Regulation of C4 Photosynthesis: Inactivation of Pyruvate,Pi Dikinase in Leaf and Chloroplast Extracts in Relation to Dark/Light Regulation in Vivo

Active pyruvate, P₁ dikinase in leaf or chloroplast extractsisolated from illuminated leaves was inactivated by incubatingwith ADP. With chloroplast extracts neither ATP nor AMP alonewas effective. Half the maximum rate of inactivation was observedwith about 55 µM ADP. The following evidence supportedthe view that ADP-mediated inactivation had a co-requirementfor low concentrations of ATP [Buchanan (1980) Ann. Rev. PlantPhysiol. 31: 341], adding hexokinase and glucose prevented inactivationby ADP [Feldhaus et al. (1975) Eur. J. Biochem. 57: 197], whenGDP and UDP were added in place of ADP they mediated rapid inactivationonly when ATP was also provided; GTP was not effective. ATPwas apparently optimally effective at about 1 µM or less.The rate of inactivation was approximately proportional to thesquare of extract concentration suggesting dependancy on a factorin the extracts in addition to active enzyme. The involvementof one or more heat labile protein factors was confirmed bytrypsin treatment of extracts. Pyruvate, P₁ dikinase inactivatedby treatment with ADP was reactivated by incubating with P₁,a property common to the inactive enzyme extracted from darkenedleaves. Thiol/disulphide interconversion was apparently notcritical in the regulation of pyruvate, P₁ dikinase. ³Present address: Department of Agricultural Chemistry, Facultyof Agriculture, Nagoya University, Chikusa, Nagoya 464, Japan. (Received September 22, 1980; Accepted December 6, 1980)     

Cardiac sympathetic and parasympathetic activity during self-regulation of heart period.

Fourteen subjects attempted to increase and 15 attempted to decrease cardiac interbeat interval (IBI) while being provided with biofeedback of IBI, T-wave vector magnitude (TWVM), or respiratory sinus arrhythmia (RSA). Subjects in both groups showed directional change in IBI relative to a tracking control task, but the three types of feedback did not differentially affect performance. Voluntary IBI increases were associated with significant increases in TWVM and RSA, and voluntary IBI decreases were associated with significant reductions in RSA and nonsignificant reductions in TWVM. This pattern of results suggests that alterations in cardiac vagal tone are involved in voluntary IBI increase and decrease tasks. The results also suggest a role for cardiac sympathetic nervous activity in voluntary IBI increase. The role of changing respiration cycle period was also investigated.     

Growth and development of biofeedback: a bibliographic update

Computerized literature searching techniques were used to examine publication patterns in the worldwide biofeedback literature. Searches were completed in the United States and in Japan for the years 1985 through 1987. The results were used to update the results of an earlier study that covered the years from 1964 through 1984. Publication growth curves were generated for several media, including scientific journal articles, books, doctoral dissertations, and popular magazine articles. Although publication of information about biofeedback remains active worldwide, there has been a declining trend in effect for the past several years. The American database grossly underestimated the number of Japanese biofeedback articles, and it is likely that the literatures of other countries outside of North America were similarly underestimated. Possible explanations for the various trends noted are discussed.