Human thresholds for perceiving sudden changes in atmospheric pressure

Thresholds for detection of the presence of sudden changes in atmospheric pressure, such as might occur in the operation of cabin pressurization systems of transport aircraft, were found to approximate 0.040 psi both for increases and decreases; thresholds for detection of direction of change were higher, but not significantly so.

Structural and enzymatic characterization of plant zymogen bodies

The zymogen body fraction of pea seeds was further investigated as to the content and localization of additional enzymes. This fraction was previously shown to contain an inactive form of amylopectin-1,6-glucosidase. An acid phosphatase was found with an optimum pH of 5.4. ATP or GTP were the preferred natural substrates, although there was no effect of Mg2+, K+, or Na+ ions on this acid nucleotide phosphatase activity. Cytochemical methods show that the ATPase is membrane-bound and that these bodies have only a single limiting membrane. No RNAse activity could be found; however, there was considerable β-galactosidase activity. It is concluded that these zymogen bodies are a distinct class of subcellular organelles in plants.