SUMMARY Pharmacological relationships between ionized calcium and cardiac electric and mechanical parameters were explored in the open-chest dog. A technique that allows the determination of reliable, repeatable concentration-response relationships in vivo was developed. This method consists of alternating infusions of sodium citrate and calcium gluconate and direct measurement of serum ionized calcium by an ion-specific electrode. With this technique, four consecutive curves for ionized calcium vs. the first derivative of the left ventricular pressure (dP/dt) were essentially superimposable within the limits of 2-10 mg/100 ml. Relationships between ionized calcium and the electrocardiograph (ECG) interval measured from the end of the S wave to the peak of the T wave (S a T c ) proved to be superior to other ECG measurements as a correlate of ionized calcium. Ionized calcium correlated better than total calcium with physiological function in several situations. Postsurgical ionized calcium levels (4.92 ± 0.10 mg/100 ml) were consistently higher than preanesthetic values (4.57 ± 0.07 mg/100 ml, P < 0.025), whereas total calcium measurements were not significantly different (X = 5.3 ± 0.10 mEq/liter, X = 5.1 ± 0.10 mEq/liter, P < 0.1). This difference in ionized calcium was shown to be able to account for significant alterations in dP/dt, suggesting that fluctuations in ionized calcium may be involved in the regulation of the contractile state of the heart. VARIATIONS in the extracellular concentration of ionized calcium (Ca 2+ ) have important effects on the electrical and mechanical function of the intact mammalian heart. In man, hypocalcemia associated with rapid transfusion of citrated blood has been implicated as a cause of decreased contractility, cardiovascular collapse, and cardiac arrest.1 " 4 Hypercalcemia has been associated with an increase in contractility in animals, 5 " 7 and conduction disturbances, ventricular irritability, and cardiac arrest have been.described in man. 8 " 10 Recent studies have shown that the fraction of myocardial calcium that is correlated with contractility is readily exchangeable and in rapid equilibrium with plasma Ca 2 " 1 ". 11- 12 Since it has been suggested that alterations in cellular calcium levels are a common mediator of a variety of pharmacological influences on the contractile state of the heart, 13 it is possible that minor as well as major changes in the extracellular Ca 2+ can have important effects on cardiac function.Because to determine quantitative relationships in vivo between Ca 2+ and myocardial response throughout a wide range of serum Ca 2+ . MethodsTwenty-two mongrel dogs weighing 14-30 kg were sedated with morphine sulfate (2 mg/kg) intramuscularly, then anesthetized with intravenous chloralose and urethane at doses of 85 mg/kg and 625 mg/kg, respectively. Ventilation was provided by a Harvard pump delivering room air through a cuffed endotracheal tube. Arterial blood gases were monitored frequently with a Corning model 165 gas analyzer and pH w...

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Chemical element mapping is an imaging tool that provides essential information on composite materials and it is crucial for a broad range of fields ranging from fundamental science to numerous applications. Methods that exploit x-ray fluorescence are very advantageous and are widely used, but require focusing of the input beam and raster scanning of the sample. Thus the methods are slow and exhibit limited resolution due to focusing challenges. We demonstrate a new focusing free x-ray fluorescence method based ghost imaging that overcomes those limitations. We combine our procedure with compressed sensing to reduce the measurement time and the exposure to radiation by more than 80%. Since our method does not require focusing, it opens the possibility for improving the resolution and image quality of chemical element maps with tabletop x-ray sources and for extending the applicability of x-ray fluorescence detection to new fields such as medical imaging and homeland security applications.

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<p>Incidence of spontaneous micrometastases</p>