The core apparatus that regulates circadian rhythm has been extensively studied over the past five years. A looming question remains, however, regarding how this apparatus is adjusted to maintain coordination between physiology and the changing environment. The diversity of stimuli and input pathways that gain access to the circadian clock are summarized. Cellular metabolic states could serve t...

A canine model was used to study the effects of different environmental stresses on the heart and coronary circulation. The heart was surgically instrumented to measure coronary blood flow, left ventricular pressure, and other cardiovascular variables. Coronary flow was recorded by telemetry. Physiologic data were processed and analyzed by analog and digital computers. By these methods the phys...