Leland C. Clark

Bio: Leland C. Clark is an academic researcher from Hospital Research Foundation. The author has contributed to research in topics: Phenethylamines & Silicone. The author has an hindex of 26, co-authored 71 publications receiving 6204 citations.

Electrode systems for continuous monitoring in cardiovascular surgery.

Abstract: Instruments capable of continuously indicating the chemical composition of blood have proved to be useful in controlling heart-lung machines, in regulating operative and postoperative management of patients, and in teaching and research. At first, such instruments were used with sensors mounted directly in the extracorporeal blood circuit that is used for perfusion of open-heart surgery patients.] Later, continuous monitoring of both machine and patients was conducted by means of continuous withdrawal of blood pumped into external cuvettes equipped with appropriate sensors. Improvement in the design and construction of electrode systems and their associated electronic instrumentation, together with the commercial development and availability of stable amplifiers and recorders, has now provided entirely satisfactory systems for the rapid and accurate measurement of blood pH, pCO2, and pOz. Electrodes for measurement of blood p 0 2 and $ 0 2 can also be used for recording these tensions in gases. By mixing blood with certain reagents, these electrodes can be used to record blood gas contents as well as tensions. Intravascular electrodes are being used to time hydrogen appearance, to detect changes in oxygen tension, and to record ascorbate indicator dilution curves. Such electrodes are proving valuable in cardiac catheterization and in evaluation of the effectiveness of corrective endocardiac surgical procedures. Speed of response, ease of use, autoclavability, smallness of size, and the practicability of using multiple electrodes simultaneously is often sufficient advantage to overcome the present lack of quantitative response of these relatively simple electrodes. By withdrawing blood through microcatheters, continuous recording of blood composition for many hours, even days, is possible, using only about 10 cc. of blood per hr. Continued development of electrode systems may extend their usefulness to the measurement of blood ions, sugar, and urea and finally result in instruments with which analyses can be performed with a minimum of reagents and with but little delay. Electrode systems readily lend themseIves to either intermittent, semiautomatic, or continuous analytical processes. Blood oxygen tension. Electrodes available at present, mounted in thermostated cuvettes, have proved very satisfactory for the measurement of p 0 2 in blood samples. Thousands of analyses have been performed with the several units available here. We have evaluated several means of utilizing electrodes to follow blood pO2 under conditions encountered in cardiovascular operating rooms and have found that analysis of individual samples, withdrawn in plastic syringes, is the least troublesome and most

Survival of Mammals Breathing Organic Liquids Equilibrated with Oxygen at Atmospheric Pressure

Abstract: Because oxygen and carbon dioxide are very soluble in certain silicone oils and fluorocarbon liquids, these liquids will support respiration of mammals. Mice and cats respiring silicone oil die shortly after return to air breathing, while those breathing fluorocarbon survive for weeks. The respiration of mice is optimally supported by these organic liquids at about 20 degrees C. In cats, arterial oxygenation is excellent, but there is some impairment of carbon dioxide elimination. All animals have suffered some pulmonary damage from breathing fluorocarbon liquids. Continued investigation of organic fluid respiration may lead to development of a safe method to support the respiration of man by liquids equilibrated with gases at atmospheric pressure.

Chronically implanted polarographic electrodes.

Abstract: Insulated metal polarographic cathodes were permanently implanted in the brains of cats, allowing continuous recording of oxygen availability. A study was made of the current flow as related to app...

Spontaneous fluctuations in brain activity observed with functional magnetic resonance imaging.

Abstract: The majority of functional neuroscience studies have focused on the brain's response to a task or stimulus. However, the brain is very active even in the absence of explicit input or output. In this Article we review recent studies examining spontaneous fluctuations in the blood oxygen level dependent (BOLD) signal of functional magnetic resonance imaging as a potentially important and revealing manifestation of spontaneous neuronal activity. Although several challenges remain, these studies have provided insight into the intrinsic functional architecture of the brain, variability in behaviour and potential physiological correlates of neurological and psychiatric disease.

Electrode systems for continuous monitoring in cardiovascular surgery.

