daytime feeder and suggest further that intestinal amylase secretion is in phase with the feeding activity of the milkfish. Although the fishes used in this study fed mostly on the naturally occurring algae in the ponds, no cellulase activity was detected in any region of the digestive tract. Less active carbohydrases that were detected include a beta-glucosidase and beta-galactosidase, both of which were of limited substrate specificity