have been discussed by Cameron (32), Johnson (33), Manley (34), and Matsuoka et al. (35).On the basis of the rather crude x-ray positional data that were available in the fall of 1966, Sandage made a photographic survey of a 4by 4-degree region surrounding Cyg XR-2. Subsequently, more accurate information was provided by the ASE-MIT group, which led to an identification of Cyg XR-2 with a 16th-magnitude blue star noted on the Palomar plates. If the identification is confirmed, Cyg XR-2 and Sco XR-1 will be "charter members" of a newly recognized class of stars, located in our own galaxy, whose x-ray luminosities considerably exceed their optical outputs. References and Notes 1. The 1967 Texas Symposium had a registration of approximately 650 persons. The organizing committee and sponsoring organizations consisted of A. have been discussed by Cameron (32), Johnson (33), Manley (34), and Matsuoka et al. (35).On the basis of the rather crude x-ray positional data that were available in the fall of 1966, Sandage made a photographic survey of a 4by 4-degree region surrounding Cyg XR-2. Subsequently, more accurate information was provided by the ASE-MIT group, which led to an identification of Cyg XR-2 with a 16th-magnitude blue star noted on the Palomar plates. If the identification is confirmed, Cyg XR-2 and Sco XR-1 will be "charter members" of a newly recognized class of stars, located in our own galaxy, whose x-ray luminosities considerably exceed their optical outputs.References and Notes 1. The 1967 Texas Symposium had a registration of approximately 650 persons. The organizing committee and sponsoring organizations consisted of A.

No abstract

The establishement of the circadian rhythm of cholesterol 7a-hydroxylase activity requires protein and RNA synthesis. The spontaneous decrease of the enzymic activity, at the end of the night, allows us to evaluate a half-life time of about two hours. The half-life time goes up to about four hours when the enzymatic activity decay is measured following cycloheximide administration. This difference suggests that an active mechanism is involved in the control of the enzyme degradation. The daily variation of the enzyme activity is regulated via the hypothalamo-hypophysis-adrenal axis. At the cellular level glucocorticoids are the most likely responsible agent. The hepatic cholesterol 7a-hydroxylase variations always parallel the plasmatic corticosterone concentration fluctuations, the latter being by far the most important adrenocortical excretion product. These two rhythms are modified in a similar manner under different physio-pathological conditions, such as the inversion of lighting in the animal room or the inversion of feeding time. Of these two parameters, the moment of food intake is the most important and accounts for the synchronisation of the rhythm in the animals. The rhythm is retained after several days of starvation but its amplitude decreases and the individual variations among the animals increase significantly at each time point.