A novel oxygen sensor which does not rely on electrochemical reduction has been used to measure the oxygenation of the murine sarcoma F in a comparative study with an existing polarographic electrode that is available commercially. The prototype luminescence sensor yielded an oxygen distribution comparable with readings made using a pO2 histograph. The percentage of regions detected that had a pO2 less than 5 mm Hg was 79 and 75 using the Eppendorf pO2 histograph and the luminescence fiber optic sensor, respectively. These values were compatible with a measured radiobiologically hypoxic fraction of 67% in this tumor. The polarographic method detected more regions with a pO2 of 2.5 mm Hg or less (69%) compared with the optical sensor (50%) (P < 0.05). This could reflect differences in the oxygen use of the sensing devices. This initial assessment indicates the potential of a fiber-optic-based oxygen-monitoring system. Such a system should have several advantages including monitoring temporal oxygen changes in a given microregion and use with NMR procedures.
There is considerable uncertainty regarding the role of sympathetic amines in the central nervous system; although some have postulated that they may be concerned with neural transmission, supporting evidence is not entirely conclusive. Nevertheless, Vogt1 has noted the presence of relatively high concentrations of sympathin in the hypothalamus and in the area postrema, with less in the midbrain and in the aqueduct, and has further demonstrated that their local concentrations may be reduced by drugs which stimulate these centers. It has long been recognized that the administration of epinephrine stimulates the waking state and increases spontaneous motor activity. It has been suggested that these effects of circulating epinephrine may in part be due to direct stimulation of ascending and descending reticular systems (Bonvallet, Dell, and Hiebel2; Dell, Bonvallet, and Hugelin3). Sensenbach et al.4 were unable to demonstrate significant alteration of cerebral oxygen consumption by the administration of arterenol (norepinephrine) or epinephrine. King et al.,5 on the other hand, reported a significant increase in cerebral oxygen con¬ sumption during epinephrine administration. The present study was undertaken in view of these conflicting reports, and the effects of arterenol and epinephrine on total cere-bral oxygen consumption and cerebral hemo¬ dynamics were studied. In the case of the latter agent, its effects upon young and elderly normotensive subjects were also in¬ vestigated.
MethodEight patients, most of whom were convales¬ cent from disorders not associated with hypo¬ tension, were studied to determine the effect of arterenol upon cerebral hemodynamics and oxygen consumption in the normotensive subject. Three of these patients were between 26 and 50 years of age, while the remainder ranged from 66 to 92 years of age. Blood pressure elevation in these subjects was accomplished by intravenous admin¬ istration of arterenol in concentrations of µ%. (levarterenol [Levophed] base) per cubic centi¬ meter given over periods of 28 to 46 minutes. Cerebral hemodynamics and total cerebral oxygen consumption were measured during the last 10 minutes of infusion.The effects of epinephrine on cerebral hemo¬ dynamics and metabolism were studied in 12 con¬ valescent normotensive hospital patients, of whom 6 were aged 23 to 47 and 6 ranged from 59 to 96 years of age. Synthetic epinephrine was adminis¬ tered by intravenous infusion for 30 to 71 minutes at varying rates, the solutions containing 2^g. to 8/ig. per cubic centimeter. As in the case of ar¬ terenol administration, cerebral hemodynamics and oxygen consumption were measured during the final 10 minutes of the infusion. Scheinberg and Stead's modificationß of Kety and Schmidt's procedure7 for the determination of cerebral blood flow was applied in this study.The oxygen content of the blood was determined by the manometric technique of Van Slyke and Neill.8 Mean arterial pressure was obtained di¬ rectly from the femoral artery by means of a damped aneroid manometer (Alman...
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