Abstract: Instruments capable of continuously indicating the chemical composition of blood have proved to be useful in controlling heart-lung machines, in regulating operative and postoperative management of patients, and in teaching and research. At first, such instruments were used with sensors mounted directly in the extracorporeal blood circuit that is used for perfusion of open-heart surgery patients.] Later, continuous monitoring of both machine and patients was conducted by means of continuous withdrawal of blood pumped into external cuvettes equipped with appropriate sensors. Improvement in the design and construction of electrode systems and their associated electronic instrumentation, together with the commercial development and availability of stable amplifiers and recorders, has now provided entirely satisfactory systems for the rapid and accurate measurement of blood pH, pCO2, and pOz. Electrodes for measurement of blood p 0 2 and $ 0 2 can also be used for recording these tensions in gases. By mixing blood with certain reagents, these electrodes can be used to record blood gas contents as well as tensions. Intravascular electrodes are being used to time hydrogen appearance, to detect changes in oxygen tension, and to record ascorbate indicator dilution curves. Such electrodes are proving valuable in cardiac catheterization and in evaluation of the effectiveness of corrective endocardiac surgical procedures. Speed of response, ease of use, autoclavability, smallness of size, and the practicability of using multiple electrodes simultaneously is often sufficient advantage to overcome the present lack of quantitative response of these relatively simple electrodes. By withdrawing blood through microcatheters, continuous recording of blood composition for many hours, even days, is possible, using only about 10 cc. of blood per hr. Continued development of electrode systems may extend their usefulness to the measurement of blood ions, sugar, and urea and finally result in instruments with which analyses can be performed with a minimum of reagents and with but little delay. Electrode systems readily lend themseIves to either intermittent, semiautomatic, or continuous analytical processes. Blood oxygen tension. Electrodes available at present, mounted in thermostated cuvettes, have proved very satisfactory for the measurement of p 0 2 in blood samples. Thousands of analyses have been performed with the several units available here. We have evaluated several means of utilizing electrodes to follow blood pO2 under conditions encountered in cardiovascular operating rooms and have found that analysis of individual samples, withdrawn in plastic syringes, is the least troublesome and most

Electrochemical Glucose Biosensors

Abstract: First-generation glucose biosensors relied on the use of the natural oxygen cosubstrate and the production and detection of hydrogen peroxide and were much simpler, especially when miniaturized sensors are concerned. More sophisticated bioelectronic systems for enhancing the electrical response, based on patterned monolayer or multilayer assemblies and organized enzyme networks on solid electrodes, have been developed for contacting GOx with the electrode support. Electrochemical biosensors are well suited for satisfying the needs of personal (home) glucose testing, and the majority of personal blood glucose meters are based on disposable (screen-printed) enzyme electrode test strips, which are mass produced by the thick film (screen-printing) microfabrication technology. In the counter and an additional “baseline” working electrode, various membranes (mesh) are incorporated into the test strips along with surfactants, to provide a uniform sample coverage. Such devices offer considerable promise for obtaining the desired clinical information in a simpler, user-friendly, faster, and cheaper manner compared to traditional assays. Continuous ex-vivo monitoring of blood glucose was proposed in 1974 and the majority of glucose sensors used for in-vivo applications are based on the GOx-catalyzed oxidation of glucose by oxygen. The major factors that play a role in the development of clinically accurate in-vivo glucose sensors include issues related to biocompatibility, miniaturization, long-term stability of the enzyme and transducer, oxygen deficit, short stabilization times, in-vivo calibration, baseline drift, safety, and convenience.

Analyte Monitoring Device And Methods Of Use

Abstract: An analyte monitor includes a sensor, a sensor control unit, and a display unit. The sensor has, for example, a substrate, a recessed channel formed in the substrate, and conductive material disposed in the recessed channel to form a working electrode. The sensor control unit typically has a housing adapted for placement on skin and is adapted to receive a portion of an electrochemical sensor. The sensor control unit also includes two or more conductive contacts disposed on the housing and configured for coupling to two or more contact pads on the sensor. A transmitter is disposed in the housing and coupled to the plurality of conductive contacts for transmitting data obtained using the sensor. The display unit has a receiver for receiving data transmitted by the transmitter of the sensor control unit and a display coupled to the receiver for displaying an indication of a level of an analyte. The analyte monitor may also be part of a drug delivery system to alter the level of the analyte based on the data obtained using the sensor.

[7] Mitochondrial respiratory control and the polarographic measurement of ADP : O ratios

Abstract: Publisher Summary This chapter discusses the mitochondrial respiratory control and the polarographic measurement of ADP : O ratios. The polarographic oxygen electrode technique is used for measuring rapid changes in the rate of oxygen utilization by cellular and subcellular systems. Although the polarographic method measures changes in oxygen concentration of photosynthetic systems, yeast cells, and nerve, but the oxygen electrode technique is applied to a study the mitochondrial respiration and oxidative phosphorytation. The principle of the oxygen electrode has been summarized, and the design of the vibrating oxygen electrode for use with speetrophotometric studies is illustrated. The oxygen electrode apparatus can be calibrated in a number of ways. A more accurate calibration of oxygen content can be obtained by gas equilibration with various nitrogen-oxygen mixtures. When tightly coupled mitochondria are suspended in an isotonic buffer, a slow rate of oxygen uptake is measured in the presence of substrate and absence of ADP. Addition of ADP causes an immediate increase in the rate of oxygen utilization. The concentration of oxygen utilized is proportional to the amount of ADP phosphorylated to ATP. The type of oxygen electrode tracings is presented from which an ADP : O ratio (equivalent to a P : O ratio) can be directly calculated.