Developmental changes in Hymenolepis citelli and Hymenolepis diminuta during patency.

Stem cell frequency, wet weight, proglottid number, and egg production were measured in Hymenolepis citelli at specific intervals between 20 and 120 days postinfection in an effort to correlate changes in stem cell frequency to other developmental parameters. Considerable variability was seen in wet weight and proglottid number, but differences did not seem to reflect any relation between these parameters and stem cell frequency. Significant differences were observed in egg production at specific postinfection periods. These appeared to correspond to changes seen in stem cell frequency during patency. Similar changes in egg production which also correspond to measured changes in stem cell frequency were recorded for Hymenolepis diminuta. Differences were also seen in number of eggs contained within gravid proglottids at various times postinfection for both species.

Regulation of ribulose bisphosphate carboxylase activity in vivo by a light-modulated inhibitor of catalysis.

The activity of ribulose 1,5-bisphosphate carboxylase [RuBPCase; 3-phospho-D-glycerate carboxylyase (dimerizing), EC 4.1.1.39] in leaf extracts of a number of species kept in the dark overnight was found to be very low. This was not the result of a change in the activation state or in the amount of enzyme that could be extracted from "dark" leaves. Rather, in Phaseolus vulgaris it was due to an inhibitor of catalysis that occupied the catalytic site of the enzyme. This inhibitor was compartmentalized in the chloroplast and its maximum concentration in both dark leaves and in intact chloroplasts made from such leaves was slightly in excess of the RuBPCase catalytic site concentration. The inhibitor (a phosphate ester) was bound preferentially to the activated form of the enzyme, apparently functioning as a positive effector of activation. Treatment of the enzyme-inhibitor complex in vitro with alkaline phosphatase could restore RuBPCase activity. In vivo, both the initial rate of disappearance and the final concentration of inhibitor in intact leaves was found to vary with light intensity, and these changes could account for observed light-dependent changes in RuBPCase activity, indicating that light modulation of inhibitor concentration controlled RuBPCase activity. Recovery of activity in vivo could be inhibited by 3-(3',4',4-dichlorophenyl)-1,1-dimethylurea.